ML16146A095
| ML16146A095 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/21/2016 |
| From: | Sattler J Jensen Hughes |
| To: | Office of Nuclear Reactor Regulation, Pacific Gas & Electric Co |
| References | |
| DCL-16-057 54006-CALC-01 | |
| Download: ML16146A095 (118) | |
Text
Enclosure Attachment 3 PG&E Letter DCL-16-057 Evaluation of Risk Significance of Permanent ILRT Extension
JENSEN HUGHES c
Advancing the Science of Safety
- Diablo Canyon Power Plant:
Evaluation of Risk Significance of Permanent ILRT Extension 54006-CALC-O 1 Prepared for:
Diablo Canyon Power Plant Project
Title:
Permanent ILRT Extension Revision: 3 Name and Date 1 1 Preparer: Justin Sattler [
8ig1itally signed by Justin Sattler j,
E>ate: 2016.04.21 14:13:29-05'00' Reviewer: Kelly Wright Review Method Design Review IZI Alternate Calculation D Approved by: Matthew Johnson Revision 3 Page 1of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension REVISION RECORD
SUMMARY
Revision Revision Summary 0 Initial Issue Minor updates made based on client comments 2 Minor updates made based on client comments 3 Minor updates made based on client comments Revision 3 Page 2of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension TABLE OF CONTENTS 1.0 PURPOSE ...................................................................................................................... 4 2.0 SCOPE ......... :................................................................................................................. 4 3.0 . REFERENCES ............................................................................................................... 6 4.0 ASSUMPTIONS AND LIMITATIONS ....................... :.............................. ;....................... 8 5.0 METHODOLOGY and analysis ....................................................................................... 9 5.1 Inputs ........................................................................................................................... 9 5.1.1 General Resources Available .............................................................;.................. 9
~.1.2 Plant Specific Inputs ............................................................................................ 12 5.1.3 Impact of Extension on Detection of Component Failures that Lead to Leakage (Small and Large) .............................................................................................. 14 ,
5.2 Analysis ........................................................................................*.............................15 5.2.1 Step 1 - Quantify the Baseline Risk in Terms of Frequency per Reactor Year ..... 16 5.2.2 Step 2 - Develop Plant-Specific Person-Rem Dose (Population Dose) ................ 19 5.2.3 Step 3- Evaluate Risk Impact of Extending Type A Test Interval from 10 to 15 Years .................................................................................................................20 5.2.4 Step 4- Determine the Change in Risk in Terms of LERF ................................... 24
.5.2.5 Step 5 - Determine the Impact on the Conditional Containment Failure Probability
....................................... ,.................................................................................. 24 5.2.6 Impact of Extension on Detection of Steel Liner Corrosion that Leads to Leakage
.............................................................................. ,........................................... 25 5.3 Sensitivities ..................................................... ~ ...........................................................28 5.3.1 Potential Impact from External Events Contribution ......................*...................... 28 5.3.2 Potential Impact from Steel Liner Corrosion Likelihood ........................................ 30 5.3.3 Expert Elicitation Sensitivity *********************************************************************.::**********32 6.0 RESULTS ......................................................................................................................34
7.0 CONCLUSION
S AND RECOMMEND~TIONS ............................. ~ ......... ,...................... 36 A. Attachment 1 ...........................................................................................*.....................38 Revision 3 Page 3of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 1.0 PURPOSE The purpose of this analysis is to provide a risk assessment of permanently extending the currently allowed containment Type A Integrated Leak Rate Test (ILRT) to fifteen years. The extension would allow for substantial cost savings as the ILRT could be deferred for additional scheduled refueling outages for the Diablo Canyon Power Plant (DCPP). The risk assessment
- ' follows the guidelines from NEI 94-01, Revision 3-A [Reference 1], the methodology used in EPRI TR-104285 [Reference 2], the NEI "Interim Guidance fot Performing Risk Impact Assessments in Support of One-Time Extensions for Containment Integrated Leakage Rate Test Surveillance Intervals" from November 2001 [Reference 3], the NRC regulatory guidance on the use of Probabilistic Risk Assessment (PRA) as stated in Regulatory Guide 1.200 as applied to ILRT interval extensions, risk insights in support of a request for a plant's licensing basis as outlined in Regulatory Guide (RG) 1.174 [Reference 4], the methodology used for Calvert Cliffs to estimate the likelihood and risk implications of corrosion-induced leakage of steel liners going undetected during the extended test interval [Reference 5], and the methodology used in EPRI 1018243, Revision 2-A of EPRI 1009325 [Reference 24].
2.0 SCOPE Revisions to 10CFR50, Appendix J (Option 8) allow individual plants to extend the Integrated Leak Rate Test (ILRT) Type A surveillance testing frequency requirement from three in ten years to at least once in ten years. The revised Type A frequency is based on an acceptable performance history defined as two consecutive periodic Type A tests at least 24 months apart in which the calculated performance leakage rate was less than limiting containment leakage rate of 1La.
The basis for the current 10-year test interval is provided in Section 11.0 of NEI 94-01, Revision
- 0, and established in 1995 during development of the performance-based Option B to Appendix J. Section 11.0 of NEI 94-01 states that NUREG-1493, "Performance-Based Containment Leak Test Program," September 1995 [Reference 6], provides the technical basis to. support rulemaking to revise leakage rate testing requirements contained in Option B to Appendix J. The basis consisted of qualitative and quantitative assessment of the risk impact (in terms of increased public dose) associated with a range of extended leakage rate test intervals. To supplement the NRC's rulemaking basis, NEI undertook a similar study. The results of that study are documented in Electric Power Research Institute (EPRI) Research Project TR-104285, "Risk Impact Assessment of Revised Containment Leak Rate Testing Intervals."
The NRC report on performance-based leak testing, NUREG-1493, analyzed the effects of containment leakage on the health and safety of the public and the benefits realized from the containment leak rate testing. In that analysis, it was determined that for a representative PWR plant (i.e., Surry), that containment isolation failures contribute less than 0.1 % to the latent risks from reactor accidents. Consequently, it is desirable to show that extending the ILRT interval will not lead to a substantial increase in risk from containment isolation failures for DCPP .
. NEI 94-01 Revision 2-A contains a Safety Evaluation Report that supports using EPRI Report No. 1009325 Revision 2-A, "Risk Impact Assessment of Extended Integrated Leak Rate Testing Intervals," for performing risk impact assessments in support of ILRT extensions [Reference 24].
The Guidance provided in Appendix Hof EPRI Report No. 1009325 Revision 2-A builds-on the EPRI Risk Assessment methodology, EPRI TR-104285. This methodology is followed to determine the appropriate risk information for use in evaluating the impact of the proposed ILRT changes.
/
It should be noted that containment leak-tight integrity is also verified through periodic in-service Revision 3 Page 4of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension inspections conducted in accordance with the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section XI. More specifically, Subsection IWE provides the rules and requirements for in-service inspection of Class MC pressure-retaining components and their integral attachments, and of metallic shell and penetration liners of Class CC pressure-retaining components and their integral attachments in light-water cooled plants. Furthermore, NRC regulations 10 CFR 50.55a(b)(2)(ix)(E) require licensees to conduct visual inspections of the accessible areas of the interior of the containment. The associated change to NEI 94-01 will require that visual examinations be conducted during at least three other outages, and in the outage during which the ILRT is being conducted. These requirements will not be changed as a result of the extended ILRT interval. In addition, Appendix J, Type B local leak tests performed to verify the leak-tight integrity of containment penetration bellows, airlocks, seals, and gaskets are also not affected by the change to the Type A test frequency. ,
The acceptance guidelines in RG 1.174 are used to assess the acceptability of this permanent extension of the Type A test interval beyond that established during the Option B rulemaking of Appendix J. RG 1.174 defines very small changes in the risk-acceptance guidelines as
- increases in Core Damage Frequency (CDF) less than 1o-s per reactor year and increases in Large Early Release Frequency (LERF) less than 10-7 per reactor year. Since the Type A test does not impact CDF, the relevant criterion is the change in LERF. RG 1.174 also defines small changes in LERF as below 1o-s per reactor year. RG 1.174 discusses defense-in-depth and encourages the use of risk analysis techniques to help el)sure and show that key principles, such as the defense-in-depth philosophy, are met. Therefore, the increase in the Conditional Containment Failure Probability (CCFP), which helps ensure the defense-in-depth philosophy is maintained, is also calculated.
Regarding CCFP, changes of up to 1.1% have been accepted by the NRC for the one-time requests for extension of ILRT intervals. In context, it is noted that a CCFP of 1/10 (10%) has been approved for application to evolutionary light water designs. Given these perspectives, a change in the CCFP of up to 1.5% is assumed to be small.
In addition, the total annual risk (person rem/year population dose) is examined to demonstrate
-- the relative ch-arige iri this parameter. While rio acceptance guidelines for these additional figures of merit are published, examinations of NUREG-1493 and Safety Evaluation Reports (SER) for one-time interval extension (summarized in Appendix G of Reference 24) indicate a range of incremental increases in population dose that have been accepted by the NRC. The range of incremental population dose increases is from :::;0.01 to 0.2 person-rem/year and/or 0.002% to 0.46% of the total accident dose. The total doses for the spectrum of all accidents (NUREG-1493 [Reference 6], Figure 7-2) result in health effects that are at least two orders of magnitude less than the NRC Safety Goal Risk. Given these perspectives, a very small population dose is defined as an increase from the baseline interval (3 tests per 10 years) dose of :::;1.0 person-rem per year or 1% of the total baseline dose, whichever is less restrictive for the risk impact assessment of the proposed extended ILRT interval.
For those plants that credit containment overpressure for the mitigation of design basis accidents, a brief description of whether overpressure is required should be included in this section. In addition, if overpressure is included in the assessment, other risk metrics such as CDF should be described and reported.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
3.0 REFERENCES
The following references were used in this calculation:
- 1. Revision 3-A to Industry Guideline for Implementing Performance-Based Option of 10 CFR Part 50, Appendix J, NEI 94-01, July 2012.
- 2. Risk Impact Assessment of Revised Containment Leak Rate Testing Intervals, EPRI, Palo Alto, CA EPRI TR-104285, August 1994.
- 3. Interim Guidance for Performing Risk Impact Assessments in Support of One-Time Extensions for Containment Integrated Leakage Rate Test Surveillance Intervals, Revision 4, developed for NEI by EPRI and Data Systems and Solutions, October 2001.
- 4. An Approach for Using Probabilistic Risk Assessment in Risk-Informed De.cisions on Plant-Specific Changes to the Licensing Basis, Regulatory Guide 1.174, May 2011.
- 5. Response to Request for Additional Information Concerning the License Amendment Request for a One-Time Integrated Leakage Rate Test Extension, Letter from Mr. C. H.
Cruse (Calvert Cliffs Nuclear Power Plant) to NRC Document Control Desk, Docket No.
50-317, March 27, 2002.
- 6. Performance-Based Containment Leak-Test Program, NUREG-1493, September 1995.
- 7. Evaluation of Severe Accident Risks: Surry Unit 1, Main Report NUREG/CR-4551, SAND86-1309, Volume 3, Revision 1, Part 1, October 1990.
- 8. Letter from R. J. Barrett (Entergy) to U.S. Nuclear Regulatory Commission, IPN-01-007, January 18, 2001.
- 9. United States Nuclear Regulatory Commission, Indian Point Nuclear Generating Unit No. 3 - Issuance of Amendment Re: Frequency of Performance-Based Leakage Rate Testing (TAC No. MB0178), April 17, 2001.
- 10. Impact of Containment Building Leakage on LWR Accident Risk, Oak Ridge National Laboratory, NUREG/CR-3539, ORNL/TM-8964, April 1984.
- 11. Reliability Analysis of Containment Isolation Systems, Pacific Northwest Laboratory, NUREG/CR-4220, PNL-5432, June 1985.
- 12. Technical Findings and Regulatory Analysis for Generic Safety Issue 11.E.4.3
'Containment Integrity Check', NUREG-1273, April 1988.
- 13. Review of Light Water Reactor Regulatory Requirements, Pacific Northwest Laboratory, NUREG/CR-4330, PNL-5809, Volume 2; June 1986.
- 14. Shutdown Risk Impact Assessment for Extended Containment Leakage Testing Intervals Utilizing ORAM', EPRI, Palo Alto, CA, TR-105189, Final Report, May 1995.
- 15. Severe Accident Risks: An Assessment for Five U. S. Nuclear Power Plants, NUREG-1150, December 1990.
- 16. United States Nuclear Regulatory Commission, Reactor Safety Study, WASH-1400, October 1975.
- 17. Calculation C.9, Revision 13, Diablo Canyon Power Plant, "Quantification of CDF and LERF for the DCPP PRA Model."
- 18. Email from Nathan R. Barber (PG&E, Diablo Canyon) to Matt Johnson, dated January 6, 2016, 7:40 AM, Fire PRA Numbers for ILRT Report.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
- 19. E.RIN Report No. C114140001-8420, "Level 3 PRA Consequence Analysis (MACCS2 MODEL) for Diablo Canyon Severe Accident Mitigation Alternatives (SAMA) Evaluation,"
December 2014.
- 20. Anthony R. Pietrangelo, One-time extensions of containment integrated leak rate test interval - additional information, NEI letter to Administrative Points of Contact, November 30, 2001.
- 21. Letter from J. A. Hutton (Exelon, Peach Bottom) to U. S. Nuclear Regulatory Commission, Docket No. 50-278, License No. DPR-56, LAR-01-00430, dated May 30, 2001.
- 22. Risk Assessment for Joseph M. Farley Nuclear Plant Regarding ILRT (Type A)
Extension Request, prepared for Southern Nuclear Operating Co. by ERIN Engineering and Research, P0293010002-1929-030602, March 2002.
- 23. Letter from D. E. Young (Florida Power, Crystal River) to U.S. Nuclear Regulatory Commission, 3F0401-11, dated April 25, 2001.
- 24. Risk Impact Assessment of Extended Integrated Leak Rate Testing Intervals, Revision 2-A of 1009325, EPRI, Palo Alto, CA. 1018243, October 2008.
- 25. Risk Assessment for Vogtle Electric Generating Plant Regarding the ILRT (Type A)
Extension Request, prepared for Southern Nuclear Operating Co. by ERIN Engineering and Research, February 2003.
- 26. Perspectives Gained from the IPEEE Program, USNRC, NUREG-1742, April 2002.
- 27. Calculation E.16, Revision 2, Diablo Canyon Power Plant, "DCPP PRA Success Criteria Notebook." *
- 28. Letter L-14-121, ML14111A291, FENOC Evaluation of the Proposed Amendment, Beaver Valley Power Station, Unit Nos. 1 and 2, April 2014.
- 29. Technical Letter Report ML112070867, Containment Liner Corrosion Operating Experience Summary, Revision 1, August 2011.
- 30. Ca-lculation PRA 01-07, Pacific Gas & Electric Company, "Risk Impact Assessment of Extending Containment Type A Test Interval," Revision 1, October 2011.
- 31. Armstrong, J., Simplified Level 2 Modeling Guidelines: WOG PROJECT: PA-RMSC-0088, Westinghouse, WCAP-16341-P, November 2005. *
- 33. Transition Report, "Pacific Gas and Electric Company Diablo Canyon Power Plant Units 1 and 2 Docket 50-275 and 50-323: Transition to 10 CFR 50.48(c) - NFPA 805:
Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants, 2001 Edition," June 2013.
- 34. Calculation N.2, Revision 1, Diablo Canyon Power Plant, "DCPP PRA Level 2 and Containment Event Tree Model."
- 35. Calculation G.2, Revision 7, Diablo Canyon Power Plant, "Human Action Analysis -
Failure Likelihood and Range Factor Calculation."
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 4.0 ASSUMPTIONS AND LIMITATIONS The following assumptions were used in the calculation:
- The technical adequacy of the DCPP PRA is either consistent with the requirements of Regulatory Guide 1.200 or where gaps exist, the gaps have been addressed, as is relevant to this ILRT interval extension, as detailed in Attachment 1.
- It is appropriate to use the DCPP internal events PRA model to effectively describe the risk change attributable to the ILRT extension. An extensive sensitivity study is done in Section 5.3.1 to show the effect of including external event models for the ILRT extension. The Fire PRA (model DC03M) and Seismic PRA [Reference 17] are used for this sensitivity analysis.
- Accident classes describing radionuclide release end states are defined consistent with EPRI methodology [Reference 2]. ,
- Ther representative containment leakage for Class 1 sequences is 1La. Class 3 accounts for increased leakage due to Type A inspection failures.
- The representative containment leakage for Class 3a sequences is 1Ola based on the previously approved methodology performed for Indian Point Unit 3 [Reference 8, Reference 9].
- The representative containment leakage for Class 3b sequences is 1OOLa based on the guidance provided in EPRI Report No. 1009325, Revision-..?-A (EPRI 1018243)
[Reference 24]. . *
- The Class 3b can be very conservatively categorized as LERF based on the previously approved methodology [Reference 8, Reference 9].
- The impact on population doses from containment bypass scenarios is not altered by the proposed ILRT extension, but is accounted for in the !=PRI methodology as a separate entry for comparison purposes. Since the containment bypass contribution to population dose is fixed, no changes in the conclusions from this analysis will result from this separate categorization. *
- The reduction in ILRT frequency does not impact the reliability of containment isolation valves to close in response to a containment isolation signal.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 5.0 METHODOLOGY AND ANALYSIS 5.1 Inputs This section summarizes the general resources available as input (Section 5.1.1) and the plant specific resources required (Section 5.1.2).
5.1.1 General Resources Available Various industry studies on containment leakage risk assessment are briefly summarized here:
- 1. NUREG/CR-3539 [Reference 1O]
- 2. NUREG/CR-4220 [Reference 11]
- 3. NUREG-1273 [Reference 12]
- 4. NUREG/CR-4330 [Reference 13]
- 6. NUREG-1493 [Reference 6]
- 7. EPRI TR-104285 [Reference 2]
1
- 8. NUREG-1150 [Reference 15] and NUREG/CR-4551 [Reference 7]
- 9. NEI Interim Guidance [Reference 3, Reference 20]
- 10. Calvert Cliffs liner corrosion analysis [Reference 5]
This first study is applicable because it provides one basis for the threshold that could be used ih the Level 2 PRA for the size of containment leakage that is considered significant and is to be included in the model. The second study is applicable because it provides a basis of the probability for significant pre-existing containment leakage at the time of a core damage accident. The third study is applicable because it is a subsequent study to NUREG/CR-4220 that undertook a more extensive evaluation of the same database. The fourth study provides an assessment of the impact of different containment leakage rates on-plant risk. The fifth study provides an assessment of the impact on shutdown risk from ILRT test interval extension. The sixth study is. the NRC's cost-benefit analysis of various alternative approaches regarding extending the test intervals and increasing the allowable leakage rates for containment integrated and local leak rate tests. The seventh study is an EPRI study of the impact of extending ILRT and local leak rate test (LLRT) intervals on at-power public risk. The eighth study provides an ex-plant consequence analysis for a 50-mile radius surrounding a plant that is used as the basis for the consequence analysis of the ILRT interval extension for DCPP. The ninth study includes the NEI recommended methodology (promulgated in two letters) for evaluating the risk associated with obtaining a one-time extension of the ILRT interval. The
- tenth study addresses the impact of age-related degradation of the containment liners on ILRT evaluations. Finally, the eleventh study builds on the previous work and includes a recommended methodology and template for evaluating the ~isk associated with a permanent 15-year extension of the ILRT interval.
- NUREG/CR-3539 [Reference 1O]
Qak Ridge National Laboratory documented a study of the impact of containment leak rates on public risk in NUREG/CR-3539. This study uses* information from WASH-1400 [Reference 16]
as the basis for its risk sensitivity calculations. ORNL concluded that the impact of leakage rates on LWR accident risks is relatively small. -
NUREG/CR-4220 [Reference 11]-
NUREG/CR-4220 is a study performed by Pacific Northwest Laboratories for the NRC in 1985.
The study reviewed over two thousand LERs, ILRT reports and other related records to Revision 3 Page 9of117
54006-CALC-01 Evaluation of Risk Significance of Perma_nent ILRT Extension calculate the unavailability of containment due to leakage.
j NUREG-1273 [Reference 121 A subsequent NRC study, NUREG-1273, performed a more extensive evaluation of the NUREG/CR-4220 database. This assessment noted that about .one-third of the reported events were leakages that were immediately detected and corrected. In addition, this study noted that local leak rate tests can detect "essentially all potential degradations" of the containment isolation system.
- NUREG/CR-4330 [Reference 131 NUREG/CR-4330 is a study that examined the risk impacts associated with increasing the allowable containment leakage rates. The details of this report have no direct impact on the modeling approach of the ,ILRT test interval extension, as NUREG/CR-4330 focuses on leakage rate and the ILRT test interval extension study focuses on the frequency of testing intervals.
However, the general conclusions of NUREG/CR-4330 are consistent with NUREG/CR-3539 and other similar containment leakage risk studies:
" ... the effect of containment leakage on overall accident risk is small since risk is aominated by accident sequences that result in failure or bypass of containment."
EPRI TR-105189 [Reference 141 The EPRI study TR-105189 is useful to the ILRT test interval extension risk assessment because it provides insight regarding the impact of containment testing on shutdown risk. This study contains a quantitative evaluation (Using the EPRI ORAM software) for two reference plants (a BWR-4 and a PWR) of the impact of extending ILRT and LLRT test intervals on shutdown risk. The conclusion from the study is that a small, but measurable, safety benefit is realized from extending the te.st intervals.
NUREG-1493 [Reference 61 NUREG-1493 is the NRC's cost-benefit analysis for proposed alternatives to reduce containment leakage testing interv~ls and/or relax allowable leakage rates. The NRC conclusions are.consistent with other similar containment leakage risk studies:
Reduction in ILRT frequency from 3 per 10 years to 1 per 20 years results in an "imperceptible" increase in risk.
Given the insensitivity of risk to the containment leak rate' and the small fraction of leak paths detected solely by Type A testing, increasing the interval between integrated leak rate tests is .
possible with minimal impact on public risk.
EPRI TR-104285 [Reference 21 Extending the risk assessment impact beyond shutdown (the earlier EPRI TR-1.05189 study},
the EPRI IR-104285 study is a quantitative evaluation of the impact of extending ILRT and LL.RT test intervals on at-power*public risk. This study com_bined IPE Level 2 models with NUREG-1150 Level 3 population dose models to perform the analysis. The study also used the approach of NUREG-1493 in calculating the increase iii pre-existing leakage probability due to extending the ILRT and LLRT test intervals. .,
EPRI TR-104285 uses a simplified Containment Event Tree to subdivide representative core damage frequencies into eight classes of containment response to a core damage accident:
1., Containment intact and isolated
- 2. Containment isolation failures dependent upon the core damage accident
- 3.
- Type A (ILRT) related containment isolation failures
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
- 4. Type B (LLRT) related containment isolation failures
- 5. Type C (LLRT) related containment isolation failures
- 6. Other penetration related containment isolation failures
- 7. Containment failures due to core damage accident phenomena
- 8. Containment bypass Consistent with the other containment leakage risk assessment studies, this study concluded:
" ... the proposed CLRT (Containment Leak Rate Tests) frequency changes would have a minimal safety impact. The change in risk determined by the analyses is small in both absolute and relative terms. For example, for the PWR analyzed, the change is about 0.04 person-rem per year ... "
NUREG-1150 [Reference 151 and NUREG/CR-4551 [Reference 71 ~
NUREG-1150 and the technical basis, NUREG/CR-4551, provide an ex-plant consequence analysis for a spectrum of accidents including a severe accident with the containment remaining
) intact (i.e., Tech _Spec Leakage). This ex-plant consequence analysis is calculated for the 50-mile radial area surrounding Surry. The ex-plant calculation can be delineated to total person-rem for each identified Accident Progression Bin (APB) from NUREG/CR-4551. With the DCPP Level 2 model end-states assigned to one of the NUREG/CR-4551 APBs, it is considered adequate to represent DCPP. (The meteorology and site differences other than' population are ass4.med not to play a significant role in this evaluation.)
NEI Interim Guidance for Performing Risk Impact Assessments In Support of One-Time Extensions for Containment Integrated Leakage Rate Test Surveillance Intervals [Reference 3, Reference 201 The guidance provided in this document builds on the EPRI risk impact assessment methodology [Reference 2] and the NRC performance-based containment leakage test program
[Reference 6], and considers approaches utilized in various' submittals, including Indian Point 3 (and associated NRC SER) and Crystal River. \
Calvert Cliffs Response to Request for Additional Information Concerning the License Amendment for a One-Time Integrated Leakage Rate Test Extension [Reference 5]
This submittal to the NRC describes a method for determining the change in likelihood, due to extending the ILRT,of detecting liner corrosion, and the corresponding change in risk. The methodology was developed for Calvert Cliffs in response to a request for additional information regarding how the potential leakage due to age-related degradation mechanisms was factored into the risk assessment for the ILRT one-time extension. The Calvert Cliffs analysis was performed for a concrete cylinder and dome and a concrete basemat, each with a steel liner.
EPRI Report No. 1009325. Revision 2-A. Risk Impact Assessment of Extended Integrated Leak Rate Testing Intervals [Reference 241 This report provides a generally applicable assessment of the risk involved in extension of ILRT test intervals to permanent 15-year intervals. Appendix H of this document provides guidance for performing plant-specific supplemental risk impact assessments and builds on the previous EPRI risk impact assessment methodology [Reference 2] and the NRC performance-based containment leakage test program [Reference 6], and considers approaches utilized in various submittals, including Indian Point 3 (and associated NRC SER) and Crystal River.
The approach included in this guidance document is used in the DCPP assessment to determine the estimated increase in risk associated with the ILRT extension. This document includes the bases for the values assigned in determining the probability of leakage for the EPRI Class 3a and 3b scenarios in this analysis, as described in Section 5.2.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 5.1.2 Plant Specific Inputs The plant-specific information used to perform the DCPP ILRT Extension Risk Assessment includes the following: *
- Level 1 Model results [Reference 17]
- Release category definitions used in the Level 2 Model [Reference 19]
- Dose within a 50-mile radius [Reference 19]
- ILRT results to demonstrate adequacy of the administrative and hardware issues
[Reference 30]
DCPP Model The Internal Events PRA Model that is used for DCPP is characteristic of the as-built plant. The current Level 1 model (DCPP PRA Model Version DC03) [Reference 17] is a large event tree, small fault tree model. The Internal Flood CDF is 7.52E-6/year for Unit 1 and 5.45E-6/year for Unit 2, and the LERF is 4.19E-7/year for Unit 1 and 3.43E-7 for Unit 2 [Refer~nce 17]. The total internal events CDF, including internal flooding, is 1.89E-5/year for Unit 1 and 1.69E-5/year for Unit 2, and the total LERF is 2.26E-6/year for Unit 1 and 2.18E-6 for Unit 2 [Reference 17].
Table 5-1 and Table 5-2 provide a summary of the Internal Events CDF and LERF results, respectively.
The total Fire CDF is 4.83E-5/year for Unit 1 and 5.24E-5/year for Unit 2; the total Fire LERF is 2.45E-6/year for Unit 1 and 2.17E-6/year for Unit 2 [Reference 18]. Refer to Section 5.3.1 for further details on external events as they pertain to this analysis.
Table 5 Internal Events QDF (DCPP PRA Model Version DC03)
Internal Events Frequency (per year)
LOCA 3.77E-06 Loss of ASW or CCW 2.63E-06 Transient 2.35E-06 SGTR 1.32E-06 Loss of 480V Switchgear Ventilation 3.88E-07 Loss ofone 125V DC 'Bus 4.33E-07 LOOP 3.53E-07 Other 1.37E-07 I
Flood 7.52E-06 (Unit 1) 5.45E-06 (Unit 2)
Total Internal Events CDF 1.89E-05(Unit1) 1.69E-05 (Unit 2) 1 Revision 3 Page 12of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Internal Events LERF (DCPP PRA Model Version DC03)
Internal Events Frequency (per year)
LOCA 2.76E-07 Loss of ASW or CCW 5.?0E-08 Transient 9.38E-08 SGTR 1.31E-06 Loss of 480V Switchgear Ventilation 5.15E-08 Loss of one 125V DC Bus 1.10E-08 LOOP 2.76E-08 Other 1.47E-08 Flood 4.19E-07(Unit1) 3.43E-07 (Unit2)
Total Internal Events LERF 2.26E-06 (Unit 1) 2.18E-06 (Unit 2)
Population Dose Calculations The population dose was calculated for the DCPP SAMA in Table 4.1-2 of Reference 19, which reports six release categories: ST1 (large early), ST2 (small early), ST3 (late), ST4 (bypass w/
AFW), STS (ISLOCA), and ST6 (intact). Class 1 frequency corresponds to ST6. Since Classes 2 and 7 do not have a release category that precisely matches, they conservatively correspond to ST1. Class 8 consists of interfacing system loss of coolant accident (ISLOCA) and steam generator tube rupture (SGTR) frequency. The ISLOCA frequency corresponds to STS. of Reference 17 presents the top 200 cutsets in the LERF model. Of the un-isolated SGTR sequences (SGTRN), 95% of them are release class RC17 and have AFW available; Table 3.2-4 of Reference 19 states ST4 is representative of RC17. Therefore, ST4 is the most representative for SGTR frequency. Table 5-3 presents dose exposures calculated from methodology described in Reference 1 and data from Reference 19. Class 3a and 3b population dose values are calculated from the Class 1 population dose and represented as 1Ola and 1OOLa, respectively, as guidance in Reference 1 dictates.
Table 5 Population Dose Accident Class Description Release (person-rem)
Containment Remains Intact 3.68E+03 2 Containment Isolation Failures 9.83E+06
/
3a Independent or Random Isolation Failures SMALL 3.68E+04 1 3b Independent or Random Isolation Failures LARGE 3.68E+05 2 Isolation Failure in which pre'-xistihg leakage is not 4 n/a dependent on sequence progression. Type B test Failures Isolation Failure in which pre-existing leakage is not 5 n/a dependent on sequence progression. Type C test Failures 6 Isolation Failure that can be verified by IST/IS or surveillance nla 7 Containment Failure induced by severe accident 9.83E+06 8 Accidents in which containment is by-passed 8.90E+053
- 1. 10*La
- 2. 100 *La
- 3. The Class 8 dose value differs from the value presented in Reference 19 because the dose is weighted based on frequency of the two Class 8 contributors: ISLOCA and SGTR.
Revision 3 Page 13of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Release Category Definitions Table 5-4 defines the accident classes used in the ILRT extension evaluation, which is consistent with the EPRI methodology [Reference 2]. These containment failure classifications are used in this analysis to determine the risk impact of extending the Containment Type A test interval, as described in Section 5.2 of this report.
Table 5 EPRI Containment Failure Classification [Reference 2]
Class Description Containment remains intact including accident sequences that do not lead to containment failure in the long term. The release of fission products (and attendant consequences) is determined by the maximum allowable leakage rate values La, under Appendix J for that plant.
Containment isolation failures (as reported in the lndivi!;fual Plant Examinations) including those accidents 2
in which there is a failure to isolate the containment.
Independent (or random) isolation failures include those accidents in which the pre-existing isolation 3
failure to seal (i.e., provide a leak-tight containment) is not dependent on the sequence in progress.
Independent (or random) isolation failures include those accidents in which the pre-existing isolation failure to seal is not dependent on the sequence in progress. This class is similar to Class 3 isolation 4
failures, but is applicable to sequences involving Type B tests and their potential failures. These are the Type B-tested components that have isolated, but exhibit excessive leakage.
Independent (or random) isolation failures including those accidents in which the pre-existing isolation 5 failure to seal is not dependent on the sequence in progress. This class is similar to Class 4 isolation failures, but is applicable to sequences involving Type C test and their potential failures.
Containment isolation failures including those leak paths covered in the plant test and maintenance 6
requirements or verified per in-service inspection and testing (ISl/IST) program.
Accidents involving containment failure induced by severe accident phenomena. Changes in Appendix J 7
testing requirements do not impact these accidents.
Accidents in which the containment is bypassed (either as an initial condition or induced by phenomena) 8 are included in Class 8. Changes in Appendix J testing requirements do not impact these accidents.
5.1.3 Impact of Extension on Detection of Component Failures that Lead to Leakage (Smail and Large)
The ILRT can detect a number of component failures such as liner breach, failure of certain bellows arrangements, and failure of some sealing surfaces, which can lead to leakage. The proposed ILRT test interval extension may influence the conditional probability of detecting these types of failures. To ensure that this effect is properly addressed, the EPRI Class 3 accident class, as defined in Table 5-3, is divided into two sub-classes, Class 3a and Cl~ss 3b, representing small and large leakage failures respectively.
- The probability of the EPRI Class 3a and Class 3b failures is determined consistent with the EPRI Guidance [Reference 24]. For Class 3a, the probability is based on the maximum likelihood estimate of failure (arithmetic average) from the available data (i.e., 2 "small" failures in 217 tests leads to "large" failures in 217 tests (i.e:, 2 / 217 = 0.0092). For Class 3b, the probabiJity is based on the Jeffreys non-informative prior (i.e., 0.5 / 218 = 0.0023).
In a follow-up letter [Reference 20] to their ILRT guidance document [Reference 3], NEI issued additional information concerning the potential that the calculated delta LERF values for several plants may fall above the "very small change" guidelines of the NRC Regulatory Guide 1.174
[Reference 4]. This additional NEI information includes a discussion of conservatisms in the quantitative guidance for b.LERF. NEI describes ways to demonstrate that, using plant-speCific calculations, the b.LERF is smaller than that calculated by the simplified method.
Revision 3 Page14of117
54006-CALG-01 Evaluation of Risk Significance of Permanent ILRT Extension The supplemental information states:
The methodology employed for determining LERF (Class 3b frequency) involves conservatively multiplying the CDF by the failure probability for this class (3b) of accident. This was done for simplicity and to maintain conservatism. However, some plant-specific accident classes leading to core damage are likely to include individual sequences that either may already .
(independently) cause a LERF or could never cause a LERF, and are thus not associated with a postulated large Type A containment leakage path (LERF). These contributors can be removed from Class 3b in the evaluation of LERF by multiplying the Class 3b probability by only that portion of CDF that may be impacted by Type A leakage.
The application of this additional guidance to the analysis for DCPP, as detailed in Section 5.2, involves subtracting the LERF from the CDF that is applied to Class 3b. To be consistent, the same change is made to the Class 3a CDF, even though these events are not considered LERF.
Consistent with the NEI Guidance [Reference 3]. the change in the leak detection probability can be estimated by comparing the average time that a leak could exist without detection. For example, the average time that a leak could go undetected with a three-year test interval is 1.5 years (3 years I 2), and the average time that a leak could exist without detection for a ten-year interval is 5 years (1Oyears/2). This change would .lead to a non-detection probability that is a factor of 3.33 (5.0/1.5) higher for the probability of a leak that is detectable only by ILRT testing.
Correspondingly, an extension of the ILRT interval to 15 years can be estimated to lead to a factor of 5 ((15/2)/1.5) increase in the non-detection probability of a leak.
It should be noted that using the methodology discussed above is very conservative compared to previous submittals (e.g., the IP3 request for a one-time ILRT extension that was approved by the NRC [Reference 9]) because it does not factor in the possibility that the failures could be detected by other tests (e.g., the Type B local leak rate tests that will still occur). Eliminating this possibility conservatively over-estimates the factor increases attributable to the ILRT extension.
5.2 Analysis The application of the approach based on the guidance contained in EPRI Report No. 1009325, Revision 2-A, Appendix H [Reference 24], EPRI TR-104285 [Reference 2] and previous risk assessment submittals on this subject [References 5, 8, 21, 22, and 23] have led to the following results. The results are displayed according to the eight accident classes defined in the EPRI report, as described in Table 5-5..
The analysis performed examined DCPP-specific accident sequences in which the containment remains intact or the containment is impaired. Specifically, the breakdown of the severe accidents, contributing to risk, was considered *in the following manner:
- Core damage sequences in which the containment remains intact initially and in the long term (EPRI TR-104285, Class 1 sequences [Reference 2]).
- Core damage sequences i.n which containment integrity is impaired due to random isolation failures of plant components other than those associated with Type B or Type C test components. For example, liner breach or bellow leakage (EPRI TR-104285, Class 3 sequences [Reference 2]).
- Accident sequences involving containment bypassed (EPRI TR-104285, Class 8 sequences [Reference 2]), large containment isolation failures (EPRI TR-104285, Class 2 sequences [Reference 2]), and small containment isolation "failure-to-seal" events (EPRI TR-104285, Class 4 and 5 sequences [Reference 2]) are accounted for in this Revision 3 Page 15of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension evaluation as part of the baseline risk profile. However, they are not affected by the ILRT frequency change.
- Class 4 and 5 sequences are impacted by changes in Type B and C test intervals; therefore, changes in the Type A test interval do not impact these sequences.
Table 5 EPRI Accident Class Definitions
, Accident Classes Description (Containment Release Type)
No Containment Failure 2 Large Isolation Failures (Failure to Close) 3a Small Isolation Failures (Liner Breach) 3b Large Isolation Failures (Liner Breach) 4 Small Isolation Failures (Failure to Seal - Type B)
_)
5 Sm.all Isolation Failures (Failure to Seal - Type C) 6 Other Isolation Failures (e.g., Dependent Failures) 7 Failures Induced by Phenomena (Early and Late) 8 Bypass (Interfacing System LOCA)
CDF All CET End States (Including Very Low and No Release)
The steps taken to perform this risk assessment evaluation are as follows:
Step 1 - Quantify the baseline risk in terms of frequency per reactor year for each of the accident classes presented in Table 5-5.
Step 2 - Develop plant-specific person-rem dose (population dose) per reactor year for each of the eight accident classes.
Step 3 - Evaluate risk impact of extending Type A test interval from 3 in 1O years to 1 in 15 years arid 1 in 10 years to 1 in 15 years.
Step 4 - Determine the change in risk in terms of Large Early Release Frequency (LERF) in accordance with RG 1.174 [Reference 4].
Step 5 -_Determine the impact on the Conditional Containment Failure Probability (CCFP).
5.2.1 Step 1 - Quantify the Baseline Risk in Terms of Frequency per Reactor Year*
As previously described, the extension of the Type A interval does not influence those accident progressions that involve large containment isolation failures, Type B or Type C testing, or containment failure induced by severe accident phenomena.
For the assessment of ILRT impacts on the risk profile, the potential for pre-existing leaks is induded in the model. (These events are represented by the Class 3 sequences in EPRI TR-104285 [Reference 2].) The question on containment integrity was modified to include the probability of a liner breach or bellows failure (due to excessive leakage) at the time of core damage .. Two failure modes were considered for the Class 3 sequences. These are Class 3a (small breach) and Class 3b (large breach).
- The frequencies for the severe accident classes defined in Table 5-5 were developed for DCPP by first determining the frequencies for Classes 1, 2, 6, 7, and 8. Table 5-6 presents the grouping of each release category in EPRI Classes based on the associated description. Table 5-7 presents the frequency and EPRI category for each sequence and t.he totals of each EPRI Revision 3 Page 16of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension classification. Table 5-8 provides a summary of the accident sequence frequencies that can lead to radionuclide release to the public and have been derived consistent with the definitions of accident classes defined in EPRI TR-104285 [Reference 2], the NEI Interim Guidance
[Reference 3], and guidance provided in EPRI Report No. 1009325, Revision 2-A [Reference 24]. Adjustments were made to the Class 3b and hence Class 1 frequencies to account for the impact of undetected corrosion of the steel liner per the methodology described in Section 5.2.6.
Note: calculations were performed with more digits than shown in this section. Therefore, minor differences may occur if the calculations in these sections are followed explicitly.
Class 3 Sequences. This group consists of all core damage accident progression bins for which a pre-existing leakage in the containment structure (e.g., containment liner) exists that can only be detected by performing a Type A ILRT. The probability of leakage detectable by a Type A ILRT is calculated to determine the impact of extending the testing interval. The Class 3 calculation is divided into two classes: Class 3a is defined as a small liner breach (La < leakage
< 1Ola), and Class 3b is defined as a large liner breach (1 Ola < leakage < 1OOLa).
Data reported in EPRI 1009325, Revision 2-A [Reference 24] states that two events could' have been detected only during the performance of an ILRT and thus impact risk due to change in ILRT frequency. There were a total of 217 successful ILRTs during this data collection period.
Therefore, the probability of leakage is determined for Class 3a as shown in the following equation:
2 Pclass3a = 217 = 0.0092 Multiplying the CDF by the probability of a Class 3a leak yields the Class 3a frequency
_ contribution in accordance with guidance provided in Reference 24. As described in Section 5.1.3, additional consideration is made to not apply failure probabilities on those cases that are already LERF scenarios. Therefore, LERF contributions from CDF are removed. The frequency of a Class 3a failure is calculated by the following equation:
2 Frequ 1class3a = Pczass3a * (CDFu1 - LERFu 1) = 217
- (1.89E-5 -2.26E-6) = 1.54E-7 2
Frequ 2class 3d. = Pclass 3a * (CDFu 2 - LERFu 2) = 217
- (1.69E-5 -2.l8E-6) = 1.35E-7 In the database of 217 ILRTs, there are zero containment leakage events that could result in a large early release. Therefore, the Jeffreys non-informative prior is used to estimate a failure rate and is illustrated in the following equations:
Number of Failures+ 1/2 Jeffreys Failure Probability= N b fT um er o ests + 1 0+1/2 Pclass3b = 217+ 1 = 0.0023 The frequency of a Class 3b failure is calculated by the following equation: (
Frequ1class3b = Pclass3b * (CDFu1 - LERFu1) = ;:a *(1.89E-5 -2.26E-6) = 3.82E-8 FreqU2class3b = Pczass3b * (CDFu2 - LERFu2) = 2*:3 *(1.69E-5 -2.18E-6) = 3.36E-8 For this analysis, the associated containment leakage for Class 3a is 1Ola and for Class 3b is 1OOLa. These assignments are consistent with the guidance provided in Reference 24.
Class 1 Sequences. This group consists of all core damage accident progression bins for which the containment remains intact (modeled as Technical Specification Leakage). Since the PRA model does not contain a Level 2 model, Class 1 is calculated as CDF- LERF. This Revision 3 Page'17of117
/
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension overestimates the Intact frequency, which is conservative for this analysis because it leads to a higher calculated change in risk due to extending the ILRT frequency. The frequency per year is initially determined from the EPRI Accident Class 1 frequency listed in Table 5-7 and then subtracting the EPRI Class 3a and 3b frequency (to preserve total GDF), calculated below:
Freqclassl = Freqczass1 - (Freqczass3a - Freqclass3b)
Class 2 Sequences. This group consists of core damage accident progression bins with large containment isolation failures. This is determined from Section C.9.8.7 of Reference 17, which states that containment isolation failure contributes 8% of internal event LERF (1.84E-6).
Therefore, the Class 2 contribution is 1.47E-7. The frequency per year for these sequences is obtained from t~e EPRI Accident Class 2 frequency listed in Table 5-7.
Class 4 Sequences. This group consists, of all core damage accident progression bins for which containment isolation failure-to-seal of Type B test components occurs. Because these failures are detected by Type B tests which are unaffected by the Type A ILRT, this group is not evaluated any further in the analysis, consistent with approved methodology.
Class 5 Sequences. This group consists of all core damage accident progression bins for which a containment isolation failure-to-seal of Type C test components occurs. Because the failures are detected by Type C tests which are unaffected by the Type A ILRT, this group is not ...,
evaluated any further in this analysis, consistent with approved methodology.
Class 6 Sequences. These are sequences that involve core damage accident progression bins for which .a failure-to-seal containment leakage due to failure to isolate the containment occurs.
These sequences are dominated by misalignment of containment isolation valves following a test/maintenance evolution. All other failure modes are bounded by the Class 2 assumptions.
This accident class is also not evaluated further.
Class 7 Sequences. This group consists of all core damage accident progression bins in which containment failure is induced by severe accident phenomena (e.g., overpressure). This frequency is calculated by subtracting the Class 1, 2, and 8 frequencies from the total GDF. For this analysis, the frequency is determined from the EPRI Accident Class 7 frequency listed in Table 5-7. '
Class 8 Sequences. This group consists of all core damage accident progression bins in which ISLOCA or SGTR occur, which contribute 3.06E-8 and 1.32E-!3, respectively. Frequencies are shown in Table 5-6. For this analysis, the total Class 8 frequency is listed in Table 5-7.
Table 5 Release Category Frequencies Containment End State EPRI Category Unit 1 Frequency (/yr) Unit 2 Frequency (/yr)
Intact Containment 1 1.67E-05 1.47E-05 Large Isolation Failure 2 1.47E-07 1.47E-07 Failures Induced by Phenomena 7 7.61E-07 6.85E-07 ISLOCA 8 3.06E-08 3.06E-08 SGTR 8 1.32E-06 . 1.32E-06 Revision 3 Page 18of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Accident Class Frequencies EPRI Category / Unit 1 Frequency (/yr) Unit 2 Frequency (/yr)
Class 1 1.67E-05 1.47E-05 Class 2 1.47E-07 1.47E-07 Class 6 N/A - Included in Class 2 Class 7 7.61E-07 6.85E-07 Class 8 1.35E-06 1.35E-06 Total (CDF) 1.89E-05 1.69E-05 Table 5 Baseline Risk Profile Class Description Unit 1 Frequency (/yr) Unit 2 Frequency (/yr)
No containment failure 1.65E-052 1.45E-052 2 Large containment isolation failures 1.47E-07 1.47E-07 3a Small isolation failures (liner breach) 1.54E-07 1.35E-07 3b Large isolation failures (liner breach) 3.82E-08 3.36E-08 4 Small isolation failures - failure to seal (type B) 5 Small isolation failures - failure to seal (type C)
Containment isolation failures (dependent 6
failure, personnel errors)
Severe accident phenomena induced failure 7 7.61E-07 6.85E-07 (early and late) 8 Containment bypass 1.35E-06 1.35E-06 Total 1.89E-05 1.69E-05
- 1. E represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 3a and 3b frequencies are subtracted from Class 1 to preserve total CDF.
5.2.2 Step 2 - Develop Plant-Specific Person-Rem Dose (Population Dose)
Plant-specific release analyses were performed to estimate the person-rem doses to the population within a 50-mile radius from the plant. The releases are based on DCPP-specific dose calculations summarized in Table 5-3. Table 5-3 provides a correlation of DCPP population dose to EPRI Accident Class. Table 5-1 O provides population dose for each EPRI accident class.
The population dose for EPRI Accident Classes 3a and 3b were calculated based on the guidance provided in EPRI Report No. 1009325, Revision 2-A [Reference 24] as follows:
EPRI Class 3a Population Dose= 10
- 3.68£+3 = 3.68£+4 EPRI Class 3b Population Dose= 100
- 3.68£+3 = 3.68£+5 Revision 3 Page 19of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Mapping of Population Dose to EPRI Accident Class EPRI Category Unit 1 Frequency (/yr) Unit 2 Frequency (/yr) Dose (person-rem)
Class 1 1.67E-05 1.47E-05 3.68E+03 Class 2 1.47E-07 1.47E-07 9.83E+06 Class 6 N/A - Included in Class 2 Class 7 7.61E-07 6.85E-07 9.83E+06 Class 8 1.35E-06 1.35E-06 8.90E+05 1
- 1. The Class 8 dose value differs from the value presented in Reference 19 because the dose is weighted based on frequency of the two Class 8 contributors: ISLOCA and SGTR.
Table 5 Baseline Population Doses Class Description Population Dose (person-rem)
No containment failure 3.68E+03 2 Large containment isolation failures 9.83E+06 3a Small isolation failures (liner breach) 3.68E+04 1 3b Large isolation failures (liner breach) 3.68E+05 2 4 Small isolation failures - failure to seal (type B) N/A 5 Small isolation failures - failure to seal (type C) N/A 6 Containment isolation failures (dependent failure, personnel errors) N/A 7 Severe accident phenomena induced failure (early and late) 9.83E+06 8 Containment bypass 8.90E+05 3
- 1. 10*La
- 2. 100*La
- 3. The Class 8 dose value differs from the value presented in Reference 19 because the dose is weighted based on frequency of the two Class 8 contributors: ISLOCA an.d' SGTR.
5.2.3 Step 3 - Evaluate Risk Impact of Extending Type A Test Interval from 10 to 15
~ra .
The next step is to evaluate the risk impact of extending the test interval from its current 10-year interval to a 15-year interval. To do this, an evalu~tion must first be made of the risk associated with the 10-year interval, since the base case applies to 3-year interval (i.e., a simplified representation of a 3-to-1 O interval).
Risk Impact Due to 10-Year Test Interval As previously stated, Type A tests impact only Class 3 sequences. For Class 3 sequences, the release magnitude is not impacted by the change in test interval (a small or large breach remains the same, even though the probability of not detecting the breach increases). Thus, only the frequency of Class 3a and Class 3b sequences is impacted. The risk contribution is
- changed based on the NEI guidance as described in Section 5.1.3 by a factor of 10/3 compared to the base case values. The Class 3a and 3b frequencies are calculated as follows:
Frequ1class3alOyr = 310
- 217 2
- 217 2
- 1.67E-5 = 5.12E-7 Frequ2class 3arnyr = -103 *217 2
- * (CDF - LERF) = -103 *-*2 217 1.47E-5 = 4.51E-7
= 13°* 2*:3 * (CDF - = 3°* 2*:3
- 1.67E-5 = 1.27E-7 1
Frequ1c1ass 3b 1oyr LERF)
Revision 3 Page 20of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Frequ2ciass3b1oyr = 13°* 2*:8 * (CDF - LERF) = 13°* 2*:8
- 1.47E-5 = 1.12E-7 The results of the calculation for a 10-year interval are presented in Table 5-11 for Unit 1 and Table 5-12 for Unit 2.
Table 5 Unit 1 Risk Profile for Once in 10 Year ILRT Class Description Frequency Contribution Population Dose Population
(/yr) (%) . (person-rem) Dose Rate (person-rem/yr)
No containment failure 2 1.60E-05 84.68% 3.68E+03 5.90E-02 Large containment isolation 2 1.47E-07 0.78% 9.83E+06 1.45E+OO failures Small isolation failures (liner 3a 5.12E-07 2.71% 3.68E+04 1.88E-02 breach)
Large isolation failures 3b 1.27E-07 0.67% 3.68E+05 4.69E-02 (liner breach)
Small isolation failures - g1 g1 g1 g1 4
failure to seal (type B)
Small isolation failures - g1 g1 g1 g1 5
failure to seal (type C)
Containment isolation 6 failures (dependent failure, g1 g1 g1 g1 personnel errors)
Severe accident 7 phenomena induced failure 7.61E-07 4.02% 9.83E+06 7.48E+OO 1
(early and late) 8 Containment bypass 1.35E-06 7.14% 8.90E+05 1.20E+OO Total 1.89E-05 1.03E+01
- 1. E represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 1 frequency is reduced by-the frequency of Class 3a and Class 3b in order to preserve total CDF.
- \
Revision 3 Page 21 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
'ii Table 5 Unit 2 Risk Profile for Once in 10 Year ILRT Class Description - Frequency Contribution Population Dose Population
(/yr) (%) (person-rem) Dose Rate (person-rem/yr)
No containment failure 2 1.41 E-05 83.70% 3.68E+03 5.19E-02 Large containment isolation 2 1.47E-07 0.87% 9.83E+06 1.45E+OO failures Small isolation failures (liner 3a 4.51E-07 2.67% 3.68E+04 1.66E-02 breach)
Large isolation failures 3b 1.12E-07 0.67% 3.68E+05 4.13E-02 (liner breach)
Small isolation failures - 1 -
4 E1 E E1 E1 failure to seal (type B)
Small isolation failures -
5 E1 £1 £1 E1 failure to seal (type C)
, Containment isolation 6 failures (dependent failure, £1 £1 £1 £1 personnel errors)*
Severe accident 7 phenomena induced failure 6.85E-07 4.07% 9.83E+06 6.74E+OO (early and late) 8 Containment bypass 1.35E-06 8.02% 8.90E+05 1.20E+OO Total 1.69E-05 9.49E+OO
- 1. E represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 1 frequency is reduced by the frequency of Class 3a and Class 3b in order to preserve total CDF.
Risk Impact Due to 15-Year Test Interval
- The risk contribution for a 15-year interval is calculated in a manner similar to the 10-year interval. The difference is in the increase in probability of leakage in Classes 3a a'nd 3b. For this case, the value used in the analysis is a factor of 5. compared to the 3-year interval value, as described in Section 5.1.3. The Class 3a and 3b frequencies are calculated as follows:
Frequ1class3a15yr = -153 * --
2 217
- 1.67E-5 = 7.68E-7 Frequ2class3a15yr = -153 * -2 217
- 1.47E-5 = 6.76E-7--
FreqU1Class3b~5yr = 3
- 2*:8 * (CDF -
15 LERF) = 5
- 2*:8
- 1.67E-5 = 1.91E-7 1
Frequ2c1ass 3bl5yr = 35
- 2*:8
- 1.47E-5 = 1.68E_-7 The results of the calculation for a 15-year interval are presented in Table 5-13 for Unit 1 and Table 5-14 for Unit 2.
Revision 3 Page 22of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Unit 1 Risk Profile for Once in 15 Year ILRT Class Description Frequency Contribution Population Dose Population
(/yr) (%) (person-rem) Dose Rate (person-rem/yr)
No containment failure 2 1.57E-05 82.99% 3.68E+03 5.78E-02 Large containment 2 1.47E-07 0.78% 9.83E+06 1.45E+OO isolation failures Small isolation failures 3a 7.68E-07 4.06% 3.68E+04 2.83E-02 (liner breach)
Large isolation failures 3b 1.91 E-07 1.01% 3.68E+05 7.03E-02 (liner breach)
Small isolation failures - £1 £1 £1 £1 4
failure to seal {!Yee B)
Small isolation failures - £1 £1 £1 £1 5
failure to seal {!Yee C)
Containment isolation 6 failures (dependent failure, £1 E1 £1 £1 eersonnel errors)
Severe accident 7 phenomena induced failure 7.61E-07 4.02% 9.83E+06 7.48E+OO
{earl}'. and late) 8 Containment bypass 1.35E-06 7.14% 8.90E+05 1.20E+OO Total 1.89E-05 1.03E+01
- 1. £represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 1 frequency is reduced by the frequency of Class 3a and Class 3b in order to preserve total CDF.
Table 5 Unit 2 Risk Profile for Once in 15 Year ILRT Class Description Frequency Contribution Population Dose Population
(/yr) (%) (person-rem) Dose Rate (person-rem/yr)
No containment failure 2 1.38E-05 82.04% 3.68E+03 5.09E-02 Large containment 2 1.47E-07 0.87% 9.83E+06 1.45E+OO isolation failures Small isolation failures 3a 6.76E-07 4.01% 3.68E+04 2.49E-02 (liner breach)
Large isolation failures 3b 1.68E-07 1.00% 3.68E+05 6.19E-02 (liner breach)
Small isolation failures - £1 £1 £1 £1 '
4 failure to seal {!Yee B)
Small isolation failures - £1 £1 £1 £1 5
failure to seal (!}'.pe C)
Containment isolation 6 failures (dependent failure, £1 £1 £1 £1 eersonnel errors)
Severe accident 7 phenomena induced failure 6.85E-07 4.07% 9.83E+06 6.74E+OO
{earl}'. and late) 8 Containment bypass 1.35E-06 8.02% 8.90E+05 1.20E+OO Total 1.69E-05 9.52E+OO
- 1. £represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 1 frequency is reduced by the frequency of Class 3a and Class 3b in order to preserve total CDF.
Revision 3 Page 23of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 5.2.4 Step 4 - Determine the Change in Risk in Terms of LERF The risk increase associated with extending the ILRT interval involves the potential that a core damage event that normally would result in only a small radioactive release from an intact containment could , in fact, result in a larger release due to the increase in probability of fa ilure to detect a pre-existing leak. With strict adherence to the EPRI guidance, 100% of the Class 3b contribution would be considered LERF.
Regulatory Gu ide 1.174 (Reference 4] provides guidance for determining the risk impact of plant-specific changes to the licensing basis. RG 1.174 [Reference 4] defines very small changes in risk as resulting in increases of CDF less than 1o-s/year and increases in LERF less than 10-7 /year, and small changes in LERF as less than 1o-s/year. Since containment overpressure is not required in support of ECCS performance to mitigate design basis accidents at DCPP, the ILRT extension does not impact CDF. Therefore , the relevant risk-impact metric is LERF.
For DCPP, 100% of the frequency of Class 3b sequences can be used as a very conservative first-order estimate to approximate the potential increase in LERF from the ILRT interval extension (consistent with the EPRI guidance methodology). Based on a 10-year test interval from Table 5-11 and Table 5-12 , the Class 3b frequency is 1.27E-07/year for Unit 1 and 1.12E-07/year for Unit 2; based on a 15-yeartest interval from Table 5-13 and Table 5-14 , the Class 3b frequency is 1.91 E-07/year for Unit 1 and 1.68E-07/year for Unit 2. Thus , the increase in the overall probability of LERF due to Class 3b sequences that is due to increasing the ILRT test interval from 3 to 15 years is 1.53E-07/year for Unit 1 and 1.35E-07/year for Unit 2. Similarly, the increase due to increasing the interval from 10 to 15 years is 6.37E-08/year for Unit 1 and 5.61E-08/year for Unit 2. As can be seen , even with the conservatisms included in the evaluation (per the EPRI methodology) , the estimated change in LERF is within the criteria for a small change when comparing the 15-year results to the current 10-year requ irement and the original 3-year requirement. Table 5-15 summarizes these results.
Table 5 Impact on LERF due to Extended Type A Testing Intervals ILRTlnspection Unit1:3Years Unit1:10 Unit1:15 Unit2:3Years Unit2:10 Unit2:15 Interval (baseline) Years Years (baseline) Years Years Class 3b (Type A 3.82E-08 1.27E-07 1.91 E-07 3.36E-08 1.12E-07 1.68E-07 LERF) b.LERF (3 year basel ine)
I 8.92E-08 1.53E-07 I 7. 85E-08 1.35E-07 b.LERF (10 year basel ine)
I 6.37 E-08 I 5.6 1E-08 The increase in the overall probability of LERF due to Class 3b sequences is greater than 10-1 .
As stated in RG 1.174 [Reference 4] , "When the calculated increase in LERF is in the range of 10-7 per reactor year to 1o-s per reactor year, appl ications will be considered only if it can be reasonably shown that the total LERF is less than 10-5 per reactor year." Baseline LERF (excluding external events) is 2.26E-06/year for Unit 1 and 2.18E-06/year for Unit 2. Therefore, there is significant margin for both the b.LERF and baseline LERF to the upper limits of Region II in RG 1.174 [Reference4] .
5.2.5 Step 5 - Determine the Impact on the Conditional Containment Failure Probability Another parameter that the NRC guidance in RG 1.174 [Reference 4] states can provide input into the decision-making process is the change in the conditional containment failure probability Revision 3 Page 24of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension (CCFP). The CCFP is defined as the probability of containment failure given the occurrence of an accident. This probability can be expressed using the following equation :
CCFP = 1 - f(ncf)
CDF where f(ncf) is the frequency of those sequences that do not result in containment failure ; this frequency is determined by summing the Class 1 and Class 3a results [Reference 24]. Table 5-16 shows the steps and results of this calculation. The difference in CCFP between the 3-year test interval and 15-year test interval is 0.808% for Unit 1 and 0.799% for Unit 2.
Table 5 Impact on CCFP due to Extended Type A Testing Intervals ILRT Inspection Unit 1: 3 Years Unit1 : 10 Unit1:15 Unit 2: 3 Years Unit 2: 10 Unit 2: 15 Interval (baseline) Years Years (baseline) Years Years f(ncf) (/yr) 1.66E-05 1.65E-05 1.65E-05 1.46E-05 1.46E-05 1.45E-05 f(ncf)/CDF 87.9% 87.4% 87 .1% 86 .8% 86.4% 86.0%
CCFP 12.14% 12.61 % 12.95% 13.16% 13.62% 13.95%
t.CCFP (3 year baseline) I 0.471 % 0.808%
I 0.466% 0.799%
t.CCFP (10 year basel ine) I 0.337%
I 0.333%
As stated in Section 2.0, a change in the CCFP of up to 1.5% is assumed to be small. The increase in the CCFP from the 3 in 10 year interval to 1 in 15 year interval is 0.808% for Unit 1 and 0. 799% for Unit 2. Therefore , this increase is judged to be very small.
5.2.6 Impact of Extension on Detection of Steel Liner Corrosion that Leads to Leakage An estimate of the likelihood and risk implications of corrosion-induced leakage of the steel liners occurring and going undetected during the extended test interval is evaluated using a methodology similar to the Calvert Cliffs liner corrosion analysis [Reference 5]. The Calvert Cliffs analysis was performed for a concrete cylinder and dome and a concrete basemat, each with a steel liner.
The following approach is used to determine the change in likelihood , due to extending the ILRT, of detecting corrosion of the containment steel liner. This likelihood is then used to determine the resulting change in risk. Consistent with the Calvert Cliffs analysis, the following issues are addressed :
- Differences between the containment basemat and the containment cylinder and dome
- The historical steel liner flaw likelihood due to concealed corrosion
- The impact of aging
- The corrosion leakage dependency on containment pressure
- The likelihood that visual inspections will be effective at detecting a flaw Assumptions
- Consistent with the Calvert Cliffs analysis , a half failure is assumed for basemat concealed liner corrosion due to the lack of identified failures (See Table 5-17 , Step 1).
- The two corrosion events used to estimate the liner flaw probability in the Calvert Cliffs previous analysis are assumed to still be applicable.
- Consistent with the Calvert Cliffs analysis, the estimated historical flaw probability is also Revision 3 Page 25of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension limited to 5.5 years to reflect the years since September 1996 when 10 CFR 50.55a started requiring visual inspection. Additional success data was not used to limit the aging impact of this corrosion issue, even though inspections were being performed prior to this date (and have been performed since the time frame of the Calvert Cliffs analysis)
(See Table 5-4, Step 1).
- Consistent with the Calvert Cliffs analysis, the steel liner flaw likelihood is assumed to double every five years. This is based solely on judgment and is included in this analysis to address the increased likelihood of corrosion as the steel liner ages (See Table 5-17, Steps 2 and 3). Sensitivity studies are included that address doubling this rate every ten years and every two years.
- In the Calvert Cliffs analysis, the likelihood of the containment atmosphere reaching the outside atmosphere, given that a liner flaw exists, was estimated as 1.1 % for the cylinder and dome, and 0.11 % (10% of the cylinder failure probability) for the basemat. These values were determined from an assessment of the probability versus containment pressure. For DCPP, the containment design pressure is 47 psig [Reference 27].
Probabilities of 1% for the cylinder and dome, and 0.1 % for the basemat are used in this analysis, and sensitivity studies are included in Section 5.3.2 (See Table 5-17, Step 4).
- Consistent with the Calvert Cliffs analysis, the likelihood of leakage escape (due to crack formation) in the basemat region is considered to 'be less 0 likely than the containment cylinder and dome region (See Table 5-17, Step 4).
- Consistent with the Calvert Cliffs analysis, a 5% visual inspection detection failure likelihood given the flaw is visible and a total detection failure likelihood of 10% is used.
To date, all liner corrosion events have been detected through visual inspection (See Table 5-17, Step 5).
- Consistent with the Calvert Cliffs analysis, all non-detectable containment failures are assumed to result in early releases. This approach avoids a detailed analysis of containment failure timing and operator recovery actions.
Table 5 Steel Liner Corrosion Base Case Step Description Containment Cylinder and Containment Basemat Dome (85%) (15%)
Historical liner flaw likelihood Events: 2 Events: 0 Failure data: containment location (Brunswick 2 and North Anna 2) Assume a half failure specific 2 I (70 x 5.5) = 5.19E-03 0.5 I (70 x 5.5) = 1.30E-03 Suceess data: based on 70 steel-lined containments and 5.5 years since the 10CFR 50.55a requirements of periodic visual inspections of containment surfaces Year Failure rate Year Failure rate Aged adjusted liner flaw likelihood During the 15-year interval, assume 2.05E-03 5.13E-04 failure rate doubles every five years average 5-10 5.19E-03 average 5-10 1.30E-03 2 15 1.43E-02 15 3.57E-03 (14.9% increase per year). The average for the 5th to 10th year set to the historical failure rate. 15 year average = 6.44E-03 15 year average = 1.61 E-03 Revision 3 Page 26of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Steel Liner Corrosion Base Case Step Description Containment Cylinder and Containment Basemat Dome (85%) (15%)
Increase in flaw likelihood between 3 and 15 years Uses aged adjusted 0.73% (1to3 years) 0.18% (1 to 3 years) 3 liner flaw likelihood (Step 2), 4.18% (1 to 10 years) 1.04% (1to10 years) assuming failure rate doubles every 9.66% (1 to 15 years) 2.41% (1to15 years) five years.
Likelihood of breach in containment 4 1% 0.1%
given liner flaw 10%
5% failure to identify visual flaws plus 5% likelihood that the flaw is not visible (not through-cylinder 100%
Visual inspection detection failure 5 but could be detected by ILRT).
likelihood Cannot be visually inspected All events have been detected through visual inspection. 5%
visible failure detection is a conservative assumption.
0.00073% (3 years) 0.000180% (3 years) 0.73% x 1% x 10% 0.18% x 0.1 % x 100%
Likelihood of non-detected 0.00418% (10 years) 0.00104% (10 years) 6 containment leakage (Steps 3 x 4 x
- 5) 4.18% x 1% x 10% 1.04% x 0.1% x 100%
0.00966% (15 years) 0.00241% (15 years) 9.66% x 1% x 10% 2.41 % x 0.1 % x 100%
The total likelihood of the corrosion-induced, non-detected containment leakage is the sum of Step 6 for the containment cylinder and dome, and the containment basemat, as summarized below for DCPP.
Table 5-18-Total Likelihood on Non-Detected Containment Leakage Due to Corrosion for DCPP
' Description At 3 years: 0.00073% + 0.000180% = 0.00091%
At 10 years: 0.00418% + 0.00104% = 0.00522%
At 15 years: 0.00966% + 0.00241% =0.01207%
The above factors are applied to those core damage accidents that are not already independently LERF or that could never result in LERF.
The two corrosion events that were initiated from the non-visible (backside) portion of the containment liner used to estimate the liner flaw probability in the Calvert Cliffs analysis are assumed to be applicable to this containment analysis. These events, one at North Anna Unit 2 (September 1999) caused by timber embedded in the concrete immediately behind the containment liner, and one at Brunswick Unit 2 (April 1999) caused by a cloth work glove embedded in the concrete next to the liner, were initiated from the nonvisible (backside) portion of the containment liner. A search of the NRC website LER database identified two additional events have occurred since the Calvert Cliffs analysis was performed. In January 2000, a 3/16-inch circular through-liner hole was found at Cook Nuclear Plant Unit 2 caused by a wooden brush handle embedded immediately behind the containment liner. The other event occurred in April 2009, where a through-liner hole approximately 3/8-inch by 1-inch in size was identified in Revision 3 Page 27of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension the Beaver Valley Power Station Unit 1 (BVPS-1) containment liner caused by pitting originating
' from the concrete side due to a piece of wood that was left behind during the original -
construction that came in contact with the steel liner. Two other containment liner through-wall hole events occurred at Turkey Point Units 3 and 4 in October 2010 and November 2006, respectively. However, these events originated from the visible side caused by the failure of the coating system, which was not designed for periodic immersion service, and are not considered to be applicable to this analysis. More recently, in October 2013, some through-wall containment liner holes were identified at BVPS-1, with a combined total area of approximately 0.395 square inches. The cause of these through-wall liner holes was attributed to corrosion originating from the outside concrete surface due to the presence of rayon fiber foreign material that was left behind during the original construction and was contacting the steel liner
[Reference 28]. For risk evaluation purposes, these five total corrosion events occurring in 66 a'
operating plants with steel containment liners over 17.1 year period from September 1996 to October 4, 2013 (i.e., 5/(66*17.1) = 4.43E-03) are bounded by the estimated historical flaw probability based on the two events in the 5.5 year period of the Calvert Cliffs analysis (i.e.,
2/(70*5.5) = 5.19E-03) incorporated in the EPRI guidance.
5.3 Sensitivities 5.3.1 Potential Impact from External Events Contribution An assessment of the impact of external events is performed. The primary purpose for this investigation is the determination of the total LERF following an increase in the ILRT testing interval from *3 in 10 years to 1 in 15 years.
Diablo Canyon has received License Amendments No. 225 and 227, dated April 14, 2016,
[Reference ML16035A441] for implementation ofNFPA 805 on Units 1 and 2, respectively. Diablo Canyon has implemented required changes to the Operating Licenses and Technical Specifications and is in the process of implementing the program and installing modifications as committed to in the License Amendment Request, Safety Evaluation, and License Amendments. Thus, it is anticipated that all of the Fire PRA related modifications will be comple,ted prior to the next scheduled Type A tests for Units 1 and 2 in the first quarter of 2019 and 2018, respectively [Reference 33]. Therefore, the NFPA 805 post-modification Fire PRA model is deemed applicable and was used for this calculation.
The Fire PR.A model DC03M was used to obtain the fire GDF and LERF values [Reference 18].
To reduce conservatism in the model, the methodology of subtracting existing LERF from GDF is also applied to the Fire PRA modeL The following shows the calculation for Class 3b:
0.5 Frequ1class3b = Pc!ass3b * (CDF - LERF) = * (4.83E 2.45E-6) = 1.0SE-7 218 0.5 Frequ2class3b = Pclass3b * (CDF - LERF) = * (5.24E~S - 2.17E-6) = 1.15E-7 218
' 10 10 0.5 Frequ1class3b1oyr = 3
- 218 * (4.83E 2.45E-6) = 3.SOE-7 10 10 0.5 Frequ2class3b10yr = 3
- 218 * (5.24E 2.17E-6) = 3.84E-7 Frequ1class3b15yr
= -153
= 5 * -,-218 * (4.83E 2.45E-6) = 5.26E-7 15 - . 0.5 Frequ2class 3bl5yr = -3 *. Pclass3b * (CDF - LERF) = 5 * -218 * (5.24E 2.17E-6) = 5.76E-7 Revision 3 Page 28of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension The Seismic PRA results estimate a CDF of 2.66E-5/year and a LERF of 3.29E-6/year
[Reference 17]. The Seismic PRA model is not unit-specific. Subtracting seismic LERF from CDF, the Class 3b frequency can be calculated by the following formulas:
Freqclass3b = Pc1ass3b * {CDF - LERF) = ~~~ * (2.66E-5 -3.29E-6) = 5.35E-8 10 10 0.5 Freqclass3b1oyr = -3
~* ~ ~ .
Freqclass3b1Syr = 3
- 218 * (2.66E-5 -3.29E-6)= 2.67E-7 The DCPP IPEEE determined that each of the "other external events evaluated contributed less than 1.0E-06 per year to core damage and was screened out as a result [Reference 32].
Therefore, the "other external events are also screened for this application.
The fire and seismic contributions to Class 3b frequencies are then combined to obtain the total external event contribution to Class 3b frequencies. The change in LERF is calculated for the 1 in 1O year and 1 in 15 year cases and the change defined for the external events in Table 5-19 for Unit 1 and Table 5-20 for Unit 2.
Table 5 Unit 1 DCPP External Event Impact on ILRT LERF Calculation Hazard EPRI Accident Class 3b Frequency LERF Increase (from 3per10 years to 1 per 15 years) 3per10 year 1 per 10 year 1 per 15 years
' 6.34E-07 External Events 1.59E-07 5.29E-07 7.93E-07 Internal Events 3.82E-08 1.27E-07 1.91E-07 1.53E-07 Combined 1.97E-07 6.56E-07 9.84E-07 7.87E-07 Table 5 Unit 2 DCPP External Event Impact on ILRT LERF Calculation Hazard EPRI Accident Class 3b Frequency LERF Increase (from 3per10 years to 1 1 per 15 years- per 15 years) 3per10 year 1 per 10 year External Events 1.69E-07 5.62E-07 8.43E-07 6.75E-07
" Internal Events 3.36E-08 1.12E-07 1.. 68E-07 1.35E-07 Combined 2.02E-07 6.74E-07 1.01E-06 8.09E-07 The internal event results are also provided to allow a composite value to be defined. When both the internal and external event contributions are combined, the total change in LERF of 7.87E-7 for Unit 1 and 8.09E-7 for Unit 2 meets the guidance for small change in risk, as it exceeds 1.0E-7/yr and remains less than 1.0E-6 change in LERF. For this change in LERF to be acceptable, total LERF must be less than *1.0E-5. The total LERF value is calculated below:
LERFu1 = LERFulinternal + LERFseismic + LERFurnre + LERFu2ciass3Bincrease
= 2.26E-6/yr + 3.29E-6/yr + 2.45E-6/yr + 7.87E-7 /yr= 8.78E-6/yr LERFu2 = LERFu2internal + LERFseismic + LERFu2fire + LERFu2ciass3Bincrease
= 2.18E-6/yr + 3.29E-6/yr + 2.17E-6/yr + 8.09E*7 /yr= 8.45E-6/yr Revision 3 Page 29of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Although the total change in LERF is somewhat close to the Regulatory Guide 1.174 limit
[Reference 4] when external event risk is included, several conservative assumptions were made in this ILRT analysis, as discussed in Sections 4.0, 5.1.3, 5.2.1, and 5.2.4; therefore the total change in LERF is considered conservative for this application. As specified in Regulatory Guide 1.174 [Reference 4], since the total LERF is less than 1.0E-5, it is acceptable for the b.LERF to be between 1.0E-7 and 1.0E-6.
5.3.2 Potential Impact from Steel Liner Corrosion Likelihood A quantitative assessment of the contribution of steel liner corrosion likelihood impact was performed for the risk impact assessment for extended ILRT intervals. The impact on the Class 3b frequency due to increases in the ILRT surveillance interval was calculated for steel liner corrosion likelihood using the relationships described in Section 5.2.6. The EPRI Category 3b frequencies for the 3 per 10-year, 10-year, and 15-year ILRT intervals were. quantified using the internal events CDF. The change in the LERF, change in CCFP, and change in Annual Dose Rate due to extending the ILRT interval from 3 in 1O years to 1 in 1O years, or to 1 in 15 years are provided in Table 5 Table 5-26. The steel liner corrosion likelihood was increased by a factor of 1000, 10000, and 100000. Except for extreme factors of 10000 and 100000, the corrosion likelihood is relatively insensitive to the results.
Table 5 Steel Liner Corrosion Sensitivity Case: Unit 1 38 Contribution 3b 3b 3b LERF LERF LERF Frequency Frequency Frequency Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 (3-per-10 to (3-per-10 to (1-per-10 to year ILRT) year ILRT) yearlLRT) 1-per-10) 1-per-15) 1-per-15)
Internal Event 38 3.82E-08 1.27E-07 1.91 E-07 8.92E-08 1.53E-07 6.37E-08 Contribution Corrosion Likelihood 3.86E-08 1.34E-07 2.14E-07 9.55E-08 1.76E-07 8.01E-08 x 1000 Corrosion Likelihood 4.17E-08 1.94E-07 4.22E-07 1.52E-07 3.80E-07 2.28E-07 x 10000 Corrosion Likelihood 7.30E-08 7.92E-07 2.50E-06 7.19E-07 2.42E-06 1.70E-06 x 100000 Table 5 Steel Liner Corrosion Sensitivity Case: Unit 2 38 Contribution 3b 3b 3b LERF LERF LERF Frequency Frequency Frequency Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 (3-per-10 to (3-per-10 to (1-per-10 to year ILRT) yearlLRT) yearlLRT) 1-per-10) 1-per-15) 1-per-15)
Internal Event 38 3.36E-08 1.12E-07 1.68E-0,7 7.85E-08 1.35E-07 5.61E-08 Contribution Corrosion Likelihood 3.39E-08 1.18E-07 1.89E-07 8.40E-08 1.55E-07 7.05E-08 x 1000 Corrosion Likelihood 3.67E-08 1.71E-07 3.71E-07 1.34E-07 3.35E-07 2.01E-07 x 10000 Corrosion Likelihood 6.43E-08 6.97E-07 2.20E-06 6.33E-07 2.13E-06 1.50E-06 x 100000 Revision 3 Page 30of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Steel Liner Corrosion Sensitivity: Unit 1 CCFP CCFP CCFP CCFP CCFP CCFP CCFP Increase Increase Increase (3-per*10 (1-per-10 (1-per-15 (3-per-1 Oto (3-per-1 Oto (1-per-10 to year ILRT) yearlLRT) yearlLRT) 1-per-10) 1-per-15) 1-per-15)
Baseline 1.21E-01 1.26E-01 1.29E-01 4.71E-03 8.08E-03 3.37E-03 CCFP Corrosion Likelihood 1.21E-01 1.26E-01 1.30E*01 4.76E-03 8.15E-03 3.40E-03 x 1000 Corrosion Likelihood 1.22E-01 1.27E-01 1.30E-01 5.14E-03 8.81E-03 3.67E-03 x 10000 Corrosion Likelihood 1.23E-01 1.32E-01 1.39E-01 9.00E-03 1.54E-02 6.43E-03 x 100000 Table 5 Steel Liner Corrosion Sensitivity: Unit 2 CCFP CCFP CCFP CCFP CCFP CCFP CC,FP Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 (3-per-10 to (3-per-10 to (1-per-10 to year ILRT) yearlLRT) year ILRT) 1-per-10) 1-per-15)
- 1-per-15)
Baseline 1.32E-01 1.36E-01 1.40E-01 4.66E-03 7.99E*03 3.33E-03.
CCFP Corrosion Likelihood .1.32E-01 1.36E-01 1.40E-01 4.70E-03 8.06E-03 3.36E-03 x 1000 Corrosion Likelihood 1.32E-01 1.37E-01 1.40E-01 5.08E-03 8.71E-03 3.63E-03 x 10000 Corrosion Likelihood 1.33E-01 1.42E-01 1.49E-01 8.90E-03 1.53E-02 6.36E-03 x 100000 Table 5 Steel Liner Corrosion Sensitivity: Unit 1 Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 year (3-per-10 to (3-per-10 to 1- (1-per-10 to y~ar ILRT) yearlLRT) ILRT) 1-per-10) per-15) 1-per-15)
Dose Rate 1.41 E-02 4.69E-02 7.03E-02 3.28E-02 5.63E-02 2.34E-02 Corrosion Likelihood 1.42E-02 *4.93E-02 7.88E-02 3.51E-02 6.46E-02 2.95E-02 x 1000 Corrosion Likelihood 1.53E-02 7.13E-02 1.5.5E-01 5.60E-02 1.40E-01 8.38E-02 x 10000 Corrosion Likelihood 2.69E-02 2.92E-01 9.19E-01 2.65E-01 8.92E-01 6.27E-01 x 100000 Revision 3 Page 31of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Steel Liner Corrosion Sensitivity: Unit 2 Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 year (3-per-10 to (3-per-10 to 1- (1-per-10 to year ILRT) yearlLRT) ILRT) 1-per-10) per-15) 1-per-15)
Dose Rate 1.24E-02 4.13E-02 6.19E-02 2.89E-02 4.95E-02 2.06E-02 Corrosion Likelihood 1.25E-02 4.34E-02 6.94E-02 3.09E-02 5.69E-02 2.59E-02 x 1000 Corrosion Likelihood 1.35E-02 6.28E-02 1.37E-01 4.93E-02 1.23E-01 7.38E-02 x 10000 Corrosion Likelihood 2.36E-02 2.57E-01 8.09E-01 2.33E-01 7.85E-01 5.52E-01 x 100000 5.3.3 Expert Elicitation Sensitivity Another sensitivity case on the impacts of assumptions regarding pre-existing containment defect or flaw probabilities of occurrence and magnitude, or size of the flaw, is performed as described in Reference 24. In this sensitivity case, an expert elicitation was conducted to develop probabilities for pre:..existing containment defects that would be detected by the ILRT only based on the historical testing data.
Using the expert knowledge, this information was extrapolated into a probability-versus-magnitude relationship for pre-existing containment defects [Reference 24]. The failure mechanism analysis also used the historical ILRT data augmented with expert judgment to develop the results. Details of the expert elicitation process and results are contained in Reference 24. The expert eli.citation process has the advantage of considering the avaiiable
- data for small leakage events, which have occurred in the data, and extrapolate those events and probabilities of occurrence to the potential for large magnitude leakage events.
The expert elicitation results are used to develop sensitivity cases for the risk impact assessment. Employing the results requires the application of the ILRT interval methodology using the expert elicitation to change the probability of pre-existing leakage in the containment.
The baseline assessment uses the Jeffreys non-informative prior and the expert elicitation sensitivity study uses the results of the expert elicitation. In addition, given the relationship between leakage magnitude and probability, larger leakage tt:iat is more representative of large early release frequency, can be reflected. For the purposes of this sensitivity, the same leakage magnitudes that are used in the basic methodology (i.e., 10 La for small and 100 La for large) are used here. Table 5-27 presents the magnitudes and probabilities associated with the Jeffreys non-informative prior and the expert elicitation used in the base methodology and this sensitivity case.
Table 5 MNGP Summary of ILRT Extension Using Expert Elicitation Values (from Reference 24)
Leakage Size (La) Expert Elicitation Mean Probability of Occurrence Percent Reduction 10 3.88E-03 86%
100 2.47E-04 91%
Taking the baseline analysis and using the values provided in Table 5-10-Table 5-14 for the expert elicitation sensitivity yields the results in Table 5-28 and Table 5-29.
Revision 3 Page 32 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Unit 1 DCPP Summary of ILRT Extension Using Expert Elicitation Values Accident ILRT Interval Class 3per10 Years 1 per 10 Years 1 per 15 Years Base Adjusted Dose Dose Rate Frequency Dose Rate Frequency Dose Rate Frequency Base (person- (person- (person- (person-Frequency rem) rem/yr) rem/yr) rem/yr) 1.67E-05 1.66E-05 3.68E+03 6.11E-02 1.64E-05 6.05E-02 1.63E-05 6.00E-02 2 1.47E-07 1.47E-07 9.83E+06 1.45E+OO 1.47E-07 1.45E+OO 1.47E-07 1.45E+OO 3a N/A 6.46E-08 3.68E+04 2.38E-03 2.15E-07 7.93E-03 3.23E-07 1.19E-02 3b NIA 4.12E-09 3.68E+05 1.51E-03 1.37E-08 5.05E-03 2.06E-08 7.57E-03 6 O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 7 7.61E-07 7.61E-07 9.83E+06 7.48E+OO 7.61E-07 7.48E+OO 7.61E-07 7.48E+OO 8 1.35E-06 1.35E-06 8.90E+05 1.20E+OO 1.35E-06 1.20E+OO 1.39E-06 1.20E+OO Totals 1.89E-05 1.89E-05 N/A 1.02E+01 1.89E-05 1.02E+01 1.89E-05 1.02E+01 LiLERF (3 per 10 vrs base)
N/A 9.60E-09 1.65E-08 LiLERF (1 per 10 yrs base)
N/A N/A 6.86E-09 CCFP 11.96% 12.01% 12.05%
Table 5 Unit 2 DCPP Summary of ILRT Extension Using Expert Elicitation Values Accident ILRT Interval Class 3per10 Years 1 per 10 Years 1 per 15 Years Base Adjusted Dose Dose Rate Frequency Dose Rate Freql!ency Dose Rate Frequency Base (person- (person- (perso!l- (person-Frequency rem) rem/yr) rem/yr) rem/yr) 1.47E-05 1.46E-05 3.68E+03 5.38E-02 1.45E-05 5.32E-02 1.44E-05 5.29E-02 2 1.47E-07 1.47E-07 9.83E+06 1.45E+OO 1.47E-07 1.45E+OO 1.47E-07 1.45E+OO 3a N/A 5.69E-08 3.68E+04 2.09E-03 1.90E-07 6.98E-03 2.85E-07 1.05E-02 3b N/A 3.62E-09 3.68E+05 1.33E-03 1.21E-08 4.44E-03 1.81E-08 6.67E-03 6 O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 7 6.85E-07 6.85E-07 9.83E+06 6.74E+OO 6.85E-07 6.74E+OO 6.85E-07 6.74E+OO 8 1.35E-06 1.35E-06 8.90E+05 1.20E+OO 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO Totals 1.69E-05 1.69E-05 N/A 9.44E+OO 1.69E-05 9.45E+OO 1.69E-05 9.45E+OO LiLERF (3 per 10 vrs base)
N/A 8.45E-09 1.45E-08 LiLERF (1 per 10 vrs base)
N/A N/A 6.04E-09 CCFP 12.98% 13.03% 13.06%
The results illustrate how the expert elicitation reduces the overall change in LERF and the overall results are more favorable with regard to the change in risk.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 6.0 RESULTS The results from this ILRT extension risk assessment for DCPP are summarized in Table 6-1 for Unit 1 and Table 6-2 for Unit 2.
Table 6 Unit 1 ILRT Extension Summary Class Dose Base Case Extend to Extend to (person-rem) 3in10 Years 1in10 Years 1 in 15 Years CDFNear Person- CDFNear' Person- CDFNear Person-RemNear RemNear RemNear 3.68E+03 1.65E-05 6.06E-02 1.60E-05 5.90E-02 1.57E-05 5.78E-02 2 9.83E+06 1.47E-07 1.45E+OO 1.47E-07 1.45E+OO 1.47E-07 1.45E+OO 3a 3.68E+04 1.54E-07 5.65E-03 5.12E-07 1.88E-02 7.68E-07 2.83E-02 3b 3.68E+b5 3.82E-08 1.41 E-02 1.27E-07 4.69E-02 1.91E-07 7.03E-02 6 O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 7 9.83E+06 7.61 E-07 7.48E+OO 7.61E-07 7.48E+OO 7.61 E-07 7.48E+OO 8 8.90E+05 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO Total 1.89E-05 1.02E+01 1.89E-05 1.03E+01 1.89E-05 1.03E+01
' ~ -
- - -~ j ILRT Dose Rate from 3a and 3b
.6.Total From 3 Years N/A 4.44E-02 7.60E-02 Dose Rate From 10 Years N/A N/A 3.17E-02
%.6.Dose From 3 Years N/A 0.434% 0.745%
Rate From 10 Years N/A N/A 0.309%
L ..
., ---. . .. --* <r ---- --- **-- ..~:* - '; 7 "'. ... . . - "'- ~ -----
. .. . '*.... I 3b Frequency (LERF)
- N/A
.6.LERF From 3 Years From 10 Years N/A 8.92E-08 N/A 1.53E-07 6.37E-08 CCFP%
From 3 Years N/A 0.471% 0.808%
.6.CCFP%
From 10 Years N/A N/A 0.337%
\
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 6 Unit 2 ILRT Extension Summary Class Dose Base Case Extend to Extend to (person-rem) 3 in 10 Years 1 in 10 Years 1in15 Years CDFNear Person- CDFNear Person- CDFNear Person-RemNear RemNear RemNear 3.68E+03 1.45E-05 5.34E-02 1.41E-05 5.19E-02 1.38E-05 5.09E-02 2 9.83E+06 1.47E-07 1.45E+OO 1.47E-07 1.45E+b0 1.47E-07 1.45E+OO 3a 3.68E+04 1.35E-07 4.97E-03 4.51E-07 1.66E-02 6.76E-07 2.49E-02 3b 3.68E+05 3.36E-08 1.24E-02 1.12E-07 4.13E-02 1.68E-07 6.19E-02 6 O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 7 9.83E+06 6.85E-07 6.74E+OO 6.85E-07 6.74E+OO 6.85E-07 6.74E+OO 8 8.90E+05 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO Total 1.69E-05 9.46E+OO 1.69E-05 9.49E+OO 1.69E-05 9.52E+OO I .. ..
ILRT Dose Rate from 3a and 3b LiTotal From 3 Years N/A 3.90E-02 6.69E-02 Dose Rate From 10 Years N/A N/A 2.79E-02
%liDose From 3 Years N/A 0.413% 0)'08%
Rate From 10 Years N/A N/A 0.294%
3b Frequency (LERF)
From 3 Years N/A 7.85E-08 1.35E-07 LiLERF From 10 Years N/A N/A 5.61E-08
-. . . . ~ ...
. I
~,
CCFP%
From 3 Years N/A 0.466% 0.799%
LiCCFP%
From 10 Years N/A N/A 0.333%
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 7 .0 CONCLUSIONS AND RECOMMENDATIONS Based on the results from Section 5.2 and the sensitivity calculations presented in Section 5.3, the following conclusions regarding tile assessment of the plant risk are associated with extending the Type A ILRT test frequency to 15 years:
- Regulatory Guide 1.174 [Reference 4] provides guidance for determining the risk impact of plant-specific changes to the licensing basis. Regulatory Guide 1.174 defines small changes in risk as resulting in increases of CDF greater than 1.0E-6/year and less than 1.0E-5/year and increases in LERF greater than t.OE-7/year and less than 1.0E-6/year.
Since the ILRT does not impact CDF, the relevant criterion is LERF. The increase in LERF resulting from a change in the Type A ILRT test interval from 3 in 10 years to 1 in 15 years is estimated as 1.53E-7/yearfor Unit 1and1.35E-7/yearfor Unit 2 using the EPRI guidance (this value increases negligibly if the risk impact of corrosion-induced leakage of the steel liners occurring and going undetected during the extended test-interval is included), and baseline LERF is 2.26E-6/year for Unit 1 and 2.18E-6/year for Unit 2. As such, the estimated change in LERF is determined to be "small" using the acceptance guidelines of Regulatory Guide 1.174 [Reference 4]. *When external event risk is included, the increase in LERF resulting from a change in the Type A ILRT test interval from 3 in 10 years to 1 in 15 years is estimated as 7.87E-7/year for Unit 1 and 8.09E-7/year for Unit 2 using the EPRI guidance, and baseline LERF is 8.78E-6/year for Unit 1 and 8.45E-6/year for Unit 2. As such, the estimated change iri LERF is determined to be "small" using the *acceptance guidelines of Regulatory Guide 1.174
[Reference 4].
- The effect resulting from changing the Type A test frequency to 1-per-15 years, measured as an increase to the total integrated plant risk for those accident sequences influenced by Type A testing, is 0.076 person-rem/year for Unit 1 and 0.067 person-rem/year for Unit 2. EPRI Report No. 1009325, Revisiory 2-A [Reference 24] states that a very small population dose is defined as an increase of s 1.0 person-rem per year, ors 1% of the total population dose, whichever is less restrictive for the risk impact assessment of the extended ILRT intervals. The results of this calculation meet these criteria. Moreover, the risk impact for the ILRT extension when compared to other severe accident risks is negligible.
- The increase in the conditional containment failure probability from the 3 in 10 year interval to 1 in 15 year interval is 0.808% for Unit 1 and 0. 799% for *unit 2. EPRI Report No. 1009325, Revision 2-A [Reference 24] states that increases .in CCFP of s 1.5% is very small. Therefore, this increase is judged to be very small.
Therefore, increasing the ILRT interv'al to 15 years is considered to be insignificant since it represents a small change to the DCPP risk profile.
Previous Assessments The NRC in NUREG-1493 [Reference 6] has previously concluded that:
- Reducing the frequency of Type A tests (ILRTs) from 3 per 1O years to 1 per 20 years was found to lead to an imperceptible increase in risk. The estimated increase in risk is very small because ILRTs identify only a few potential containment leakage paths that cannot be identified by Type B or Type C testing, and the leaks that have been found by Type A tests have been only marginally above existing-requirements.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
- Given the insensitivity of risk to containment leakage rate and the small fraction of leakage paths detected solely by Type A testing, increasing the interval between integrated leakage-rate tests is possible with minimal impact on public risk. The impact of relaxing the ILRT frequ~ncy beyond 1 in 20 years has not been evaluated. Beyond testing the performance of containment penetrations, ILRTs also test integrity of the containment structure.
The findings for DCPP confirm these general findings on a plant-specific basis considering the severe accidents evaluated for DCPP, the DCPP containment failure modes, and the local population surrounding DCPP.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension A. ATTACHMENT 1 A.1. Internal Events PRA Quality Statement for Permanent 15-Year ILRT Extension PG&E conducted an Internal Events Peer Review in December 2012. The full-scope Peer Review that included internal events and internal floods portions of the DCPP PRA was performed in accordance with RG 1.200, Rev. 2, and ASME/ANS RA-Sa-2009. The review provided Facts and Observations (F&Os) regarding the model and identified 94 supporting requirements within the internal events. and internal floods portions of the model that did not meet Capability Category (CAT) II. All findings have been either resolved by additional analysis or evaluated in terms of their impact on the ILRT extension, and dispositioned as presented in Table A-1 Internal Events PRA Peer Review- Facts and Observations.
No changes have been made to the Internal Events or Internal Floods PRA models since the Peer Review that would constitute an upgrade.
Internal floods findings and their disposition are presented in Table A-2. Findings associated with internal floods are addressed but have no impact on the ILRT extension application.
PG&E conducted a Seismic PRA Peer Review in January 2013. The full-scope Peer Review that also included a review of seismic hazard and fragility analyses was performed in accordance with RG 1.200, Rev. 2, and ASME/ANS RA-Sa-2009.
A.2. Fire PRA Quality Statement for Permanent 15-Year ILRT Extension The FPRA is adequate to support the ILRT extension analysis. The DCPP FPRA was reviewed in January 2008 as part of the pilot application of the NEl-07-12 Peer Review process. The 2008 Peer Review was conducted against the requirements of the ANS Standard "FPRA Methodology" ANSl/ANS-58.23-2007. At the time of this first Peer Review, certain technical elements of the FPRA had not been completed, and it was agreed that the second phase of the Peer Review would be performed when all the technical elements of the FPRA were completed.
The second phase of the Peer Review was completed in December 2010. The 201 O Peer R/eview was conducted against the requirements of Section 4 of the ASME/ANS Combined PRA Stand9rd.
The Peer Review noted a number of F&Os. The F&Os and the disposition of the F&Os are provided in Table A-3.
All FPRA related F&Os, except SF-A5-01 against SR SF-A5, have been addressed and dispositioned as closed. SF-A5-01 tracks the implementation (revision of the fire brigade training procedure) of a recommendation related to fire brigade training requirement dealing with seismically induced fires. See Attachment S, Table S-3, Item S-3.25 of Reference 33 for more details. This item has no impact on the ILRT extension analysis.
Per the 2010 Peer Review, the DCPP FPRA met Capability Category II or better in all SRs but two (SRs CF-A1 and FSS-D7). These two SRs are listed in Table A-3. These.SRs have since been addressed and now considered as met at CC-II.
Table A-3 also listed the SRs from the 2008 Peer Review that did not meet CC-II or better quality requirements. However, as documented in Tables V-1 and V-2, these 2008 SRs have been re-reviewed during the 2010 Peer Review and all of the SRs were found met at CC-II or better.
No changes have been made to the FPRA model since the Peer Reviews that would constitute an upgrade.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Based on the Peer Reviews, Independent Third Party Reviews, and the resolution of F&Os, the DCPP FPRA model includes no deviations from NUREG/CR-6850 approaches, and contains no unreviewed analysis methods (UAMs).
A.3. Seismic PRA Quality Statement for Permanent 15-Y~ar ILRT Extension The seismic hazard and fragilities are currently being updated. The Seismic hazard update incorporates the most recent site-specific seismic data. The Peer Review team reviewed the methodologies used in the hazard and fr~gility analyses and found them to be acceptable. The current SPRA model provides a reasonable estimate of the seismic CDF and LERF for the purposes of the ILRT extension analysis.
Section 5 cif the ASME/ANS Combined PRA Standard contains a total of 77 Supporting Requirements (SRs) under three technical elements. As a result of this review, a total of 60 F&Os were generated. These included five "Best Practices," 18 "Suggestions, and 37 "Findings." Table A-4 presents Seismic PRA Peer Review Findings and Observations and their effect on the ILRT extension analysis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension IE-A5 IE-A5-01, NOT Closed Discussion: PERFORM a systematic evaluation of each Each system was screened for potential This is resolved.
MET, system, including support systems, to assess the possibility of initiating events. If a system did not There is no impact systematic an initiating event occurring due to a failure of the system. screen, the system was reviewed on the ILRT review of each Basis for Significance: There is no evidence in the against the existing Initiating Events Extension Risk system documentation (including Section C.1 of PLG-0637) that analysis to confirm that a bounding or Analysis.
demonstrates that EVERY system in the plant was reviewed as representative initiating event is a potential IE contributor. Discussion with DCPP PRA personnel modeled in the DCPP Internal Events confirmed this conclusion. PRA.
Possible Resolution: Collect list of all plant systems and meet with plant personnel to address the gap. An interview of operations representative was conducted to confirm the system screening and to discuss low power or NPOs for each system. Table H.1.6-10 of PRA Cale H.1.6 Rev 8 documented the review.
IE-A7 IE-A7-01, NOT Closed Discussion: SR IE-A?: In the identification of the initiating Twice-Daily Shift Manager Turnover This is resolved.
MET, events, INCORPORATE Reports, On-line/Off-line Daily Log, and There is no impact Associated SRs: (a) events that have occurred at conditions other than at-power Outage History were reviewed for on the ILRT IE-AB(CC-1), IE- operation (i.e., during low-power or shutdown conditions), and potential initiating events. No new Extension Risk A9(CC-I), events for which it is determined that the event could also occur during initiating events were discovered during Analysis.
occurred other than at-power operation. the review of the turnover repo_rts, daily at-power (b) events resulting in a controlled shutdown that includes a logs, and outage history. Low and non-scram prior to reaching low-power conditions, unless it is power operation events were discussed determined that an event is not applicable to at-power as part of the system screening operation. performed to resolve F&O IE-A5. The SR IE-AB: INTERVIEW plant personnel (e.g., operations, review was documented in Table H.1.6-maintenance, engineering, safety analysis) to determine if 10 of PRA Cale H.1.6 Rev 8.
potential initiating events have been overlooked.
SR IE-A9: REVIEW plant-specific and review industry operating experience for initiating event precursors, for identifying additional initiating events.
Twice-Daily Shift Manager Turnover Reports, On-line/Off-line Daily Log, and Outage History were reviewed for potential initiating events. No new initiating events were discovered during the review of the turnover reports, daily logs, and outage history. Low and non-power operation events were discussed as part of the system screening performed to resolve F&O IE-A5.
Significance to the FPRA and NFPA-805 LAR:
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status *Finding/Observation Disposition Cat II Requirement Extension The only aspeqt of the F&O that re~ult in a change to the internal events PRA is the discussion of the internal events low-power and non-power operations events review for initiating events. This has no impact on the FPRA, and only affects the documentation of the internal events PRA since there are no new initiating events and therefore no changes to the Internal Events PRA model.
Basis for Significance: SR IE-A7: The DCPP PRA has not addressed either requirements (a) or (b) for SR IE-A7, i.e.,
neither (a) a review of events that have occurred at conditions other than at-power operation that could also occur during at-power operation and would lead to a unique IE nor (b) a review of events resulting in an unplanned controlled shutdown that includes a scram prior to reaching low-power conditions. Note that the SR calls for a review of historical events.
SR IE-AB: no interviews were conducted with plant personnel to determine if potential .initiating events have been overlooked.
SR IE-A9: the plant-specific operating experience was not reviewed for initiating event precursors to identify additional initiatin events IE-C5 IE-C5-01, NOT Closed Discussion: Calculate initiating event frequencies on a reactor- .As demonstrated in PRA Cale 13-12 Since this has MET, IE year basis. Include in the initiating event analysis the plant Revision 0, the difference between the insignificant on the Frequency based availability, such that the frequencies are weighted by the capacity factors of both Units 1 and 2 is final CDF/LERF results, on a reactor year fraction of time the plant is at-power. less than 1%. Using the combined there is negligible basis Basis for Significance: IE frequencies are converted to events capacity fact instead of unit specific impact on the ILRT per calendar year by multiplying by the site critical hours per factors has insignificant impact on the Extension Risk calendar year factor calculated from site operating experience. final CDF/LERF results. Analysis.
However, SR IE-C5 requires this factor to be calculated on a
, plant unit operating year basis. This distinguishes differences in the plant units' operating experience.
Possible Resolution: Revise the conversion factors from a site to a ~lant s~ecific basis.
IE-C10 IE-C10-01, MET, Closed Discussion: If fault-tree modeling is IE fault trees were evaluated and This was a combination of one used for initiating events, CAPTURE.within the initiating event documentation was added to Section documentation issue Structure, System fault tree models all relevant combinations of events involving 4.2.3 of Cale B.1 to address the IE fault - and is resolved.
or Component the annual frequency of one component failure combined with tree documentation discussed above. There is no impact (SSC) failure with the unavailability (or failure during the repair time of the first on the ILRT the unavailability of component) of other components. Extension Risk other SSCs. Anal sis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Basis for Significance: Use of plant specific information in the Internal Events Fault Trees (!EFT) was not evident.
There was no discussion in the !EFT. Use of plant specific information in the IEFT was not evident. There was no discussion in the IEFT documentation regarding the treatment of common cause events. There is no discussion of how the 24-hour and 365-day exposure intervals are factored into the model.
There is no discussion of whether the success criteria used for the mitigating fault trees are applicable (or not) for the IEFT.
The Common Cause Failure (CCF) treatment in the !EFT should be described in order to verify that the appropriate exposure intervals are applied based on equipment rotational practices.
Possible Resolution: Evaluate and document the !EFT success criteria. Expand the !EFT documentation to address the all of above issues.
IE-C14 IE-C14-01, NOT Closed Discussion: In the ISLOCA frequency analysis, INCLUDE the Table C.4. 7-5 of Cale C.4. 7 Revision 9 This is resolved; no MET, following features of plant and procedures that influence the lists the containment penetrations and model change was Interfacing System ISLOCA frequency: (a) configuration of potential pathways disposition regarding their potential as necessary. There is Loss of Coolant including numbers an ISLOCA pathway was developed. A no impact on the Accident (ISLOCA) and types of valves and their relevant failure modes and the set of screening criteria were developed ILRT Extension Risk frequency existence, size, and positioning of relief valves (b) provision of consistent with the SR requirement. Analysis.
protective interlocks (c) relevant surveillance test (d) the These criteria were used explicitly to capability of secondary system piping. screen each potential ISLOCA pathway.
The unscreened ISLOCA flow paths are Basis for Significance: There is no systematic review of all consistent with what modeled in containment penetrations performed for or in the ISLOCA RISKMAN.
calculation. All penetrations that are screened out need to be Also, impact of Surveillance test was justified, yet this process was not evident in the documentation. added to the documentation.
Review of relevant surveillance test procedures is needed to meet this SR. other requirements specified in SR IE-C14 must also be evaluated and documented.
Possible Resolution: Create a table of all containment penetrations and disposition their potential as an ISLOCA pathway. Impact of surveillance test procedures should be explicitly documented. Explanation of RISKMAN treatment of ISLOCA quantification should be documented. Document all requirements of the SR.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension IE-C15 IE-C15-01, NOT Closed Discussion: CHARACTERIZE the uncertainty in the initiating Parametric uncertainty for IE This is resolved.
MET, event frequencies and PROVIDE mean values for use in the frequencies is given in H.1.6 as Range There is no impact Associated SR: IE- quantification of the PRA results. Factors (Error Factors) for LOCA IEs on the ILRT C1 and alpha/beta values for gamma Extension Risk (MET), uncertainty Basis for Significance: No discussion of uncertainty distributions. Analysis.
associated with IEs. parameters for IEFT was located in Calculation Files C.10 and H.1.6. This is required to meet SR IE-C15 and is necessary to document the process used to calculate the IE frequencies per SR IE-C1.
Possible Resolution: Provide a discussion of uncertainties (preferably in Calculation H.1.6).
IE-D1 IE-D1-01, NOT Closed Discussion: The DCPP PRA documentation is not written in References to PLG-0637 as the basis This was a MET, . manner that facilitates PRA applications, upgrades, and peer have been taken out and information documentation issue Associated SRs: review. In great part, this is probably due to the fact that this has been included in the new and is resolved.
IE-D2 documentation heavily references the original DCPP PRA calculation revisions for system There is no impact (NOT MET), IE-D3 documents, especially PLG-0637. This mak~s it difficult to notebooks, initiating event notebooks, on the ILRT (NOT MET), AS-C1 understand details of the model, difficult to confirm that the event tree notebooks, and other PRA Extension Risk (NOT MET), SY-C1 model addresses PRA requirements, and difficult to update and development documentation. Analysis.
(NOT MET), DA-E1 use it for PRA applications. This finding applies to elements IE, (NOT MET), QU-F1 AS; SY, DA, QU, LE, IFPP, IFSO, IFSN, and IFQU.
(NOT MET), LE-G1 (NOT MET), IFPP- Basis for Significance: The DCPP PRA documentation is not 81 (NOT MET), written in manner that facilitates PRA applications, upgrades, IFS0-81 (NOT and peer review. In great part, this is probably due to the fact MET), IFSN-A5 that this documentation heavily references the original DCPP (MET), IFSN-81 PRA documents, especially PLG-0637. This makes it difficult to (Nor MET), IFQU- understand details of the model, difficult to confirm that the 81 (MET) model addresses PRA requirements, and difficult to update and use it for PRA applications.
Possible Resolution: In the summary document, Calculation file B.1, describe each aspect of the model development, referencing supporting calculations. And, these supporting calculations should provide additional details of the analysis to the level of documentation to demonstrate that all SRs are met.
This approach, in essence, suggests abandoning the heavy reliance on PLG-0637, which does not meet many requirements of the PRA Standard and creating a set of "living" PRA documents that fully meet these requirements. This would not only eliminate the need to "patch" deficiencies of the PLG-0637 Revision 3 Page 43of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension documentation but also provide a means to much more easily document model updates - thereby facilitating use of the model and document in future risk applications.
IE-D2 IE-02-01, NOT Closed Discussion: DOCUMENT the processes used to select, group, Re IE-A3: Section 4.2.1 of Cale B.1 This is resolved.
MET, and screen the initiating events and to model and quantify the Revision 1 references to Cale H.1.6, There is no impact Associated SRs: initiating event frequencies, including the inputs, methods, and which discusses use of plant-specific on the ILRT IE-A3 (MET), IE- results. For example, this documentation typically includes: experience. Extension Risk A 10(MET), (a) the functional categories considered and the specific Analysis.
IE-B3(CC-ll), IE- initiating events included in each Re IE-A 10: Section 6.2 of Cale B.1 C2(MET), IE- Revision 1 describes the potential for C3(MET), IE- Basis for Significance: IE-A3: CALCULATION FILE B.1 the loss of Instrument Air system as a C4(MET), IE-CB should reference Tables H1 .6-5, 6, 7, and B to demonstrate dual unit initiator.
(MET), IE-C9 compliance with SR IE-A3.
(MET), IE-C10 Re IE-B3: The Total Loss of (MET), IE-C12 IE-A 10: The DCPP PRA documentation does not describe the Condensate Flow initiator was moved (MET), IE-D1 (NOT potential for the loss of IA as a dual Unit initiator. from PLMFW to TLMFW as MET), documented in Table 4.4 of Cale B.1 documentation IE-B3: Table 4-3 of Calculation File B.1: indicates that the Revision 1. Cale H.1.6 Revision 8 also TOTAL Loss of Condensate Flow was subsumed into the reflects this change.
Partial Loss of Feedwater initiator. This is inappropriate. DCPP PRA personnel agreed and indicated that this is an editorial Re IE-C2: In Attachment 2 of Cale H.1.6 error. This should be corrected. Revision 8 clearly states "freeze date" for the Unit 2 IE data.
IE-C2: Table H.1.6-5 of Calculation File H.1.6 states that the Unit 1 IE data is updated through March Re IE-C3: Recovery actions credited in 31, 2009; however, no "freeze date" is provided for the Unit 2 IE the system fault trees used for initiating data. This date should be provided. events (e.g., Top Event AI for loss of the ASW or Top Event ex for loss of all IE-C3: Credited recovery actions should be documented. CCW system) are documented in Success Criteria section of the system IE-C4: Calculation File H.1.6 does not provide details notebooks such as D.2.6 for the ASW associated with generation of mean and uncertainty parameters system and D.2.7 for the CCW system.
associated with the generic data (from NUREG/CR-692B) nor does it provide any details on the Bayesian calculations. This Re IE-C4: Tables H.1.6-2 and H.1.6-8 information should be documented (preferably in Calculation provide details of the distribution H.1.6) in order to facilitate future updates. parameters associated with the generic data, DCPP experience, and Bayesian IE-CB, IE-C9, IE-C10, and IE-C11: There updated results.
is insufficient documentation describing the construction of the
!EFT. This includes a lack of documentation regarding the Re IE C-8, IE-C9, IE-C10, IE-C11: IE treatment of CCF, how the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and 365 day exposure fault trees are discussed in detail in the Revision 3 Page 44of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension intervals are factored into the model, the success criteria used applicable system notebooks (i.e for for the IEFT, and the use of plant specific information in the Loss of CCW initiator, Cale D.2.7).
assessment of recovery actions used in the IEFT. CCFs are discussed in H.1. Recovery actions are discussed in C.8. Cale 8.1 IE-C12: A detailed discussion comparing the DCPP PRA IE discusses the System Initiator frequencies with generic data sources and explaining Quantification Methodology in Section differences is not documented. This is required to demonstrate 7.2.4.
r that SR IE-C12 is met.
Re IE-C 12: Section H.1.6. 7 of Cale Possible Resolution: Revise documentation to address the H.1.6 Revision 8 discusses comparison above issues. of the DCPP plant specific IE freguencies with generic data.
AS-B3 AS-83-01, NOT Closed Discussion: This .SR states, "For each accident sequence, A new system notebook, 1.1 Revision 0 This is resolved .
MET, . IDENTIFY the phenomenological conditions created by the was created to document the review of There is no impact Associated SRs: accident progression. phenomenological conditions for all on the ILRT AS- 83 (NOT Phenomenological impacts include generation of harsh initiating events for their impacts on the Extension Risk MET), SY-A18 environments affecting temperature, pressure, debris, water success of the system or function. Analysis.
(MET), SY- A21 levels, humidity, etc. that could impact the success of the (MET), SY-A23 system or function under consideration ... " Based on this review, the following (MET), SY- 814 model changes were made.
(MET), Basis for Significance: Based on a review of accident Credit was conservatively removed for phenomenological sequence documents, there does not appear to be a review of the Instrument Air System (IA) for Main conditions created phenomenological conditions created by each accident Steam- Line Break and Feedwater-Line by accident sequence. Environmental Qualification (EQ) Program Break (Outside of Containment) progressions documentation was provided, however, there may be non- initiators in the PRA model as their safety-related components that are affected by an accident impacts could not be verified.
sequence that were not reviewed/included for the accident impact on the functionality of the component. Credit was also removed for the operator action to make-up to the Possible Resolution: Include a sequence level review of RWST in the event of an Interfacing phenomenological conditions and include those that affec~ the System LOCA (ISLOCA) due to success of systems/functions in the accident sequence potentially high radiation conditions in analyses. areas that operators need to enter to eerform necessa~ actions.
AS-B7 AS-B7-01, Closed Discussion: This SR requires the modeling of time-phased Current time phased recovery in Section This was a MET, time-phased dependencies. G.4.1.1 of Cale G.4 uses correct battery documentation issue dependencies depletion times. Section D.2.1.2.4.1 of and is resolved.
Basis for Significance: Time-phased dependencies were Cale D.2.1.2 Revision 1O was revised to There is no impact found to be modeled in the accident sequences (e.g., AC power correct inconsistency between Cale G.4 on the ILRT recovery and DC battery depletion). However, the and D.2.1.2. Extension .Risk documentation has inconsistencies that need to be resolved. Anallsis.
Revision 3 Page 45of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension One example of an inconsistency is that the battery depletion time in documents G.4 and D.2.1.2 are not the same (5.75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br /> vs.12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />).
Possible Resolution: Ensure that PRA documentation reflects the actual times used in the model and that PRA documentation is consistent.
AS-C2 AS-C2-01, NOT Closed Discussion: This SR requires the documentation of processes Documentation related finding This was a MET, used to develop accident sequences. associated with accident sequence documentation issue Documenting documentation. and is resolved.
processes used to Basis for Significance: AS-A11-01 and AS-87-01 identify Refer to disposition for F&Os AS-A11- There is no impact develop accident issues related to the documentation of the accid~nt sequence 01 and AS-87-01. on the ILRT sequences analyses. Extension Risk Possible Resolution: Improve the accident sequence Analysis.
documentation to accurately reflect what is modeled.
SC-A1 SC-A1-01, NOT Closed Discussion: This SR states "USE the definition of "core The definition of core damage . This is resolved.
MET, damage" provided in Section 1-2 of this Standard. If core dependent on collapsed water level was There is no impact Associated SR: SC- damage has been defined differently than in Section 1-2, (a) removed from the documentation. on the ILRT A2 (NOT MET), IDENTIFY any substantial differences from the Section 1-2 MAAP runs were updated using the Extension Risk definition of core definition (b) PROVIDE the bases for the selected definition." core damage definition of > 1800°F Analysis.
damage peak fuel temperature.
Basis for Significance: Based on the information in E.16, Revision 0, two definitions of Core Damage are used in the Prior to this update, core uncovery was DCPP Internal Events. The first definition, Peak Node used as the end point in the timing temperature >1800°F is a valid success criterion, and meets the analysis for the HRA. The use of core definition in Section 1-2 of the Standard. However, the second uncovery vs. peak clad temperature of criterion of "the time until the water level is collapsed below the 1800°F results in a slightly conservative top of active fuel" is not a valid definition since the definition of time available for the HFE. Converting Core Damage as written in Section 1-2 requires the the collapsed water level uncovery of consideration of uncover and heat-up, and this definition does fuel criteria to Peak Control not consider heat-up. Additionally, it is not valid to have two Temperature (PCT) of 1800°F would not separate definitions for the same end state. adversely affect the timing requirements.
Possible Resolution: Remove the second definition of Core Damage, and do all analyses and timings using the Peak Node tem~eratures >1800°F.
SC-A4 SC-A4-01, NOT Closed Discussion: This SR states "IDENTIFY mitigating systems that Cale B.1 was revised to include an This is resolved.
MET, are shared between Units, and the manner in which the sharing evaluation of two shared system Diesel There is no impact shared systems is performed should both Units experience a common initiating Fuel Oil (DFO) and Instrument Air (IA) on the ILRT between Units event (e.g., LOOP)." systems in Section 6.2 of ~evision 1. Extension Risk Anal sis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review--Facts and Observations SR 2009 ASME/ANS Status Impact on ILRT Finding/Observation Disposition Cat II Requirement Extension Basis for Significance: A review of the documentation did not reveal where shared systems were identified and discussed with respect to how they were credited in dual Unit scenarios.
Discussion with DCPP personnel identified that there are not many shared systems at DCPP and they are not typically credited. However, the identification of which systems are shared between the Units, and how they are credited is not documented anywhere. For example, no discussion on the DG Fuel Oil transfer system is provided, although it is a known shared system. Therefore it is not possible to verify that a shared system is not inadvertently credited in the analyses during dual Unit scenarios.
Possible Resolution: Document which systems in the PRA are shared systems at DCPP, and discuss how they are credited in the Internal Events PRA, including how they are credited during dual Unit initiators. Verify that the shared systems are modeled consistent with their availability during dual Unit initiators.
SC-AS SC-AS-01, NOT Closed Discussion: This SR states: SPECIFY an appropriate mission PG&E reviewed the fire and internal This is resolved.
MET, time for the modeled accident sequences. For sequences in events accident sequences, success There is no impact
_mission time which stable plant conditions have been achieved, USE a criteria and associated thermo-hydraulic on the ILRT minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Mission times for individual (TH) runs for various non-LOCA and Extension Risk SSCs that function during the accident sequence may be less LOCA sequences (MAAPs 13-04, 13- Analysis.
than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> as long as an appropriate set of SSCs and 06, 13-07, 13-08) to verify that a stable operator actions are modeled to support the full sequence plant condition could be achieved for a mission time. For example, if following a LOCA, low pressure minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The injection is available for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, after which recirculation is review included verification whether required, the mission time for LPSI may be 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and the individual SSCs can support the mission time for recirculation may be 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />. For sequences minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> as in which stable plant conditions would not be achieved by 24 currently credited in the PRA models.
hours using the modeled plant equipment and human actions, PERFORM additional evaluation or modeling by using an The review concluded that for scenarios appropriate technique. Examples of appropriate techniques where a stable hot shutdown condition include: was desired, the Condensate Storage (a) assigning an appropriate plant damage state for the Tank (CST) inventory would be sequence; depleted in less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> unless (b) extending the mission time, and adjusting the affected additional secondary inventory was analyses, to the point at which conditions can be shown to made available. The PRA model at the reach acceptable values; or time of the internal events peer review (c) modeling additional system recovery or operator actions for did not contain the equipment or the seguence, in accordance with reguirements stated in the operator actions necessary to assess Revision 3 Page 47of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status _ Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Systems Analysis and Human Reliability sections of this whether a stable state was reached Standard, to demonstrate that a successful outcome is using Auxiliary Feedwater (AFW) achieved. cooling along. For the Internal Events model, long-term AFW cooling is Basis for Significance: Notebook E.16, Revision 0 states "A cr~dited only if the Closed Loop 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time is assumed sufficient to obtain a stable Residual Heat Removal (RHR) cooling plant condition, either hot standby or cold shutdown after an is not available. In the Fire PRA, only initiating event has occurred." This SR requires verification-that long-term AFW cooling is credited; a safe, stable endpoint is obtained, and specifies using a Closed Loop RHR cooling is not minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. No discussion could be credited.
found that verified that each accident sequence actually reached a safe stable state at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> could be identified. For Small LOCA (SLOCA) sequences, a RCS leakage and injection by itself.is Possible Resolution: Each accident sequence needs to be not sufficient to cooldown and bring the reviewed to ensure that the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time is valid to RCS pressure to the RHR entry reach a safe stable state, and this review needs to be condition. These sequences require documented. For any accident sequence that is identified that AFW cooling to reduce the RCP does not reach a safe, stable state at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the time to pressure and temperature prior to reach a safe, stable state needs to be identified, and the model depletion of the Refueling Water updated accordingly. If R_HR entry conditions are met prior to 24 Storage Tanks (RWST) and switch-over hours, then entry into shuf down cooling (use of RHR for long to the RHR Containment Recirculation.
term heat removal) needs to be included in the accident The results of the TH runs for various sequence, or a valid reason for not modeling RHR needs to be sizes of small LOCA show that the provided. existing CST volume is sufficient to support such secondary cooling function. Therefore a supplemental secondary inventory supply within 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time is not required to mitigate Internal Events or fire induced SLOCA sequences.
For Medium and Large LOCA (MLOCA and LLOCA) sequ~nces, the TH runs indicate that the RCS is rapidly depressurized and the additional cooling via the AFW is not necessary.
- Therefore a make-up to the CST within 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time is not required to mitigate MLOCA or LLOCA sequences. _
Revision 3 Page 48of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension As discussed above, supplemental secondary-inventory is required for non-LOCA scenarios in order to maintain a stable hot shutdown condition for a minimum of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The Fire and Internal Events models are updated to incorporate .additional inventory requirements by adding the equipment necessary to align alternate AFW water supply sources and an operator action based on the existing Operating Procedures. (AR PK 10-01 and OP D-1:V).
For LOCA scenarios, Residual Heat Removal (RHR) is required and modeled within the FPRA to reach a stable end state. In order to ensure that a stable end state is reached in the fire analysis, the FPRA model was updated to include a required supplemental water supply to AFW for non-LOCA scenarios.
SC-A5 SC-A5-02, NOT Closed Discussion: This SR states: SPECIFY an appropriate mission Reviewed success criteria and verified This is resolved.
MET, time for the modeled accident sequences. For sequences in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is acceptable Looked at MAAP There is no impact mission time which stable plant conditions have been achieved, USE a runs. on the ILRT minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Mission times for individual Extension Risk SSCs that function during the accident sequence may be less E.16 Rev 1 Documentation revised to Analysis.
than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, as long as an appropriate set of SSCs and include some text of this review:
operator actions are modeled to support the full sequence MAAP Cales were reviewed (MAAP 13-mission time. For example, if following a LOCA, low pressure 06, 13-07, 13-08) and run past 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> injection is available for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, after which recirculation is to verify that a safe stable state was required, the mission time for LPSI may be 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and the achieved. RHR entry conditions were mission time for recirculation may be 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />. also reviewed for the applicable accident sequences.
For sequences in which stable plant conditions would not be achieved by 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> using the modeled plant equipment and For LOCA scenarios, Residual Heat human actions, PERFORM additional evaluation or modeling by Removal (RHR) is required and using an appropriate technique. Examples of appropriate modeled within the FPRA to reach a techniques include: stable end state. In order to ensure that a stable end -state is reached in the fire Revision 3 Page 49of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension (a) assigning an appropriate plant damage state for the analysis, the FPRA model was updated sequence; . to include a required supplemental (b) extending the mission time, and adjusting the affected water supply to AFW for non-LOCA analyses, to the point at.which conditions can be shown to scenarios.
reach acceptable values; or (c) modeling additional system recovery or operator actions for A new Top Event "AWR" representing the sequence, in accordance with requirements stated in the long term availability of the AFW supply Systems Analysis and Human Reliability sections of this water is modeled. Associated event Standard, to demonstrate that a successful outcome is trees (i.e., Fl RELTREE and SLTREE) achieved. and their split fraction rules and event.
Basis for Significance: Several accident sequences were Update: A new Top Event "AWR" identified where RHR entry conditions were met prior to representing long term availability of the 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, but RHR was not required for success in the accident AFW supply water is modeled.
sequence. If RHR is not questioned, then the end state may not Associated event trees (i.e., LATETREE
- be stable since heat removal via the SGs will be diminished as and SLTREE) and their split fraction decay heat lowers, and RHR will be required to maintain rules and event tree structures were temperatures long term. modified to incorporate the new top event. PRA Cales C.4.2 and E.2 were Possible Resolution: Ensure that all accident sequences are updated to reflect the above changes.
modeled to the actual safe, stable end state. If RHR entry conditions are met prior to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, then entry into shut down cooling (use of RHR for long term heat removal) needs to be included in the accident sequence, or a valid reason for not modeling RHR needs to be provided.
SC-83 SC-83-01, NOT Closed Discussion: SR SC-83 states "When defining success criteria, Additional MAAP runs were performed This is resolved.
MET, USE thermal/hydraulic, structural,. or other analyses/evaluations to define new LOCAbreak size (MAAP There is no impact Associated SRs: appropriate to the event being analyzed, and accounting for a 13-03 Rev 0). on the ILRT SC- 81 (CC-11), lE- level of detail consistent with the initiating event grouping (HLR- Extension Risk 84 (MET), 1E-C1 IE-B) and accident sequence modeling (HLR-AS-A and HLR- SLOCA < 2.75" Analysis.
(MET), 1E-C13 (CC- AS-B)." 2.75" < MLOCA < 6" I/II), LOCA break LLOCA > 6" sizes Basis for Significance: The current success criterion for LOCAs is based on plant capabilities and system responses. SLOCA and MLOCA frequencies were The specific break sizes associated with the transitions between updated and documented in H.1.6 Rev the LOCA definitions have not been adequately justified. Based 8.
on PRA12-14, several MAAP analyses have been performed to verify the equipment needed to successfully respond to the Cale E.16 Revision 1 (Success Criteria) break size (runs are done for 1, 2, 3, 5, 7, 12, and 16 breaks), incorporated these changes.
but no runs could be found to validate the transition points between the break sizes. Per the requirement, thermal hydrauli~ evaluations are required at a level of detail to support Revision 3 Page 50of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension the definitions/break sizes so that the appropriate initiating event frequencies can be determined.
Possible Resolution: Perform additional thermal hydraulic analyses to determine the actual LOCA break sizes where the success criteria changes (e.g., break size above which Charging is not sufficient, break size where Containment Spray is first required, etc.). Once the new break sizes are determined, determine the correct Initiating Event frequency associated with the newly defined break ranges.
SC-83 SC-83-02, NOT Closed Discussion: This SR states "When E.16 updated (Revision 1) to include This is resolved.
MET, defining success criteria, USE thermal/hydraulic, structural, or ISLOCA MAAP Calculation with a 2.75" There is no impact Associated SR: SC- other analyses/evaluations appropriate to the event being break for success criteria. To be on the ILRT 81 (CC-II), verify analyzed, and accounting for a level of detail consistent with the consistent with the updated SLOCA Extension Risk Small Loss of initiating event grouping (HLR-IE-B) and accident sequence success criteria (previously a break size Analysis.
Cooling Accident modeling (HLR-AS-A and HLR-AS-B)." < 2.0", but now< 2.75"), the lower break (SLOCA) size via size limit for ISLOCA of 2.75" was MAAP Basis for Significance: In Calculation E16, Revision 0, (which analyzed.
is not referenced anywhere in the discussion of ISLOCAs in the body of the E16 Calculation), the MAAP analysis referenced for According to MAAP case HR-OL-01 b, the success criteria validation is based on an 8 inch ISLOCA, the flow rate from a -2.75" break at 570 F and not on a 2 inch ISLOCA. The use of an 8 inch break size is immediately following a LOCA is inappropriate because the required equipment and timing approx. 4660 GPM (MAAP break associated with responding to a 2 inch break would be flowrate of 166381 LB/HR with density significantly different than the required equipment and timing of 5.9478 lb/gal).
associated with an 8 inch break.
For a 2" break, case HR-OL-01 a, the Additionally, the E16 Calculation implies that the RHR pumps break flowrate is approx. 2470 GPM are unavailable due to a lack of suction from the sump, but the (MAAP break flowrate of 880045 L13/HR ISLOCA Calculation (which is not referenced anywhere in the with density of 5.9478 lb/gal).
E16 Calculation), C.4.7 Revision 8, makes an assumption that the RHR pumps would be unavailable since they would be Top Event SM was changed to reflect subjected to extreme pressures/temperatures. The assumption 2.75" break size and leak rate. Sections that the RHR pumps would be unavailable during all ISLOCA E.10.4.3 and E.10.5.3 of Cale E.10 sequences is overly conservative compared to industry norms Revision 10 reflects this change.
for modeling ISLOCAs, and compared to the modeling at similar power plants. This assumption should be re-evaluated to be more realistic and in-line with current industry practices.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Possible Resolution: Perform additional MAAP analyses of smaller ISLOCA sizes to verify that the success criteria specified is valid, and update as appropriate.
SC-84 SC-84-01, MET, Closed Discussion: This SR states "USE analysis models and The success criteria from the design This is resolved.
define Large Break computer codes that have sufficient capability to model the basis analysis is consistent with the There is no impact Loss of Coolant conditions of interest in the determination of success criteria for MAAP based success criteria and a on the ILRT Accidents CDF, and that provide results representative of the plant. A review of this non-MAAP based Extension Risk (LBLOCAs) qualitative evaluation of a relevant application ot'codes, models, accident analysis shows that the current Analysis.
or analyses that has been used for a similar class of plant (e.g., PRA model success Criteria is Owner's Group generic studies) may be used. USE computer appropriate.
codes and models only within known limits of applicability."
Basis for Significance: The MAAP code is used in support of all LOCA break sizes at DCPP. However, the MAAP code has known limitations with respect to its modeling of large LOCAs, and is not a valid code to use for determining success criteria for LBLOCAs. Although the limitations of the MAAP code are included in the MAAP 4 Users Guide, they are not summarized anywhere in the DCPP analyses, so it is not clear that the limitations of the code were considered when developing the DCPP success criteria.
Possible Resolution: Define the success criteria for LBLOCAs based on the criteria in the FSAR or on a specific analysis using a computer code that is capable of evaluating LBLOCAs such as CENTS, RETRAN, or RELAP.
SC-84 SC-84-02, MET, Closed Discussion: This SR states "USE analysis models and Conditions in Table E.16-3, and the MC This is resolved.
AlWT definition computer codes that have sufficient capability to model the top event of Attachment 4 of Cale E.16 There is no impact conditions of interest in the determination of success criteria for (Revision1) were updated to be on the ILRT CDF, and that provide results representative of the plant. A consistent with the current model, and Extension Risk qualitative evaluation of a relevant application of codes, models, Attachment 8. The basis for the change Analysis.
or analyses that has been used for a similar class of plant (e.g., in Unfavorable MTC threshold from -7 to Owner's Group generic studies) may be used. USE computer -5.5 is explained in the Rev 7 notes of codes and models only within known limits of applicability." E.11 which updates "the MTC issue based on new information for cycle 10, Basis for Significance: The discussion in E.16, Revision 0, which begins on Unit 1 in March, 1999.
associated with the Anticipated Transient Without Trip (ATWT) The fuel constitution for cycle 10 is scenarios of concern and the success criteria for A TWT is not substantially different than cycle 9 with consistent. Table E.16.2 identifies 12 AlWT scenarios, but the respect to the value being used for top success criteria developed does not clearly consider each of event MC. The new MC value is .01,
- these AlWT scenarios. *Section E.16.5.6 states that the using a threshold of -5.5 pcm per Revision 3 Page 52of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension success criteria for AlWT is developed for the following criteria degree F instead of-7 pcm per degree and the success criteria is discussed in detail in Attachment 8: F. This is consistent with new analysis and the cycle 10 fuel loading AlWT 1 - Turbine Trip Successful, Power Level> 80%, MTG< characteristics to ensure that RCS
-7 pcm/For Turbine Trip Successful, Power Level< 80%, MTG pressure does not exceed 3200 pounds.
> -7 pcm/F The system transient analysis, reactor AlWT 2 -Turbine Trip Successful, Power Level> 80%, MTG> and Westinghouse fuel engineers have
-7 pcm/F been consulted and documentation has AlWT 3 - Turpine Trip Successful, Power Level< 80%, MTG< been provided from Westinghouse to
-7 pcm/F PG&E concurrent with this change." -
ATWT 4-Turbine Trip Fails AR0445958 But Attachment 8 is not based on these criteria. Attachment 8 evaluates:
- 1. Turbine trip within 30 seconds; 100% power; MTG< -5.5 pcm/°F.
- 2. Turbine trip within 30 seconds; 80% power; MTG > -5.5 pcm/°F.
- 3. Turbine trip within 30 seconds; 100% power; MTG> -5.5 pcm/°F.
- 4. Turbine trip within 1 minute; 80% power; MTG < -5.5 pcm/°F.
- 5. No turbine trip.
- 6. Main feedwater lost.
- 7. Turbine trip and reactor coolant pump coastdown.
None. Core melt assumed if these events combined with a failure to trip.
Calculation File C.4.6, Revision 9, states that the basis for the MTG of-7pcm/F could not be identified, but no definitive answer as to the basis for the -5.5 was provided either. The actual criteria for DCPP specific AlWT conditions needs to be defined, justified, and evaluated for system response required to mitigate theATWT.
Possible Resolution: Determine what the DCPP AlWT definition is (DCPP specific pcm/F values) and determine the actual system level success criteria required to mitigate the various AlWT accident sequences.
SC-85 SC-85-01, MET, Closed Discussion: This SR states "USE analysis models and The impact of not crediting feed and This is resolved.
crediting PORVs for computer codes that have sufficient capability to model the bleed for small LOCA scenarios was There is no impact Revision 3 Page 53of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension depressurization conditions of interest in the determination of success criteria for determined to be approximately 1E-8/yr on the ILRT when AFWnot CDF, and that provide results representative of the plant. A CDF (Reference 36). Although the risk Extension Risk available qualitative evaluation of a relevant application of codes, models, benefit for this credit is' not significant, it Analysis.
or analyses that has been used for a similar class of plant (e.g., could contribute some risk benefit in Owner's Group generic studies) may be used. USE computer certain configurations, such as an AFW codes and models only within known limits of applicability." pump being inoperable. Therefore, the DCPP PRA model has been updated to Basis for Significance: In Calculation File 8.1, Revision 0, ensure that small LOCA scenarios there is a documentation of a comparison of success criteria for correctly credit the use of feed and DCPP to the success criteria at similar plants. One outlier was bleed when appropriate.
noted. This outlier is that the success criteria for a small LOCA without AFW available is assumed to result in core damage at
References:
- 1. PG&E PRA Calculation DCPP, but the use of PORVs to depressurize and cooldown is File PRA 13-13, Rev 0, "Small LOCA credited at similar plants. The basis for not crediting the use or Feed and Bleed" PORVs at DCPP for depressurization and cooldown is not documented, and discussions with plant PRA personnel did not identify any reason that the PORVs could not be credited at DCPP. Since the PORVs appear to be a valid option at DCPP, they should be credited in these accident sequences.
Possible Resolution: Update the accident sequence progression for Small LOCAs and include credit for using the PO RVs to depressurize and cooldown for those sequences where AFW is not available, or justify not crediting it. If the Emergency Operating Procedure (EOP) network uses the PORVs for this application, it should be credited in the PRA.
SC-C2 SC-C2-01, NOT Closed Discussion: The process followed for developing the success Removed the collapsed water level This is resolved.
MET, not clear
- criteria for each accident scenario is not clearly documented. definition of Core Damage and now use There is no impact process of For example, there are two definitions of core damage used, the Peak Node temperature of greater than on the ILRT developing the basis for the timing of human actions is not clear (two criteria 1B00°F. Extension Risk success criteria used - but nothing showing why both are acceptable), the Analysis_.
limitations of the software used for the success criteria is not The use of collapsed water level is documented, etc. conservative for HRA timing evaluation.
In addition, the conse.rvatism is limited Basis for Significance: The overall process used to develop due to the short amount of time the DCPP success criteria, including identification of the between uncovery of active fuel and supporting engineering bases, inputs, methods, and results is peak clad temperature of 1800°F.
not clearly documented. Particular items noted include:
Limitations of computer codes There are two definitions of core damage used in the DCPP- addressed in SC-84-01. Impact of and there should only be one. (See F&O SC-A1-01)
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension ATWT success criteria addressed in The calculations used to support the success criteria for various SC-84-02.
accident sequences is not always clearly identified - for example, the basis for the A TWT success criteria is not clear, and the discussion in the E.16 Report uses two difference criteria for pcm/F. (See F&O SC-84-02)
The limitations associated with the computer codes used in support of the success criteria are not documented in the DCPP calculations or reports.
The bases for establishing the time available for human actions is suspect since some of the HRAs are based on a core damage of 1800°F, while others are based on a core damage definition of "water below top of active fuel" - the use of 2 different definitions of core damage is incorrect, plus there is no discussion as to when/how it was determined which timing to use for which operator action - should base the time available for all operator actions on the core damage definition of 1800° F peak clad temperature.
Possible Resolution: Update the documentation to specifically address the elements identified in the SC SR. At a minimum, the list provided in SC-C2 should be reviewed, and the applicable items listed in the SR should be clearly documented in the Success Criteria calculation/document.
SC-C3 SC-C3-01, NOT Closed Discussion: This SR states: Document the sources of model PRA Calculation 8.1 (Revision 1) and This was a, MET, uncertainty and related assumptions (as identified QU-E1 and C.10 (Revision 5) documents the documentation issue Associated SRs: QU-E2) associated with the development of success criteria. assumptions and uncertainties and is resolved.
IE- D3 (NOT MET), There is a similar requirement to document sources of associated with each technical elements There is no impact SY- C3 (NOT uncertainty and assumptions for the other elements of the PRA o(different hazard groups. As on the ILRT MED, as well. suggested in this F&O, these Extension Risk Documenting \
documents have been updated by Analysis.
source of Basis for Significance: A review of many of the PRA systematically reviewing PRA uncertainties elements identified that there was not summarization of the development documents (e.g., system sources of uncertainty or assumptions associated with the notebooks, success criteria notebook, individual PRA element. The documentation of these items is event-tree notebooks, etc.).
required by the standard, and these items should be used as the basis for determining which sensitivity studies need to be performed for the PRA.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Possible Resolution: Go through each of the individual PRA element reports and calculations and identify and summarize the sources of uncertainty and the assumptions associated with the element being documented. These sources of uncertainty and assumptions should then be used as the basis for determining what sensitivity studies need to be performed for the DCPP PRA.
SY-A4 SY-A4-01, NOT Closed Discussion: PERFORM plant walkdowns and interviews with DCPP PRA models were prepared by This is resolved.
MET, knowledgeable plant personnel (e.g., engineering, plant industry and in-house experts in 1988. There is no impact walkdown and operations, etc.) to confirm that the systems analysis correctly Per the PRA configuration control on the ILRT interview reflects the as-built, as-operated plant. programs (i.e., TS1.NR3 and AWP E- Extension Risk Basis for Significance: Based on discussion with DCPP PRA 028), DCPP PRA has been updated as Analysis.
personnel, neither plant walkdowns nor interviews with needed to reflect the as-built and as-knowledgeable plant personnel were performed to confirm that operated plant (e.g., review of the the systems analysis correctly reflects the as-built, as- operated procedure changes, design changes, plant. This is required for CC-111111. equipment reliability, etc.).
Possible Resolution: Perform walkdowns and interviews.
The models and their technical )
elements have been continuously refined and/or corrected for errors through their uses in applications.
Many different talk-th roughs of accident scenarios have been performed since the original development of the PRA that confirm the accuracy of the accident response model.
Attachment 1 to HRA Calculation G.2, "Human Action Analysis - Failure Likelihood and Range Factor Calculation, Revision 6 dated November 2012 document the operator and training personnel interviews that were conducted the fall of 2012 to review PRA initiators and consider whether any initiators or initiating event categories had been omitted. The similar operator interviews were documented in Attachment 3 of Cale H.1.6 Revision 8.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension In addition, new MAAP runs (documented in PRA12-13 "MAAP HRA Cases") were performed and the human error probabilities (HEPs) were updated to reflect the 'new timing. It is not likely the current models including Internal Events and Fire still contain gross model errors or assumptions which result in significant deviation from the as- builUas-operated plant condition or configuration.
Numerous walkdowns performed for the Fire and Seismic PRAs have been performed within the last 5 years and no evidence that the systems analysis differs from the as-built, -as-operated lant was noted.
SY-A16 SY-A16-01, NOT Closed Discussion: In the system model, Pre-initiators review was performed and This is resolved.
MET, INCLUDE Human Factors Engineering (HFEs) that cause the pre- initiator HFEs were identified in G.1 There is no impact Associated SR: / system or component to be unavailable when demanded. Rev 2. All newly identified miscalibration on the ILRT HR-A1 (NOT These events are referred to as pre-initiator human events. and misposition HFEs were included in Extension Risk MET), (See also Human Reliability Analysis, 2-2.5.) the PRA model. Analysis.
modeling of pre-initiators Basis for Significance: Review of the AFW system fault tree indicates that no pre-initiator HFEs are modeled. Given that the AFW is a standby system, at least one pre-initiator HFE (e.g.,
failure to restore pump after maintenance or testing) is expected to be in the model. Related SR HR-A1 and F&O HR-A1-01.
Possible Resolution: Either model the pre-initiator and others like it in other standby systems and trains or justify and document whi'. it is not needed.
SY-A20 SY-A20-01, NOT Closed Discussion: INCLUDE events representing the simultaneous Simultaneous unavailability of This was a MET, simultaneous unavailability of redundant equipment when this is a result of redundant safety- related equipment documentation issue unavailability of planned activity (see DA-C14). due to planned activity is excluded from and is resolved.
redundant SSCs consideration. This is consistent with TS There is no impact Basis for Significance: Per discussion with DCPP PRA 3.0.3 restrictions for safety-related on the ILRT personnel, simultaneous unavailability of redundant safety- equipment. Extension Risk related eguiEment due to Elanned activit~ is excluded from Anal~sis.
(
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Stat~s Finding/Observation Disposition Impact on ILRT Cat II Requirement Extension consideration. This is consistent with Technical Specification Examination_ of the 12-week rolling (TS) 3.0.3 restrictions for safety-related equipment. This MOW matrix at DCPP did not identify assumption is. reasonable. However, this approach is not any planned, repetitive activity which documented. In addition, this assumption is probably not would cause coincident unavailability appropriate for non-safety equipment, whose unavailability is due to maintenance for redundant not restricted by TS. An example of this is multiple IA equipment (both intra-system and compressors concurrently out of service. intersystem). Calculation or modeling of coincident maintenance unavailability Possible Resolution: Either account for allowed simultaneous was therefore unnecessary.
of redundant equipment or document justification of it is not modeled. The above justification was included in Section H.1.2 of PRA Calculation H.1 Revision 1.
SY-A23 SY-A23-01, Closed Discussion: DEVELOP system model nomenclature in a The AFW basic events were renamed to This is resolved.
MET, consistent consistent manner to allow model manipulation and to represent be consistent with system/component There is no impact system model the same designator when a component failure mode is used in failure mode nomenclature used on the ILRT nomenclature multiple systems or trains. throughout the PRA model. ~xtension Risk Analysis.
Basis for Significance: Based on discussion with DCPP PRA The changes are documented in PRA personnel, consistent system/component failure mode Cale E.2 Rev 12.
- nomenclature is used in all system notebooks, except the AFW notebook.
This occurred as a result of a modeling oversight.
Possible Resolution: Correct condition for AFW and document system/component failure model nomenclature.
SY-B3 SY-B3-01, NOT Closed Discussion: ESTABLISH common Common Cause failure of Safety Inject This was a MET, cause failure groups by using a logical, systematic process that (SI) system components is modeled and documentation issue CCF groups considers similarity in common cause groups are defined and is resolved.
(a) service conditions within the model. The review comment There is no impact (b) environment is that the common cause groups are on the ILRT (c) design or manufacturer not documented in the system Extension Risk (d) maintenance notebook. Analysis.
JUSTIFY the basis for selecting common cause component Documentation was revised for all groups. systems to specifically list the common cause that is modeled.
Candidates for common cause failures include, for example:
(a) motor-operated valves (b) pumps (c) safety-relief valves Revision 3 Page 58of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (d) air-operated valves (e) solenoid-operated valves (f) check valves (g) diesel generators (h) batteries (i) inverters and battery charger U) circuit breakers Basis for Significance: No documentation was found for the Common Cause Failure (CCF) group definition. for the SI top event. DCPP PRA staff indicated that this is a known gap. For other systems, CCF groups appear to generally be defined inside of RISKMAN files but not in the documentation.
Possible Resolution: Close gaps in CCF group definitions and basis in all system notebooks.
SY-88 SY-88-01, NOT Closed Discussion: IDENTIFY spatial and environmental hazards that The IEPRA incorporated the results of This was a MET, may impact multiple systems or redundant components in the room heat-up calculations and system documentation issue Associated SR: SY- same system, and ACCOUNT for them in the system fault tree success dependency on HVAC. The* and is resolved.
814 (MET), spatial or the accident sequence evaluation.* results of room heat-up calculations There is no impact and environmental provide a basis for operator action on the ILRT hazards impacting Basis for Significance: No discussion of room heatup and timing or to demonstrate that a loss of Extension Risk multiple SSCs dependence on HVAC could be found in the sampled system cooling would not impact modeled Analysis.
notebooks. No discussion of spatial and environmental SSCs. A SSC requiring cooling is dependencies could be found in the sampled system considered failed if the cooling is not notebooks. After discussions with DCPP personnel, we available due to failure of the HVAC identified additional documentation not provided earlier that was SSC and if operators fail to establish available to potentially address these gaps. However, the alternate ventilation/cooling within the SN8s do not have this discussion nor references and therefore time estimated based on the room heat-the PRA does not meet this SR. up calculations.
Possible Resolution: Provide a discussion of spatial and Documentation of the effects of room environmental dependencies in each system notebook. heatup is available and references plant Incorporate any impacts from these considerations on SSCs in specific room heatup calculations.
the system notebooks documentation as well in the models. These results are not reiterated within the individual system notebooks but system modeling is consistent with the room heatue calculations.
SY-810 SY-810-01, Closed Discussion: MODEL those systems that are required for PG&E performed a systematic This is resolved.
NOT MET, initiation and actuation of a system. In the model quantification, evaluation of modeling of permissives There is no impact INCLUDE the ~resence of the conditions needed for automatic and interlocks in the Internal Events on the ILRT Revision 3 Page 59of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension modeling of actuation (e.g., low vessel water level). INCLUDE permissive PRA (IEPRA) and documented in PRA Extension Risk permissive and and lockout signals that are required to complete actuation Cale 14-01, Rev 1. Analysis.
interlocks logic. The evaluation includes identification and modeling of (1) those systems that Basis for Significance: The treatment of permissive and are required for initiation and actuation interlocks could not be located in the system notebooks. of a system, (2) the conditions needed for automatic actuation (e.g., low vessel Possible Resolution: Model permissive and interlocks and water level), and (3) control features document in system notebooks. (e.g.;protection and control permissive, lock-out signals, and component interlocks that are required to complete actuation logic, as required in the Supporting Requirement (SR) of Section 2 of AMSE/ANS RA~SA-2009 Standard.
Based on the results of the review, permissive and interlocks of the following SSCs are included in the Internal Events model; 8701/8702, 8982A/B, and 9003A/B, 8804A/B.
SY-815 SY-815-01, Closed Discussion: INCLUDE operator interface dependencies To address this F&O, the DCPP This is resolved.
NOT MET, across systems or trains, where applicable. procedures were reviewed to identify There is no impact intersystem realignment and calibration activities for on the ILRT operator Basis for Significance: A review of several system notebooks all systems and components including Extension Risk dependency indicate that DCPP did include human actions that had the any dependencies between activities Analysis.
potential to impact multiple trains of a given system and components. This review was (miscalibration) and actions from one system that could impact performed in order to be consistent with the function of another system. the ANS/ASME Standard supporting requirements and is documented in Possible Resolution: Close gap. revision 2 of PRA calculation G.1.
As a result of this review, additional pre-initiator HFEs were identified in standby systems and were quantified using the EPRI HRA Calculator THERP module.
Although pre-initiator dependency across Trains was identified due to misposition and included in the DCPP HFEs, none of the HFEs involved miscalibration across systems or trains.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension SY-C2 SY-C2-01, NOT Closed Discussion: DOCUMENT the systems analysis in a manner SY-A22: 'Cale File E.17 Rev 0 states the This was a MET, that facilitates PRA applications, upgrades', and peer review. following: "No credit is taken for documentation issue Associated SRs: Basis for Significani;e: SY-A22: Based on discussion with component or system operability for and is resolved.
SY- A22 (CC-II), DCPP PRA personnel, credit for system operability is taken only beyond design rated capabilities unless There is no impact SY-81 (MET), SY- if design capabilities are not exceeded. supported by appropriate testing, on the ILRT 83 (NOT MET), This modeling assumption should be documented in the system engineering analysis or operational Extension Risk SY-86 (MET), notebooks. data." Analysis.
SY-87 (CC-II), SY- SY-81: NUREG/CR-5485 for CCF is not referenced in the 89 (MET), SY-811 documentation related to modeling intra-system common cause SY-81: NUREG/CR-5485 for CCF is (MET), failures. now referenced in H.1 Rev 1 documentation SY-86: The need for the HVAC system support is not discussed SY-B6/B9: Room Heat-ups and thermal in the SI system notebook. This and other system notebooks fragilities are explained in E.16.5.8 of should be reviewed and, if appropriate, revised to describe the Success Criteria Notebook. The HVAC dependencies. original analysis for mission time ventilation requirements - Appendix A of SY-87: Success criteria and timing is not discussed in the PLG-0637 was added to E.16. This system notebooks. Success criteria are provided but references document shows that only the SSPS are not provided. For example, a reference or basis for the and the 480V switchgear are vulnerable assumed time for high pressure recirculation of 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> is not to loss of ventilation during the mission provided in the high pressure system notebook. Similarly, no time. All other systems which normally discussion of the potential for and effects of room heat-up in use ventilation systems do not need system notebooks reviewed. This information should be them to operate within the mission time.
documented in the system notebooks. New revisions of these notebooks put the ventilation requirement more SY-89: References need to be added to the system notebooks prominently in the main body under the to describe HVAC dependency. heading, "Support Systems."
SY-811: Gaps were found in the system notebooks regarding Furthermore, these new revisions the discussion of available inventories of air, power, and cooling contain references to PLG-0637 (where to support the mission time. the ventilation requirement is determined).
Possible Resolution: Ensure that all system notebooks address the above issues and that the system models address SY-87: *All system notebooks were these issues appropriately. ., reviewed for mission times and timing success criteria, and the following changes were made:
- The Success Criteria section for E.4 "ECCS high pressure system" Rev10 has been completely rewritten with Revision 3 Page 61 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension references to 6-hour and 18-hour mission times removed. No model change is required since a 24-hour mission time was previously used, and continues to be used.
- D.2.1.2 "125Vvital DC system" Rev10 has the following text added to the Success Criteria section: "A 2-hour mission time is considered sufficient because transfer to the startup power source or the diesel generators is automatic and nearly instantaneous; and in the case that human action is required to restore the 4kV busses, 21 minutes is the time it takes for operators to manually perform the transfer according to the analyses done for ZHEAC1 and ZHEAC2 found in the HRA Calculator Report (Reference 35)."
- References were added to D.2.8 "AMSAC System"
- Cale E.11 Revision 11 - Top Event RS Success Criteria was revised to remove timing criteria and state that the top event is not credited in the current model.
- The success criteria in E.3.4.3 was revised for top events OB, OBS, and PO such that there is no explicit requirement for the PO RVs to remain open for six hours.
- Reference to G.4 Electric Power Recovery Model was added to D.2.1.5 Rev 12 Diesel Generator Systems and D.2.1.6 Rev 11 Diesel Transfer System to help justify the 6-hour mission time for non-seismic Revision 3 Page 62of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Rev,iew - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension events in the Success Criteria Subsection.
SY-811: Section E.16.5.10 was added to Success Criteria Notebook Cale E.16 Revision 1 which includes discussion about available inventories of air, power, and cooling to support mission times.
HR-A1 HR-A1-01, NOT Closed Discussion: Supporting requirements HR-A1 and A2 discuss To address this F&O, OCPP procedures This is resolved.
MET, the identification of pre-accident HRA based on whether the were reviewed to identify realignment There is no impact Associated SRs: procedure or practice involves realignment (A 1) or calibration and calibration activities. This review on the ILRT HR-A2 (NOT (A2). Per the standard, these criteria should be performed was performed in order to be consistent Extension Risk MET), SY-A16 before going to the screening method performed in Attachment with the ANS/ASME Standard Analysis.
. (NOT MET), pre- 4. supporting requirements HR-A1 and initiator HRAs HR-A2. This review is documented in Basis for Significance: Some potential pre-accident HRAs revision 2 of PRA calculation G.1.
could be screened too early.
As a result of this review, additional pre-Possible Resolution: Review the procedures and practices initiator HFEs were identified for against whether it involves realignment or calibration. inclusion into the PRA model and were quantified using the EPRI HRA Calculator TH ERP module. These new HFEs were incorporated into the PRA model.
HR-A3 HR-A3-01, MET, Closed Discussion: Pre-initiator HRA screening criteria 30 could Screening criterion 30 was faulty in that This is resolved.
preinitiator HRAs remove restoration errors prematurely. If a system or train is it included system or component There is no impact automatically actuated following an event, then a restoration automatic actuation. As the F&O on the ILRT error of manual valves in the flow path could be missed. correctly points out, a system may be Extension Risk Examples include mis-positioning of a valve in the standby automatically actuated without changing Analysis.
CCW pump train if it receives an automatic start signal on low the position of the component in header pressure and misposition of a valve in SI pump train if question. To address this F&O, all of the the valve does not automatically open on an ESFAS signal. screening criteria, including criterion 30, were reviewed and revised as Basis for Significance: Mispositioned events could be missed necessary to ensure that the criteria in the modeling. applied specifically to the component being operated/calibrated. The OCPP Possible Resolution: Review the process for identifying pre- procedures were then reviewed against accident HRAs. the new criteria to identify realignment and calibration activities. This review is Revision 3 Page 63of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT'Extension Table A-1 Internal Events PRA Peer'Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension documented in revision 2 of PRA calculation G.1.
HR-C3 HR-C3-01, Closed Discussion: HR-C3 states "INCLUDE the impact of To address this F&O, the DCPP This is resolved.
NOT MET, miscalibration as a mode of failure of initiation of standby procedures were reviewed to identify There is no impact consideration systems." While the pre-accident HRA document discusses the realignment and calibration activities. on the ILRT of mis- reasons for not including common miscalibration, the PRA This review was performed in order to Extension Risk calibration Standard requires inclusion of miscalibration events. be consistent with the ANS/ASME Analysis.
Standard supporting requirements and Basis for Significance: The exclusion of the miscalibration is documented in revision 2 of PRA contradicts to the requirement. calculation G.1 ~
Possible Resolution: Include the consideration of As a result of this review, new pre-miscalibration. initiator mis-calibration HFEs were identified and were quantified using the EPRI HRA Calculator TH ERP module.
These new HFEs were incorporated into the PRA model.
HR-D3 HR-D3-01, Closed Discussion: The detailed pre-accident HFEs in Section New sections (G.1.4.3.1.6, G.1.4.3.2.6, This is resolved.
CC-I, pre- G.1.3.3 do not discuss the quality of procedures, administrative and G.1.4.3.3.6) dealing with procedure There is no impact initiator HFEs controls, or Man-Machine Interface (MMI) requirements in and human- machine interface quality on the ILRT performing the assessments. has been added to G.1 Rev. 2. Extension Risk Analysis.
Basis for Significance: The quality of procedures, administrative controls, and human-machine interface reviews are required to meet CC-11/111 requirements in HR-D3.
Possible Resolution: Address the issues identified in this F&O.
HR-E1 HR-E1-01, ME;T, Closed Discussion: This SR States: When identifying the key human The basis for significance is incorrect. No issues were Associated SR: SY- response actions REVIEW: The DCPP PRA does credit operator identified. There is A17 (MET), (a) the plant-specific emergency operating procedures, and actions that manually start pumps and no impact on the crediting manual other relevant procedures (e.g., AOPs, annunciator response operate valves when the automatic ILRT Extension Risk verification steps procedures) in the context of the accident scenarios signal fails. Data variable ZHEOS1 Analysis.
when auto failed (b) system operation such that an understanding of how the addresses tbe manual start of ESF system(s) functions and the human interfa'ces with the system is pumps and the operation of ESF valves obtained. on failure of the SSPS signal.
Additionally the DCPP PRA credits the Basis for Significance: Currently, there are no operator manual start and/or alignment of actions associated with starting pumps or aligning valves even standby equipment upon failure of the when the EOP network specifically states "Verify" pump started running train. Basic events CCOP2, or "Verify" valve open/closed. In the event the automatic signal aligning the backup CCW heat Revision 3 Page 64of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Req'uirement Extension fails to start the pump or align the valve, credit should be taken exch?nger on failure of the running for the Operator backing up the automatic signal. CCW heat exchanger and CVHE1, transferring to the unselected control Possible Resolution: Review the EOP/AOP Procedure room ventilation sub train, are two network and identify those pumps/valves whose desired examples.
function is "Verified" by the Operators, and add an Operator action to perform the action given failure of the automatic signal. A review was performed to verify that no manual recovery for failure of an automatic signal that could be credited was missed. In order to avoid unnecessary complexity in the PRA model, the scope of the review was limited to risk significant basic events.
The risk significant basic events were reviewed in conjunction with the emergency operating procedures (EOPs) to determine if any additional manual recoveries of automatic signal failures could be found. No additional operator actions were identified that could mitigate the failure of an automatic signal for risk significant components. Therefore, no change to the DCPP PRA model is required.
HR-E3 HR-E3-01, CC-I, Closed Discussion: This SR States: TALK THROUGH (i.e., review in Operator interviews were re-performed This was a consistent detail) with plant operations and training personnel the and documented in the G.2 Rev 7 HRA documentation issue interpretation procedures and sequence of events to confirm that database for each applicable operator and is resolved.
of procedures interpretation of the procedures is consistent with plant action. There is no impact observations and training procedures. on th.e ILRT Many different talk-through of accident Extension Risk Basis for Significance: Attachment 1 of Calculation G.2, scenarios have been performed since Analysis.
Revision 6, summarizes the talk through performed with original development of the PRA that Operations and Training personnel. However, there is no confirm the accuracy of the accident discussion on how the specific scenarios discussed were response model. Attachment 1 to selected, the questions posed to the Operators, the entire Calculation G.2 identifies the scenario sequence of procedures followed in the response to the types that were discussed with four accident sequence, etc. Additionally, all that is contained in separate operators and with training, Attachment 1 is a summary of the PRA interpretation of the talk- including the procedure path that would through, but the actual Operator interview sheets are not be followed. The interviews focused on included. the key scenarios such as LOCA, loss of AFW, and SGTR that are known to Revision 3 Page 65of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Without having the basis for why the scenarios discussed were be risk-significant. It is common when selected, it is not possible to ensure that the most risk- conducting operator interviews to significant, or important Operator actions were discussed. consolidate scenarios to maximize the Additionally, without the Operator Interview sheets it is not benefit of the limited time available with possible to verify what the operators/trainers said, and that the the operators. In addition, routine responses were taken in context. procedure reviews are performed in order to ensure that procedure changes Possible Resolution: Provide the basis for the accident have not changed the as-built plant sequences discussed, and ensure that the list includes all risk response.
significant operator actions. Find the actual Operator Interview sheets, and include them with the report. For any risk significant operator actions that Operator Interview sheets cannot be found, perform an additional Operator interview, including documentation of the interview, to ensure that the interpretation of the procedures is correct.
HR-E4 HR-E4-01, CC-I, Closed Discussion: This SR States: USE simulator observations or Simulator observations were performed This is resolved.
confirming talk-through with .operators to confirm the response models for on 3/27/2014 for response models and There is no impact response models scenarios modeled. a statement is inserted in Section 5 of on the ILRT via simulator Cale G.2 Revision 7. Extension Risk observations or Basis for Significance: Attachment 1 of Calculation G.2, Analysis.
talk-through Revision 6, summarizes the_ talk through performed with Operations and Training personnel. However, there is no discussion associated with confirming that the response models (i.e., MMP runs) used to support the PRA are realistic.
Additionally, no documentation of the use of simulator observations to confirm the response models can be found.
Possible Resolution: Category I does not require using simulator observations or talk-through with operators to confirm the response models. However, to get to a Category 11/111, a confirmation of the response models, either using simulator observations of operator talk-through, is required.
HR-G5 HR-G5-01, CC-II, Closed Discussion: The required time to complete actions used in the Operator interviews were re-performed This is resolved.
Associated SRs: HRA Calculator for is documented in Calculation File G.1 HFE and documented in Section 5, There is no impact HR- E3 (CC-I), HR- datasheets. These datasheets generally indicate that this time Attachment 1 and HRA database of on the ILRT E4 (CC-I), is based on operator interviews. This meets SR Category II. Cale G.2 Rev 7 for each applicable Extension Risk verification of the However, because for other HFEs, not basis for the required operator action. Response times were Analysis.
time estimates in time is provided. F&O HR-B5-01 documents this deficiency. verified via interviews.
HRA via observation of Basis for Significance: The basis for the required time to complete actions used in the HRA Calculator for is not Revision 3 Page 66of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension simulators or walk- documented in Calculation File G.1 or in the HRA Calculator through file. In order to fully meet SR HR-G5 to Category II, these times should be based on either walk-throughs, talk-through, or simulator observations.
Possible Resolution: Perform the required walkthroughs, talk-through, or simulator observations* and revise the time
- estimates, if necessary. Document these in the HRA Calculator and Calculation File G2.
HR-G6 HR-G6-01, MET, Closed Discussion: Section 7.2 of Calculation Correction: The HFEs referred in this This was a combining identical File G2 documents several checks performed to check the F&O should be read as ZHEF04 and documentation issue HF Es reasonableness of the HEPs of the post initiator HF Es relative ZHEF05 and is resolved.
to each other. This is considered adequate for the SR to be There is no impact met. A review of the final set of HFEs indicates that two appear ZHEF05 is the HEP for 1 normal power on the ILRT to be essentially identical; these have the same HEPs: ZHFE04 source unavailable. Extension Risk and ZHFE05. These two should be combined into one HFE, Analysis.
since the use of both could adversely affect the HRA ZHEF04 is the HEP for both normal dependence analysis and the impact of the state of knowledge power sources unavailable.
correlation in the quantified results. This is documented in F&O HR-G6-01. ZHEF05 is the HEP for operator action to align a backup power supply to the Basis for Significance: A review of the final set of HFEs Diesel Fuel Oil Pump when one of the indicates that two HFEs appear to be essentia.lly identical; these normal power sources is unavailable.
have the same HEPs: ZHFE04 and ZHFE05. These two ZHEF04 is similar except used in cases should be combined into one HFE, since the use of both could where both normal power sources are adversely affect the HRA dependence analysis and the impact unavailable. These HFEs are similar but of the state of knowledge correlation in the quantified results. not identical Possible Resolution: Combine HFEs ZHFE04 and ZHFEO The two HEPs never appear in the into a single HFE. same cutsets because of the mutually exclusive house event impacts used in the top event split fractions.
Because they do not appear in the same cutsets, the dependency between two HFEs is immaterial. The current model is adequate and no model changes are needed.
In order to address the reviewer's concern, some documentation changes were made to clarify the diesel fuel oil Revision 3 Page 67of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension modeling. Table 7 .1 of Cale G.2 Revision 7 and Section D.2.1.6.5.5 of Cale D.2.1.6 Revision 11 were updated to include better descriptions of the HEPs. Riskman data descriptions were also updated to avoid confusion.
HR-G7 HR-G?-01, Closed Discussion: Section C.9.8 (Human Error Probability (HEP) A detailed Internal Events model HRA This is resolved.
NOT MET, \ Dependency Study) and Attachment 7 of Calculation dependency was performed and There is no impact HFE C.9 document the DCPP PRA post initiator HFE dependency documented in PRA Cale G.3, Revision on the ILRT dependencies analysis. This document discusses a review of dependence 0. Changes to the Internal Events model Extension Risk between actions, but does not list a set of operator actions that were identified and incorporated to Analysis.
were evaluated or how the dependence between actions is DC03.
dependent.
Basis for Significance: DCPP personnel discussed the process used to identify and evaluate HRA dependencies; however, the process does not seem to provide a thorough means for identifying and accounting for dependent human actions.
Possible Resolution: Evaluate the dependency of HFEs according to the requirements of the SR.
HR-H2 HR-H2-01, Closed Discussion: This SR States: CREDIT All HFEs were re-reviewed. The minor This is resolved.
MET, staffing level operator recovery actions only if, on a plant-specific basis, the change to non-Operations staffing There is no impact assumed in HRA following occur: levels does not impact existing HFEs. on the ILRT (a) a procedure is available arid operator training has included Extension Risk the action as part of crew's training, or justification for the Analysis.
omission for one or both is provided (b) "cues" (e.g., alarms) that alert the operator to the recovery action provided procedure, training, or skill of the craft exist (c) attention is given to the relevant performance shaping factors provided in HR-G3 (d) there is sufficient manpower to perform the action.
Basis for Significance: Calculation G.2, Revision 6, discusses the "normal" staffing levels at the plant and implies that these are the staffing levels used in the analysis. A review of the HRA calculator files shows that the staffing levels listed in the HRA calculator include electricians, Instrument & Controls (l&C),
Health Physics (HP), and Chemistry personnel in addition to the Operations staff. Based on discussions with DCPP personnel, the non-Operations personnel are not on-site 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, 7 days Revision 3 Page 68of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension a week, but are available via call-in - so they should not be credited for shorter term responses. Additionally, minimum Operations staffing levels should be used when evaluating the post-initiator recovery actions.
Possible Resolution: Identify what the minimum Operations staffing levels are, and ensure that the HRA failure/success probabilities are based on these manpower levels. Additionally, ensure that non-Operations personnel are not credited as being available immediately - but account for the time that will be reguired to call them in.
DA-C1 DA-C1-01, NOT Closed Discussion: This SR requires the use of recognized sources The DCPP PRA Data Update This is resolved.
MET, for generic data for component failure rates, common cause calculation (PRA Cale H.1, Revision 1) There is no impact use of the latest failures, and off-site power recovery. included a reference to NUREG/CR- on the ILRT industry 5485 for CCF methodology and NRC's Extension Risk documentation for Basis for Significance: It is evident from the data analysis "CCF Parameter Estimations, 2010 Analysis.
SSC failure rate, (Calculation File H.1) that the latest generic data (NUREG/CR- Update" for the updated CCF factors.
CCF, and offsite 6928) is used for component failure rates and probabilities; power recovery however, it is not evident that recognized sources are utilized The Electric Power Recovery Model for common cause failures and off-site power recovery. calculation (G.4 Revision 9) included a reference to INEEUEXT-04-02326 for Possible Resolution: Ensure that the latest industry the AC power recovery probability data.
documentation is utilized for the listed generic data and reference them in the DCPP data ~ackage.
DA-C4 DA-C4-01, Closed Discussion: This SR states, "When evaluating maintenance or Cale H.1 Rev 1 (Section H.1.5.2 and This was a NOT MET, other relevant records to extract plant-specific component H.1.5.3) documents detailed basis for documentation issue Associated failure event data, DEVELOP a clear basis for the identification component failure identification. Also, and is resolved.
SR: DC-C3 (NOT of events as failures. Cale B.1 Rev 1 Section 9.2.2 contains .a There is no impact MET), basis summary of this. on the ILRT for identification DISTINGUISH between those degraded states for which a Extension Risk of an event as failure, as modeled in the PRA, would have occurred during the Added the below text to H.1.5.3 and Analysis.
a failure mission and those for which a failure would not have occurred included a table for screened out (e.g., slow pick-up to rated speed). failures in Table H.1-7:
INCLUDE all failures that would have resulted in a failure to The remaining records were reviewed perform the mission as defined in the PRA." by the PRA group to eliminate er:itries that were not considered valid for the Basis for Significance: There was no evidence found in the purposes of this calculation. This data documentation that a clear basis for the identification of includes degraded states for which a events as failures was developed. Also, no evidence was found failure would not have occurred during that degraded states were distinguished as being PRA Revision 3 Page 69of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension applicable or not. Possible Resolution: Document the the PRA mission time and retaining evidence and the basis for the identification of events as those that would have occurred.
failures.
DA-C5 DA-C5-01, Closed Discussion: No discussion is documented on how failure The failure events of the "2009 Failure This is resolved.
NOT MET, events were re-reviewed for inclusion. In reviewing the data Events" spreadsheet of the "H1 Comp There is no impact documenting provided in the Integrated Relational Data System (IRDS) Failure Tables Rev 1.xls" workbook on the ILRT evaluation of failure
- spreadsheet, only one case was found where the same were reviewed and it was found that Extension Risk events component was failed twice on consecutive days. there were two separate failure events Analysis.
for the S-44/E-44 super component on Basis for Significance: Without documentation, it cannot be consecutive days (11/26/2005; determined if these were both counted as failures. This SR is 11/27/2005). One of the events was covered under the Maintenance Rule methodology. screened out from further analysis, leaving one event to represent both.
Possible Resolution: Expand documentation to reference this methodology. Calculation File H.1 - Documents methodology for H.1 was updated to include the review of plant failure events occurring close in time as one or methodology used in removing these multiple events. types of repeat failures.
DA-C6 DA-C6-01, MET, Closed Discussion: In Data Notebook H.1, Component Operating Data analysis was reviewed and PMT This is resolved.
removing post- Experience section, it states that "the failure rate determination demands were removed from the count. There is no impact maintenance from requires the total number of demands (for demand failure One Data variable (ZTPATS, Turbine on the ILRT demand counts variables) or the total operating hours (for fail-to-run (operate) Driven AFW Pump Failure to Start) was Extension Risk variables) for the prescribed updating period. These updated and new variable was included Analysis.
calculations are based on the number of components, number in the current FPRA model.
of surveillance tests and maintenance events, and operating hours of the reactor and other systems." In addition, multi tables A change in the failed-to-start in H.1 provided maintenance and test demands, durations and probability of the Turbine Driven AFW other plant specific information based various plant data (TDAFW) impacts both the Internal sources. However, certain post- maintenance tests were Events and Fire model. This change included; these should not be accounted for as per SR. was included as part of the routine data update performed in 2014.
Basis for Significance: Per SR requirement, it should not account for post-maintenance tests as stated in the SR.
Possible Resolution: Remove post-maintenance from demand countin .
DA-C10 DA-C10-01, Closed Discussion: Per review and discussion with DCPP personnel, Documentation was added to Section This was a NOT MET, No no document to prove this SR was met. H.1.5.1 of Cale H.1 Revision 1: documentation issue document and is resolved.
Basis for Significance: It needs to demonstrate this SR was Credit is taken for successful demands There is no impact
- met as specified in the SR. from surveillance tests by mapping the on the ILRT ZT-variables to applicable surveillance Extension Risk test procedures and reviewing the test Analysis.
Revision 3 Page 70of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/~bservation Disposition Cat II Requirement Extension Possible Resolution: Perform the items required for this SR procedures themselves. Tables of the and document them. Unit 1 and Unit 2 demands are shown in the "Tables_ALL_With_Summary_2013_Up date;xlsm" spreadsheet. This also contains comments on the failure mode for these surveillance tests. Component failure modes are not broken down into sub-elements or causes.
DA-C14 DA-C14-01, Closed Discussion: It does not appear that a search for instances of Examined the 12-week rolling MOW_ This was a NOT MET, coincident maintenance 'was performed since there is no matrix at DCPP and did not identify any documentation issue Associated reference tci it in Data Notebook H.1. planned, repetitive activity which would and is resolved.
SR: SY- cause coincident unavailability There is no impact A20 (NOT Basis for Significan*ce: Need to assess routine activities for due to maintenance for redundant on the ILRT fl!IET), planned multiple component unavailable or document that Maintenance equipment (both Extension Risk Rule practices do not allow for routine instances of multiple intra-system and intersystem). Analysis.
trains or equipment being unavailable. Calculation or modeling of coincident maintenance unavailability was Possible Resolution: Perform this review or document that therefore unnecessary.
coincident maintenance on redundant trains is not performed.
Validate by, review of data. The above statement was added in Section H.1.2 of Cale H.1 Revision 1.
DA-C16 DA-C16-01, Closed Discussion: No documentation for explaining the disposition of Section H.1.6.4 of Cale H.1.6 Revision 8 This is resolved.
MET; plant specific LOOP events could be identified in the Initiating documents the treatment of DCPP There is no impact disposition of Events document provided to the reviewers. specific LOOP event. on the ILRT plant specific Extension Risk LOOP events Basis for Significance: Such documentatiQn is necessary to Specifically, one LOPPC Diablo Canyon Analysis.
meet the SR requirement.
- event on 5/15/2000 removed from generic data and classified as a plant _
Possible Resolution: Close gaps in documenting the specific LNVEL event (See Attachment dispositioning of PS LOOP events in development of basis for 2 of H.1.6 for Unit 1).
IE fre uenc .
DA-D4 DA-D4-01, - Closed Discussion: No documentation found in Data Calculation for The Bayesian updating is done using This is resolved.
CC-11/111, following related to the Bayesian Update- tests to ensure that the Riskman Data Module. Throughout There is no impact Associated SR: DA- the updating is accomplished correctly and that the generic - the process, Riskman shows the analyst on the ILRT E 1 (NOT MET), parameter estimates are consistent with the plant-specific a plot of the prior distribution, and a plot Extension Risk tests and check of .application include the following: of the prior distribution together with the Analysis.
_data updates (a) confirmation that the Bayesian updating does not produce a posterior distribution. Riskman also posterior distribution with a single bin histogram shows various stats for these (b) examination of the cause of any unusual (e.g., multimodal) distributions such as the mean, median, posterior distribution shapes and range factor. This process helps, the Revision 3 Page 71of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (c) examination of inconsistencies between the prior distribution analyst determine if the update and the and the plant-specific evidence to confirm that they are distributions are valid and make sense.
appropriate (d) confirmation that the Bayesian updating algorithm provides The Bayesian update checks for all meaningful results over the range of values being considered failure rates and all initiating events (e) confirmation of the reasonableness of the posterior were added as an attachment to the distribution mean value Data Update file (H.1 ). The Bayesian updates for flooding frequencies and Basis for Significance: Finding F&O is because that much of maintenance events were also checked the SR requirement is not present. using the same criteria, but the screen shots from those Bayesian updates Possible Resolution: Provide documentation for the were not included here. All distributions, performances of these tests and checks as recommended in including priors and posteriors, with the Standard. their plots and statistics are stored in the Riskman files.
DA-D6 DA-D6-01, CC-Ill, Closed Discussion: Update use of references in Data calculation. A reference to NUREG/CR-5485 was This was a documenting added in Section H.1.1 of Cale H.1 documentation issue method and Basis for Significance: Per conversation with DCPP staff, Revision 1. and is resolved.
references in data NUREG/CR-5485 was used for CCF methodology; however this There is no impact calculation is not li!)ted as a reference or in discussions in the calculation. on the ILRT Extension Risk Possible Resolution: Update Data calculation clearly / Analysis.
discussing the methodolog}'. used and correct references.
DA-D8 DA-D8"01, NOT Closed Discussion: No documentation of analysis done on impact on Evaluation of DCN impacts are made as No issues were MET, data of design changes (such as recirculation sump screen part of the design change process and identified. There is Documenting Design Change Notices (DCNs), or new charging pump DCNs) documented during the design change no impact on the evaluation of could be found in the data calculation. process using a task via associated ILRT Extension Risk design changes on design change tracking SAPN. For Analysis.
impact on data Basis for Significance: Assessing the data is part of the SR example, the conclusion of the requirement. assessment performed for the new charging pump concluded that the pump Possible Resolution: Include documentation of analysis should be added to the model.
performed to evaluate impact on data for DCNs incorporated in th_e PRA model in the Data calculation. On a routine basis as part of model maintenance, all design changes since the last model update are re-reviewed again for im~acts on the model.
DA-E2 DA-E2-01, NOT Closed Discussion: Documents provided to peer review team do not In general, all PRA documentation is This was a MET, facilitate review. Additional questions and uncontrolled backup updated to .include all information in a documentation issue Associated SR: DA- materials such as spreadsheets had to be obtained to get a single calculation file without external and is resolved.
D5 ~CC-llll, traceable basis for the Data Calculation. There is no imeact Revision 3 Page 72of117
54006-CALC-01 Evaluation of Risk Significance* of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension documentation attachments or spreadsheets, including on the ILRT Basis for Significance: The peer review team felt the lacking data calculation files. Extension Risk of documentation as required by the SR is significant. Analysis.
System and component boundaries are Possible Resolution: Improve the documentation as required described in the system calculations.
by SR and consider every detail of the requirements stated in the SR. The model used in the actual PRA model is listed in the C.9 (Quantification of CDF and LERF). This is done only in this C.9 as not all calculations are required to be updated or revised for each model release.
Sources for data is listed in H.1 Title of H.1 includes time period used for data.
Uncertainty is in PRA Cale C.10.
QU-C2 QU-C2-01, NOT Closed Discussion: Based on discussion with DCPP personnel, the A detailed Internal Events model HRA This is resolved.
MET, HFE human action dependencies are not evaluated with a minimum dependency was performed and There is no impact dependency default value to prevent underestimating risk. documented in PRA Cale G.3, Revision on the ILRT
- 0. Changes to the Internal Events model Extension Risk Basis for Significance: The issue identified in this F&O either Analysis. -
were identified and incorporated to needs to be performed or justified with alternative means to DC03.
ensure proper consideration of risk contributions.
Possible Resolution: It needs to justify adequate risk contributions are considered.
QU-04 QU-04-01, CC-I, Closed Discussion: The Category II requirements for this SR, Resolved and documented in Section This was a comparison to other "COMPARE results to those from similar plants and IDENTIFY C.9.8.6 of Calculation C.9 Revision 13 documentation issue similar plants causes for significant differences. For example, Why is LOCA a by performing a more in-depth and is resolved.
large contributor for one plant and not another?" comparison with other Westinghouse 4- There is no impact loop plants. on the ILRT Basis for Significance: DCPP has performed and documented Extension Risk a comparison to other similar plants for the CDF results. Analysis.
However, in order to meet this requirement to Category II, a further level of comparison is required.
Possible Resolution: Justification and/or actions are needed to assess the difference, especially significant differences of modeling assumptions and treatment with similar ~lant.
QU-F2 QU-F2-01, NOT Closed Discussion: This SR provides several details of items The results of quantification and risk This was a MET, expected to be seen in the quantification documentation. insights of the base model (i.e., Model documentation issue and is resolved.
Revision 3 Page 73of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASMEIANS Impact on ILRT SR Status FindinglObservation Disposition Cat II Requirement Extension Associated SR: Basis for Significance: Items listed in this SR were not located of Record) are documented in Cale C.9 There is no impact QU- F1 (NOT in the documentation (e.g., item b). Also, issues identified in Revision 13 and C.10 Revision 5. on the ILRT MET), other QU SRs point out details that should be documented in Extension Risk documentation the quantification package. Analysis.
Possible Resolution: Improve the documentation for the quantification calculation.
QU-F6 QU-F6-01, NOT Closed Discussion: This SR states, "DOCUMENT the quantitative The following statement was added to This was a MET, definition used for significant basic event, significant cutset, Section C.9.7 of Cale C.9 Revision 13: documentation issue documenting significant accident sequence. If other than the definition used and is resolved.
definition of in Part 2, JUSTIFY the alternative." "Significant sequences are defined as There is no impact significant being the top 95% contributors to a on the ILRT Basis for Significance: Although the quantitative definition for specific hazard group and having an Extension Risk significant accident sequence is given in the DCPP individual contribution of 1% to that Analysis.
documentation, there was no definition for significant basic hazard group."
event located.
Basic Event importance (RAW) to CDF Possible Resolution: Provide the necessary definitions in and LERF are shown in Attachments 16 DCPP documentation. and 17 of C.9, respectively. Significant Basic Events are those defined as having a RAW importance greater than 2.0.
LE-C2 LE-C2-01, NOT Closed Discussion: This SR states: INCLUDE realistic treatment of As documented in PRA Cale 14-02 It is stated that the MET, modeling of feasible operator actions following the onset of core damage Revision 0, all SAMG procedures were addition of operator operator actions consistent with applicable procedures, e.g., EOPs/SAMGs, reviewed. No additional human actions actions would not be following the onset proceduralized actions, or Technical Support Center guidance. would be worthwhile to credit in the worthwhile to add; of core damage PRA due to credit already being taken however, additional Basis for Significance: The current LERF analysis states that as part of core damage mitigation and actions could be there are no post-core damage operator actions available or due to high uncertainty and non- credited in the FPRA credited. However, a review of plant procedures identified that prescriptive actions in the procedures. that would reduce there are several SAMG procedures available that do include LERF. Treatment is post-core damage actions that need to be reviewed and conservative for credited as applicable. overall LERF. While reduction in LERF Possible Resolution: Review the SAMG procedures, and any would lead to an other available post-core damage procedures, and credit the increase in Class 3b, available actions as appropriate. the change is expected to be small, and there is significant margin for L':.LERF to the u er Revision 3 Page 74of117
54006-CALC-01 EYaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension level ofRG 1.174 Region II (see Section 5.2.4).
Therefore, the ILRT analysis is not adverse! affected.
LE-D7 LE-D7-01, CC-II, Closed Discussion: This SR states: PERFORM containment isolation As documented in Cale E.8 Revision 8, This is resolved.
realistic _ analysis in a realistic manner. INCLUDE consideration of both a systematic evaluation of containment There is no impact containment the failure of containment isolation systems to perform properly penetrations was performed and on the ILRT isolation analysis and the status of safety systems that do not have automatic documented in a separate spreadsheet. Extension Risk isolation provisions. A set of screening criteria were Analysis.
developed consistent with the Basis for Significance: For the containment isolation, there is requirement of this SR, and consistent no documentation readily available that shows a traceable basis with large early release definition. Each for the list of Configuration Identification (Cl) valves that are containment penetration is dispositioned present in the model and the systematic disposition of all of the explicitly using this set of screening containment penetrations that are not in the model. criteria.
Possible Resolution: Provide a systematic evaluation of all FCV-253/254 was moved to top event containment penetrations to arrive at the list of valves that are CP top due to 2" break size being used present in the Cl model. as boundary for large release. Also, identified that 8100/8112 and 8149A/B and 8149C and 8152 that were scoped into CP.
LE-E2 LE-E2-02, Closed Discussion: This SR states: USE realistic parameter PG&E has an existing calculation for 2 Using a small MET, definition of estimates to characterize accident progression phenomena. and 4 inch containment bypass sizes. containment L.ERF with 3" Using the same methodology as this isolation size is not Opening Basis for Significance: Calculation N.2, Revision 0 states existing calculation, a 3 inch size was conservative for "Using the Westinghouse Owners Group Definition for Large evaluated and determined to be an ilLERF but is Early Release Frequency (LERF) in WCAP-16378 a acceptable size for LERF purposes. conservative for total containment leak rate analysis would show that an equivalent LERF. While pipe break diameter that would result in a large release is about However, DCPP has decided to reduction in LERF 3." However, no actual calculation verifying this expected break conservatively use 2" for containment would lead to an size can be located. bypass size. As documented in increase in Class 3b, Resolution section of F&O LE-D7-01, the change is Possible Resolution: Perform and document a calculation containment isolation analysis was re- expected to be verifying that the 3 inch break size is accurate for the DCPP performed based on greater than 2" small, and there is LERF related containment leak rate. definition of the large release path in significant margin for Cale E.8 Revision 8. ilLERF to the upper level ofRG 1.174 Re ion II see Revision 3 Page 75of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Section 5.2.4). There is no impact on the ILRT Extension Risk Anal sis.
LE-F2 LE-F2-01, MET, Closed Discussion: This SR states: REVIEW contributors for This F&O has no impact on the ILRT This was a review of LERF reasonableness (e.g., to assure excessive conservatism have Extension Risk Analysis. The F&O is documentation issue sequences for not skewed the results, level of plant-specificity is appropriate related to documentation of the baseline and is resolved.
reasonableness for significant contributors, etc.) LERF results, and identified outdated There is no impact results and assumptions. The seal on the ILRT Basis for Significance: The LERF contributors were re- LOCA split fractions were confirmed to Extension Risk reviewed for reasonableness, but the quantification report (C.9, not have changed since the Level 2 Analysis.
Revision 11) discussion does not reflect the latest LERF analysis was performed, so there are no quantification cutsets, Additionally, there is an assumption in the model updates required to address this N.2, Revision 0 notebook that states "It is assumed that the issue. Reviewing and documenting the conditional core damage probability for different seal LOCA most current results and assumptions sizes is the same. This assumption may not be correct but is for LERF would not impact the adopted in the.absence of information at a more detailed level calculations of risk changes for the ILRT from the Level 1 PRA." The Level 1 RCP Seal LOCA model is Extension Risk Analysis.
now developed to a detailed enough level to get the actual Conditional Core Damage Probabilities (CCDPs), so this assumption needs to be remov~,d and the actual composition of HANNS and HANNI PDS (fraction of sequences which are seal LOCAs) needs to be used.
Possible Resolution: Update Section C.9.9.1.B of the C.9 report to reflect the current LERF cutsets and insights. Revise the N.2 calculation and RCP Seal LOCA PDS split fractions to ensure that the actual RCP Seal LOCA CCDPs are used to reflect the correct split fractions.
- LE-G3 LE-G3-01, NOT Closed Discussion: This SR states: DOCUMENT the relative C.9 Rev 13 has contributions (along This was a MET, documenting contribution of contributors (i.e., plant damage states, accident with discussion) to LERF as well as documentation issue LERF calculation progression sequences, phenomena, containment challenges, CDF. and is resolved.
containment failure modes) to LERF. There is no impact on the ILRT Basis for Significance: Although the LERF model has been Extension Risk quantified and the cutsets are available to determine the relative Analysis.
contribution of contributors, this information is not documented in the LERF calculation, and the information in the quantificati,0n calculation does not reflect the latest results, and does not include all the types of contributions discussed in this SR.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Possible Resolution: Update the quantification calculation (C.9) or the LERF calculation (N.2) with the information required b this SR.
LE-G5 LE-G5-01, NOT Closed Discussion: This SR states: IDENTIFY limitations in the The DCPP PRA model includes a This was a MET, limitations in LERF analysis that would impact applications. complete Level 2 detailed analysis. documentation issue the LERF analysis There are currently no general and is resolved.
-Basis for Significance: The limitations in the various portions limitations in the LERF analysis that There is no impact of the analyses that would impact applications are not identified would impact applications. Any special on the ILRT or discussed. case limitations impacting an application Extension Risk are specifically identified on a case-by- Analysis.
Possible Resolution: Identify and discuss the limitations of the case basis.
various analyses that would impact applications.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension IFSO-A6 IFSO-A6-01, Closed Discussion: The walkdown reports include spray sources Attachment E.1 Revision 1 of Section 7 This was a MET, spray near the equipment and states that the equipment is spray of the Internal Flooding PRA Calculation documentation issue prptection protected. However, the documentation does not discuss what F.4 Revision 1 documents the spray and is resolved.
is credited as spray protection and what the limitations of that target component screening process. There is no impact protection are. For instance, is there a source that could spray For spray susceptible mitigating on the ILRT on the equipment where the spray protection would not be equipment where there is a spray Extension Risk effective? source in the area, whether the Analysis.
equipment is protected is determined Basis for Significance: Without documenting how spray and documented in Table E.1-1, based protection is credited, the plant may change or remove it on insight gained in the internal flooding without the PRA analysts understanding that the internal floods PRAs performed in the industry, field analysis is negatively affected. walkdown, and/or DCPP plant database regarding equipment environment Possible Resolution: Where spray protection is credited, qualifications. For components not include the source and limitations of the spray protection. screened in Table E.1.1, a field walkdown is performed to collect information for quantitatively modeling the spray scenarios. These are documented in sections E.1.2 and E.1.3 for Unit 1 and 2, respectively. The newly identified spray scenarios are included in Appendix E of Section 7, Revision 1 of the Internal Flooding PRA Report.
IFSN-A3 IFSN-A3-01, Closed Discussion: Reviewed associated notebooks and For infinite flood sources, and large This was a NOT MET, auto attachments, no evidence for each flood area and for each flood sources, auto and/or operator documentation issue and/or operator source the applicable and relevant either auto and/or operator responses to terminate or contain a and is resolved.
responses responses was identified if it has the probability to terminate or flood are considered. For infinite flood There is no impact contain a flood propagation. sources, considerations were provided on the ILRT in resolution to IFSN-A 10-01. For Extension Risk Basis for Significance: Such proper identification is not just example, to terminate flood due to the Analysis.
to meet this SR but it also would enable to properly meet other Circulating Water pipe break, credit was SRs and model development and risk insights. taken for the automatic pump trip feature based on float switch mounted Possible Resolution: Identify per SR requirements. on the condenser pit walls. For large flood sources such as fire water pipe break with water source from raw water storage reservoir, HFEs were developed for operator actions to terminate the flood. See Appendix G of Section 9, Revision 1 of the Internal Flooding PRA Report, and Section 10:
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Revision 1 of the Internal Flooding PRA Report for development of these HFEs.
For other flood sources, scenario modeling including modeling of plant response is developed on a flood area and/or scenario specific basis. For example, for flood sources with limited source inventory (e.g., chilled water pipe breaks), termination of flooding would occur if the source system is de leted.
IFSN-A8 IFSN-AB-01, Closed Discussion: This SR requires the identification of drain lines Section 7.3, Revision 1 of the Internal No issues were MET, drain line paths and back flow through drain lines involving failed check Flooding PRA Report documents the identifi.ed. There is and back flow valves, pipe and cable penetrations, etc., as stated in the SR. identification of propagation pathways at no impact on the paths Currently it is stated that drains were no credited. This does DCPP. Due to the open layout design ILRT Extension Risk not eliminate the need for the identification. To meet this SR it and numerous openings in different Analysis.
needs to review drain drawings to identify the path or credit elevations of the Auxiliary Building and past drain line studies explicitly. Cable trays, etc. Turbine Buildings (e.g., open stairways and grate-covered floor openings),
Basis for Significance: Did not identify as required by the floods originating in one level is standard SR. These conditions could be screened out later, expected to propagate freely to the but need to be identified first as specified by this SR. basement of the building. There is a subsection in section 7.3 discussing Possible Resolution: Identify accordingly. drainage system; backflow of water is not a significant issue in the Auxiliary Building because of the physical layout of the building. There are large open areas outside the pump rooms, and the pump rooms are elevated above the pipe tunnel, where water would collect.
There is also a subsection in section 7.3 discussing unsealed cable tray/conduit and pipe penetrations. For the cases in which pipe penetrations are not sealed, other significantly larger propagation pathways are present; one example is Containment Penetration Area El 115',
the gap along the containment wall is a much larger propagation pathway than pipe penetrations through the floor. As a response to this F&O, in water level Revision 3 Page 79of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension rise timing estimation for nominal flood originated at Fuel Handling Building El.
100' (the corridor area 31, the AFW pump room 3-Q-1, or 3-Q-2), drain flow through floor drains and then drain lines to the Auxiliary Building sump is estimated, as documented in Section 7, Revision 1 of the Internal Flooding PRA Re ort.
IFSN-A9 IFSN-A9-01, Closed Discussion: No calculations were provided to the review Flood calculations were performed for No issues were NOT MET, flood team that shows the flooding rates and the time to equipment selected areas where bounding identified. There is depth and damage. The calculations are needed to determine assumptions were too severe and more no impact on the propagation propagation beyond the initial flood area. detailed analysis was required, ILRT Extension Risk including flood areas with limited Analysis.
Basis for Significance: Calculations for flood areas with a drainage paths and large flood source large capacity are needed to show that the flood does not capacities. The calculations consider propagate without some action to mitigate the flood. flood rates, flood propagation through door gaps, opening between rooms and Possible Resolution: Perform flood calculations to show floor drains. The flooding depth (level flooding depth and propagation to other areas. If older rise) timing is evaluated in these calculations exist that show the flooding depth and calculations, as documented in propagation, review and revise these to meet the current PSA Appendix E of Section 7, Revision 1 of standard requirements. the Internal Flooding PRA Report.
IFSN-A10 IFSN-A10-01, Closed Discussion: Table 4-1 lists the flood source capacities for The size of infinite flood sources, No issues were MET, size of flood each water source, but subsequent evaluations ot the flooding Circulating Water, Auxiliary Saltwater identified. There is sources scenarios do not mention the impact of emptying that source and Firewater from the raw water no impact on the on the flood depth in the areas or the subsequent propagation reservoir, were included in the flood ILRT Extension Risk of infinite water sources to various other areas without scenario development along with the Analysis.
operator action to isolate the flood. flood area, source, flood rate, SSC damage and operator actions. System Basis for Significance: The size of the flood source is not design and plant flood mitigation really considered beyond the initial scoping of the flood features were considered for these sources. infinite sources, which are documented in Section 7.3 of Revision 1 of Section 7 Possible Resolution: To determine the true impact of of the Internal Flooding PRA Report.
flooding, include the size of the flood source and what could be For the Circulating Water Turbine flooded if infinite sources, such as circulating water and ASW Building flood the automatic pump trip are not isolated. feature based on the float switches mounted on the condenser pit walls is credited and modeled. For the ASW flood in the CCW heat exchanger room Revision 3 Page 80of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension it is concluded that it is not credible to postulate a flood propagation scenario that would cause damage to the emergency diesel generators and offsite power based on the limited flood rate, the ASW pumps tripping terminates the flood and numerous control room alarms. Operator actions to isolate the raw water reservoir are credited and modeled for flood scenarios in the Auxiliary, Fuel Handling and Turbine Buildings. If these credited operator actions and automatic trip functions are failed additional SSCs are assumed to be dama ed.
IFSN-A11 IFSN-A11-01, Closed Discussion: The impact of large flooding sources in areas For the Turbine Building flood This is resolved.
NOT MET, multi- that could impact both Units has not been considered. For scenarios, ASW and Circulating Water There is no impact Units effect instance, Circulating Water and ASW are considered infinite piping failure is assumed to cause a on the ILRT sources since they take suction from the ocean. The Turbine dual unit trip. ASW and Circulating Extension Risk Building is a large open area that contains the turbines for both Water pipe breaks in the intake Analysis.
Units. However, a possible duel Unit scram due to a very structure causing dual unit trip are not large flood in these areas was not considered. Similarly, the considered credible scenarios (see Intake structure contains SSCs for both Units that could also Appendix E of Section 7, Revision 1 of result in a dual Unit scram due to a pipe break in a large the Internal Flooding PRA Report.). In source such as ASW. response to this F&O, pipe failures in Auxiliary Building flood areas that are Basis for Significance: The impacts of floods effecting multi- shared between the two units are Units must be considered. included in the flood initiator frequency count for both units (as documented in Possible Resolution: Update the flood analysis to consider Appendix G of Section 9, Revision 1 of large floods impacting multi-Units. the Internal Flooding PRA Report).
IFSN-A12 IFSN-A12-01, Closed Discussion: Based on the discussion of building features, it The scenarios in Appendix E of This is resolved.
MET, screening appears that flooding scenarios are screened or assumed not Section 7, Revision 1 of the Internal There is no impact of flood scenarios to propagate bas~d on drains, curbs and barriers between Flooding PRA Report were reviewed. on the ILRT rooms. This screening implicitly assumes that the leak is Additional propagation scenarios Extension Risk smaller than the drain capacity and/or that the operators take previously screened in Revision O were Analysis.
action to reduce or stop the flow before water backs up into the identified and scoped in with flood room and fails additional equipment or propagates beyond the source capacity and propagation paths room. Table E-1 in the flooding document discusses screening considered in characterization and of numerous flooding scenarios for propagation. The quantification of the flood scenarios. In propagation screenings do not look at accumulation on the addition, select human failure events Revision 3 Page 81 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension area where the water is going and whether equipment in that (HFE) were developed to model the area would be impacted due to flood or whether the flood flood isolation for large flood sources could propagate beyond the se9ond flood area to another area such as Firewater from the raw water and damage equipment. reservoir. Failure of these HFEs result Basis for Significance: Many flooding scenarios are in additional PRA equipment damage qualitatively screened by making undocumented assumptions beyond the original source flood area, and suppositions and thus prematurely screening these such as both RHR pumps being flooding scenarios. The propagation dqes not appear to damaged whenever the 54' pipe tunnel consider source capacity and spread beyond the second area. in the Auxiliary Building is flooded Large flooding sources can propagate to several rooms beyond its capacity volume.
IFPP-A5 IFPP-A5-01, Closed Discussion: Walkdown documentation in Section 5 of the Walkdowns were performed in response This was a MET, walkdown Internal floods report has a lot of blank fields associated with to IFSO-AB-01 for spray screening and documentation issue documents the flooding sources in the areas. The equipment list is modelling, and to IFSNA12-01 for and is resolved.
generally complete but appears to be a download of the propagation scenarios. For the few There is no impact Appendix R Safe Shutdown Equipment list. Therefore, it is instances where additional pipings are on the ILRT difficult to determine if all flooding sources in a zone have been identified, the Section 5 walkdown table Extension Risk identffied and is difficult to know what sources have been is updated. The process of identifying Analysis.
included or not. equipment list is discussed in detail in Section 3.3 Rev 0 and Rev 1. It Basis for Significance: Hard for a reviewer or regulator to involves using multiple information determine that all flood scenarios have been properly sources as a starting point, such as IPE dispositioned. internal flooding, current fire PRA, and current internal events PRA. A Possible Resolution: Improve the documentation to address comprehensive review of the initially the concerns identified in the F&O. compiled list of components was performed to identify those equipment which can be damaged by flooding effects and whose damage would affect the accident initiation and/or mitigating functions.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension PP-C2 PP-C2-01 (2008), Closed No explicit justification for the exclusion of locations Attachment 3 was added to PRA Cale F.3.1 This was a NOT MET, exclusion within the licensee controlled area is provided in the to identify all of the permanent buildings on documentation of areas FPRA documentation. Because the global boundary the site and to address the potential fire issue and is encompasses all of the Fire Hazards Analysis (FHA) effects in order to justify their inclusion or resolved. There is areas, and adds certain areas not included in the FHA, exclusion from the Global Plant Analysis no impact on the this is unlikely to be a problem. Boundary. ILRT Extension SR PP-C2 calls explicitly for providing this Further discussion is provided in Section 4 of Risk Analysis.
documentation. Since it has not been done, this SR is F.3.1.
not met. During the 2010 peer review, the (Note: This F&O was generated during the January 2008 PP SR, PP-C2 was reviewed and judged to review. be met.
ES-B1 ES-B1-02 (2008), Closed The intent of ES-B1 per Discussion 2 is that it is iterative. This F&O has been resolved by additional The exclusion of CC I, need to verify The analysis does not demonstrate that excluded analysis. The risk significance of excluded systems from the the basis of components are revisited to determine if the systems and equipment has been Fire PRA is excluding low system/component should be added due to importance documented in the uncertainty and sensitivity conservative for importance SSC of risk. Reference Section 7.7.1.c and Section 3.2 for analysis to justify the firial set of SSCs the ILRT valid systems and components considered. Discussion 2 of credited in the fire PRA. application. The ES-B1 reviews the importance of using an iterative With this F&O resolved, along with additional other part of this approach to validate the assumptions made in the initial F&Os ES-B1-03 (2008) and ES-B1-01 F&O is related to review of components to include. Even though systems (2010), SR ES-B 1 is judged to be met at documentation.
such as Main Feed I Condensate are not important to the Capability Category II based on the Therefore, there is internal events model, they may be important to specific verification of low risk importance of excluded no adverse impact fire areas once initial results are reviewed. Reference SSCs. The 2010 peer review identified a on the ILRT Section 7. 7 .1.c and Section 3.2 for systems and similar finding (see ES-B1-01 (2010) below), Extension Risk components considered. but concluded that SR ES- B1 is met at Analysis.
Add step to process to review the assumptions and Capability Category II.
determine if systems /components originally excluded due to significance should be added.
(Note: This F&O was generated during the January 2008 review.
ES-B1 ES-B1-03 (2008), Closed The component selection considers spurious operations This F&O has been resolved by additional This is closed.
CC I, not including a including MSOs that could affect system operation. The analysis and model updates. A sensitivity There is no impact recovery action for result of this review is the failure of associated analysis was performed and documented to on the ILRT potentially significant components without consideration for recovery. For evaluate the risk significance of EOP and Extension Risk scenario, specifically example, spurious operations of equipment that could post-fire recovery actions. Important actions Analysis.
the drain-down of cause a loss of Refueling Water Tank (RWST) inventory have been added to the fire PRA model.
the RWST results in a loss of the RWST for the purposes of With this F&O resolved, along with additional injection and subsequent recirculation. This results in a F&Os ES-B1-02 (2008) and ES-B1-01 loss of primary inventory control function and heat (2010), SR ES-B1 is judged to be met at Caeabili!l Cate~o~ II. The 2010 eeer review Revision 3 Page 83of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension removal (feed and bleed). This is showing as being concluded that SR ES-81 is met at Capability conservative and significantly affecting results. Category II.
From discussion #2: Ultimately the selected equipment and the resulting FPRA plant response model must be sufficiently complete that the objectives with respect to level of detail, realism, and accuracy as stated in Table 1-1 of this standard are met consistent with the intended capability category.
Evaluate significance of not including recovery actions and equipment and include where appropriate.
(Note: This F&O was generated during the January 2008 review.
ES-81 ES-81-01 (2010), Closed Calculation F.3.2 does not explicitly include a step to This F&O has been resolved by additional The exclusion of CC II, need to verify review the assumptions used to exclude components or analysis. The risk significance of excluded systems from the the basis of systems that were excluded to verify that these systems and equipment has been Fire PRA is excluding low components can remain excluded based on risk documented in the uncertainty and sensitivity conservative for importance SSC significance. The DCPP response indicates that the analysis to justify the final set of SSCs the ILRT' valid uncertainty of excluded components and systems is credited in the fire PRA. application. The addressed in F.3.15. With this F&O resolved, along with additional other part of this A review of Calculation F.3.15 does not indicate any F&Os ES-81-03 (2008) and ES-81-01 F&O is related to discussion of the uncertainty of the exclusion of (2010), SR ES-81 is judged to be met at documentation.
components or systems based on risk significance under Capability Category II based on the Therefore, there is Section 3.3.2 of the calculation. verification of low risk importance of excluded no adverse impact SS Cs. The 2010 peer review identified a on the ILRT Basis for Significance: The iteration to validate that the Extension Risk assumption to exclude components or systems needs to similar finding (see ES-81-01 (2010) below),
but concluded that SR ES- 81 is met at Analysis.
be performed to ensure that the model is not excessively conservative to meet a Capability Category II. Capability Category II.
Possible Resolution: Perform a sensitivity analysis of components or systems that were excluded during the ES task to confirm that they are not risk significant.
(Note: This F&O was generated during the December 2010 review).
ES-82 ES-82-01 (2010), Closed MSO review does not appear to evaluate and disposition This F&O has been resolved by additional This F&O has documentation the effects of multiple spurious operations on calculations reviews and model updates. The qualitative been resolved by inconsistencies and to support the success criteria in the FPRA. This includes screening criteria used to evaluate the impact additional reviews
.errors in MSO system success criteria such as multiple flow diversion of MSOs on the function success criteria was and model documentation. paths and timing associated with manual actions. CC-II supplemented by additional reviews to updates. There is needs to consider the effect on two sEurious oEerations confirm there were no situations in which the no imEact on the Revision 3 Page 84of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension per train and the effect on the system success criteria. effects of coincident MSOs would impact ILRT Extension Multiple spurious operations may affect the success system success criteria. As a result, MSO of Risk Analysis.
criteria for the train in either required system pressurizer power- operated relief valves performance functions and/or supporting manual actions. (PORVs) was considered as requiring Not performing this review could have impact on system mitigation as a medium-break instead of a success and HRA. Review multiple operational effects on small-break LOCA.
calculations that support system and train success. The 2010 peer review concluded that SR ES-(Note: This F&O was generated during the January 2008 B2 is met at Capability Category Ill.
review.
CS-A2 CS-A2-03 (2008), Closed A review of Appendix R circuits has not been completed DCPP Action Request A0414724 addressed This is closed.
CC Ill, incomplete to find potential circuit failures that could lead to the this issue in November 2000 in response to There is no impact circuit analysis for bypass of MOV torque and limit switches. Where NRC IE Notice 92-18. on the ILRT the bypass of MOV damage to MOV is possible, credit for manual actions to During the 2010 peer review, SR CS-A2 was Extension Risk torque and limit credit operation of the valves need to be removed. Credit judged to be met at CC-II but a new F&O CS- Analysis.
switches. for valve operation could be taken when valve positioning A2-01 was added. Refer to F&O CS-A2-01 may not be available due to physical valve damage. (2010) for details.
Review existing circuit analysis for MOVs where shorts could bypass the torque and limit switch and determine if valve damage could occur. If so, validate that manual actions to recover the valve position are not credited in the FPRA.
(Note: This F&O was generated during the January 2008 review).
CS-A2 CS-A2-01 (2010), Closed F&O: In response to NRC IE Notice 92-18, a review of This F&O has been resolved by additional This is closed.
CC II, expand NRC safety-related MOVs was performed in Evaluation AR analyses. Action request (AR) A0414724 There is no impact IN 92-18 to MOVs A0414724. A review should be conducted to confirm that documented the review of MOVs credited in on the ILRT required to support MOVs from the internal events PRA that are credited in the Appendix R analysis to address NRC Extension Risk the manual actions the FPRA, but are not included in the above evaluation Information Notice 92-19. Additional review of Analysis.
in the FPRA. are added to that evaluation. If not, then credit for the fire PRA identified additional MOVs not in manual operation of the affected MOVs should be the scope of AR A04J 472d. These MOVs removed from the FPRA. have been evaluated for this failure mode to Basis for Significance: This action is required to meet the ensure that manual operation of the MOV is SR. The evaluation AR A0414724 only addressed MOVs not improperly credited, and the that are credited for Appendix R Safe Shutdown. Any documentation has been revised to reflect new MOVs credited from the internal events PRA for the the additional evaluations.
FPRA have not necessarily been evaluated for With this F&O resolved, SR CS-A2 is judged mechanical damage resulting from a stalled condition, to be met at Capability Category II. (The and may not be capable of manual operation.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Possible Resolution: See text of F&O above. 2010 peer review concluded that SR CS-A2 (Note: This F&O was generated during the December is met at Capability Category II.)
2010 review).
CS-A? CS-A?-01 (2008), Closed Components added associated with ISLOCA Sequences This F&O has been resolved by a model The current Fire NOT MET, 3-Phae in Table 7-4 of the Component Selection Calculation did update. Cables associated with isolation PRA model is hot short not appear to have 3-Phase Hot Short Analysis in the valves where spurious actuation due to three- conservative for circuit analysis. This includes CVCS valves 8112 and phase hot shorts could result in an ISLOCA the ILRT 8100, and RHR valves 8701 and 8702. have been verified in the model, and extension Requirement not met for major ISLOCA pathways. additional cables for valves identified have application.
Add in to the analysis the cable impact and analysis for been added. NUREG/CR-7150 guidance Therefore, there is valves mentioned above, and ensure the impact is recommends screening of 3-phase proper no adverse impact modeled in the PRA. polarity hot shorts; therefore, the current Fire on the ILRT (Note: This F&O was generated during the January 2008 PRA model is conservative for the ILRT Extension Risk review). extension application. Analysis.'
The 2010 peer review concluded that SR CS-A? is met.
CS-A10 CS-A 10-01 (2008), Closed The Assumptions for Guaranteed failure (GF) in the This F&O has been resolved by additional This is resolved.
NOT MET, potential Impact Matrix for the 50 or so components not traced has analysis. The risk significance of excluded There is no impact high CDF impact of resulted in conservatism in the CCDP for the FPRA systems and equipment has been on the ILRT the assumptions of results. The present CCDP for a baseline PRA run is a documented in the uncertainty and sensitivity Extension Risk guaranteed failure of factor of 40. higher than the internal events, which may in analysis to justify the final set of SSCs Analysis.
non-traced SSCs. part be due to assumptions on the GF issue. This results credited in the fire PRA.
in a significantly too high.GDF for Fire for all scenarios, With this F&O resolved, along with additional and may be one of the main contributors to the overall F&Os ES-81-03 (2008) and ES-81-01 high GDF initially estimated. A review of Cale (2010), SR ES-B 1 is judged to be met at 134Draft.doc and the Impact matrix was performed. In Capability Category II based on the general, all components id~ntified in the component verification of low risk importance of excluded selection process were traced, and the tracing results are SS Cs.
in the impact matrix. However, many of the components The 201 O peer review concluded that SR CS-that were listed as credited under Component Selection were actually not traced and assumed failed, as A 10 is met at Capability Category Ill.
identified as a Guaranteed Failure in the Matrix. A review of th~ FDS1 results was performed, with the lowest FDS1 CCDP of 5.3E-05. This is about a factor of 40 higher than the reactor trip CCDP (1.4E-06). What this indicates is that between the assumptions in the equipment selection task IA, MFW, Containment Spray not credited) and the components not traced in the Cable Revision 3 Page 86of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Selection, the CCDP for the FPRA is a factor of 40 too high.
Review the FDS1 results for several scenarios, and determine the assumptions that are most affecting the results. Based on this review, perform cable routing and circuit analysis needed to remove the assumptions, and re-run the FDS1 results. Once a baseline FDS1 result is similar to the internal events PRA CCDP (with the HEP set back to the original internal events PRA results), then the remaining assumed component failures can likely remain .. This may need to be looked at again for multiple initiating events and for higher CCDP events where the assumed failures can become important for certain scenarios.
(Note: This F&O was generated during the January 2008 review.
CS-A11 CS-A 11-01 (2008), Closed In discussions with the PRA staff, there were several This F&O has been resolved by a This was resolved NOT MET, lack of components, where Appendix R basis was used to documentation update. The cables bya documenting the determine the cable routing, without specific cable/circuit associated with the 480 V switchgear HVAC documentation basis for assumed review and routing. This includes Cable Room, Battery and damper were analyzed and traced. The update. There is cable routing, room, and 480 VAC switchgear room dampers (which remaining assumed cable routing were no impact on the Associated SRs: - results in a loss of Heating Ventilation and Air reviewed and the documentation updated to ILRT Extension CSC3, FSS-E4. Conditioning (HVAC)). This event is important in the document the basis for the routing Risk Analysis.
PRA, as evidence by the baseline results analysis assumptions provided by DCPP, which shows this to be the number 1 The 2010 peer review concluded that SRs scenario due to an increased HEP event for non- CS-A 11 and CS-C3 are not applicable.
recovery of loss of HVAC. Due to the failure to document the use of the Appendix R basis for the cable routing, a finding was developed to add this documentation to the PRA. Without the documentation, it is not possible to determine where the cable tracing results come from for these components. Additionally, these components are always assumed failed for fires in areas where the component cables are assumed to be located.
Add the documentation for components not specifically traced into the PRA, and the basis for the resulting routing. This can then be input into the uncertainty results discussion, including the fire modeling (FSS) uncertain .
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (Note: This F&O was generated during the January 2008 review.
PRM-A4 PRM-A4-01 (2008), Closed Uncertainty and Sensitivity and Analysis (Task 15) have Note: This SR in 2007 Standard has been This is resolved.
NOT MET, not been performed yet. This item could not be verified. deleted from 2009 Standard. There is no impact incomplete Once the FPRA model becomes stable, perform Task 15 PRA Cale F.3.15 has been prepared on the ILRT Uncertainty and to account for uncertainties and sensitivities. documenting the Uncertainty and Sensitivity Extension Risk Sensitivity analysis. (Note: This F&O was generated during the January 2008 Analysis. Analysis.
review.
PRM- PRM-813-01 (2008), Closed DCPP has not reviewed accident progression beyond
- This F&O has been resolved a model update. This is resolved.
813 NOT MET, core damage considering fire failures. It is recommended The LERF model for fires has been There is no impact incomplete that DCPP perform this review and docu.ment it. completed and documented. on the ILRT quantification of In reviewing the draft report, DCPP contested this finding The 2010 peer review team concluded that Extension Risk LERF model, and said that they had performed a screening review the SR PRM-814 is met. Analysis.
Associated SRs: containment penetrations to identify potential sources of PRM-814. fire-induced containment isolation failures. DCPP provided a copy of Calculation F.3.3.1, Rev. 0, dated June 6, 2006, documenting this review. A subsequent review of this document indicated that DCPP had performed a thorough review of all containment penetrations using a documented set of screening criteria. As a result of this review, DCPP retained 59 penetrations for further evaluation as potential sources for containment isolation failure:
However, at the time of the review, as discussed in Table 4-13, the quantification was still in process and there was not enough information or documentation to determine the extent to which fire-induced containment isolation failures had been incorporated into the model and addressed in the final quantification. This finding stands until DCPP has completed the quantification and*
documented the results and the final model. However, based on the additional information provided, it seems likely that DCPP will meet this requirement when they have completed the quantification.
(Note: This F&O was generated during the January 2008 review.
PRM- PRM-815-01 (2010), Closed F&O:. F.3.2 states that "The possibility of multiple open Revision 1 to Calculation F.3.2.1 has been This is resolved.
815 MET, lack of pathways (<3") should also be considered." A review of changed such that Section 4 and Attachment There is no impact the remaining small isolation pathways shows that the
- 1 now include the dispositioning of non- on the ILRT likelihood of combined events leadin~ to a eathwa~ >3~' is screened containment eenetrations .based on Revision 3 Page 88of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension documenting low very low and could likely be screened. However, this is the size of equivalent opening gi~en multiple Extension Risk probability of not documented. pathways. Analysis.
multiple Basis for Significance: All new fire-related LERF open pathways . pathways that were identified in F.3.2.1 have not been leading to greater formally dispositioned and docum_ented.
than 3" opening, Associated SRs: Possible Resolution: The PRM documentation should be PRM-C1 updated to disposition all potential LERF pathways applicable to the FPRA that were identified in F:3.2.1.
(Note: This F&O was generated during the December 201 O review).
PRM-C1 PRM-C1-02 (2010), Closed F&O: F.3.5, Section 6.4.2.1(Step4) states: "It is This F&O has been resolved by a model The newRCP MET, modeling of assumed in the model that the installation of the high update. The RCP seal model was modified seal modelling is new low leakage temperature RCP seals has the benefit excluding the based on the vendor guidance documents to based on the RCP RCP seals. possibility of an RCP Seal LOCA on loss of cooling to the include both human error and random failure seals to be seals." This was verified in the rules (Appendix I) which modes. installed. The Fire have split fraction SEO (with a value of 0.0), as the first PRA model rule in SE, set to be default as success (i.e., SEO= 1). results presented However, neither the Flowserve N-9000 nor the new in this report are Westinghouse shutdown seal (SOS) are guaranteed to based on this not develop a Seal LOCA in the event of loss of seal model, which injection and thermal barrier cooling. Both seal types provides require an operator action to trip the RCPs (not modeled reasonable in DCPP FPRA) and both seals have a nominal failure estimates of Fire rate (e.g., on the order of 1E-3) even when the RCPs are PRA CDF and successfully tripped (not modeled in DCPP FPRA). LERF for this Basis for Significance: RCP seal LOCA can be a application.
significant contributor to fire CDF in PWRs, even with Therefore, there is newer seals (either- N-9000 or Westinghouse SOS). no impact on the ILRT Extension Assuming that no operator action is required and that the Risk Analysis.
seal cannot fail (i.e., failure probability= 0.0) may significantly affect the results and/or insights of the FPRA.
Possible Resolution: Add modeling for RCP seal failure, including the need for operator action to trip the RCPs.
WCAP-16175 provides guidance and values for RCP seal failure rates for N-9000 seals. If Westinghouse SOS seals are expected to be installed, Westinghouse should Revision 3 Page 89of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension be able to provide approximate failure rates and required operator timing.
(Note: This F&O was generated during the December
- 2010 review .
PRM-D1 PRM-D1-01 (2008), Closed Documentation for the Plant Response model has This F&O has been resolved by completion This is resolved.
NOT MET, the PRM portions in draft and other portions not complete. This is of the plant response model documentation. There is no impact report is in draft form due to the current status of the project with the plant The 2010 peer review concluded SR PRM- on the ILRT response model undergoing updates. C1 is met. Extension Risk Once the model becomes stable, update F.3.5 with how Analysis.
the model was developed and updated the PRA model documentation as necessary to account for model changes used to acc~unt for FPRA evaluation capability.
(Note: This F&O was generated during the January 2008 review).
FSS-A5 FSS-A5-01 (2008), Closed For many compartments, target sets associated with high This F&O has been resolved by a model This is resolved.
NOT MET, risk compartments and ignition sources has not been update. Since the initial peer review in 2008, There is no impact incomplete completed. A review of fire compartment 388-100 was the fire PRA scenarios have been completed on the ILRT development of performed to evaluate the adequacy of the scenario and documented. The 2010 peer review Extension Risk detailed fire selection method. This is not in line with the intent of this identified an industry best practice for this Analysis.
scenarios requirement as provided in Discussions #1 and 2. High element.
risk compartments not evaluated in a level of depth The 2010 peer review concluded SR FSS-A5 sufficient to understand the results. is met at Capability Category Ill.
FSS-A6 FSS-A6-01 (2008), Closed The main control room analysis is not complete. This This F&O has been resolved by completion This is resolved.
NOT MET, item could not be verified. of the MCR analysis. The fire modeling of the There is no impact incomplete the fire (Note: This F&O was generated during the January 2008 MCR has been performed and documented. on the ILRT modeling of the Main review). The 2010 peer review concluded SR FSS-A6 Extension Risk Control Room is met at Capability Category I/II. Analysis.
MCR FSS-81 FSS-81-01 (2008), Closed Scenarios that require MCR abandonment/reliance on This F&O has been resolved by a model and This is resolved NOT MET, MCR ex-control room operator actions have not been documentation update. The control room since the RAI 03 abandonment developed. MCR abandonment criteria is identified in abandonment criteria are consistent with model, which analysis, Associated Main Control Room Fire Risk Analysis but not justified NUREG/CR-6850, and this is documented incorporated the SRs: FSS-82. based on review of draft Main Control Room Fire Risk with the RAJ 03 model. The RAJ 03 model revised MCR Analysis. MCR abandonment criteria identified but includes the risk contribution of MCR abandonment justification not provided as required in the SR. abandonment in the Fire PRA CDF and model, is used in
'Complete fire scenario development and evaluation MGR LERF. the external scenarios and scenarios that reguire either MCR events sensitivi~.
Revision 3 Page 90of117-1'
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension D
Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension abandonment or ex-control room operator manual With this F&O resolved, FSS-81 is judged to Therefore, there is actions. be met. no impact on the (Note: This F&O was generated during the January 2008 ILRT Extension review}. Risk Analysis.
FSS-C2 FSS-C2-01 (2008), Closed For Capability Categories II & Ill, a time-dependent This F&O has been resolved with a model This is resolved.
CC I, lack of time assessment of heat release rate is called for scenarios update. Time dependent HRRs have been There is no.impact dependent heat important to risk. In the compartments for which scenario developed and implemented using the t2 fire on the ILRT release rate development was examined, heat release rates for most growth, peak, and decay per NUREG/CR- Extension Risk components (e.g., cabinets) were constant with time. 6850. Analysis.
Time-dependent heat release rates were assessed in at The 2010 peer review concluded SR FSS-A6 least some cases for target cables. The scenarios is met at Capability Category 11/111.
examined are important contributors to risk. To achieve Capability Category II or Ill, time dependent assessment of the heat release rates is required.
More detailed assessment of the heat release rates may contribute to reducing the assessed frequencies for these scenarios and compartments.
(Note: This F&O was generated during the January 2008 review).
FSS-C5 FSS-C5-01 (2008), Closed A technical basis is needed 1to justify the use of damage The F&O has been resolved with a model This is resolved.
CC I/II, justification. temperatures for qualified cable when a limited amount update. The fire modeling of all fire areas There is no impact for the use of of non-qualified cable is installed in the plant. Use of containing thermoplastic cables (or cables of on the ILRT damage criteria of damage temperatures for qualified cables may be non- unknown material which are assumed to.be Extension Risk qualified cable for conservative for targets that include nonqualified cables. thermoplastic) were updated, and now Analysis.
non-qualified cable. Pursue identification of nonqualified cable routes or considers appropriate damage criteria for develop severity factors that may be applied to targets unqualified cables.
that may: include nongualified cables.
FSS-C5 FSS-C5-01 (2010), Closed NOTE: This finding was identified in 2008 review and re- The F&O has been resolved with a model This is resolved.
CC I/II, treatment of identified in 2010 review. update. The fire modeling of all fire areas There is no impact thermoplastic cables F&O: DCPP fire modeling reports indicate that the containing thermoplastic cables (or cables of on the ILRT damage/ignition temperature at DCPP is based on unknown material which are assumed to be Extension Risk thermoset cabling which was concluded from thermoplastic) were updated, and now Analysis.
performance of PRA calculation F.3.6.1, which considers appropriate damage criteria for established that all raceways and conduit at DCPP unqualified cables.
contain thermoset cabling. This review identified less than 1% (350 cables) of plant cables as being thermoplastic and 5.19% (2,229 cables) of cables were constructed of unknown materials based on this it was Revision 3 Page 91 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension concluded that thermoset damage criteria should be applied to all fire modeling targets and self-ignited cable fires need not be considered. While this information clearly demonstrates that most cables at DCPP are qualified a very small percentage is non-qualified and those cables could damage/ignite at lower non-qualified cable damage temperatures.
Basis for Significance: A very limited set of non-qualified cables exist in the plant which should be evaluated using lower damage/ignition temperatures. If these cables are present in a fire scenario for which fire modeling was performed use of damage criteria for qualified cable may be non-conservative.
Possible Resolution: Identify the routing of cables with un-qualified or unknown cable construction. Screen such cables which are located in areas where no fire modeling was performed or the cables are routed in conduits. In cases where such cables are routed in cable trays in risk-significant areas reevaluate the treatment of targets where these cables are routed.
(Note: This F&O was generated during the December 201 O review .
FSS-C8 FSS-C8-01 (2008), Closed Fire Wrap is not discussed in the fire area analysis This F&O has been resolved with a model This is resolved.
NOT MET, treatment performed for the PRA, and the technical justification for update and documentation update. There is no impact of fire wrap credited wrap is not provided as required by FSS-C8. Credited fire wrap in each fire area and fire on the ILRT Provide a description of when fire wrap is credited, a list scenario is documented in the risk modeling Extension Risk of fire areas and components where it is credited and workbook . Analysis.
.reference to the technical justification for the fire wrap The 2010 peer review concluded SR FSS-C8 qualifications in the FPRA. Additionally, provide is met.
documentation of the wrap effectiveness, including the maintenance of the wrap (no mechanical damage) and the review of the wrap against direct flame impingement from a high hazard ignition source.
(Note: This F&O was generated during the January 2008 review.
FSS-03 FSS-03-01 (2008), Closed Fire modeling is not complete. Spreadsheets have been This F&O has been resolved by completion This is resolved.
CC I, fire modeling is completed for eight areas and one CFAST model is of fire modeling and documentation. There is no impact not completed for all completed based on submittal to Peer Review. on the ILRT Revision 3 Page 92of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations r 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension screened areas Complete Fire Modeling Task and documentation to The 2010 peer review concluded SR FSS- Extension Risk satisfy this. SR.
- 03 is met at Capability Category Ill. Analysis.
(Note: This F&O was generated during the January 2008 review).
FSS-D? FSS-D?-01 (2010), Closed F&O: To meet Capability Category II, it should be This F&O has been resolved by additional This is resolved.
CC I, use of plant demonstrated that the system has not experienced
- review with no model change required. A There is no impact specific data for outlier behavior relative to system unavailability. A review review of plant-specific maintenance and on the ILRT suppression and of data and results of Calculation M-1079 indicates that testing data for fire suppression and Extension Risk detection systems the plant smoke detector unavailability is similar to the detection systems was performed and results Analysis.
generic unavailability. There does not.appear to be a documented. It was concluded that these similar review performed for the heat detectors or the fire systems have not experienced outlier suppression systems. behavior compared to the generic data Basis for Significance: The analysis currently meets applied in the fire PRA.
Capability Category I. This finding discusses the gap that With this F&O resolved, SR FSS-D? is needs. to be addressed to meet Capability Category II for judged to be met at Capability Category II.
this Supporting Requirement.
Possible Resolution: Perform a review of plant-specific maintenance and testing data for fire suppression and other fire detection systems in order to characterize the unavailability ofthese systems to confirm that here are no outliers.
(Note 1: Tliis F&O was generated during the December 2010 review).
(Note 2: After the issue of the draft peer review report, PG&E requested that the peer review team revisit this F&O. The review team caucused and decided that the F&O will stay as originally written. The PG&E's request and the review team's conclusions are documented in Appendix C).
FSS-08 FSS-08-01 (2008), Closed The effectiveness of the fire detection and suppression This F&O has been resolved by a This is resolved.
MET, suitability of systems is included in the fire modeling spreadsheets; documentation update. The effectiveness of There is no impact detection and however evidence of an evaluation of the suitapility of the automatic detection and suppression on the ILRT suppression systems , detection and suppression systems and specific features systems has been evaluated during Extension Risk that may impact these systems was not identified. walkdowns and inspections, and has been Analysis.
This information *is contained to some degree in the FHA included in revised documentation.
- but specific discussion in the fire modeling calculations should be included. SR requires specific discussion of suitability of detection and suppression systems and Revision 3 Page 93of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension specific analysis unit features that may impact these systems. Include write-up in fire modeling calculations to discuss these attributes.
(Note: This F&O was generated during the January 2008 review).
FSS-09 FSS-09-01 (2008), Closed Qualitative analysis of the smoke analysis is included in This F&O has been resolved by completion This is resolved.
CC I, incomplete individual fire modeling spreadsheets; although the of the smoke damage analysis; no model There is no impact smoke damage approach used is good, this activity is not yet complete. change was required. The smoke damage on the ILRT analysis Smoke analysis has been performed for smoke transport analysis was completed with no new risk- Extension Risk through bus ducts. This analysis needs to be completed significant scenarios identified. Smoke Analysis.
for all affected compartments. damage was evaluated based on the Complete smoke damage analysis for all affected guidance in Appendix T of NUREG/CR-6850.
compartments. The 2010 peer review concluded that SR 1(Note: This F&O was generated during the January 2008 FSS-09 is met at Capability Category 111111.
review).
FSS- FSS-010-01 (2008), Closed Confirmatory walkdowns have not been performed to This F&O has been resolved by a This is resolved.
010 NOT MET, verify that as-built plant conditions or detection, documentation update. Confirmatory There is no impact confirmatory suppression, etc. have been characterized appropriately walkdowns have been performed for fire on the ILRT walkdown of for each analyzed fire scenario. The site has high scenarios per the fire modeling procedure Extension Risk detection and confidence in the accuracy of drawings and initial and documented in the fire modeling Analysis.
suppression system walkdowns used to establish fire scenario parameters workbooks.
not done are accurate; however the information gath~red has not The 2010 peer review concluded that SR been validated. FSS-010 is met at Capability Category 111111.
Perform confirmatory walkdowns to validate fire model inputs.
(Note: This F&O was generated during the January 2008 review.
FSS- FSS-011-01 (2008), Closed Confirmatory walkdowns have not been performed to This F&O has been resolved by a This is closed.
011 NOT MET, confirm that the combinations of fire sources and target documentation update. Confirmatory There is no impact confirmatory sets appropriately represent the as-built plant conditions. walkdowns have been performed for fire on the ILRT walkdown of fire (Note: This F&O was generated during the January 2008 scenarios per the fire modeling procedure as Extension Risk source and targets review). documented in the fire modeling workbooks. Analysis.
not done The 2010 peer review concluded that SR FSS-Of1 is met with a new finding - refer to F&O FSS-011-01 (below).
FSS- FSS-011-01 (2010), Closed F&O: Fire modeling for some of the electrical cabinets DCPP committed to install the incipient OCPP committed 011 MET, crediting the (i.e., Cabinets PK109, RAR, RFWM, RG, detection system in SSPS room and Cable to install the inCiEient detection RNASB/RNARA/RNARB, RN01, RNP1, RNP2, & SEreadin9 Rooms of both Units ~SAPN inciEient detection Revision 3 Page 94of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension system for some of RTFW) located in Fire Compartment 7A include credit for 50365080). It is anticipated that all of the Fire system in SSPS electrical cabinets in incipient detection which is not yet installed. PRA related modifications will be completed room and Cable the Cable Spreading Basis for Significance: Incipient detection has not been prior to the next scheduled Type A tests for Spreading Rooms Room installed accordingly credit for this system does not Units 1 and 2 in the first quarter of 2019 and of both Units reflect current plant conditions., Crediting this detection 2018, respectively (see Section 5.3.1 for (SAPN may mask risk associated with these cabinets. details). The fire areas for the detection 50365080).
system were selected based on risk insights Therefore, this is Possible Resolution: The incipient detection sysJem from the FPRA model being developed as closed, and there should be installed as planned or the scenarios that part of NFPA 805. is no impact on credit this system should be revised to eliminate credit The modeling methodology of crediting and the ILRT for incipient detection.
incorporating the incipient detection system Extension Risk (Note: This F&O was generated during the December (in-cabinet) in the FPRA model followed FAQ Analysis.
2010 review).
08-0046 and is documented in Rev 3 of the Fire Modeling Procedure (EPM-DPFP-001),
Section 8.4.2.
At DCPP the incipient detection system will be installed only in the SSPS and CSR rooms, which are not continuously occupied.
It is not used in an area-wide application or in the Main Control Room.
FSS-E1 FSS-E1-01 (2010), Closed F&O: During conduct of the peer review walkdown in The suggestion F&O has been resolved with This is closed.
MET, validating type compartment 7A it was noted that both heat and smoke a model update. See F&O FSS-CS-01 (2008) There is no impact of detection system detection is provided in the area. This compartment is above. on the ILRT (smoke or heat) protected with a C02 fire suppression system which is Extension Risk credited in the Cable credited for the FPRA. The documentation contained in Analysis.
Spreading room the fire modeling report does not address whether this system is cross-zoned or not. Typically such a system would require activation of one heat or two smoke detectors to activate the C02 system. The fire modeling
- was predicated on activation of a single heat detector which is likely accurate for this system however the system function should be validated and accurate modeling of system response should be documented.
Basis for Significance: Fire modeling parameter needs to be validated.
Possible Resolution: Validate fire detection and suppression system operation and ensure proper modeling.
Revision 3 Page 95of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (Note: This F&O was generated during the December 2010 review).
FSS-E2 FSS-E2-01 (2010), Closed F&O: The basis for the establishment of a fire This F&O has been resolved by additional This is resolved.
MET, use of generic suppression system unavailability factor of 0.01 is not review with no model change required. A There is no impact unavailability for the clear. Documentation included in Section 5.8 of the fire review of plant-specific maintenance and on the ILRT suppression system modeling reports indicates that this value was adopted testing data for fire suppression and Extension Risk based on a lack of plant-specific information and that this detection systems was performed and results Analysis.
value equates to 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> of exposure per year. The documented. It was concluded that these report indicates that the value is based on an estimate of systems have not experienced outlier maintenance activities however no additional detail is behavior compared to the generic data provided. applied in the fire PRA.
Basis for Significance: The rationale used to justify the With this F&O resolved, SR FSS-E2 is use of this unavailability factor is not provided. judged to be met at Capability Category II.
Possible.Resolution: The write-up provided as rationale for this unavailability factor should be expanded to discuss why the 0.01 value is representative or bounding of DCPP fire suppression system unavailability.
(Note 1: This F&O was generated during the December 2010 review).
(Note 2: After the issue of the draft peer review report, PG&E requested that the peer review team revisit this F&O. The review team caucused and decided that the F&O will stay as originally written.).
FSS-E3 FSS-E3-01 (2008), Closed The Fire Modeling and accident sequence analysis does This F&O has been resolved by a This is resolved NOT MET, fire not include a characterization of uncertainty, either documentation update. The uncertainty and the modeling uncertainty qualitative or quantitative. associated with fire modeling has been uncertainty Provide a quantitative characterization of uncertainty identified and characterized in the analysis does not factors in the fire modeling and sequence analysis, for documentation. affect Fire PRA significant fire scenarios, per FSS-E3. The 2010 peer review concluded that SR values used in the ILRT Extension (Note: This F&O was generated during the January 2008 FSS-E3 is met at Capability Category Ill.
Risk Analysis.
review).
Therefore, there is no impact on the ILRT Extension Risk Anal sis.
FSS-F1 FSS-F1-01 (2008), Closed Exposed Structural Steel Analysis/Review has not been This F&O has been resolved by a This is resolved.
NOT MET, exposed performed. documentation update. The exposed There is no impact structure steel on the ILRT Revision 3 Page 96of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension analysis not done Perform Exposed Structural Steel Analysis per FSS-F1 structural steel analysis has been completed Extension Risk to F3. and documented. Analysis.
(Note: This F&O was generated during the January 2008 The 2010 peer review concluded that SR review). FSS-FI is met at Capability Category I/II.
FSS-G1 FSS-G1-01 (2008), Closed Multi-Compartment Analysis has not be performed. This F&O has ~een resolved by a This is resolved.
NOT MET, multi- Complete Analysis for Multi-Compartment Scenarios for documentation update. The multi- There is no impact compartment FSS-G1 to G6. compartment analysis has been completed on the ILRT analysis was done. and documented. Extension Risk (Note: This F&O was generated during the January 2008 Analysis.
review). The 201 O peer review concluded that SR FSS-G1 is met.
FSS-H1 FSS-H1-01 (2008), Closed Documents reviewed are in-progress and at various This F&O has been resolved by completing This is resolved.
NOT MET, lack of levels of completion. Fire modeling is currently in- the analysis and documentation .. Fire There is no impact documentation of the process; the detailed fire modeling analyses have not modeling has been completed and on the ILRT detailed fire been fully documented. Documentation of uncertainty documented in detailed fire modeling Extension Risk modeling, analysis, multi-compartment analysis and fire scenario workbooks. Analysis.
Associated F&Os: confirmatory walkdowns is required. See F&O FSS-E3-01 (2008) (above) for SR H2 through H10. Complete analysis and accompanying documentation. completion of the uncertainty analysis.
(Note: This F&O was generated during the January 2008 See F&O FSS-G1-01 (2008) (above) for review). completion of the multi-compartment analysis.
The 2010 peer review concluded that SR FSS-H1 is met.
FSS-H4 FSS-H4-01 (2008), Closed The input values for each modeling tool used is This F&O has been resolved by completing This is resolved.
MET, incomplete documented in the corresponding attachment to Cale. the analysis and documentation. Fire There is no impact detailed fire File No. 3.11 a; however because the detailed fire modeling has been completed and on the ILRT modeling and modeling task has not been completed satisfaction of this documented in detailed fire modeling Extension Risk documentation of fire SR is not complete. workbooks. Analysis.
modeling inputs. Complete Fire Modeling Task and documentation to satisfy this SR.
(Note: This F&O was generated during the January 2008 review).
FSS-H5 FSS-H5-01 (2008), Closed The fire modeling output results for each analyzed fire This F&O has been resolved by completing This is closed.
CC I, incomplete scenarios are documented in the respective Calculation the analysis and documentation. Fire There is no impact detailed fire File No. 3.11 a attachments; however the completed modeling has been completed and on the ILRT modeling analyses and documentation are not finalized. No documented in detailed fire modeling Extension Risk and parametric evidence of uncertainty evaluations was identified. Fire Analysis.
uncertaint:,: modelin9 results are documented for com~leted Revision 3 Page 97of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension analyses/scenarios; documentation of remaining workbooks. The results of the parameter scenarios must be performed. Parameter uncertainty uncertainty was performed and documented.
evaluations should be conducted to achieve CC-II. The 2010 peer review concluded that SR Complete and document results for remaining scenarios FSS-H5 is met at Capability Category II, with including parameter uncertainty evaluations. a new finding; see FSS-H5-01 (2010) below.
(Note: This F&O was generated during the January 2008 review.
FSS-H5 FSS-H5-01 (2010), Closed F&O: The documentation in the Risk Modeling This F&O has been resolved by a This is resolved.
CC II, lack of Workbooks (Attachment 2 of the Detailed Fire Modeling documentation update. The risk modeling There is no impact documenting the Reports) does not clearly identify the cause of the target workbooks have been revised to identify the on the ILRT cause of the target damage (i.e., heat effects, smoke). Section 5.8 of the cause of target damage. Extension Risk damage, Associated report does discuss the impact of smoke damage, and Analysis.
SRs: FSS-D9 discussions with the analyst indicate that smoke damage is a consideration and can be the cause of target damage. However, the analysis results do not differentiate, and so it cannot be easily determined if target damage is due to smoke.
Basis for Significance: Needed to meet the SR.
Possible Resolution: Document fire modeling output results for each analyzed fire scenario in a manner that facilitates FPRA applications, upgrades, and peer review.
(Note: This F&O was generated during the December 2010 review).
IGN-A4 IGN-A4-01 (2008), Closed DCPP documented their review of plant-specific fire This F&O has been resolved by a This is closed.
CC II, possible experience between 1996 and 2006 in Attachment 10 to documentation update. The two DG fires There is no impact Bayesian update for F.3.6. As stated in Section 5.3, "Based on the review of have been further reviewed and additional on the ILRT Diesel Generator fire the plant fire events and the facts that: ( 1) there was no justification for not using the plant-specific Extension Risk frequency or provide unusual pattern in the fire events, (2) no common-cause experience has been documented. The use Analysis.
justification, problem was identified for two fire events associated with of generic fire frequency data without a Associated SRs: the Diesel Generators, and (3) there were only a small Bayesian update has been specifically IGN-B4. number of "potentially challenging" fire events in last 10 addressed as a source of uncertainty.
years of plant operation, it is decided that a plant-specific update of the generic fire frequencies is not warranted."
However, the two Diesel Generator fires in 20 plant years translate to a rough fire frequency of about 1E-1/plant year. This is approximately an order of magnitude greater than the generic frequency. DCPP should consider either performing a Bayesian update for the Diesel Generator fire frequency or providing a more Revision 3 Page 98of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension detailed justification of the basis for not performing the Bayesian update. If DCPP does not perform the update, they should add this to their list of epistemic sources of uncertainty. (Note: This F&O was generated during the January 2008 review).
QNS-81 QNS-81-01 (2008), Closed Compartments with risk below the screening criteria and This F&O has been resolved by a This is resolved.
NOT MET, lack of the risk results are not documented in F.3.5. It is not documentation update. The documentation There is no impact documenting the possible to verify that all fire areas/compartments was confirmed to list the fire compartments on the ILRT screened fire areas, identified in the plant partitioning have been analyzed. with risk below the screening criteria, Extension Risk Associated SRs: Add a list of all fire areas/compartments analyzed to the including both GDF and LERF. Analysis.
QNS-D1 results in F.3.5, including those below the 1E-07/year The 2010 peer review concluded that SR GDF. QNS-81 is met.
(Note: This F&O was generated during the January 2008 review).
QNS-81 QNS-81-02 (2008), Closed Screening Results as supplied in F.3.5, Step 6.2 do not This F&O has been resolved by a This is resolved.
NOT MET, lack of provide LERF results. LERF results are part of the documentation update. The documentation There is no impact LERF screening screening criteria (and criteria for determining additional was confirmed to list the fire compartments on the ILRT results, Associated modeling for Diablo) identified in Section 5.2. Without with risk below the screening criteria, Extension Risk SRs: QNS-D1 LERF results, some fire areas may not be analyzed, including both GDF and LERF. Analysis.
even though LERF results are too hig.h. Perform and The 2010 peer review concluded that SR document the LERF results in Section 6.2 of F.3.5 for QNS-81 is met.
screened and unscreened fire areas/compartments.
(Note: This F&O was generated during the January 2008 review).
CF-A1 CF-A1-02 (2008), Closed Circuit Failure Probabilities in Attachment 2 are This F&O has been resolved by a model This is resolved.
CC I, circuit failure incorrectly combined when there are multiple cables in a update. The circuit failure mode probability There is no impact probability estimate fire area. For example, two cables with a spurious calculations have been revised to properly on the ILRT involving dependent/ operation probability of 0.1 each are added as 0.1 + combine multiple cable failure probabilities. Extension Risk independent circuits 0.1*(1-0.1) = 0.19. In most cases, when the first cable is The 2010 peer review concluded that this SR Analysis.
(e.g., off-schemeor damaged (and does not spuriously actuate), the was met at Capability Category I with a new interlock circuits) grounding of the cable will blow the fuse of the finding F&O CF-A1-01 (2010).
component. Damage to the second cable will have no impact on the component and should not be considered in the probability calculation. Discussions with the NUREG/CR-6850 authors indicate thatthe write-up on this issue is confusing in NUREG/CR-6850, but the interpretation in Diablo FPRA is not correct for most circuits. Most Com[:!onents include multi[:!le com[:!onents Revision 3 Page 99of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension in each fire area. This means that on average, the spurious operation probabilities used are conservative by a factor of 2.
Use the bounding generic spurious operation probability for each component in each fire area as a starting point.
For components with off-scheme or interlock circuits, which are supplied from an independent power supply should be considered additive. Other circuits should be considered dependent and not additive.
(Note: This F&O was generated during the January 2008 review).
CF-A1 CF-A1-01 (2010), Closed F&O: Detailed circuit failure analyses have been This F&O has been resolved with a model This is resolved.
CC I, detailed circuit performed and documented. However, only a few of the update. The circuit failure probabilities were There is no impact failure calculation circuit failure probability calculations make use of the updated for basic events yvith risk reduction on the ILRT based on specific methodology provided in FAQ 080047. A substantial worth (RRW) values greater than 1.05 for fire Extension Risk circuit configuration number of risk significant components (based on RRW) CDF and LERF employing the FAQ 08-0047 Analysis.
for risk significant need to have circuit failure probabilities updated, since methodology.
components using
- the current calculations are conservative. Additionally, With this F&O resolved, PG&E judges that appropriate method for probabilities with more than two events, the equations SR CF-A 1 is now met at Capability Category (e.g., FAQ 08-047) in Attachment 2 should be checked. For example, with 3 111111, based on consideration of the specific events A, B and C, the exclusive OR calculation should circuit configuration for risk-significant be: A+ B + C - A*B - A*C - B*C + A*B*C components.
Basis for Significance: CC 11/111 requires that risk-significant events have circuit failure calculations performed based on the specific circuit configuration and appropriate method (FAQ 08-0047).
Possible Resolution: Review the risk rankings for fire induced failures and spurious events. Calculate the conditional failure probabilities for these events based on the specific circuit configuration and accounting for the method discussed in FAQ 080047.
(Note: This F&O was generated during the December 2010 review).
CF-A2 CF-A2-01 (2008), Closed Uncertainty values and distribution types for the circuit This F&O has been resolved with a This is resolved.
NOT MET, failure probabilities was not provided in the analysis files, documentation update. The documentation There is no impact .
Uncertainty values CF tables or in RISKMAN. was revised to add a discussion on on the ILRT and distribution
- The CF values are from NUREG/CR6850, Chapter 10. distribution types and uncertainty values for Extension Risk types for the circuit Use of these and an assumed distribution can be used to the circuit failure probabilities. Analysis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Cat II Requirement
- Status Finding/Observation Disposition Extension failure probabilities characterize the uncertainty for each spurious operation The 2010 peer review concluded that SR CF-was not provided. probability. When spurious operation probabilities are A2 is met.
combined, the riew uncertainty may need to be estimated. *
(Note: This F&O was generated during the January 2008' review).
- HRA-A3 HRA-A3-01 (2010), Closed' Section 6.4 of Calculation File No. F.3.12, "Post-fire This F&O has been resolved by additional This CC II, basis for Human Reliability Analysis" states that the FPRA review and update of the documentation. The documentation screening undesired screened all undesired actions in response to spurious screening basis for all annunciators and issue is resolved.
actions in response annunciators [and indications]. The basis for screening indications was reviewed and confirmed to be There is no impact to spurious many spurious or erroneous indications .is either acceptable. The specific examples identified on the ILRT annunciators inadequate or not provided in the FPRA documentation. were corrected in the documentation. Extension Risk Examples: Analysis.
- F.3.2, Attachment 7 identifies 6 alarms that could result in operator taking action without any other cues. The actions taken in response to these spurious annunciators were determined to be recoverable, and were screened based on the fact that the recovery action was estimated to be less than 5E-2. There is no basis for Why this screening level is appropriate.
- There are some adverse actions listed in F.3.12 Table C-4 that do not appear to be discussed or dispositioned anywhere else (e.g., E-1, steps 14, 16, and 17).
- There are many alarm responses in Attachment 7 of F.3.2, (pages 18, 19 and 20), which do not require verification, but had been screened out without proper basis.
- The screening disposition for several operator actions in F.3.12 Table C-2 does not appear to be complete. For spurious RWST level indication, the screening disposition states that the spurious indication "Could be screened" based on redundancy, but there is an open-ended "However. .. " at the end of the disposition.
There are other examples in Table C-2 where the screening criteria are not definitive, as the disposition states "Could be screened ... " (e.g., E-0, Steps'26 and Revision 3 Page 101 of 117 ,
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension 27). The screening criteria should be stated explicitly, as opposed to suggested with the phrase 'could be.'
HRA-81 HRA-81-01 (2008), Closed The validity of the actions as they were defined and This F&O has been resolved by additional This is resolved.
MET, additional evaluated for the internal events PRA has generally be evaluations and model updates. A review There is no impact instrumentation considered appropriately as they are carried over into the was conducted of operator actions to identify on the ILRT beyond that explicitly FPRA. The availability of indications, context for the additional equipment or cables to be Extension Risk addressed in the actions, etc., has been assessed in modifying the evaluated; this included the feed-and-bleed Analysis.
internal events PRA existing analyses to apply for fire scenarios. action.
(e.g., RCS pressure One potential exception was encountered. The HFEs and temperature relating to failure to initiate feed-and-bleed cooling (e.g.,
indications in event ZHEOB1_0) account for indications relating to support of Bleed and steam generator level. These indications provide the Feed operation. cues for initiating feed-and-bleed cooling. The procedure includes a caution and instructions for maintaining RCS conditions (pressure and temperature) within bounds to ensure adequate heat removal but not excessive cool down. For the internal events, this control function is not addressed; it is implicitly taken to be successful. There are sufficient indications of RCS conditions and the time available is such that this is probably adequate. For some plants, at least, this control function can be critical to the long-term success of the action. For the DCPP fire analysis, the availability of only equipment and cables associated with steam-generator levels have been addressed for this HFE. If control is required and if instruments needed to support control could be affected by fires in particular compartments\ this is not being tracked. This is an element of the manner in which the HFEs are addressed as they are adapted from the internal events PRA to the fire analysis that needs to be considered. It is expected to affect a very small number of HFEs.
This event should be evaluated to determine if additional equipment and cables should be addressed. A review should be made of other HFEs for which additional instrumentation beyond that explicitly addressed for internal initiators (and therefore captured for the fire analysis) is credited.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Obseniation Disposition Cat II Requirement Extension (Note: This F&O was generated during the January 2008 review).
HRA-C1 HRA-C1-01 (2008), Closed R-1736044-1728, Dated August 10, 2007, documents The internal events HRA was updated in This is closed.
NOT MET, open the results of the Diablo Car:iyon focused scope Peer 2012 and included review and resolution of There is no impact F&Os from the Review of HRA. This document contains a number of the previous F&Os. Results of the updated on the ILRT focused peer review Facts and Observations documenting specific issues internal event HRA were incorporated into Extension Risk of HRA in 2007 affecting the application of the methodology in general the fire HRA. Analysis.
and some specific HFEs. These F&Os have not been The 2010 peer review concluded that SR resolved for the Level 1 HRA as yet. There was no HRA-C1 is met at Capability Category II with indication that DCPP had reviewed these issues for any a new finding F&O HRA-C1-01 (2010).
impact on their fire HRA. Several of these new F&Os were reviewed to determine if any of identified issues had the potential to influence the fire HRA and to determine if the impacted HFEs had carried over to the Fire HRA. In the limited spot-check, two such HFEs, ZHEF04 and ZHOE1, were identified. They are associated with the new F&Os, HR-F2-1, HR-G3-2 and HR-G3-3. The issues identified in these F&Os could be influenced by fire conditions. There is no indication that DCPP had reviewed these issues in preparing the fire HRA. There is some indication that the DCPP's methodology for developing screening HEPs may, at least in part, cover some of the issues. Note that for ZHECV1, one of the other HFEs referenced one of the fire variants for this HFE, ZHECV1_0, but only the base case was quantified in the HRA course. Furthermore, Table 2 and Table A-1 contain the base case value and the _o case value.
DCPP needs to review the F&Os in H1736044-1728 to determine if any of the issues could be influenced by a fire and if so any of the impacted HFEs carried over into the FPRA were. DCPP should then identify how they addressed these issues in the fire HRA.
(Note: This F&O was generated during the January 2008 review).
HRA-C1 HRA-C1-02 (2008), Closed HFEs adapted from the internal events PRA have been This F&O has been resolved by completion This is closed.
NOT MET, no evaluated for general fire conditions, using bounding of the detailed analyses for the important There is no impact detailed analyses parameters for some elements of the analysis. operator actions modeled in the fire PRA. on the ILRT address in Revision 3 Page 103of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension conditions Additional cause-based mechanisms (in the cause-based The 2010 peer review concluded that SR Extension Risk associated with a decision-tree method that forms the basis for assessing HRA-C1 is met at Capability Category II with Analysis.
specific fire scenario. the s;ognitive contribution in their HRA approach) have a new finding F&O HRA-C1-01 (2010).
been considered to account generally for fire conditions.
For example, branch points different from those for the equivalent HFE in the internal events PRA are selected for cases in which the fire scenario implies that a partial set of indications would be available In addition, the recovery factors internal to the cause-based assessment have been set to 1.0, rather than retained at the values assessed for the HFE in the internal events PRA. The execution assessment has also been modified, both to remove this internal recovery and to increase the execution time. For HFEs reflecting actions identified from the fire response procedure, a screening assessment has been performed. No detailed analyses of HFEs have been completed, either to address conditions associated with a specific fire scenario, or to adjust further the factors treated as bounding in the analysis. This process is planned as the fire quantification progresses, but clearly has not been completed. Moreover, it would appear likely that at least some HFEs would need to be treated using a time-reliability correlation, because the cause-based approach may not adequately capture time constraints. It is not clear that this is planned at the current time.
The detailed assessment of fire scenarios will need to be supported by detailed treatment of HFEs. The detailed assessment will need to be completed for fire scenarios that contribute to core-damage frequency. Moreover, it is likely that additional methods will need to be applied to assess HFEs corresponding to time constrained actions.
(Note: This F&O was generated during the January 2008 review).
HRA-C1 HRA-C1-01 (2010), Closed F&O: Human action dependencies have been accounted This F&O has been resolved by completion This is closed.
CC II, HRA for in the FPRA. The internal events HRA (from which of the fire PRA HRA dependency analysis. There is no impact dependency analysis the Fire HRA events were developed) dependency on the ILRT analysis is complete, and only four new fire-specific Extension Risk events have been added. The final check for de~endent Anal:z'.sis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS St t Impact on ILRT SR Finding/Observation .Disposition Cat II Requirement a us Extension operator actions (quantification of the FPRA with HEPs set to a high value) has not been completed.
Basis for Significance: The evaluation with all HEPs set to a high value will ensure that no dependencies have been overlooked.
Possible Resolution: Check for dependent HFEs in the FPRA model by quantifying it with HEPs set to a high value.
(Note: This F&O was generated during the December 2010 review).
HRA-D1 HRA-01-01 (2008), Closed No recovery analysis beyond the HFEs included initially This F&O has been resolved by a model This is closed.
NOT MET, recovery in the model has yet been identified. For example, some update. A review of the dominant scenarios There is no impact actions for risk scenarios that appear to be contributing include loss of and areas was conducted, and appropriate on the ILRT significant fire offsite power independent of the fire effects. recovery actions were added to the model. Extension Risk scenarios Consideration of the recovery of offsite power has not yet Screening analyses were initially Analysis.
been made. Consideration of recovery will be necessary incorporated followed by detailed analyses in conjunction with the definition and assessment of for the important operator actions modeled.
detailed fire scenarios. The 2010 peer review concluded that SR The recovery analysis will need to be performed as the HRA-01 is met at Capability Category II.
sequence quantification progresses from bounding to detailed.
(Note: This F&O was generated during the January 2008 review).
HRA-E1 HRA-E1-01 (2008), Closed F.3.12, the fire HRA analysis report contains a set of The internal events HRA was updated in This is closed.
NOT MET, open assumptions (see page 3 of 1167). The first assumption 2012 and included review and resolution of There is no impact F&Os from 2007 is "The internal events PRA and HRA are complete and the previous F&Os. Results of the updated on the ILRT focused HRA peer in compliance with the ASME PRA Standard [1] Category internal event HRA were incorporated into Extension Risk review II as endorsed by Reg. Guide 1.200 ". However, R- the fire HRA. Analysis.
1736044-1728, Dated August 10, 2007, documents the The 2010 peer review concluded that SR results of the Diablo Canyon focused scope Peer Review HRA-C1 is met at Capability Category II with of HRA. This document contains a number of Facts and a new finding F&O HRA-C1-01 (2010).
Observations documenting specific issues affecting the application of the methodology in general and some specific HFE. These F&Os have not been resulted for the Level 1 HRA as yet. Based on these F&Os, several of the RA-Sb-2005 HRA SRs are identified as being not met. Thus, it cannot be uneguivocally stated that the Revision 3 Page 105of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension DCPP HRA is in full compliance with the ASME PRA Standard.
DCPP needs to address/resolve the new F&Os in R-1736044-1728, Dated August 10, 2007.
(Note: This F&O was generated during the J.anuary 2008 review).
HRA-E1 HRA-E1-02 (2008), Closed Documentation of the initial (screening or bounding) This F&O has been resolved by completion This is closed.
NOT MET, methods has been completed, but the manner in which of the detailed HRA analyses and There is no impact uncertainty analysis more detailed assessments will be performed is not yet documentation of uncertainty considerations. on the ILRT documented. The detailed assessments of HFEs and of The 2010 peer review concluded that SR Extension Risk recovery actions are not yet documented because the HRA-E1 is met. Analysis.
analyses have not 1been performed. Documentation of assumptions and sources of uncertainty has also not yet been done. Documentation currently is limited to the methods used for the general treatment of HFEs as they are adapted to the FPRA, and for the screening analysis of HFEs associated with actions identified from the fire response procedure.
Documentation of the detailed treatment of HF Es, of recovery analyses, and of the assumptions and uncertainties will need to be developed.
(Note: This F&O was generated during the January 2008 review).
SF-A1 SF-A1-01 (2010), Closed F&O: Diablo Canyon Calculation F.3.13, Rev. 0 covers This F&O has been resolved by a This is closed.
MET, clarify which Seismic-Fire interaction. This calculation uses a part of documentation update. The documentation There is no impact areas were the IPEEE submittal as the basis to conclude that all fire was revised to demonstrate the areas on the ILRT considered in the scenarios resulting from an earthquake are identified and considered in the IPEEE walkdown were Extension Risk IPEEE walkdown qualitatively analyzed. The IPEEE submittal bases much consistent with the global plant analysis Analysis.
of these conclusions on a walkdown. While the boundary (GPAB) considered in the current identification of seismically-induced fires appears to be fire PRA, and that the conclusions reasonable, the IPEEE does not provide sufficient adequately support the seismic-fire documentation of what areas were considered and what interaction analysis.
areas were screened out. At present, there does not appear to be sufficient documentation to support the conclusions relating to this SR in the calculation.
Basis for Significance: The SR is judged to be met, even though this supporting information is needed to meet the SR. The reguired information is needed to fully meet the Revision 3 Page 106of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension SR. Note, however, that item this item does not impact the results of the FPRA.
Possible Resolution: It is recommended that either the supporting data for the IPEEE plant walkdown be reviewed to provide more bases for identifying seismic-fire interaction scenarios, or another walkdown be done and documented to identify seismically induced fires in support of this SR.
(Note: This F&O was generated during the December 2010 review).
SF-A3 SF-A3-01 (2010), Closed F&O: The SR SF-A3 requires assessment of the This F&O has been resolved by a This is resolved.
MET, no clear potential for common-cause failure of multiple fire documentation update. The documentation There is no impact conclusion that SR suppression systems due to the seismically-induced was revised to disposition CCF of fire on the ILRT SF-A3 is met. failure of supporting systems. Diablo Canyon Calculation protection systems due to a seismic event as Extension Risk F.3.13, Rev. 0 addresses seismic-fire interaction. Section not credible. Analysis.
6.2 addresses SR SF-A3. While there is a lot of supporting information in this section, there is no.clear conclusion made that this SR is met. There needs to be a clear conclusion drawn that the SR is met based on the supporting information.
Basis for Significance: Even though the review team concluded that this SR is met, this item is needed to meet the SR.
Possible Resolution: Rewrite Section 6.2 of the Calculation F.3.13 to draw the conclusion that SR SF-A3 is met.
(Note: This F&O was generated during the December 2010 review).
SF-A5 SF-A5-01 (2010), Open F&O: Diablo Canyon Calculation F.3.13, Rev. 0 covers Update to the training program is being The status of MET, TQ1.DC12 Seismic-Fire interaction. In this calculation it was noted tracked by a plant action item, and will be training has no needed to be revised that a Notification SAPN 50294777 (Task 23) has been closed when SAP Notification50294777, impact on created to revise TQ1 .DC12 to include fire brigade Task #23 is implemented fully. The status of calculations of risk training to cope with a seismically-induced fires and training has no impact on calculations of risk changes associated system, ~quipment, communications and changes associated with the ILRT Extension associated with brigade ac_cess logistics. This recommendation needs to Risk Analysis. the ILRT be implemented in order to meet this SR. The review Extension Risk team is judging this SR to meet, however, an F&O has Analysis.
Therefore, there is Revision 3 Page 107of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension been written to require implementation of this no impact on the recommendation .. ILRT Extension Basis for Significance: The SR is judged to be met Risk Analysis.
assuming that_this recommendation is being implemented.
Possible Resolution: Implement the suggested recommendation.
(Note: This F&O was generated during the December 2010 review).
FQ-B1 FQ-B1-01 (2008), Closed The sequence quantification is in process but is in a This F&O has been resolved by completion This is closed.
NOT MET, complete preliminary state. It does not yet meet the requirements of quantification of the fire PRA model and There is no impact quantification and of FQ-B 1, FQ-01, FQ-E1 and FQ-F1. Completion of the the associated documentation. on the ILRT document the quantification process is obviously essential for the fire The 2010 peer review concluded that SR FQ- Extension Risk results, Associated analysis. - 81 is met with on new F&O FQ-B1-01 (2010). Analysis.
SRs: FQ-C1, FQ-D1, It is expected that the quantification process will be FQ-E1, and FQ-F1. carried through consistent with the manner in which it has been started.
(Note: This F&O was generated during the January 2008 review).
FQ-B1 FQ-81-01 (2010), Closed F&O: The FPRA does not achieve convergence: at the This F&O has been resolved by a model This is closed.
MET, truncation current truncation level of 1E-8. below the scenario _ update. The truncation level in the fire PRA There is no impact analysis, Associated frequency. Establishing a proper truncation level is model is documented to demonstrate on the ILRT F&Os: FQ-F1-01. required by QU-B2 and QU-83 (the QU-8 SRs are convergence. Extension Risk referenced in FQB1). The FPRA truncation is discussed Analysis.
in F.3.5, Appendix S; the increases in GDF and LERF by lowering the truncation one order of magnitude are 12%
and 24%, respectively.
Basis for Significance: A proper truncation level is required to ensure that quantification results properly reflect the risk contributors, and that significant sequences and/or contributors are not eliminated. The increases in GDF and LERF by lowering the truncation frequency by one order of magnitude are greater than 5% (QU-B3 requirement).
Possible Resolution: Use lower truncation limit or address model issues which may be causing convergence problem.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension (Note: This F&O was generated during the December 2010 review).
UNC-A1 UNC-A 1-01 (2008), Closed The FPRA shall identify key sources of CDF and LERF This F&O has been resolved by completion This is resolved.
NOT MET, uncertainties, including key assumptions and modeling of the uncertainty and sensitivity analyses There is no impact uncertainty analysis approximations. These uncertainties shall be and documentation. on the ILRT not done, Associated characterized such that their impacts on the results are The 2010 peer review concluded that SR Extension Risk SRs: UNC-A2, understood. Uncertainty and sensitivity analysis have UNC-A1 is met with one new F&O UNC-A1- Analysis.
UNCA3 not completed yet, Items could not be verified for SRs 01 (2010).
UNC-A1, UNC-A2 & UNC-A3 therefore, assumed as not met.
Once the FPRA model becomes stable, perform the CDF and LERF uncertainties, including key assumptions and modeling approximations.
(Note: This F&O was generated during the January 2008 review).
MU-A1 MU-A1-01 (2008), Closed DCPP has an Administrative Procedure for Control of the This F&O has been resolved by updating the This is closed.
MET, update PRA PRA, TS3.NR1. While this procedure is written at a administrative procedures to address There is no impact administrative relatively high level, but appears to focus primarily on the changes in PRA technology and industry OE. on the ILRT procedures .to internal events PRA. DCPP intends to use this process The 2010 peer review concluded that SR Extension Risk include fire for control of the maintenance and update of the FPRA. MU-A 1 is met. Analysis.
considerations, In general, the process in TS3.NR1 appears to be Associated SRs: applicable for the FPRA but it should be modified to MUA2, MU-81 specifically address fire specific issues.
through 84, MU-C1, For this review, TS3.NR1 was reviewed against the MU MU-E1, MU-F1 SRs which are based on Section 5 of RA-Sb-2005 with the assumption that the words "FPRA" are inserted for "PRA" and assuming that DCPP will update the process to specifically address the FPRA and any unique _aspects thereof.
DCPP should update TS3.NR1 to specifically address the FPRA and any unique aspects thereof. In particular, TS3.NR1 and appropriate plant process and procedures should be updated to require monitoring changes to the Fire Protection Program and evaluating any plant changes that impact the Fire Protection Program for potential impact on the FPRA. Section 5.4, PRA Software should also be modified to explicitly call out any codes such as Modular Accident Analysis Program Revision 3 Page 109of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (MMP), the HRA Calculator or fire modeling codes that are not are ready controlled under other QA requirements.
(Note: This F&O was generated during the January 2008 review).
Update from PRA RAI 1.m: F&O MU-A 1-01 (2008) observes that the PRA administrative procedure focuses on internal events, and therefore needs to be updated to address the FPRA per the guidance in the PRA Standard. F&O MU-A2-01 (2008) observes that the licensee's procedure does not require monitoring changes in PRA technology and industry experience.
The disposition to these F&Os explains that "DCPP Procedures AWP E-028 and TS3.NR1 will provide the overall program of the PRA model maintenance and upgrade." Though implementation Item S-3.26 of the LAR commits to new pli:int administrative procedure AWP E-028 for scheduling updates and controlling associated models and files, there does not appear to be a process for updating the applicable administrative procedures. It is not clear whether improvements to the applicable administrative procedures have been performed yet. Explain whether the cited improvements to the administrative procedures have already been performed or are.included in an existing implementation item listed in LAR Attachment S, Table S-3. If the cited improvements have not yet been made and are not described in an existing implementation item, then discuss the method to ensure that the cited improvements in FPRA procedure TS3.NR1 will be made before it is used as a basis in self-approval of post-transition changes.
MU-A2 MU-A2-01 (2008), Closed DCPP has an Administrative Procedure for Control of the This F&O has been resolved by.updating the This is closed.
NOT MET, include PRA, TS3.NR1. This procedure does not explicitly administrative procedures to address There is no impact monitoring, require monitoring changes in PRA technology and changes in PRA technology and industry OE. on the ILRT reviewing changes in industry experience. The 2010 peer review concluded that SR Extension Risk PRA technology and Update Section 5.1.3 of TS3.NR 1 to explicitly require MU-A2 is met. Analysis.
industry OEs monitorin1:1/reviewin1:1 chan1:1es in PRA technololi!;t and Revision 3 Page 110of117
54006-CALC-01 Evaluation of Risk Significance of Perma,nent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension industry experience on an every other Unit 2 outage basis.
(Note: This F&O was generated during the January 2008 review).
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement The seismic peer review was performed against a draft version of the Diablo Canyon seismic PRA model, which used updated hazard and fragilities analyses. As noted, the current seismic PRA model, which uses the existing hazard analysis and fragilities, is proposed to be used for the ILRT Extension; therefore, the F&Os for the seismic hazard model (SHA) and seismic fragility model (SFR) elements do not apply to the model proposed to be used.
SPR-81 SPR-81-01, MET, Open Observation: The human action analysis is carried forward from the This F&O is judged to have no significant basis for delay time internal events is adjusted based on time delay defined in Attachment 1, impact on the ILRT Extension Risk in seismic HRA Evaluate Seismic Event Mitigation Strategies (Task 2). The delay times Analysis. The seismic HRA is rel.atively are generic for all actions and it is not clear how they were defined. The unimportant, and any increase in HEP refined results for the first 3 ranges seem to be overly refined given the values would not have a significant impact experience database. Further, a task analysis for the additional work on seismic risk.
load in response to the seismic event was not documented Basis for Significance: It is believed that the seismic influence is considerable with relation to operator stress particularly with regard to higher accelerations. The timing consideration is one factor to address due to delayed responses occurring as operators recover from the effects of the seismic event. The current timing impacts the OCR/TRC method but does not appear to influence the C8DTM method. Given that the internal analysis already assumes a high stress level the net result is that the proceduralized actions are effectively insensitive to seismic effects which seem unrealistic and controlled by the methods selected.
Possible Resolution: A re-evaluation of the actions with regard to the seismic evaluation and considerations with regard to the methods selected and perform a reasonableness assessment of the results. In any case the rationale for the generic time and the changes in delay time by acceleration range needs to be sufficiently documented to provide adequate support the final approach.
SPR-81 SPR-81-02, MET, Open Observation: The model for lower acceleration credits the restoration of This F&O has no impact on the ILRT diesel mission time the diesel generators. The assessment appears to assume the same Extension Risk Analysis. The DG recovery conditions and timing as found in the internal events analysis assuming a is only credited for non-seismic failures for 6-hour mission time. This appears to be inconsistent with the general lower acceleration earthquakes. No diesel guidance for the study that the EDGs are to function for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> due to recoveries are credited for scenarios in the impact of the seismic event on the offsite grid which the components suffer a seismic Basis for Significance: The use of the internal events analysis is based failure; therefore, the impacts of the seismic on a convolution using experience data for all causes of offsite power event on the recovery action will be loss and is not consistent with the situation being addressed. Use of this . minimized. The failure probability and basis value for seismic is not appropriate. was reviewed and confirmed to be correct for seismic events.
Possible Resolution: Revise the assessment to be based on 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review- Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement SPR~81 SPR-81-03, offsite Open* Observation: The fragility for the offsite power is based on DCL-90-205 This F&O will be resolved by additional power fragility which examines the seismic capacity for the 230kV switchyard. It does review and model update if required. The not address external impacts of transmission lines to the site or potential current SPRA model provides a reasonable for other failures that would occur beyond DCPP. estimate of the seismic CDF and LERF for Basis for Significance: The typical value for the median capacity for the purposes of the ILRT extension risk offsite power is on the order of 0.3g mpga (0.7 MSA) and it would be analysis.
expected that a probability of failure at DCPP would exceed that found for most plants due to the awareness of seismic impacts. The documentation indicates a performance of 1.4g MSA (ZOSPWR). The first seismic range is from 0.2g MSA to 1.25 MSA and the associated probability (SOP1) is 0.0144. Given that the capacity should cross 0.5 somewhere over this range, the calculated value appear to understate the probability. Further the next range is up to 1. 75g MSA with an average value of 5.37E-01. Overall the range appears to be under predicting the likelihood of a loss of offsite power.
Possible Resolution: Review the method and determine if the calculation is accurate.
SPR-82 SPR-82-01, NOT Open Observation: The current HFE basis appears to not include any impacts This F&O has no significant impact on the MET, operator gained from operator interviews related to how the seismic event would ILRT Extension Risk Analysis. The seismic interviews in HFE impact timing or other stress factors necessary to adjust the internal HRA is relatively unimportant, and any basis events HFE for seismic. The basis for selecting generic time delays used increase in HEP values would not have a to modify time delay does not appear to be based on any consideration significant impact on seismic risk.
for timing and the complexity of the scenario. It also appears to have little impact on the assessed unreliability for the seismic-specific events.
Basis for Significance: The time windows and cues would be altered based on the seismic event. Following any significant seismic event staff will be involved in verification activities which may delay subsequent activities modeled in the PRA and slow response. Stress may also be present for larger seismic events as the operations staff will have increased workload restoring the plant following the event.
Possible Resolution: Re-baseline the timing for events addressed (counted) in the SPRA using additional operator discussions and considering as a minimum the impact of higher accelerations in terms of work load.
SPR-82 SPR-82-02, NOT Open Observation: No dependency assessment has been developed for the This F&O has no significant impact on the MET, seismic HRA seismic PRA at this point. ILRT Extension Risk Analysis. The seismic dependency HRA is relatively unimportant, and any Revision 3 Page 113of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement Basis for Significance: The current assessment does not account for increase in dependent HEP values would dependence between postulated operator actions as is required by back not have a significant impact on seismic reference HR-G7. risk.
Possible Resolution: Define the HFE combinations in the seismic PRA and complete the assessment for dependence in keeping with the standard.
SPR-83 SPR-83-01, NOT Open Observation: The standard requires defined criteria and documentation This F&O has no impact on the ILRT MET, no of the screening process. The DCPP SPRA does define the criteria for Extension Risk Analysis. Because the acceleration the screening (SS Cs with capacity >11 g); however, there is no original seismic PRA model was developed screening criteria description of*usage of a systematic process for screening SSCs for the concurrent with the internal events PRA DCPP SPRA model. model, no screening was used. Updating Possible Resolution: Add documentation that considers and the documentation to better describe this dispositions all plant equipment for inclusion in the SPRA model, and process will not impact the calculations of clearly provide a documented basis for the final SEL for which the risk changes for the ILRT Extension Risk fragilities are developed and used in the SPRA quantification. Provide a Analysis.
list of the screened out SS Cs in a table so that this process is understood by future reviewers.
SPR-88 SPR-88-01, NOT Open Observation: The model includes a recovery of the Emergenc/'f:Jlesel The diesel generator recovery referenced MET, EOG Generators (EOGs) following a seismic event with an intensity where by the reviewer is only credited for non-recovery they did not fail due to seismic considerations but rather. due to random seismic failures for lower acceleration failures. The analysis appears to utilize the same analysis as utilized in earthquakes. No diesel recoveries are the internal events analysis without alteration and is based on a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> credited for scenarios in which the duration. components suffer a seismic failure Basis for Significance: The use of a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> duration would be therefore the impacts of the seismic event inconsistent with the ground rules applied in the seismic model and on the recovery action will be minimized.
would understate the probability of failing to restore onsite sources. It is The diesel basic events in the seismic also not considered appropriate to include non-seismic experience for model use a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time.
higher accelerations due to resources being displaced to address other plant issues. The standard curves found in most the literature are not considered appropriate.
Possible Resolution: Review the existing assessment and ensure that the EOG recovery is consistent with the need to provide onsite power for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. If EOG recovery is retained, it should be adjusted to reflect the impact that increasing severity and the potential for aftershocks are addressed.
SPR-89 SPR-89-01, CCI, Open Observation: No time or task analysis seems to be developed or This F&O has no significant impact on the*
time-motion study documented to provide the basis on an individual action to demonstrate ILRT Extension Risk Analysis. The seismic Revision 3 Page 114of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement the ability to perform the action and to estimate not only initial delay but HRA is relatively unimportant, and any delays in diagnosis and implementation. increase in HEP values would not have a Basis for Significance: The current assessment only captures in a very significant impact on seismic risk. The time general basis the initial delay and does not provitje any delay impact for delay used in the seismic HRA was based resources being diverted or delayed to do on scenario specific interviews with Operations personnel; therefore, it is expected that these values are valid, and therefore additional documentation may be needed to resolve this F&O.
SPR~B11 SPR-811-01, MET, Open Observation: Table 1 in PRA Calculation F.6 includes a number of This F&O has is judged to have no seismically induced failure modes that would result in loss on inventory with the potential for significant impact on the ILRT Extension floods flood impacts that go beyond the local seismic failure. For example, Risk Analysis. The unconditional seismic Containment Spray Pump failure mode is line break, loss of contents. failure probability for SSCs that could result These failure modes should be considered during the seismic-induced flooding was reviewed to estimate the flood walk down. impact of this issue. In all cases, the total Basis for Significance: Equipment failure modes include a number of unconditional failure probability for these potential flood sources. types of SSCs (piping, tanks, etc.) was less than 1 E-06. Therefore, the potential impact Possible Resolution: Examine the potential for expanded damage from of additional seismically induced flooding is seismically induced flood during the walk down. not significant. Therefore, resolution of this F&O is judged not to significantly impact the calculations of risk changes for the ILRT Extension Risk Analysis.
SPR-C1 SPR-C1-01, MET, Open Observation and Basis for Significance: The DC SPRA model reflects This F&O has no adverse impact on the chattering of solid the as-built, as-operated plant with some exceptions. These include the ILRT Extension Risk Analysis.
state relays conservatism assumption related to the solid state protective relays on Conservatisms in the seismic response of
- the 4kV breakers and the updated charging pump. components will not adversely impact the Possible Resolution: Evaluate the impact of the solid chatter of relays calculations of risk changes for the ILRT and the charging pump. Extension Risk Analysis.
SPR-E1 SPR-E1-01, MET, Open Observation: Due to the definition of the hazard bins, the failure fragility This F&O has no adverse impact on the expand number of probability for offsite power (SOP) has a value of 0.014 in the first bin and ILRT Extension Risk Analysis. The issue is bins to allow for a 0.54 in the second bin. The discrete bins do not provide a good how the initiator binning is used to credit better fragility representation of the offsite power fragility curve in this range. While . operator recovery actions. Because the representation RISKMAN properly handles this in the fragility calculation with the use of upper bin boundary was used in developing 1OD-bin representation of the fragility curve in each initiator bin, the use operator actions and not bin midpoint of the mid-point may not accurately reflect the range of plant conditions values, the operator actions are for HRA and recovery. conservative for a given range of Revision 3 Page 115of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement Basis for Significance: Due to the range of the first bin compared to acceleration. If additional binning is added, the change in fragility for offsite power, it is possible that the first bin is it is possible that more credit could be non-conservative for the upper portion of that bin. taken for a recovery action at lower Possible Resolution: Expanding the number of bins would allow for a accelerations. Therefore, resolution of this better representation of fragility in discrete bins. F&O would not to adversely impact the calculations of risk changes for the ILRT Extension Risk Analysis.
SPR-E1 SPR-E1-02, MET, Open Observation: In the definition of the hazard bins, the last bin represents This F&O has no impact on the ILRT expand bins 3 to 4g median acceleration. However, at this level, the conditional Extension Risk Analysis. Redefining the covering hazard probability of large early release (CLERP) is still well below 1.0. The hazard bin to ensure LERF importance can above 4.0g current model accounts for this by assuming that the value of CLERP for be assessed has no impact on the earthquakes above 4g is 0.1, and applying this residual to the LERF calculations of risk changes for the ILRT results outside the RISKMAN model. While this may be a reasonable Extension Risk Analysis.
assumption with regard to the total LERF value, it results in loss of information regarding the relative importance of LERF contributors ..
Basis for Significance: This approximation results in loss of information regarding the contributors to LERF.
Possible Resolution: Expand the number of hazard bins, with bins that represent the hazard above 4.0 g. The last bin should be chosen so that the CLERP value is close to 1.0.
SPR-E1 SPR-E1-05, MET, Open Observation: The RISKMAN event tree ELECPWR appears to have an This F&O will have no significant impact on error in ELECPWR error in the rules for top event DH, specifically split fraction set DH1 SB to the ILRT Extension Risk Analysis. A review DH63SB. These use the macro SEISB when they should be using of the error concluded that it will not impact "SEISA + SEISB." the results of the seismic PRA, and Basis for Significance: This error will likely not be important to the therefore will not impact the calculations of results because it represents the lower acceleration bins. In addition, this risk changes for the ILRT Extension Risk was the only error identified in the seismic-related rules that were re- Analysis.
reviewed.
Possible Resolution: Correct the error and verify that the error was not important to the results.
SPR-E5 SPR-E5-01, NOT Open Observation: PRA Calculation C.9 provides point estimates for CDF This F&O has no impact on the ILRT MET, no and LERF, but does not address uncertainty distributions. Extension Risk Analysis. Seismic uncertainty Basis for Significance: The SR requires estimating or addressing parametric uncertainty analysis does not distribution uncertainty distributions for CDF and LERF. impact the quantitative results and will not provided impact the calculations of risk changes for Possible Resolution: Use RISKMAN Monte Carlo tools to calculate the ILRT Extension Risk Analysis.
uncertainty distributions for CDF and LERF.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement SPR-F1 SPR-F1-01, NOT Open Observation: The SPRA documentation says in a number of places that This F&O has no impact on the ILRT MET, modeling of the SPRA takes no credit for cross ties between Units following a seismic Extension Risk Analysis. The issue was cross ties between event (e.g., Page 2 of Attachment 2 to F.6). However, the RISKMAN reviewed and it was determined that the Units event tree model does not guarantee failure of all cross-tie options for model appropriately addresses availability seismic events. As a result, it is not clear that the model is consistent for opposite unit equipment. Therefore, with the documentation. resolution of this F&O will not impact the Basis for Significance: Potential inconsistency between documentation calculations of risk changes for the ILRT and model. Extension Risk Analysis.
Possible Resolution: Either revise the Event Tree models so that it is assured that no credit is taken for cross-ties or provide justification for specific cross-ties (for example, at low acceleration levels where independent hardware failures dominate, cross-tie options may be appropriate).
SPR-F1 SPR-F1-02, NOT Open Observation: The current documentation includes references to PLG- This F&O has no impact on the ILRT MET, roadmap 0637, but it is not clear how much of that 1988 document is still valid and Extension Risk Analysis. Clarification of between current relied on. documentation will not impact the documents and Basis for Significance: Unclear what current documentation is. calculations of risk*changes for the ILRT PLG-0637 Extension Risk Analysis.
Possible Resolution: Provide a roadmap from current documentation (e.g., Calculation F.6) back to specific sections of PLG-0637 that are still current.
SPR-F1 SPR-F1-05, NOT Open Observation: Page 22 of PRA Calculation F.6 implies that shutdown This F&O has no impact on the ILRT MET, document seals are inclµded in the model. While it is understood that these may be Extension Risk Analysis. The current future plant mods added in the future, the documentation should reflect the as-built plant. seismic PRA model does not include credit Basis for Significance: Documentation is not consistent with as-built for these seals. The documentation issue plant.
- identified by this F&O does not impact the calculations of risk changes for the ILRT Possible Resolution: Remove this reference to shutdown seals. Extension Risk Analysis.
SPR-F3 SPR-F3-01, NOT Open Observation: Some modeling uncertainties and assumptions are This F&O has no impact on the ILRT MET, complete identified throughout the documentation. However, no complete Extension Risk Analysis. Improving the sources of model documentation of sources of model uncertainty and assumptions was documentation of model uncertainty and uncertainty and identified. assumptions will not impact the calculations assumptions Basis for Significance: This is required by the SR. of risk changes for the ILRT Extension Risk Analysis.
Possible Resolution: Analyze and document the sources of model uncertainty and assumptions in the plant response model.
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Enclosure Attachment 3 PG&E Letter DCL-16-057 Evaluation of Risk Significance of Permanent ILRT Extension
JENSEN HUGHES c
Advancing the Science of Safety
- Diablo Canyon Power Plant:
Evaluation of Risk Significance of Permanent ILRT Extension 54006-CALC-O 1 Prepared for:
Diablo Canyon Power Plant Project
Title:
Permanent ILRT Extension Revision: 3 Name and Date 1 1 Preparer: Justin Sattler [
8ig1itally signed by Justin Sattler j,
E>ate: 2016.04.21 14:13:29-05'00' Reviewer: Kelly Wright Review Method Design Review IZI Alternate Calculation D Approved by: Matthew Johnson Revision 3 Page 1of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension REVISION RECORD
SUMMARY
Revision Revision Summary 0 Initial Issue Minor updates made based on client comments 2 Minor updates made based on client comments 3 Minor updates made based on client comments Revision 3 Page 2of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension TABLE OF CONTENTS 1.0 PURPOSE ...................................................................................................................... 4 2.0 SCOPE ......... :................................................................................................................. 4 3.0 . REFERENCES ............................................................................................................... 6 4.0 ASSUMPTIONS AND LIMITATIONS ....................... :.............................. ;....................... 8 5.0 METHODOLOGY and analysis ....................................................................................... 9 5.1 Inputs ........................................................................................................................... 9 5.1.1 General Resources Available .............................................................;.................. 9
~.1.2 Plant Specific Inputs ............................................................................................ 12 5.1.3 Impact of Extension on Detection of Component Failures that Lead to Leakage (Small and Large) .............................................................................................. 14 ,
5.2 Analysis ........................................................................................*.............................15 5.2.1 Step 1 - Quantify the Baseline Risk in Terms of Frequency per Reactor Year ..... 16 5.2.2 Step 2 - Develop Plant-Specific Person-Rem Dose (Population Dose) ................ 19 5.2.3 Step 3- Evaluate Risk Impact of Extending Type A Test Interval from 10 to 15 Years .................................................................................................................20 5.2.4 Step 4- Determine the Change in Risk in Terms of LERF ................................... 24
.5.2.5 Step 5 - Determine the Impact on the Conditional Containment Failure Probability
....................................... ,.................................................................................. 24 5.2.6 Impact of Extension on Detection of Steel Liner Corrosion that Leads to Leakage
.............................................................................. ,........................................... 25 5.3 Sensitivities ..................................................... ~ ...........................................................28 5.3.1 Potential Impact from External Events Contribution ......................*...................... 28 5.3.2 Potential Impact from Steel Liner Corrosion Likelihood ........................................ 30 5.3.3 Expert Elicitation Sensitivity *********************************************************************.::**********32 6.0 RESULTS ......................................................................................................................34
7.0 CONCLUSION
S AND RECOMMEND~TIONS ............................. ~ ......... ,...................... 36 A. Attachment 1 ...........................................................................................*.....................38 Revision 3 Page 3of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 1.0 PURPOSE The purpose of this analysis is to provide a risk assessment of permanently extending the currently allowed containment Type A Integrated Leak Rate Test (ILRT) to fifteen years. The extension would allow for substantial cost savings as the ILRT could be deferred for additional scheduled refueling outages for the Diablo Canyon Power Plant (DCPP). The risk assessment
- ' follows the guidelines from NEI 94-01, Revision 3-A [Reference 1], the methodology used in EPRI TR-104285 [Reference 2], the NEI "Interim Guidance fot Performing Risk Impact Assessments in Support of One-Time Extensions for Containment Integrated Leakage Rate Test Surveillance Intervals" from November 2001 [Reference 3], the NRC regulatory guidance on the use of Probabilistic Risk Assessment (PRA) as stated in Regulatory Guide 1.200 as applied to ILRT interval extensions, risk insights in support of a request for a plant's licensing basis as outlined in Regulatory Guide (RG) 1.174 [Reference 4], the methodology used for Calvert Cliffs to estimate the likelihood and risk implications of corrosion-induced leakage of steel liners going undetected during the extended test interval [Reference 5], and the methodology used in EPRI 1018243, Revision 2-A of EPRI 1009325 [Reference 24].
2.0 SCOPE Revisions to 10CFR50, Appendix J (Option 8) allow individual plants to extend the Integrated Leak Rate Test (ILRT) Type A surveillance testing frequency requirement from three in ten years to at least once in ten years. The revised Type A frequency is based on an acceptable performance history defined as two consecutive periodic Type A tests at least 24 months apart in which the calculated performance leakage rate was less than limiting containment leakage rate of 1La.
The basis for the current 10-year test interval is provided in Section 11.0 of NEI 94-01, Revision
- 0, and established in 1995 during development of the performance-based Option B to Appendix J. Section 11.0 of NEI 94-01 states that NUREG-1493, "Performance-Based Containment Leak Test Program," September 1995 [Reference 6], provides the technical basis to. support rulemaking to revise leakage rate testing requirements contained in Option B to Appendix J. The basis consisted of qualitative and quantitative assessment of the risk impact (in terms of increased public dose) associated with a range of extended leakage rate test intervals. To supplement the NRC's rulemaking basis, NEI undertook a similar study. The results of that study are documented in Electric Power Research Institute (EPRI) Research Project TR-104285, "Risk Impact Assessment of Revised Containment Leak Rate Testing Intervals."
The NRC report on performance-based leak testing, NUREG-1493, analyzed the effects of containment leakage on the health and safety of the public and the benefits realized from the containment leak rate testing. In that analysis, it was determined that for a representative PWR plant (i.e., Surry), that containment isolation failures contribute less than 0.1 % to the latent risks from reactor accidents. Consequently, it is desirable to show that extending the ILRT interval will not lead to a substantial increase in risk from containment isolation failures for DCPP .
. NEI 94-01 Revision 2-A contains a Safety Evaluation Report that supports using EPRI Report No. 1009325 Revision 2-A, "Risk Impact Assessment of Extended Integrated Leak Rate Testing Intervals," for performing risk impact assessments in support of ILRT extensions [Reference 24].
The Guidance provided in Appendix Hof EPRI Report No. 1009325 Revision 2-A builds-on the EPRI Risk Assessment methodology, EPRI TR-104285. This methodology is followed to determine the appropriate risk information for use in evaluating the impact of the proposed ILRT changes.
/
It should be noted that containment leak-tight integrity is also verified through periodic in-service Revision 3 Page 4of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension inspections conducted in accordance with the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section XI. More specifically, Subsection IWE provides the rules and requirements for in-service inspection of Class MC pressure-retaining components and their integral attachments, and of metallic shell and penetration liners of Class CC pressure-retaining components and their integral attachments in light-water cooled plants. Furthermore, NRC regulations 10 CFR 50.55a(b)(2)(ix)(E) require licensees to conduct visual inspections of the accessible areas of the interior of the containment. The associated change to NEI 94-01 will require that visual examinations be conducted during at least three other outages, and in the outage during which the ILRT is being conducted. These requirements will not be changed as a result of the extended ILRT interval. In addition, Appendix J, Type B local leak tests performed to verify the leak-tight integrity of containment penetration bellows, airlocks, seals, and gaskets are also not affected by the change to the Type A test frequency. ,
The acceptance guidelines in RG 1.174 are used to assess the acceptability of this permanent extension of the Type A test interval beyond that established during the Option B rulemaking of Appendix J. RG 1.174 defines very small changes in the risk-acceptance guidelines as
- increases in Core Damage Frequency (CDF) less than 1o-s per reactor year and increases in Large Early Release Frequency (LERF) less than 10-7 per reactor year. Since the Type A test does not impact CDF, the relevant criterion is the change in LERF. RG 1.174 also defines small changes in LERF as below 1o-s per reactor year. RG 1.174 discusses defense-in-depth and encourages the use of risk analysis techniques to help el)sure and show that key principles, such as the defense-in-depth philosophy, are met. Therefore, the increase in the Conditional Containment Failure Probability (CCFP), which helps ensure the defense-in-depth philosophy is maintained, is also calculated.
Regarding CCFP, changes of up to 1.1% have been accepted by the NRC for the one-time requests for extension of ILRT intervals. In context, it is noted that a CCFP of 1/10 (10%) has been approved for application to evolutionary light water designs. Given these perspectives, a change in the CCFP of up to 1.5% is assumed to be small.
In addition, the total annual risk (person rem/year population dose) is examined to demonstrate
-- the relative ch-arige iri this parameter. While rio acceptance guidelines for these additional figures of merit are published, examinations of NUREG-1493 and Safety Evaluation Reports (SER) for one-time interval extension (summarized in Appendix G of Reference 24) indicate a range of incremental increases in population dose that have been accepted by the NRC. The range of incremental population dose increases is from :::;0.01 to 0.2 person-rem/year and/or 0.002% to 0.46% of the total accident dose. The total doses for the spectrum of all accidents (NUREG-1493 [Reference 6], Figure 7-2) result in health effects that are at least two orders of magnitude less than the NRC Safety Goal Risk. Given these perspectives, a very small population dose is defined as an increase from the baseline interval (3 tests per 10 years) dose of :::;1.0 person-rem per year or 1% of the total baseline dose, whichever is less restrictive for the risk impact assessment of the proposed extended ILRT interval.
For those plants that credit containment overpressure for the mitigation of design basis accidents, a brief description of whether overpressure is required should be included in this section. In addition, if overpressure is included in the assessment, other risk metrics such as CDF should be described and reported.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
3.0 REFERENCES
The following references were used in this calculation:
- 1. Revision 3-A to Industry Guideline for Implementing Performance-Based Option of 10 CFR Part 50, Appendix J, NEI 94-01, July 2012.
- 2. Risk Impact Assessment of Revised Containment Leak Rate Testing Intervals, EPRI, Palo Alto, CA EPRI TR-104285, August 1994.
- 3. Interim Guidance for Performing Risk Impact Assessments in Support of One-Time Extensions for Containment Integrated Leakage Rate Test Surveillance Intervals, Revision 4, developed for NEI by EPRI and Data Systems and Solutions, October 2001.
- 4. An Approach for Using Probabilistic Risk Assessment in Risk-Informed De.cisions on Plant-Specific Changes to the Licensing Basis, Regulatory Guide 1.174, May 2011.
- 5. Response to Request for Additional Information Concerning the License Amendment Request for a One-Time Integrated Leakage Rate Test Extension, Letter from Mr. C. H.
Cruse (Calvert Cliffs Nuclear Power Plant) to NRC Document Control Desk, Docket No.
50-317, March 27, 2002.
- 6. Performance-Based Containment Leak-Test Program, NUREG-1493, September 1995.
- 7. Evaluation of Severe Accident Risks: Surry Unit 1, Main Report NUREG/CR-4551, SAND86-1309, Volume 3, Revision 1, Part 1, October 1990.
- 8. Letter from R. J. Barrett (Entergy) to U.S. Nuclear Regulatory Commission, IPN-01-007, January 18, 2001.
- 9. United States Nuclear Regulatory Commission, Indian Point Nuclear Generating Unit No. 3 - Issuance of Amendment Re: Frequency of Performance-Based Leakage Rate Testing (TAC No. MB0178), April 17, 2001.
- 10. Impact of Containment Building Leakage on LWR Accident Risk, Oak Ridge National Laboratory, NUREG/CR-3539, ORNL/TM-8964, April 1984.
- 11. Reliability Analysis of Containment Isolation Systems, Pacific Northwest Laboratory, NUREG/CR-4220, PNL-5432, June 1985.
- 12. Technical Findings and Regulatory Analysis for Generic Safety Issue 11.E.4.3
'Containment Integrity Check', NUREG-1273, April 1988.
- 13. Review of Light Water Reactor Regulatory Requirements, Pacific Northwest Laboratory, NUREG/CR-4330, PNL-5809, Volume 2; June 1986.
- 14. Shutdown Risk Impact Assessment for Extended Containment Leakage Testing Intervals Utilizing ORAM', EPRI, Palo Alto, CA, TR-105189, Final Report, May 1995.
- 15. Severe Accident Risks: An Assessment for Five U. S. Nuclear Power Plants, NUREG-1150, December 1990.
- 16. United States Nuclear Regulatory Commission, Reactor Safety Study, WASH-1400, October 1975.
- 17. Calculation C.9, Revision 13, Diablo Canyon Power Plant, "Quantification of CDF and LERF for the DCPP PRA Model."
- 18. Email from Nathan R. Barber (PG&E, Diablo Canyon) to Matt Johnson, dated January 6, 2016, 7:40 AM, Fire PRA Numbers for ILRT Report.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
- 19. E.RIN Report No. C114140001-8420, "Level 3 PRA Consequence Analysis (MACCS2 MODEL) for Diablo Canyon Severe Accident Mitigation Alternatives (SAMA) Evaluation,"
December 2014.
- 20. Anthony R. Pietrangelo, One-time extensions of containment integrated leak rate test interval - additional information, NEI letter to Administrative Points of Contact, November 30, 2001.
- 21. Letter from J. A. Hutton (Exelon, Peach Bottom) to U. S. Nuclear Regulatory Commission, Docket No. 50-278, License No. DPR-56, LAR-01-00430, dated May 30, 2001.
- 22. Risk Assessment for Joseph M. Farley Nuclear Plant Regarding ILRT (Type A)
Extension Request, prepared for Southern Nuclear Operating Co. by ERIN Engineering and Research, P0293010002-1929-030602, March 2002.
- 23. Letter from D. E. Young (Florida Power, Crystal River) to U.S. Nuclear Regulatory Commission, 3F0401-11, dated April 25, 2001.
- 24. Risk Impact Assessment of Extended Integrated Leak Rate Testing Intervals, Revision 2-A of 1009325, EPRI, Palo Alto, CA. 1018243, October 2008.
- 25. Risk Assessment for Vogtle Electric Generating Plant Regarding the ILRT (Type A)
Extension Request, prepared for Southern Nuclear Operating Co. by ERIN Engineering and Research, February 2003.
- 26. Perspectives Gained from the IPEEE Program, USNRC, NUREG-1742, April 2002.
- 27. Calculation E.16, Revision 2, Diablo Canyon Power Plant, "DCPP PRA Success Criteria Notebook." *
- 28. Letter L-14-121, ML14111A291, FENOC Evaluation of the Proposed Amendment, Beaver Valley Power Station, Unit Nos. 1 and 2, April 2014.
- 29. Technical Letter Report ML112070867, Containment Liner Corrosion Operating Experience Summary, Revision 1, August 2011.
- 30. Ca-lculation PRA 01-07, Pacific Gas & Electric Company, "Risk Impact Assessment of Extending Containment Type A Test Interval," Revision 1, October 2011.
- 31. Armstrong, J., Simplified Level 2 Modeling Guidelines: WOG PROJECT: PA-RMSC-0088, Westinghouse, WCAP-16341-P, November 2005. *
- 33. Transition Report, "Pacific Gas and Electric Company Diablo Canyon Power Plant Units 1 and 2 Docket 50-275 and 50-323: Transition to 10 CFR 50.48(c) - NFPA 805:
Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants, 2001 Edition," June 2013.
- 34. Calculation N.2, Revision 1, Diablo Canyon Power Plant, "DCPP PRA Level 2 and Containment Event Tree Model."
- 35. Calculation G.2, Revision 7, Diablo Canyon Power Plant, "Human Action Analysis -
Failure Likelihood and Range Factor Calculation."
Revision 3 Page 7of117.
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 4.0 ASSUMPTIONS AND LIMITATIONS The following assumptions were used in the calculation:
- The technical adequacy of the DCPP PRA is either consistent with the requirements of Regulatory Guide 1.200 or where gaps exist, the gaps have been addressed, as is relevant to this ILRT interval extension, as detailed in Attachment 1.
- It is appropriate to use the DCPP internal events PRA model to effectively describe the risk change attributable to the ILRT extension. An extensive sensitivity study is done in Section 5.3.1 to show the effect of including external event models for the ILRT extension. The Fire PRA (model DC03M) and Seismic PRA [Reference 17] are used for this sensitivity analysis.
- Accident classes describing radionuclide release end states are defined consistent with EPRI methodology [Reference 2]. ,
- Ther representative containment leakage for Class 1 sequences is 1La. Class 3 accounts for increased leakage due to Type A inspection failures.
- The representative containment leakage for Class 3a sequences is 1Ola based on the previously approved methodology performed for Indian Point Unit 3 [Reference 8, Reference 9].
- The representative containment leakage for Class 3b sequences is 1OOLa based on the guidance provided in EPRI Report No. 1009325, Revision-..?-A (EPRI 1018243)
[Reference 24]. . *
- The Class 3b can be very conservatively categorized as LERF based on the previously approved methodology [Reference 8, Reference 9].
- The impact on population doses from containment bypass scenarios is not altered by the proposed ILRT extension, but is accounted for in the !=PRI methodology as a separate entry for comparison purposes. Since the containment bypass contribution to population dose is fixed, no changes in the conclusions from this analysis will result from this separate categorization. *
- The reduction in ILRT frequency does not impact the reliability of containment isolation valves to close in response to a containment isolation signal.
I Revision 3 Page 8of117
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 5.0 METHODOLOGY AND ANALYSIS 5.1 Inputs This section summarizes the general resources available as input (Section 5.1.1) and the plant specific resources required (Section 5.1.2).
5.1.1 General Resources Available Various industry studies on containment leakage risk assessment are briefly summarized here:
- 1. NUREG/CR-3539 [Reference 1O]
- 2. NUREG/CR-4220 [Reference 11]
- 3. NUREG-1273 [Reference 12]
- 4. NUREG/CR-4330 [Reference 13]
- 6. NUREG-1493 [Reference 6]
- 7. EPRI TR-104285 [Reference 2]
1
- 8. NUREG-1150 [Reference 15] and NUREG/CR-4551 [Reference 7]
- 9. NEI Interim Guidance [Reference 3, Reference 20]
- 10. Calvert Cliffs liner corrosion analysis [Reference 5]
This first study is applicable because it provides one basis for the threshold that could be used ih the Level 2 PRA for the size of containment leakage that is considered significant and is to be included in the model. The second study is applicable because it provides a basis of the probability for significant pre-existing containment leakage at the time of a core damage accident. The third study is applicable because it is a subsequent study to NUREG/CR-4220 that undertook a more extensive evaluation of the same database. The fourth study provides an assessment of the impact of different containment leakage rates on-plant risk. The fifth study provides an assessment of the impact on shutdown risk from ILRT test interval extension. The sixth study is. the NRC's cost-benefit analysis of various alternative approaches regarding extending the test intervals and increasing the allowable leakage rates for containment integrated and local leak rate tests. The seventh study is an EPRI study of the impact of extending ILRT and local leak rate test (LLRT) intervals on at-power public risk. The eighth study provides an ex-plant consequence analysis for a 50-mile radius surrounding a plant that is used as the basis for the consequence analysis of the ILRT interval extension for DCPP. The ninth study includes the NEI recommended methodology (promulgated in two letters) for evaluating the risk associated with obtaining a one-time extension of the ILRT interval. The
- tenth study addresses the impact of age-related degradation of the containment liners on ILRT evaluations. Finally, the eleventh study builds on the previous work and includes a recommended methodology and template for evaluating the ~isk associated with a permanent 15-year extension of the ILRT interval.
- NUREG/CR-3539 [Reference 1O]
Qak Ridge National Laboratory documented a study of the impact of containment leak rates on public risk in NUREG/CR-3539. This study uses* information from WASH-1400 [Reference 16]
as the basis for its risk sensitivity calculations. ORNL concluded that the impact of leakage rates on LWR accident risks is relatively small. -
NUREG/CR-4220 [Reference 11]-
NUREG/CR-4220 is a study performed by Pacific Northwest Laboratories for the NRC in 1985.
The study reviewed over two thousand LERs, ILRT reports and other related records to Revision 3 Page 9of117
54006-CALC-01 Evaluation of Risk Significance of Perma_nent ILRT Extension calculate the unavailability of containment due to leakage.
j NUREG-1273 [Reference 121 A subsequent NRC study, NUREG-1273, performed a more extensive evaluation of the NUREG/CR-4220 database. This assessment noted that about .one-third of the reported events were leakages that were immediately detected and corrected. In addition, this study noted that local leak rate tests can detect "essentially all potential degradations" of the containment isolation system.
- NUREG/CR-4330 [Reference 131 NUREG/CR-4330 is a study that examined the risk impacts associated with increasing the allowable containment leakage rates. The details of this report have no direct impact on the modeling approach of the ,ILRT test interval extension, as NUREG/CR-4330 focuses on leakage rate and the ILRT test interval extension study focuses on the frequency of testing intervals.
However, the general conclusions of NUREG/CR-4330 are consistent with NUREG/CR-3539 and other similar containment leakage risk studies:
" ... the effect of containment leakage on overall accident risk is small since risk is aominated by accident sequences that result in failure or bypass of containment."
EPRI TR-105189 [Reference 141 The EPRI study TR-105189 is useful to the ILRT test interval extension risk assessment because it provides insight regarding the impact of containment testing on shutdown risk. This study contains a quantitative evaluation (Using the EPRI ORAM software) for two reference plants (a BWR-4 and a PWR) of the impact of extending ILRT and LLRT test intervals on shutdown risk. The conclusion from the study is that a small, but measurable, safety benefit is realized from extending the te.st intervals.
NUREG-1493 [Reference 61 NUREG-1493 is the NRC's cost-benefit analysis for proposed alternatives to reduce containment leakage testing interv~ls and/or relax allowable leakage rates. The NRC conclusions are.consistent with other similar containment leakage risk studies:
Reduction in ILRT frequency from 3 per 10 years to 1 per 20 years results in an "imperceptible" increase in risk.
Given the insensitivity of risk to the containment leak rate' and the small fraction of leak paths detected solely by Type A testing, increasing the interval between integrated leak rate tests is .
possible with minimal impact on public risk.
EPRI TR-104285 [Reference 21 Extending the risk assessment impact beyond shutdown (the earlier EPRI TR-1.05189 study},
the EPRI IR-104285 study is a quantitative evaluation of the impact of extending ILRT and LL.RT test intervals on at-power*public risk. This study com_bined IPE Level 2 models with NUREG-1150 Level 3 population dose models to perform the analysis. The study also used the approach of NUREG-1493 in calculating the increase iii pre-existing leakage probability due to extending the ILRT and LLRT test intervals. .,
EPRI TR-104285 uses a simplified Containment Event Tree to subdivide representative core damage frequencies into eight classes of containment response to a core damage accident:
1., Containment intact and isolated
- 2. Containment isolation failures dependent upon the core damage accident
- 3.
- Type A (ILRT) related containment isolation failures
- Revision 3 Page 10of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
- 4. Type B (LLRT) related containment isolation failures
- 5. Type C (LLRT) related containment isolation failures
- 6. Other penetration related containment isolation failures
- 7. Containment failures due to core damage accident phenomena
- 8. Containment bypass Consistent with the other containment leakage risk assessment studies, this study concluded:
" ... the proposed CLRT (Containment Leak Rate Tests) frequency changes would have a minimal safety impact. The change in risk determined by the analyses is small in both absolute and relative terms. For example, for the PWR analyzed, the change is about 0.04 person-rem per year ... "
NUREG-1150 [Reference 151 and NUREG/CR-4551 [Reference 71 ~
NUREG-1150 and the technical basis, NUREG/CR-4551, provide an ex-plant consequence analysis for a spectrum of accidents including a severe accident with the containment remaining
) intact (i.e., Tech _Spec Leakage). This ex-plant consequence analysis is calculated for the 50-mile radial area surrounding Surry. The ex-plant calculation can be delineated to total person-rem for each identified Accident Progression Bin (APB) from NUREG/CR-4551. With the DCPP Level 2 model end-states assigned to one of the NUREG/CR-4551 APBs, it is considered adequate to represent DCPP. (The meteorology and site differences other than' population are ass4.med not to play a significant role in this evaluation.)
NEI Interim Guidance for Performing Risk Impact Assessments In Support of One-Time Extensions for Containment Integrated Leakage Rate Test Surveillance Intervals [Reference 3, Reference 201 The guidance provided in this document builds on the EPRI risk impact assessment methodology [Reference 2] and the NRC performance-based containment leakage test program
[Reference 6], and considers approaches utilized in various' submittals, including Indian Point 3 (and associated NRC SER) and Crystal River. \
Calvert Cliffs Response to Request for Additional Information Concerning the License Amendment for a One-Time Integrated Leakage Rate Test Extension [Reference 5]
This submittal to the NRC describes a method for determining the change in likelihood, due to extending the ILRT,of detecting liner corrosion, and the corresponding change in risk. The methodology was developed for Calvert Cliffs in response to a request for additional information regarding how the potential leakage due to age-related degradation mechanisms was factored into the risk assessment for the ILRT one-time extension. The Calvert Cliffs analysis was performed for a concrete cylinder and dome and a concrete basemat, each with a steel liner.
EPRI Report No. 1009325. Revision 2-A. Risk Impact Assessment of Extended Integrated Leak Rate Testing Intervals [Reference 241 This report provides a generally applicable assessment of the risk involved in extension of ILRT test intervals to permanent 15-year intervals. Appendix H of this document provides guidance for performing plant-specific supplemental risk impact assessments and builds on the previous EPRI risk impact assessment methodology [Reference 2] and the NRC performance-based containment leakage test program [Reference 6], and considers approaches utilized in various submittals, including Indian Point 3 (and associated NRC SER) and Crystal River.
The approach included in this guidance document is used in the DCPP assessment to determine the estimated increase in risk associated with the ILRT extension. This document includes the bases for the values assigned in determining the probability of leakage for the EPRI Class 3a and 3b scenarios in this analysis, as described in Section 5.2.
Revision 3 Page 11of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 5.1.2 Plant Specific Inputs The plant-specific information used to perform the DCPP ILRT Extension Risk Assessment includes the following: *
- Level 1 Model results [Reference 17]
- Release category definitions used in the Level 2 Model [Reference 19]
- Dose within a 50-mile radius [Reference 19]
- ILRT results to demonstrate adequacy of the administrative and hardware issues
[Reference 30]
DCPP Model The Internal Events PRA Model that is used for DCPP is characteristic of the as-built plant. The current Level 1 model (DCPP PRA Model Version DC03) [Reference 17] is a large event tree, small fault tree model. The Internal Flood CDF is 7.52E-6/year for Unit 1 and 5.45E-6/year for Unit 2, and the LERF is 4.19E-7/year for Unit 1 and 3.43E-7 for Unit 2 [Refer~nce 17]. The total internal events CDF, including internal flooding, is 1.89E-5/year for Unit 1 and 1.69E-5/year for Unit 2, and the total LERF is 2.26E-6/year for Unit 1 and 2.18E-6 for Unit 2 [Reference 17].
Table 5-1 and Table 5-2 provide a summary of the Internal Events CDF and LERF results, respectively.
The total Fire CDF is 4.83E-5/year for Unit 1 and 5.24E-5/year for Unit 2; the total Fire LERF is 2.45E-6/year for Unit 1 and 2.17E-6/year for Unit 2 [Reference 18]. Refer to Section 5.3.1 for further details on external events as they pertain to this analysis.
Table 5 Internal Events QDF (DCPP PRA Model Version DC03)
Internal Events Frequency (per year)
LOCA 3.77E-06 Loss of ASW or CCW 2.63E-06 Transient 2.35E-06 SGTR 1.32E-06 Loss of 480V Switchgear Ventilation 3.88E-07 Loss ofone 125V DC 'Bus 4.33E-07 LOOP 3.53E-07 Other 1.37E-07 I
Flood 7.52E-06 (Unit 1) 5.45E-06 (Unit 2)
Total Internal Events CDF 1.89E-05(Unit1) 1.69E-05 (Unit 2) 1 Revision 3 Page 12of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Internal Events LERF (DCPP PRA Model Version DC03)
Internal Events Frequency (per year)
LOCA 2.76E-07 Loss of ASW or CCW 5.?0E-08 Transient 9.38E-08 SGTR 1.31E-06 Loss of 480V Switchgear Ventilation 5.15E-08 Loss of one 125V DC Bus 1.10E-08 LOOP 2.76E-08 Other 1.47E-08 Flood 4.19E-07(Unit1) 3.43E-07 (Unit2)
Total Internal Events LERF 2.26E-06 (Unit 1) 2.18E-06 (Unit 2)
Population Dose Calculations The population dose was calculated for the DCPP SAMA in Table 4.1-2 of Reference 19, which reports six release categories: ST1 (large early), ST2 (small early), ST3 (late), ST4 (bypass w/
AFW), STS (ISLOCA), and ST6 (intact). Class 1 frequency corresponds to ST6. Since Classes 2 and 7 do not have a release category that precisely matches, they conservatively correspond to ST1. Class 8 consists of interfacing system loss of coolant accident (ISLOCA) and steam generator tube rupture (SGTR) frequency. The ISLOCA frequency corresponds to STS. of Reference 17 presents the top 200 cutsets in the LERF model. Of the un-isolated SGTR sequences (SGTRN), 95% of them are release class RC17 and have AFW available; Table 3.2-4 of Reference 19 states ST4 is representative of RC17. Therefore, ST4 is the most representative for SGTR frequency. Table 5-3 presents dose exposures calculated from methodology described in Reference 1 and data from Reference 19. Class 3a and 3b population dose values are calculated from the Class 1 population dose and represented as 1Ola and 1OOLa, respectively, as guidance in Reference 1 dictates.
Table 5 Population Dose Accident Class Description Release (person-rem)
Containment Remains Intact 3.68E+03 2 Containment Isolation Failures 9.83E+06
/
3a Independent or Random Isolation Failures SMALL 3.68E+04 1 3b Independent or Random Isolation Failures LARGE 3.68E+05 2 Isolation Failure in which pre'-xistihg leakage is not 4 n/a dependent on sequence progression. Type B test Failures Isolation Failure in which pre-existing leakage is not 5 n/a dependent on sequence progression. Type C test Failures 6 Isolation Failure that can be verified by IST/IS or surveillance nla 7 Containment Failure induced by severe accident 9.83E+06 8 Accidents in which containment is by-passed 8.90E+053
- 1. 10*La
- 2. 100 *La
- 3. The Class 8 dose value differs from the value presented in Reference 19 because the dose is weighted based on frequency of the two Class 8 contributors: ISLOCA and SGTR.
Revision 3 Page 13of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Release Category Definitions Table 5-4 defines the accident classes used in the ILRT extension evaluation, which is consistent with the EPRI methodology [Reference 2]. These containment failure classifications are used in this analysis to determine the risk impact of extending the Containment Type A test interval, as described in Section 5.2 of this report.
Table 5 EPRI Containment Failure Classification [Reference 2]
Class Description Containment remains intact including accident sequences that do not lead to containment failure in the long term. The release of fission products (and attendant consequences) is determined by the maximum allowable leakage rate values La, under Appendix J for that plant.
Containment isolation failures (as reported in the lndivi!;fual Plant Examinations) including those accidents 2
in which there is a failure to isolate the containment.
Independent (or random) isolation failures include those accidents in which the pre-existing isolation 3
failure to seal (i.e., provide a leak-tight containment) is not dependent on the sequence in progress.
Independent (or random) isolation failures include those accidents in which the pre-existing isolation failure to seal is not dependent on the sequence in progress. This class is similar to Class 3 isolation 4
failures, but is applicable to sequences involving Type B tests and their potential failures. These are the Type B-tested components that have isolated, but exhibit excessive leakage.
Independent (or random) isolation failures including those accidents in which the pre-existing isolation 5 failure to seal is not dependent on the sequence in progress. This class is similar to Class 4 isolation failures, but is applicable to sequences involving Type C test and their potential failures.
Containment isolation failures including those leak paths covered in the plant test and maintenance 6
requirements or verified per in-service inspection and testing (ISl/IST) program.
Accidents involving containment failure induced by severe accident phenomena. Changes in Appendix J 7
testing requirements do not impact these accidents.
Accidents in which the containment is bypassed (either as an initial condition or induced by phenomena) 8 are included in Class 8. Changes in Appendix J testing requirements do not impact these accidents.
5.1.3 Impact of Extension on Detection of Component Failures that Lead to Leakage (Smail and Large)
The ILRT can detect a number of component failures such as liner breach, failure of certain bellows arrangements, and failure of some sealing surfaces, which can lead to leakage. The proposed ILRT test interval extension may influence the conditional probability of detecting these types of failures. To ensure that this effect is properly addressed, the EPRI Class 3 accident class, as defined in Table 5-3, is divided into two sub-classes, Class 3a and Cl~ss 3b, representing small and large leakage failures respectively.
- The probability of the EPRI Class 3a and Class 3b failures is determined consistent with the EPRI Guidance [Reference 24]. For Class 3a, the probability is based on the maximum likelihood estimate of failure (arithmetic average) from the available data (i.e., 2 "small" failures in 217 tests leads to "large" failures in 217 tests (i.e:, 2 / 217 = 0.0092). For Class 3b, the probabiJity is based on the Jeffreys non-informative prior (i.e., 0.5 / 218 = 0.0023).
In a follow-up letter [Reference 20] to their ILRT guidance document [Reference 3], NEI issued additional information concerning the potential that the calculated delta LERF values for several plants may fall above the "very small change" guidelines of the NRC Regulatory Guide 1.174
[Reference 4]. This additional NEI information includes a discussion of conservatisms in the quantitative guidance for b.LERF. NEI describes ways to demonstrate that, using plant-speCific calculations, the b.LERF is smaller than that calculated by the simplified method.
Revision 3 Page14of117
54006-CALG-01 Evaluation of Risk Significance of Permanent ILRT Extension The supplemental information states:
The methodology employed for determining LERF (Class 3b frequency) involves conservatively multiplying the CDF by the failure probability for this class (3b) of accident. This was done for simplicity and to maintain conservatism. However, some plant-specific accident classes leading to core damage are likely to include individual sequences that either may already .
(independently) cause a LERF or could never cause a LERF, and are thus not associated with a postulated large Type A containment leakage path (LERF). These contributors can be removed from Class 3b in the evaluation of LERF by multiplying the Class 3b probability by only that portion of CDF that may be impacted by Type A leakage.
The application of this additional guidance to the analysis for DCPP, as detailed in Section 5.2, involves subtracting the LERF from the CDF that is applied to Class 3b. To be consistent, the same change is made to the Class 3a CDF, even though these events are not considered LERF.
Consistent with the NEI Guidance [Reference 3]. the change in the leak detection probability can be estimated by comparing the average time that a leak could exist without detection. For example, the average time that a leak could go undetected with a three-year test interval is 1.5 years (3 years I 2), and the average time that a leak could exist without detection for a ten-year interval is 5 years (1Oyears/2). This change would .lead to a non-detection probability that is a factor of 3.33 (5.0/1.5) higher for the probability of a leak that is detectable only by ILRT testing.
Correspondingly, an extension of the ILRT interval to 15 years can be estimated to lead to a factor of 5 ((15/2)/1.5) increase in the non-detection probability of a leak.
It should be noted that using the methodology discussed above is very conservative compared to previous submittals (e.g., the IP3 request for a one-time ILRT extension that was approved by the NRC [Reference 9]) because it does not factor in the possibility that the failures could be detected by other tests (e.g., the Type B local leak rate tests that will still occur). Eliminating this possibility conservatively over-estimates the factor increases attributable to the ILRT extension.
5.2 Analysis The application of the approach based on the guidance contained in EPRI Report No. 1009325, Revision 2-A, Appendix H [Reference 24], EPRI TR-104285 [Reference 2] and previous risk assessment submittals on this subject [References 5, 8, 21, 22, and 23] have led to the following results. The results are displayed according to the eight accident classes defined in the EPRI report, as described in Table 5-5..
The analysis performed examined DCPP-specific accident sequences in which the containment remains intact or the containment is impaired. Specifically, the breakdown of the severe accidents, contributing to risk, was considered *in the following manner:
- Core damage sequences in which the containment remains intact initially and in the long term (EPRI TR-104285, Class 1 sequences [Reference 2]).
- Core damage sequences i.n which containment integrity is impaired due to random isolation failures of plant components other than those associated with Type B or Type C test components. For example, liner breach or bellow leakage (EPRI TR-104285, Class 3 sequences [Reference 2]).
- Accident sequences involving containment bypassed (EPRI TR-104285, Class 8 sequences [Reference 2]), large containment isolation failures (EPRI TR-104285, Class 2 sequences [Reference 2]), and small containment isolation "failure-to-seal" events (EPRI TR-104285, Class 4 and 5 sequences [Reference 2]) are accounted for in this Revision 3 Page 15of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension evaluation as part of the baseline risk profile. However, they are not affected by the ILRT frequency change.
- Class 4 and 5 sequences are impacted by changes in Type B and C test intervals; therefore, changes in the Type A test interval do not impact these sequences.
Table 5 EPRI Accident Class Definitions
, Accident Classes Description (Containment Release Type)
No Containment Failure 2 Large Isolation Failures (Failure to Close) 3a Small Isolation Failures (Liner Breach) 3b Large Isolation Failures (Liner Breach) 4 Small Isolation Failures (Failure to Seal - Type B)
_)
5 Sm.all Isolation Failures (Failure to Seal - Type C) 6 Other Isolation Failures (e.g., Dependent Failures) 7 Failures Induced by Phenomena (Early and Late) 8 Bypass (Interfacing System LOCA)
CDF All CET End States (Including Very Low and No Release)
The steps taken to perform this risk assessment evaluation are as follows:
Step 1 - Quantify the baseline risk in terms of frequency per reactor year for each of the accident classes presented in Table 5-5.
Step 2 - Develop plant-specific person-rem dose (population dose) per reactor year for each of the eight accident classes.
Step 3 - Evaluate risk impact of extending Type A test interval from 3 in 1O years to 1 in 15 years arid 1 in 10 years to 1 in 15 years.
Step 4 - Determine the change in risk in terms of Large Early Release Frequency (LERF) in accordance with RG 1.174 [Reference 4].
Step 5 -_Determine the impact on the Conditional Containment Failure Probability (CCFP).
5.2.1 Step 1 - Quantify the Baseline Risk in Terms of Frequency per Reactor Year*
As previously described, the extension of the Type A interval does not influence those accident progressions that involve large containment isolation failures, Type B or Type C testing, or containment failure induced by severe accident phenomena.
For the assessment of ILRT impacts on the risk profile, the potential for pre-existing leaks is induded in the model. (These events are represented by the Class 3 sequences in EPRI TR-104285 [Reference 2].) The question on containment integrity was modified to include the probability of a liner breach or bellows failure (due to excessive leakage) at the time of core damage .. Two failure modes were considered for the Class 3 sequences. These are Class 3a (small breach) and Class 3b (large breach).
- The frequencies for the severe accident classes defined in Table 5-5 were developed for DCPP by first determining the frequencies for Classes 1, 2, 6, 7, and 8. Table 5-6 presents the grouping of each release category in EPRI Classes based on the associated description. Table 5-7 presents the frequency and EPRI category for each sequence and t.he totals of each EPRI Revision 3 Page 16of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension classification. Table 5-8 provides a summary of the accident sequence frequencies that can lead to radionuclide release to the public and have been derived consistent with the definitions of accident classes defined in EPRI TR-104285 [Reference 2], the NEI Interim Guidance
[Reference 3], and guidance provided in EPRI Report No. 1009325, Revision 2-A [Reference 24]. Adjustments were made to the Class 3b and hence Class 1 frequencies to account for the impact of undetected corrosion of the steel liner per the methodology described in Section 5.2.6.
Note: calculations were performed with more digits than shown in this section. Therefore, minor differences may occur if the calculations in these sections are followed explicitly.
Class 3 Sequences. This group consists of all core damage accident progression bins for which a pre-existing leakage in the containment structure (e.g., containment liner) exists that can only be detected by performing a Type A ILRT. The probability of leakage detectable by a Type A ILRT is calculated to determine the impact of extending the testing interval. The Class 3 calculation is divided into two classes: Class 3a is defined as a small liner breach (La < leakage
< 1Ola), and Class 3b is defined as a large liner breach (1 Ola < leakage < 1OOLa).
Data reported in EPRI 1009325, Revision 2-A [Reference 24] states that two events could' have been detected only during the performance of an ILRT and thus impact risk due to change in ILRT frequency. There were a total of 217 successful ILRTs during this data collection period.
Therefore, the probability of leakage is determined for Class 3a as shown in the following equation:
2 Pclass3a = 217 = 0.0092 Multiplying the CDF by the probability of a Class 3a leak yields the Class 3a frequency
_ contribution in accordance with guidance provided in Reference 24. As described in Section 5.1.3, additional consideration is made to not apply failure probabilities on those cases that are already LERF scenarios. Therefore, LERF contributions from CDF are removed. The frequency of a Class 3a failure is calculated by the following equation:
2 Frequ 1class3a = Pczass3a * (CDFu1 - LERFu 1) = 217
- (1.89E-5 -2.26E-6) = 1.54E-7 2
Frequ 2class 3d. = Pclass 3a * (CDFu 2 - LERFu 2) = 217
- (1.69E-5 -2.l8E-6) = 1.35E-7 In the database of 217 ILRTs, there are zero containment leakage events that could result in a large early release. Therefore, the Jeffreys non-informative prior is used to estimate a failure rate and is illustrated in the following equations:
Number of Failures+ 1/2 Jeffreys Failure Probability= N b fT um er o ests + 1 0+1/2 Pclass3b = 217+ 1 = 0.0023 The frequency of a Class 3b failure is calculated by the following equation: (
Frequ1class3b = Pclass3b * (CDFu1 - LERFu1) = ;:a *(1.89E-5 -2.26E-6) = 3.82E-8 FreqU2class3b = Pczass3b * (CDFu2 - LERFu2) = 2*:3 *(1.69E-5 -2.18E-6) = 3.36E-8 For this analysis, the associated containment leakage for Class 3a is 1Ola and for Class 3b is 1OOLa. These assignments are consistent with the guidance provided in Reference 24.
Class 1 Sequences. This group consists of all core damage accident progression bins for which the containment remains intact (modeled as Technical Specification Leakage). Since the PRA model does not contain a Level 2 model, Class 1 is calculated as CDF- LERF. This Revision 3 Page'17of117
/
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension overestimates the Intact frequency, which is conservative for this analysis because it leads to a higher calculated change in risk due to extending the ILRT frequency. The frequency per year is initially determined from the EPRI Accident Class 1 frequency listed in Table 5-7 and then subtracting the EPRI Class 3a and 3b frequency (to preserve total GDF), calculated below:
Freqclassl = Freqczass1 - (Freqczass3a - Freqclass3b)
Class 2 Sequences. This group consists of core damage accident progression bins with large containment isolation failures. This is determined from Section C.9.8.7 of Reference 17, which states that containment isolation failure contributes 8% of internal event LERF (1.84E-6).
Therefore, the Class 2 contribution is 1.47E-7. The frequency per year for these sequences is obtained from t~e EPRI Accident Class 2 frequency listed in Table 5-7.
Class 4 Sequences. This group consists, of all core damage accident progression bins for which containment isolation failure-to-seal of Type B test components occurs. Because these failures are detected by Type B tests which are unaffected by the Type A ILRT, this group is not evaluated any further in the analysis, consistent with approved methodology.
Class 5 Sequences. This group consists of all core damage accident progression bins for which a containment isolation failure-to-seal of Type C test components occurs. Because the failures are detected by Type C tests which are unaffected by the Type A ILRT, this group is not ...,
evaluated any further in this analysis, consistent with approved methodology.
Class 6 Sequences. These are sequences that involve core damage accident progression bins for which .a failure-to-seal containment leakage due to failure to isolate the containment occurs.
These sequences are dominated by misalignment of containment isolation valves following a test/maintenance evolution. All other failure modes are bounded by the Class 2 assumptions.
This accident class is also not evaluated further.
Class 7 Sequences. This group consists of all core damage accident progression bins in which containment failure is induced by severe accident phenomena (e.g., overpressure). This frequency is calculated by subtracting the Class 1, 2, and 8 frequencies from the total GDF. For this analysis, the frequency is determined from the EPRI Accident Class 7 frequency listed in Table 5-7. '
Class 8 Sequences. This group consists of all core damage accident progression bins in which ISLOCA or SGTR occur, which contribute 3.06E-8 and 1.32E-!3, respectively. Frequencies are shown in Table 5-6. For this analysis, the total Class 8 frequency is listed in Table 5-7.
Table 5 Release Category Frequencies Containment End State EPRI Category Unit 1 Frequency (/yr) Unit 2 Frequency (/yr)
Intact Containment 1 1.67E-05 1.47E-05 Large Isolation Failure 2 1.47E-07 1.47E-07 Failures Induced by Phenomena 7 7.61E-07 6.85E-07 ISLOCA 8 3.06E-08 3.06E-08 SGTR 8 1.32E-06 . 1.32E-06 Revision 3 Page 18of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Accident Class Frequencies EPRI Category / Unit 1 Frequency (/yr) Unit 2 Frequency (/yr)
Class 1 1.67E-05 1.47E-05 Class 2 1.47E-07 1.47E-07 Class 6 N/A - Included in Class 2 Class 7 7.61E-07 6.85E-07 Class 8 1.35E-06 1.35E-06 Total (CDF) 1.89E-05 1.69E-05 Table 5 Baseline Risk Profile Class Description Unit 1 Frequency (/yr) Unit 2 Frequency (/yr)
No containment failure 1.65E-052 1.45E-052 2 Large containment isolation failures 1.47E-07 1.47E-07 3a Small isolation failures (liner breach) 1.54E-07 1.35E-07 3b Large isolation failures (liner breach) 3.82E-08 3.36E-08 4 Small isolation failures - failure to seal (type B) 5 Small isolation failures - failure to seal (type C)
Containment isolation failures (dependent 6
failure, personnel errors)
Severe accident phenomena induced failure 7 7.61E-07 6.85E-07 (early and late) 8 Containment bypass 1.35E-06 1.35E-06 Total 1.89E-05 1.69E-05
- 1. E represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 3a and 3b frequencies are subtracted from Class 1 to preserve total CDF.
5.2.2 Step 2 - Develop Plant-Specific Person-Rem Dose (Population Dose)
Plant-specific release analyses were performed to estimate the person-rem doses to the population within a 50-mile radius from the plant. The releases are based on DCPP-specific dose calculations summarized in Table 5-3. Table 5-3 provides a correlation of DCPP population dose to EPRI Accident Class. Table 5-1 O provides population dose for each EPRI accident class.
The population dose for EPRI Accident Classes 3a and 3b were calculated based on the guidance provided in EPRI Report No. 1009325, Revision 2-A [Reference 24] as follows:
EPRI Class 3a Population Dose= 10
- 3.68£+3 = 3.68£+4 EPRI Class 3b Population Dose= 100
- 3.68£+3 = 3.68£+5 Revision 3 Page 19of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Mapping of Population Dose to EPRI Accident Class EPRI Category Unit 1 Frequency (/yr) Unit 2 Frequency (/yr) Dose (person-rem)
Class 1 1.67E-05 1.47E-05 3.68E+03 Class 2 1.47E-07 1.47E-07 9.83E+06 Class 6 N/A - Included in Class 2 Class 7 7.61E-07 6.85E-07 9.83E+06 Class 8 1.35E-06 1.35E-06 8.90E+05 1
- 1. The Class 8 dose value differs from the value presented in Reference 19 because the dose is weighted based on frequency of the two Class 8 contributors: ISLOCA and SGTR.
Table 5 Baseline Population Doses Class Description Population Dose (person-rem)
No containment failure 3.68E+03 2 Large containment isolation failures 9.83E+06 3a Small isolation failures (liner breach) 3.68E+04 1 3b Large isolation failures (liner breach) 3.68E+05 2 4 Small isolation failures - failure to seal (type B) N/A 5 Small isolation failures - failure to seal (type C) N/A 6 Containment isolation failures (dependent failure, personnel errors) N/A 7 Severe accident phenomena induced failure (early and late) 9.83E+06 8 Containment bypass 8.90E+05 3
- 1. 10*La
- 2. 100*La
- 3. The Class 8 dose value differs from the value presented in Reference 19 because the dose is weighted based on frequency of the two Class 8 contributors: ISLOCA an.d' SGTR.
5.2.3 Step 3 - Evaluate Risk Impact of Extending Type A Test Interval from 10 to 15
~ra .
The next step is to evaluate the risk impact of extending the test interval from its current 10-year interval to a 15-year interval. To do this, an evalu~tion must first be made of the risk associated with the 10-year interval, since the base case applies to 3-year interval (i.e., a simplified representation of a 3-to-1 O interval).
Risk Impact Due to 10-Year Test Interval As previously stated, Type A tests impact only Class 3 sequences. For Class 3 sequences, the release magnitude is not impacted by the change in test interval (a small or large breach remains the same, even though the probability of not detecting the breach increases). Thus, only the frequency of Class 3a and Class 3b sequences is impacted. The risk contribution is
- changed based on the NEI guidance as described in Section 5.1.3 by a factor of 10/3 compared to the base case values. The Class 3a and 3b frequencies are calculated as follows:
Frequ1class3alOyr = 310
- 217 2
- 217 2
- 1.67E-5 = 5.12E-7 Frequ2class 3arnyr = -103 *217 2
- * (CDF - LERF) = -103 *-*2 217 1.47E-5 = 4.51E-7
= 13°* 2*:3 * (CDF - = 3°* 2*:3
- 1.67E-5 = 1.27E-7 1
Frequ1c1ass 3b 1oyr LERF)
Revision 3 Page 20of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Frequ2ciass3b1oyr = 13°* 2*:8 * (CDF - LERF) = 13°* 2*:8
- 1.47E-5 = 1.12E-7 The results of the calculation for a 10-year interval are presented in Table 5-11 for Unit 1 and Table 5-12 for Unit 2.
Table 5 Unit 1 Risk Profile for Once in 10 Year ILRT Class Description Frequency Contribution Population Dose Population
(/yr) (%) . (person-rem) Dose Rate (person-rem/yr)
No containment failure 2 1.60E-05 84.68% 3.68E+03 5.90E-02 Large containment isolation 2 1.47E-07 0.78% 9.83E+06 1.45E+OO failures Small isolation failures (liner 3a 5.12E-07 2.71% 3.68E+04 1.88E-02 breach)
Large isolation failures 3b 1.27E-07 0.67% 3.68E+05 4.69E-02 (liner breach)
Small isolation failures - g1 g1 g1 g1 4
failure to seal (type B)
Small isolation failures - g1 g1 g1 g1 5
failure to seal (type C)
Containment isolation 6 failures (dependent failure, g1 g1 g1 g1 personnel errors)
Severe accident 7 phenomena induced failure 7.61E-07 4.02% 9.83E+06 7.48E+OO 1
(early and late) 8 Containment bypass 1.35E-06 7.14% 8.90E+05 1.20E+OO Total 1.89E-05 1.03E+01
- 1. E represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 1 frequency is reduced by-the frequency of Class 3a and Class 3b in order to preserve total CDF.
- \
Revision 3 Page 21 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
'ii Table 5 Unit 2 Risk Profile for Once in 10 Year ILRT Class Description - Frequency Contribution Population Dose Population
(/yr) (%) (person-rem) Dose Rate (person-rem/yr)
No containment failure 2 1.41 E-05 83.70% 3.68E+03 5.19E-02 Large containment isolation 2 1.47E-07 0.87% 9.83E+06 1.45E+OO failures Small isolation failures (liner 3a 4.51E-07 2.67% 3.68E+04 1.66E-02 breach)
Large isolation failures 3b 1.12E-07 0.67% 3.68E+05 4.13E-02 (liner breach)
Small isolation failures - 1 -
4 E1 E E1 E1 failure to seal (type B)
Small isolation failures -
5 E1 £1 £1 E1 failure to seal (type C)
, Containment isolation 6 failures (dependent failure, £1 £1 £1 £1 personnel errors)*
Severe accident 7 phenomena induced failure 6.85E-07 4.07% 9.83E+06 6.74E+OO (early and late) 8 Containment bypass 1.35E-06 8.02% 8.90E+05 1.20E+OO Total 1.69E-05 9.49E+OO
- 1. E represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 1 frequency is reduced by the frequency of Class 3a and Class 3b in order to preserve total CDF.
Risk Impact Due to 15-Year Test Interval
- The risk contribution for a 15-year interval is calculated in a manner similar to the 10-year interval. The difference is in the increase in probability of leakage in Classes 3a a'nd 3b. For this case, the value used in the analysis is a factor of 5. compared to the 3-year interval value, as described in Section 5.1.3. The Class 3a and 3b frequencies are calculated as follows:
Frequ1class3a15yr = -153 * --
2 217
- 1.67E-5 = 7.68E-7 Frequ2class3a15yr = -153 * -2 217
- 1.47E-5 = 6.76E-7--
FreqU1Class3b~5yr = 3
- 2*:8 * (CDF -
15 LERF) = 5
- 2*:8
- 1.67E-5 = 1.91E-7 1
Frequ2c1ass 3bl5yr = 35
- 2*:8
- 1.47E-5 = 1.68E_-7 The results of the calculation for a 15-year interval are presented in Table 5-13 for Unit 1 and Table 5-14 for Unit 2.
Revision 3 Page 22of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Unit 1 Risk Profile for Once in 15 Year ILRT Class Description Frequency Contribution Population Dose Population
(/yr) (%) (person-rem) Dose Rate (person-rem/yr)
No containment failure 2 1.57E-05 82.99% 3.68E+03 5.78E-02 Large containment 2 1.47E-07 0.78% 9.83E+06 1.45E+OO isolation failures Small isolation failures 3a 7.68E-07 4.06% 3.68E+04 2.83E-02 (liner breach)
Large isolation failures 3b 1.91 E-07 1.01% 3.68E+05 7.03E-02 (liner breach)
Small isolation failures - £1 £1 £1 £1 4
failure to seal {!Yee B)
Small isolation failures - £1 £1 £1 £1 5
failure to seal {!Yee C)
Containment isolation 6 failures (dependent failure, £1 E1 £1 £1 eersonnel errors)
Severe accident 7 phenomena induced failure 7.61E-07 4.02% 9.83E+06 7.48E+OO
{earl}'. and late) 8 Containment bypass 1.35E-06 7.14% 8.90E+05 1.20E+OO Total 1.89E-05 1.03E+01
- 1. £represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 1 frequency is reduced by the frequency of Class 3a and Class 3b in order to preserve total CDF.
Table 5 Unit 2 Risk Profile for Once in 15 Year ILRT Class Description Frequency Contribution Population Dose Population
(/yr) (%) (person-rem) Dose Rate (person-rem/yr)
No containment failure 2 1.38E-05 82.04% 3.68E+03 5.09E-02 Large containment 2 1.47E-07 0.87% 9.83E+06 1.45E+OO isolation failures Small isolation failures 3a 6.76E-07 4.01% 3.68E+04 2.49E-02 (liner breach)
Large isolation failures 3b 1.68E-07 1.00% 3.68E+05 6.19E-02 (liner breach)
Small isolation failures - £1 £1 £1 £1 '
4 failure to seal {!Yee B)
Small isolation failures - £1 £1 £1 £1 5
failure to seal (!}'.pe C)
Containment isolation 6 failures (dependent failure, £1 £1 £1 £1 eersonnel errors)
Severe accident 7 phenomena induced failure 6.85E-07 4.07% 9.83E+06 6.74E+OO
{earl}'. and late) 8 Containment bypass 1.35E-06 8.02% 8.90E+05 1.20E+OO Total 1.69E-05 9.52E+OO
- 1. £represents a probabilistically insignificant value or a Class that is unaffected by the Type A ILRT.
- 2. The Class 1 frequency is reduced by the frequency of Class 3a and Class 3b in order to preserve total CDF.
Revision 3 Page 23of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 5.2.4 Step 4 - Determine the Change in Risk in Terms of LERF The risk increase associated with extending the ILRT interval involves the potential that a core damage event that normally would result in only a small radioactive release from an intact containment could , in fact, result in a larger release due to the increase in probability of fa ilure to detect a pre-existing leak. With strict adherence to the EPRI guidance, 100% of the Class 3b contribution would be considered LERF.
Regulatory Gu ide 1.174 (Reference 4] provides guidance for determining the risk impact of plant-specific changes to the licensing basis. RG 1.174 [Reference 4] defines very small changes in risk as resulting in increases of CDF less than 1o-s/year and increases in LERF less than 10-7 /year, and small changes in LERF as less than 1o-s/year. Since containment overpressure is not required in support of ECCS performance to mitigate design basis accidents at DCPP, the ILRT extension does not impact CDF. Therefore , the relevant risk-impact metric is LERF.
For DCPP, 100% of the frequency of Class 3b sequences can be used as a very conservative first-order estimate to approximate the potential increase in LERF from the ILRT interval extension (consistent with the EPRI guidance methodology). Based on a 10-year test interval from Table 5-11 and Table 5-12 , the Class 3b frequency is 1.27E-07/year for Unit 1 and 1.12E-07/year for Unit 2; based on a 15-yeartest interval from Table 5-13 and Table 5-14 , the Class 3b frequency is 1.91 E-07/year for Unit 1 and 1.68E-07/year for Unit 2. Thus , the increase in the overall probability of LERF due to Class 3b sequences that is due to increasing the ILRT test interval from 3 to 15 years is 1.53E-07/year for Unit 1 and 1.35E-07/year for Unit 2. Similarly, the increase due to increasing the interval from 10 to 15 years is 6.37E-08/year for Unit 1 and 5.61E-08/year for Unit 2. As can be seen , even with the conservatisms included in the evaluation (per the EPRI methodology) , the estimated change in LERF is within the criteria for a small change when comparing the 15-year results to the current 10-year requ irement and the original 3-year requirement. Table 5-15 summarizes these results.
Table 5 Impact on LERF due to Extended Type A Testing Intervals ILRTlnspection Unit1:3Years Unit1:10 Unit1:15 Unit2:3Years Unit2:10 Unit2:15 Interval (baseline) Years Years (baseline) Years Years Class 3b (Type A 3.82E-08 1.27E-07 1.91 E-07 3.36E-08 1.12E-07 1.68E-07 LERF) b.LERF (3 year basel ine)
I 8.92E-08 1.53E-07 I 7. 85E-08 1.35E-07 b.LERF (10 year basel ine)
I 6.37 E-08 I 5.6 1E-08 The increase in the overall probability of LERF due to Class 3b sequences is greater than 10-1 .
As stated in RG 1.174 [Reference 4] , "When the calculated increase in LERF is in the range of 10-7 per reactor year to 1o-s per reactor year, appl ications will be considered only if it can be reasonably shown that the total LERF is less than 10-5 per reactor year." Baseline LERF (excluding external events) is 2.26E-06/year for Unit 1 and 2.18E-06/year for Unit 2. Therefore, there is significant margin for both the b.LERF and baseline LERF to the upper limits of Region II in RG 1.174 [Reference4] .
5.2.5 Step 5 - Determine the Impact on the Conditional Containment Failure Probability Another parameter that the NRC guidance in RG 1.174 [Reference 4] states can provide input into the decision-making process is the change in the conditional containment failure probability Revision 3 Page 24of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension (CCFP). The CCFP is defined as the probability of containment failure given the occurrence of an accident. This probability can be expressed using the following equation :
CCFP = 1 - f(ncf)
CDF where f(ncf) is the frequency of those sequences that do not result in containment failure ; this frequency is determined by summing the Class 1 and Class 3a results [Reference 24]. Table 5-16 shows the steps and results of this calculation. The difference in CCFP between the 3-year test interval and 15-year test interval is 0.808% for Unit 1 and 0.799% for Unit 2.
Table 5 Impact on CCFP due to Extended Type A Testing Intervals ILRT Inspection Unit 1: 3 Years Unit1 : 10 Unit1:15 Unit 2: 3 Years Unit 2: 10 Unit 2: 15 Interval (baseline) Years Years (baseline) Years Years f(ncf) (/yr) 1.66E-05 1.65E-05 1.65E-05 1.46E-05 1.46E-05 1.45E-05 f(ncf)/CDF 87.9% 87.4% 87 .1% 86 .8% 86.4% 86.0%
CCFP 12.14% 12.61 % 12.95% 13.16% 13.62% 13.95%
t.CCFP (3 year baseline) I 0.471 % 0.808%
I 0.466% 0.799%
t.CCFP (10 year basel ine) I 0.337%
I 0.333%
As stated in Section 2.0, a change in the CCFP of up to 1.5% is assumed to be small. The increase in the CCFP from the 3 in 10 year interval to 1 in 15 year interval is 0.808% for Unit 1 and 0. 799% for Unit 2. Therefore , this increase is judged to be very small.
5.2.6 Impact of Extension on Detection of Steel Liner Corrosion that Leads to Leakage An estimate of the likelihood and risk implications of corrosion-induced leakage of the steel liners occurring and going undetected during the extended test interval is evaluated using a methodology similar to the Calvert Cliffs liner corrosion analysis [Reference 5]. The Calvert Cliffs analysis was performed for a concrete cylinder and dome and a concrete basemat, each with a steel liner.
The following approach is used to determine the change in likelihood , due to extending the ILRT, of detecting corrosion of the containment steel liner. This likelihood is then used to determine the resulting change in risk. Consistent with the Calvert Cliffs analysis, the following issues are addressed :
- Differences between the containment basemat and the containment cylinder and dome
- The historical steel liner flaw likelihood due to concealed corrosion
- The impact of aging
- The corrosion leakage dependency on containment pressure
- The likelihood that visual inspections will be effective at detecting a flaw Assumptions
- Consistent with the Calvert Cliffs analysis , a half failure is assumed for basemat concealed liner corrosion due to the lack of identified failures (See Table 5-17 , Step 1).
- The two corrosion events used to estimate the liner flaw probability in the Calvert Cliffs previous analysis are assumed to still be applicable.
- Consistent with the Calvert Cliffs analysis, the estimated historical flaw probability is also Revision 3 Page 25of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension limited to 5.5 years to reflect the years since September 1996 when 10 CFR 50.55a started requiring visual inspection. Additional success data was not used to limit the aging impact of this corrosion issue, even though inspections were being performed prior to this date (and have been performed since the time frame of the Calvert Cliffs analysis)
(See Table 5-4, Step 1).
- Consistent with the Calvert Cliffs analysis, the steel liner flaw likelihood is assumed to double every five years. This is based solely on judgment and is included in this analysis to address the increased likelihood of corrosion as the steel liner ages (See Table 5-17, Steps 2 and 3). Sensitivity studies are included that address doubling this rate every ten years and every two years.
- In the Calvert Cliffs analysis, the likelihood of the containment atmosphere reaching the outside atmosphere, given that a liner flaw exists, was estimated as 1.1 % for the cylinder and dome, and 0.11 % (10% of the cylinder failure probability) for the basemat. These values were determined from an assessment of the probability versus containment pressure. For DCPP, the containment design pressure is 47 psig [Reference 27].
Probabilities of 1% for the cylinder and dome, and 0.1 % for the basemat are used in this analysis, and sensitivity studies are included in Section 5.3.2 (See Table 5-17, Step 4).
- Consistent with the Calvert Cliffs analysis, the likelihood of leakage escape (due to crack formation) in the basemat region is considered to 'be less 0 likely than the containment cylinder and dome region (See Table 5-17, Step 4).
- Consistent with the Calvert Cliffs analysis, a 5% visual inspection detection failure likelihood given the flaw is visible and a total detection failure likelihood of 10% is used.
To date, all liner corrosion events have been detected through visual inspection (See Table 5-17, Step 5).
- Consistent with the Calvert Cliffs analysis, all non-detectable containment failures are assumed to result in early releases. This approach avoids a detailed analysis of containment failure timing and operator recovery actions.
Table 5 Steel Liner Corrosion Base Case Step Description Containment Cylinder and Containment Basemat Dome (85%) (15%)
Historical liner flaw likelihood Events: 2 Events: 0 Failure data: containment location (Brunswick 2 and North Anna 2) Assume a half failure specific 2 I (70 x 5.5) = 5.19E-03 0.5 I (70 x 5.5) = 1.30E-03 Suceess data: based on 70 steel-lined containments and 5.5 years since the 10CFR 50.55a requirements of periodic visual inspections of containment surfaces Year Failure rate Year Failure rate Aged adjusted liner flaw likelihood During the 15-year interval, assume 2.05E-03 5.13E-04 failure rate doubles every five years average 5-10 5.19E-03 average 5-10 1.30E-03 2 15 1.43E-02 15 3.57E-03 (14.9% increase per year). The average for the 5th to 10th year set to the historical failure rate. 15 year average = 6.44E-03 15 year average = 1.61 E-03 Revision 3 Page 26of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Steel Liner Corrosion Base Case Step Description Containment Cylinder and Containment Basemat Dome (85%) (15%)
Increase in flaw likelihood between 3 and 15 years Uses aged adjusted 0.73% (1to3 years) 0.18% (1 to 3 years) 3 liner flaw likelihood (Step 2), 4.18% (1 to 10 years) 1.04% (1to10 years) assuming failure rate doubles every 9.66% (1 to 15 years) 2.41% (1to15 years) five years.
Likelihood of breach in containment 4 1% 0.1%
given liner flaw 10%
5% failure to identify visual flaws plus 5% likelihood that the flaw is not visible (not through-cylinder 100%
Visual inspection detection failure 5 but could be detected by ILRT).
likelihood Cannot be visually inspected All events have been detected through visual inspection. 5%
visible failure detection is a conservative assumption.
0.00073% (3 years) 0.000180% (3 years) 0.73% x 1% x 10% 0.18% x 0.1 % x 100%
Likelihood of non-detected 0.00418% (10 years) 0.00104% (10 years) 6 containment leakage (Steps 3 x 4 x
- 5) 4.18% x 1% x 10% 1.04% x 0.1% x 100%
0.00966% (15 years) 0.00241% (15 years) 9.66% x 1% x 10% 2.41 % x 0.1 % x 100%
The total likelihood of the corrosion-induced, non-detected containment leakage is the sum of Step 6 for the containment cylinder and dome, and the containment basemat, as summarized below for DCPP.
Table 5-18-Total Likelihood on Non-Detected Containment Leakage Due to Corrosion for DCPP
' Description At 3 years: 0.00073% + 0.000180% = 0.00091%
At 10 years: 0.00418% + 0.00104% = 0.00522%
At 15 years: 0.00966% + 0.00241% =0.01207%
The above factors are applied to those core damage accidents that are not already independently LERF or that could never result in LERF.
The two corrosion events that were initiated from the non-visible (backside) portion of the containment liner used to estimate the liner flaw probability in the Calvert Cliffs analysis are assumed to be applicable to this containment analysis. These events, one at North Anna Unit 2 (September 1999) caused by timber embedded in the concrete immediately behind the containment liner, and one at Brunswick Unit 2 (April 1999) caused by a cloth work glove embedded in the concrete next to the liner, were initiated from the nonvisible (backside) portion of the containment liner. A search of the NRC website LER database identified two additional events have occurred since the Calvert Cliffs analysis was performed. In January 2000, a 3/16-inch circular through-liner hole was found at Cook Nuclear Plant Unit 2 caused by a wooden brush handle embedded immediately behind the containment liner. The other event occurred in April 2009, where a through-liner hole approximately 3/8-inch by 1-inch in size was identified in Revision 3 Page 27of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension the Beaver Valley Power Station Unit 1 (BVPS-1) containment liner caused by pitting originating
' from the concrete side due to a piece of wood that was left behind during the original -
construction that came in contact with the steel liner. Two other containment liner through-wall hole events occurred at Turkey Point Units 3 and 4 in October 2010 and November 2006, respectively. However, these events originated from the visible side caused by the failure of the coating system, which was not designed for periodic immersion service, and are not considered to be applicable to this analysis. More recently, in October 2013, some through-wall containment liner holes were identified at BVPS-1, with a combined total area of approximately 0.395 square inches. The cause of these through-wall liner holes was attributed to corrosion originating from the outside concrete surface due to the presence of rayon fiber foreign material that was left behind during the original construction and was contacting the steel liner
[Reference 28]. For risk evaluation purposes, these five total corrosion events occurring in 66 a'
operating plants with steel containment liners over 17.1 year period from September 1996 to October 4, 2013 (i.e., 5/(66*17.1) = 4.43E-03) are bounded by the estimated historical flaw probability based on the two events in the 5.5 year period of the Calvert Cliffs analysis (i.e.,
2/(70*5.5) = 5.19E-03) incorporated in the EPRI guidance.
5.3 Sensitivities 5.3.1 Potential Impact from External Events Contribution An assessment of the impact of external events is performed. The primary purpose for this investigation is the determination of the total LERF following an increase in the ILRT testing interval from *3 in 10 years to 1 in 15 years.
Diablo Canyon has received License Amendments No. 225 and 227, dated April 14, 2016,
[Reference ML16035A441] for implementation ofNFPA 805 on Units 1 and 2, respectively. Diablo Canyon has implemented required changes to the Operating Licenses and Technical Specifications and is in the process of implementing the program and installing modifications as committed to in the License Amendment Request, Safety Evaluation, and License Amendments. Thus, it is anticipated that all of the Fire PRA related modifications will be comple,ted prior to the next scheduled Type A tests for Units 1 and 2 in the first quarter of 2019 and 2018, respectively [Reference 33]. Therefore, the NFPA 805 post-modification Fire PRA model is deemed applicable and was used for this calculation.
The Fire PR.A model DC03M was used to obtain the fire GDF and LERF values [Reference 18].
To reduce conservatism in the model, the methodology of subtracting existing LERF from GDF is also applied to the Fire PRA modeL The following shows the calculation for Class 3b:
0.5 Frequ1class3b = Pc!ass3b * (CDF - LERF) = * (4.83E 2.45E-6) = 1.0SE-7 218 0.5 Frequ2class3b = Pclass3b * (CDF - LERF) = * (5.24E~S - 2.17E-6) = 1.15E-7 218
' 10 10 0.5 Frequ1class3b1oyr = 3
- 218 * (4.83E 2.45E-6) = 3.SOE-7 10 10 0.5 Frequ2class3b10yr = 3
- 218 * (5.24E 2.17E-6) = 3.84E-7 Frequ1class3b15yr
= -153
= 5 * -,-218 * (4.83E 2.45E-6) = 5.26E-7 15 - . 0.5 Frequ2class 3bl5yr = -3 *. Pclass3b * (CDF - LERF) = 5 * -218 * (5.24E 2.17E-6) = 5.76E-7 Revision 3 Page 28of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension The Seismic PRA results estimate a CDF of 2.66E-5/year and a LERF of 3.29E-6/year
[Reference 17]. The Seismic PRA model is not unit-specific. Subtracting seismic LERF from CDF, the Class 3b frequency can be calculated by the following formulas:
Freqclass3b = Pc1ass3b * {CDF - LERF) = ~~~ * (2.66E-5 -3.29E-6) = 5.35E-8 10 10 0.5 Freqclass3b1oyr = -3
~* ~ ~ .
Freqclass3b1Syr = 3
- 218 * (2.66E-5 -3.29E-6)= 2.67E-7 The DCPP IPEEE determined that each of the "other external events evaluated contributed less than 1.0E-06 per year to core damage and was screened out as a result [Reference 32].
Therefore, the "other external events are also screened for this application.
The fire and seismic contributions to Class 3b frequencies are then combined to obtain the total external event contribution to Class 3b frequencies. The change in LERF is calculated for the 1 in 1O year and 1 in 15 year cases and the change defined for the external events in Table 5-19 for Unit 1 and Table 5-20 for Unit 2.
Table 5 Unit 1 DCPP External Event Impact on ILRT LERF Calculation Hazard EPRI Accident Class 3b Frequency LERF Increase (from 3per10 years to 1 per 15 years) 3per10 year 1 per 10 year 1 per 15 years
' 6.34E-07 External Events 1.59E-07 5.29E-07 7.93E-07 Internal Events 3.82E-08 1.27E-07 1.91E-07 1.53E-07 Combined 1.97E-07 6.56E-07 9.84E-07 7.87E-07 Table 5 Unit 2 DCPP External Event Impact on ILRT LERF Calculation Hazard EPRI Accident Class 3b Frequency LERF Increase (from 3per10 years to 1 1 per 15 years- per 15 years) 3per10 year 1 per 10 year External Events 1.69E-07 5.62E-07 8.43E-07 6.75E-07
" Internal Events 3.36E-08 1.12E-07 1.. 68E-07 1.35E-07 Combined 2.02E-07 6.74E-07 1.01E-06 8.09E-07 The internal event results are also provided to allow a composite value to be defined. When both the internal and external event contributions are combined, the total change in LERF of 7.87E-7 for Unit 1 and 8.09E-7 for Unit 2 meets the guidance for small change in risk, as it exceeds 1.0E-7/yr and remains less than 1.0E-6 change in LERF. For this change in LERF to be acceptable, total LERF must be less than *1.0E-5. The total LERF value is calculated below:
LERFu1 = LERFulinternal + LERFseismic + LERFurnre + LERFu2ciass3Bincrease
= 2.26E-6/yr + 3.29E-6/yr + 2.45E-6/yr + 7.87E-7 /yr= 8.78E-6/yr LERFu2 = LERFu2internal + LERFseismic + LERFu2fire + LERFu2ciass3Bincrease
= 2.18E-6/yr + 3.29E-6/yr + 2.17E-6/yr + 8.09E*7 /yr= 8.45E-6/yr Revision 3 Page 29of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Although the total change in LERF is somewhat close to the Regulatory Guide 1.174 limit
[Reference 4] when external event risk is included, several conservative assumptions were made in this ILRT analysis, as discussed in Sections 4.0, 5.1.3, 5.2.1, and 5.2.4; therefore the total change in LERF is considered conservative for this application. As specified in Regulatory Guide 1.174 [Reference 4], since the total LERF is less than 1.0E-5, it is acceptable for the b.LERF to be between 1.0E-7 and 1.0E-6.
5.3.2 Potential Impact from Steel Liner Corrosion Likelihood A quantitative assessment of the contribution of steel liner corrosion likelihood impact was performed for the risk impact assessment for extended ILRT intervals. The impact on the Class 3b frequency due to increases in the ILRT surveillance interval was calculated for steel liner corrosion likelihood using the relationships described in Section 5.2.6. The EPRI Category 3b frequencies for the 3 per 10-year, 10-year, and 15-year ILRT intervals were. quantified using the internal events CDF. The change in the LERF, change in CCFP, and change in Annual Dose Rate due to extending the ILRT interval from 3 in 1O years to 1 in 1O years, or to 1 in 15 years are provided in Table 5 Table 5-26. The steel liner corrosion likelihood was increased by a factor of 1000, 10000, and 100000. Except for extreme factors of 10000 and 100000, the corrosion likelihood is relatively insensitive to the results.
Table 5 Steel Liner Corrosion Sensitivity Case: Unit 1 38 Contribution 3b 3b 3b LERF LERF LERF Frequency Frequency Frequency Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 (3-per-10 to (3-per-10 to (1-per-10 to year ILRT) year ILRT) yearlLRT) 1-per-10) 1-per-15) 1-per-15)
Internal Event 38 3.82E-08 1.27E-07 1.91 E-07 8.92E-08 1.53E-07 6.37E-08 Contribution Corrosion Likelihood 3.86E-08 1.34E-07 2.14E-07 9.55E-08 1.76E-07 8.01E-08 x 1000 Corrosion Likelihood 4.17E-08 1.94E-07 4.22E-07 1.52E-07 3.80E-07 2.28E-07 x 10000 Corrosion Likelihood 7.30E-08 7.92E-07 2.50E-06 7.19E-07 2.42E-06 1.70E-06 x 100000 Table 5 Steel Liner Corrosion Sensitivity Case: Unit 2 38 Contribution 3b 3b 3b LERF LERF LERF Frequency Frequency Frequency Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 (3-per-10 to (3-per-10 to (1-per-10 to year ILRT) yearlLRT) yearlLRT) 1-per-10) 1-per-15) 1-per-15)
Internal Event 38 3.36E-08 1.12E-07 1.68E-0,7 7.85E-08 1.35E-07 5.61E-08 Contribution Corrosion Likelihood 3.39E-08 1.18E-07 1.89E-07 8.40E-08 1.55E-07 7.05E-08 x 1000 Corrosion Likelihood 3.67E-08 1.71E-07 3.71E-07 1.34E-07 3.35E-07 2.01E-07 x 10000 Corrosion Likelihood 6.43E-08 6.97E-07 2.20E-06 6.33E-07 2.13E-06 1.50E-06 x 100000 Revision 3 Page 30of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Steel Liner Corrosion Sensitivity: Unit 1 CCFP CCFP CCFP CCFP CCFP CCFP CCFP Increase Increase Increase (3-per*10 (1-per-10 (1-per-15 (3-per-1 Oto (3-per-1 Oto (1-per-10 to year ILRT) yearlLRT) yearlLRT) 1-per-10) 1-per-15) 1-per-15)
Baseline 1.21E-01 1.26E-01 1.29E-01 4.71E-03 8.08E-03 3.37E-03 CCFP Corrosion Likelihood 1.21E-01 1.26E-01 1.30E*01 4.76E-03 8.15E-03 3.40E-03 x 1000 Corrosion Likelihood 1.22E-01 1.27E-01 1.30E-01 5.14E-03 8.81E-03 3.67E-03 x 10000 Corrosion Likelihood 1.23E-01 1.32E-01 1.39E-01 9.00E-03 1.54E-02 6.43E-03 x 100000 Table 5 Steel Liner Corrosion Sensitivity: Unit 2 CCFP CCFP CCFP CCFP CCFP CCFP CC,FP Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 (3-per-10 to (3-per-10 to (1-per-10 to year ILRT) yearlLRT) year ILRT) 1-per-10) 1-per-15)
- 1-per-15)
Baseline 1.32E-01 1.36E-01 1.40E-01 4.66E-03 7.99E*03 3.33E-03.
CCFP Corrosion Likelihood .1.32E-01 1.36E-01 1.40E-01 4.70E-03 8.06E-03 3.36E-03 x 1000 Corrosion Likelihood 1.32E-01 1.37E-01 1.40E-01 5.08E-03 8.71E-03 3.63E-03 x 10000 Corrosion Likelihood 1.33E-01 1.42E-01 1.49E-01 8.90E-03 1.53E-02 6.36E-03 x 100000 Table 5 Steel Liner Corrosion Sensitivity: Unit 1 Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 year (3-per-10 to (3-per-10 to 1- (1-per-10 to y~ar ILRT) yearlLRT) ILRT) 1-per-10) per-15) 1-per-15)
Dose Rate 1.41 E-02 4.69E-02 7.03E-02 3.28E-02 5.63E-02 2.34E-02 Corrosion Likelihood 1.42E-02 *4.93E-02 7.88E-02 3.51E-02 6.46E-02 2.95E-02 x 1000 Corrosion Likelihood 1.53E-02 7.13E-02 1.5.5E-01 5.60E-02 1.40E-01 8.38E-02 x 10000 Corrosion Likelihood 2.69E-02 2.92E-01 9.19E-01 2.65E-01 8.92E-01 6.27E-01 x 100000 Revision 3 Page 31of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Steel Liner Corrosion Sensitivity: Unit 2 Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Dose Rate Increase Increase Increase (3-per-10 (1-per-10 (1-per-15 year (3-per-10 to (3-per-10 to 1- (1-per-10 to year ILRT) yearlLRT) ILRT) 1-per-10) per-15) 1-per-15)
Dose Rate 1.24E-02 4.13E-02 6.19E-02 2.89E-02 4.95E-02 2.06E-02 Corrosion Likelihood 1.25E-02 4.34E-02 6.94E-02 3.09E-02 5.69E-02 2.59E-02 x 1000 Corrosion Likelihood 1.35E-02 6.28E-02 1.37E-01 4.93E-02 1.23E-01 7.38E-02 x 10000 Corrosion Likelihood 2.36E-02 2.57E-01 8.09E-01 2.33E-01 7.85E-01 5.52E-01 x 100000 5.3.3 Expert Elicitation Sensitivity Another sensitivity case on the impacts of assumptions regarding pre-existing containment defect or flaw probabilities of occurrence and magnitude, or size of the flaw, is performed as described in Reference 24. In this sensitivity case, an expert elicitation was conducted to develop probabilities for pre:..existing containment defects that would be detected by the ILRT only based on the historical testing data.
Using the expert knowledge, this information was extrapolated into a probability-versus-magnitude relationship for pre-existing containment defects [Reference 24]. The failure mechanism analysis also used the historical ILRT data augmented with expert judgment to develop the results. Details of the expert elicitation process and results are contained in Reference 24. The expert eli.citation process has the advantage of considering the avaiiable
- data for small leakage events, which have occurred in the data, and extrapolate those events and probabilities of occurrence to the potential for large magnitude leakage events.
The expert elicitation results are used to develop sensitivity cases for the risk impact assessment. Employing the results requires the application of the ILRT interval methodology using the expert elicitation to change the probability of pre-existing leakage in the containment.
The baseline assessment uses the Jeffreys non-informative prior and the expert elicitation sensitivity study uses the results of the expert elicitation. In addition, given the relationship between leakage magnitude and probability, larger leakage tt:iat is more representative of large early release frequency, can be reflected. For the purposes of this sensitivity, the same leakage magnitudes that are used in the basic methodology (i.e., 10 La for small and 100 La for large) are used here. Table 5-27 presents the magnitudes and probabilities associated with the Jeffreys non-informative prior and the expert elicitation used in the base methodology and this sensitivity case.
Table 5 MNGP Summary of ILRT Extension Using Expert Elicitation Values (from Reference 24)
Leakage Size (La) Expert Elicitation Mean Probability of Occurrence Percent Reduction 10 3.88E-03 86%
100 2.47E-04 91%
Taking the baseline analysis and using the values provided in Table 5-10-Table 5-14 for the expert elicitation sensitivity yields the results in Table 5-28 and Table 5-29.
Revision 3 Page 32 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 5 Unit 1 DCPP Summary of ILRT Extension Using Expert Elicitation Values Accident ILRT Interval Class 3per10 Years 1 per 10 Years 1 per 15 Years Base Adjusted Dose Dose Rate Frequency Dose Rate Frequency Dose Rate Frequency Base (person- (person- (person- (person-Frequency rem) rem/yr) rem/yr) rem/yr) 1.67E-05 1.66E-05 3.68E+03 6.11E-02 1.64E-05 6.05E-02 1.63E-05 6.00E-02 2 1.47E-07 1.47E-07 9.83E+06 1.45E+OO 1.47E-07 1.45E+OO 1.47E-07 1.45E+OO 3a N/A 6.46E-08 3.68E+04 2.38E-03 2.15E-07 7.93E-03 3.23E-07 1.19E-02 3b NIA 4.12E-09 3.68E+05 1.51E-03 1.37E-08 5.05E-03 2.06E-08 7.57E-03 6 O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 7 7.61E-07 7.61E-07 9.83E+06 7.48E+OO 7.61E-07 7.48E+OO 7.61E-07 7.48E+OO 8 1.35E-06 1.35E-06 8.90E+05 1.20E+OO 1.35E-06 1.20E+OO 1.39E-06 1.20E+OO Totals 1.89E-05 1.89E-05 N/A 1.02E+01 1.89E-05 1.02E+01 1.89E-05 1.02E+01 LiLERF (3 per 10 vrs base)
N/A 9.60E-09 1.65E-08 LiLERF (1 per 10 yrs base)
N/A N/A 6.86E-09 CCFP 11.96% 12.01% 12.05%
Table 5 Unit 2 DCPP Summary of ILRT Extension Using Expert Elicitation Values Accident ILRT Interval Class 3per10 Years 1 per 10 Years 1 per 15 Years Base Adjusted Dose Dose Rate Frequency Dose Rate Freql!ency Dose Rate Frequency Base (person- (person- (perso!l- (person-Frequency rem) rem/yr) rem/yr) rem/yr) 1.47E-05 1.46E-05 3.68E+03 5.38E-02 1.45E-05 5.32E-02 1.44E-05 5.29E-02 2 1.47E-07 1.47E-07 9.83E+06 1.45E+OO 1.47E-07 1.45E+OO 1.47E-07 1.45E+OO 3a N/A 5.69E-08 3.68E+04 2.09E-03 1.90E-07 6.98E-03 2.85E-07 1.05E-02 3b N/A 3.62E-09 3.68E+05 1.33E-03 1.21E-08 4.44E-03 1.81E-08 6.67E-03 6 O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 7 6.85E-07 6.85E-07 9.83E+06 6.74E+OO 6.85E-07 6.74E+OO 6.85E-07 6.74E+OO 8 1.35E-06 1.35E-06 8.90E+05 1.20E+OO 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO Totals 1.69E-05 1.69E-05 N/A 9.44E+OO 1.69E-05 9.45E+OO 1.69E-05 9.45E+OO LiLERF (3 per 10 vrs base)
N/A 8.45E-09 1.45E-08 LiLERF (1 per 10 vrs base)
N/A N/A 6.04E-09 CCFP 12.98% 13.03% 13.06%
The results illustrate how the expert elicitation reduces the overall change in LERF and the overall results are more favorable with regard to the change in risk.
Revision 3 Page 33of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 6.0 RESULTS The results from this ILRT extension risk assessment for DCPP are summarized in Table 6-1 for Unit 1 and Table 6-2 for Unit 2.
Table 6 Unit 1 ILRT Extension Summary Class Dose Base Case Extend to Extend to (person-rem) 3in10 Years 1in10 Years 1 in 15 Years CDFNear Person- CDFNear' Person- CDFNear Person-RemNear RemNear RemNear 3.68E+03 1.65E-05 6.06E-02 1.60E-05 5.90E-02 1.57E-05 5.78E-02 2 9.83E+06 1.47E-07 1.45E+OO 1.47E-07 1.45E+OO 1.47E-07 1.45E+OO 3a 3.68E+04 1.54E-07 5.65E-03 5.12E-07 1.88E-02 7.68E-07 2.83E-02 3b 3.68E+b5 3.82E-08 1.41 E-02 1.27E-07 4.69E-02 1.91E-07 7.03E-02 6 O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 7 9.83E+06 7.61 E-07 7.48E+OO 7.61E-07 7.48E+OO 7.61 E-07 7.48E+OO 8 8.90E+05 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO Total 1.89E-05 1.02E+01 1.89E-05 1.03E+01 1.89E-05 1.03E+01
' ~ -
- - -~ j ILRT Dose Rate from 3a and 3b
.6.Total From 3 Years N/A 4.44E-02 7.60E-02 Dose Rate From 10 Years N/A N/A 3.17E-02
%.6.Dose From 3 Years N/A 0.434% 0.745%
Rate From 10 Years N/A N/A 0.309%
L ..
., ---. . .. --* <r ---- --- **-- ..~:* - '; 7 "'. ... . . - "'- ~ -----
. .. . '*.... I 3b Frequency (LERF)
- N/A
.6.LERF From 3 Years From 10 Years N/A 8.92E-08 N/A 1.53E-07 6.37E-08 CCFP%
From 3 Years N/A 0.471% 0.808%
.6.CCFP%
From 10 Years N/A N/A 0.337%
\
Revision 3 Page 34of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table 6 Unit 2 ILRT Extension Summary Class Dose Base Case Extend to Extend to (person-rem) 3 in 10 Years 1 in 10 Years 1in15 Years CDFNear Person- CDFNear Person- CDFNear Person-RemNear RemNear RemNear 3.68E+03 1.45E-05 5.34E-02 1.41E-05 5.19E-02 1.38E-05 5.09E-02 2 9.83E+06 1.47E-07 1.45E+OO 1.47E-07 1.45E+b0 1.47E-07 1.45E+OO 3a 3.68E+04 1.35E-07 4.97E-03 4.51E-07 1.66E-02 6.76E-07 2.49E-02 3b 3.68E+05 3.36E-08 1.24E-02 1.12E-07 4.13E-02 1.68E-07 6.19E-02 6 O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 7 9.83E+06 6.85E-07 6.74E+OO 6.85E-07 6.74E+OO 6.85E-07 6.74E+OO 8 8.90E+05 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO 1.35E-06 1.20E+OO Total 1.69E-05 9.46E+OO 1.69E-05 9.49E+OO 1.69E-05 9.52E+OO I .. ..
ILRT Dose Rate from 3a and 3b LiTotal From 3 Years N/A 3.90E-02 6.69E-02 Dose Rate From 10 Years N/A N/A 2.79E-02
%liDose From 3 Years N/A 0.413% 0)'08%
Rate From 10 Years N/A N/A 0.294%
3b Frequency (LERF)
From 3 Years N/A 7.85E-08 1.35E-07 LiLERF From 10 Years N/A N/A 5.61E-08
-. . . . ~ ...
. I
~,
CCFP%
From 3 Years N/A 0.466% 0.799%
LiCCFP%
From 10 Years N/A N/A 0.333%
Revision 3 Page 35of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension 7 .0 CONCLUSIONS AND RECOMMENDATIONS Based on the results from Section 5.2 and the sensitivity calculations presented in Section 5.3, the following conclusions regarding tile assessment of the plant risk are associated with extending the Type A ILRT test frequency to 15 years:
- Regulatory Guide 1.174 [Reference 4] provides guidance for determining the risk impact of plant-specific changes to the licensing basis. Regulatory Guide 1.174 defines small changes in risk as resulting in increases of CDF greater than 1.0E-6/year and less than 1.0E-5/year and increases in LERF greater than t.OE-7/year and less than 1.0E-6/year.
Since the ILRT does not impact CDF, the relevant criterion is LERF. The increase in LERF resulting from a change in the Type A ILRT test interval from 3 in 10 years to 1 in 15 years is estimated as 1.53E-7/yearfor Unit 1and1.35E-7/yearfor Unit 2 using the EPRI guidance (this value increases negligibly if the risk impact of corrosion-induced leakage of the steel liners occurring and going undetected during the extended test-interval is included), and baseline LERF is 2.26E-6/year for Unit 1 and 2.18E-6/year for Unit 2. As such, the estimated change in LERF is determined to be "small" using the acceptance guidelines of Regulatory Guide 1.174 [Reference 4]. *When external event risk is included, the increase in LERF resulting from a change in the Type A ILRT test interval from 3 in 10 years to 1 in 15 years is estimated as 7.87E-7/year for Unit 1 and 8.09E-7/year for Unit 2 using the EPRI guidance, and baseline LERF is 8.78E-6/year for Unit 1 and 8.45E-6/year for Unit 2. As such, the estimated change iri LERF is determined to be "small" using the *acceptance guidelines of Regulatory Guide 1.174
[Reference 4].
- The effect resulting from changing the Type A test frequency to 1-per-15 years, measured as an increase to the total integrated plant risk for those accident sequences influenced by Type A testing, is 0.076 person-rem/year for Unit 1 and 0.067 person-rem/year for Unit 2. EPRI Report No. 1009325, Revisiory 2-A [Reference 24] states that a very small population dose is defined as an increase of s 1.0 person-rem per year, ors 1% of the total population dose, whichever is less restrictive for the risk impact assessment of the extended ILRT intervals. The results of this calculation meet these criteria. Moreover, the risk impact for the ILRT extension when compared to other severe accident risks is negligible.
- The increase in the conditional containment failure probability from the 3 in 10 year interval to 1 in 15 year interval is 0.808% for Unit 1 and 0. 799% for *unit 2. EPRI Report No. 1009325, Revision 2-A [Reference 24] states that increases .in CCFP of s 1.5% is very small. Therefore, this increase is judged to be very small.
Therefore, increasing the ILRT interv'al to 15 years is considered to be insignificant since it represents a small change to the DCPP risk profile.
Previous Assessments The NRC in NUREG-1493 [Reference 6] has previously concluded that:
- Reducing the frequency of Type A tests (ILRTs) from 3 per 1O years to 1 per 20 years was found to lead to an imperceptible increase in risk. The estimated increase in risk is very small because ILRTs identify only a few potential containment leakage paths that cannot be identified by Type B or Type C testing, and the leaks that have been found by Type A tests have been only marginally above existing-requirements.
Revision 3 Page 36of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension
- Given the insensitivity of risk to containment leakage rate and the small fraction of leakage paths detected solely by Type A testing, increasing the interval between integrated leakage-rate tests is possible with minimal impact on public risk. The impact of relaxing the ILRT frequ~ncy beyond 1 in 20 years has not been evaluated. Beyond testing the performance of containment penetrations, ILRTs also test integrity of the containment structure.
The findings for DCPP confirm these general findings on a plant-specific basis considering the severe accidents evaluated for DCPP, the DCPP containment failure modes, and the local population surrounding DCPP.
Revision 3 Page 37of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension A. ATTACHMENT 1 A.1. Internal Events PRA Quality Statement for Permanent 15-Year ILRT Extension PG&E conducted an Internal Events Peer Review in December 2012. The full-scope Peer Review that included internal events and internal floods portions of the DCPP PRA was performed in accordance with RG 1.200, Rev. 2, and ASME/ANS RA-Sa-2009. The review provided Facts and Observations (F&Os) regarding the model and identified 94 supporting requirements within the internal events. and internal floods portions of the model that did not meet Capability Category (CAT) II. All findings have been either resolved by additional analysis or evaluated in terms of their impact on the ILRT extension, and dispositioned as presented in Table A-1 Internal Events PRA Peer Review- Facts and Observations.
No changes have been made to the Internal Events or Internal Floods PRA models since the Peer Review that would constitute an upgrade.
Internal floods findings and their disposition are presented in Table A-2. Findings associated with internal floods are addressed but have no impact on the ILRT extension application.
PG&E conducted a Seismic PRA Peer Review in January 2013. The full-scope Peer Review that also included a review of seismic hazard and fragility analyses was performed in accordance with RG 1.200, Rev. 2, and ASME/ANS RA-Sa-2009.
A.2. Fire PRA Quality Statement for Permanent 15-Year ILRT Extension The FPRA is adequate to support the ILRT extension analysis. The DCPP FPRA was reviewed in January 2008 as part of the pilot application of the NEl-07-12 Peer Review process. The 2008 Peer Review was conducted against the requirements of the ANS Standard "FPRA Methodology" ANSl/ANS-58.23-2007. At the time of this first Peer Review, certain technical elements of the FPRA had not been completed, and it was agreed that the second phase of the Peer Review would be performed when all the technical elements of the FPRA were completed.
The second phase of the Peer Review was completed in December 2010. The 201 O Peer R/eview was conducted against the requirements of Section 4 of the ASME/ANS Combined PRA Stand9rd.
The Peer Review noted a number of F&Os. The F&Os and the disposition of the F&Os are provided in Table A-3.
All FPRA related F&Os, except SF-A5-01 against SR SF-A5, have been addressed and dispositioned as closed. SF-A5-01 tracks the implementation (revision of the fire brigade training procedure) of a recommendation related to fire brigade training requirement dealing with seismically induced fires. See Attachment S, Table S-3, Item S-3.25 of Reference 33 for more details. This item has no impact on the ILRT extension analysis.
Per the 2010 Peer Review, the DCPP FPRA met Capability Category II or better in all SRs but two (SRs CF-A1 and FSS-D7). These two SRs are listed in Table A-3. These.SRs have since been addressed and now considered as met at CC-II.
Table A-3 also listed the SRs from the 2008 Peer Review that did not meet CC-II or better quality requirements. However, as documented in Tables V-1 and V-2, these 2008 SRs have been re-reviewed during the 2010 Peer Review and all of the SRs were found met at CC-II or better.
No changes have been made to the FPRA model since the Peer Reviews that would constitute an upgrade.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Based on the Peer Reviews, Independent Third Party Reviews, and the resolution of F&Os, the DCPP FPRA model includes no deviations from NUREG/CR-6850 approaches, and contains no unreviewed analysis methods (UAMs).
A.3. Seismic PRA Quality Statement for Permanent 15-Y~ar ILRT Extension The seismic hazard and fragilities are currently being updated. The Seismic hazard update incorporates the most recent site-specific seismic data. The Peer Review team reviewed the methodologies used in the hazard and fr~gility analyses and found them to be acceptable. The current SPRA model provides a reasonable estimate of the seismic CDF and LERF for the purposes of the ILRT extension analysis.
Section 5 cif the ASME/ANS Combined PRA Standard contains a total of 77 Supporting Requirements (SRs) under three technical elements. As a result of this review, a total of 60 F&Os were generated. These included five "Best Practices," 18 "Suggestions, and 37 "Findings." Table A-4 presents Seismic PRA Peer Review Findings and Observations and their effect on the ILRT extension analysis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension IE-A5 IE-A5-01, NOT Closed Discussion: PERFORM a systematic evaluation of each Each system was screened for potential This is resolved.
MET, system, including support systems, to assess the possibility of initiating events. If a system did not There is no impact systematic an initiating event occurring due to a failure of the system. screen, the system was reviewed on the ILRT review of each Basis for Significance: There is no evidence in the against the existing Initiating Events Extension Risk system documentation (including Section C.1 of PLG-0637) that analysis to confirm that a bounding or Analysis.
demonstrates that EVERY system in the plant was reviewed as representative initiating event is a potential IE contributor. Discussion with DCPP PRA personnel modeled in the DCPP Internal Events confirmed this conclusion. PRA.
Possible Resolution: Collect list of all plant systems and meet with plant personnel to address the gap. An interview of operations representative was conducted to confirm the system screening and to discuss low power or NPOs for each system. Table H.1.6-10 of PRA Cale H.1.6 Rev 8 documented the review.
IE-A7 IE-A7-01, NOT Closed Discussion: SR IE-A?: In the identification of the initiating Twice-Daily Shift Manager Turnover This is resolved.
MET, events, INCORPORATE Reports, On-line/Off-line Daily Log, and There is no impact Associated SRs: (a) events that have occurred at conditions other than at-power Outage History were reviewed for on the ILRT IE-AB(CC-1), IE- operation (i.e., during low-power or shutdown conditions), and potential initiating events. No new Extension Risk A9(CC-I), events for which it is determined that the event could also occur during initiating events were discovered during Analysis.
occurred other than at-power operation. the review of the turnover repo_rts, daily at-power (b) events resulting in a controlled shutdown that includes a logs, and outage history. Low and non-scram prior to reaching low-power conditions, unless it is power operation events were discussed determined that an event is not applicable to at-power as part of the system screening operation. performed to resolve F&O IE-A5. The SR IE-AB: INTERVIEW plant personnel (e.g., operations, review was documented in Table H.1.6-maintenance, engineering, safety analysis) to determine if 10 of PRA Cale H.1.6 Rev 8.
potential initiating events have been overlooked.
SR IE-A9: REVIEW plant-specific and review industry operating experience for initiating event precursors, for identifying additional initiating events.
Twice-Daily Shift Manager Turnover Reports, On-line/Off-line Daily Log, and Outage History were reviewed for potential initiating events. No new initiating events were discovered during the review of the turnover reports, daily logs, and outage history. Low and non-power operation events were discussed as part of the system screening performed to resolve F&O IE-A5.
Significance to the FPRA and NFPA-805 LAR:
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status *Finding/Observation Disposition Cat II Requirement Extension The only aspeqt of the F&O that re~ult in a change to the internal events PRA is the discussion of the internal events low-power and non-power operations events review for initiating events. This has no impact on the FPRA, and only affects the documentation of the internal events PRA since there are no new initiating events and therefore no changes to the Internal Events PRA model.
Basis for Significance: SR IE-A7: The DCPP PRA has not addressed either requirements (a) or (b) for SR IE-A7, i.e.,
neither (a) a review of events that have occurred at conditions other than at-power operation that could also occur during at-power operation and would lead to a unique IE nor (b) a review of events resulting in an unplanned controlled shutdown that includes a scram prior to reaching low-power conditions. Note that the SR calls for a review of historical events.
SR IE-AB: no interviews were conducted with plant personnel to determine if potential .initiating events have been overlooked.
SR IE-A9: the plant-specific operating experience was not reviewed for initiating event precursors to identify additional initiatin events IE-C5 IE-C5-01, NOT Closed Discussion: Calculate initiating event frequencies on a reactor- .As demonstrated in PRA Cale 13-12 Since this has MET, IE year basis. Include in the initiating event analysis the plant Revision 0, the difference between the insignificant on the Frequency based availability, such that the frequencies are weighted by the capacity factors of both Units 1 and 2 is final CDF/LERF results, on a reactor year fraction of time the plant is at-power. less than 1%. Using the combined there is negligible basis Basis for Significance: IE frequencies are converted to events capacity fact instead of unit specific impact on the ILRT per calendar year by multiplying by the site critical hours per factors has insignificant impact on the Extension Risk calendar year factor calculated from site operating experience. final CDF/LERF results. Analysis.
However, SR IE-C5 requires this factor to be calculated on a
, plant unit operating year basis. This distinguishes differences in the plant units' operating experience.
Possible Resolution: Revise the conversion factors from a site to a ~lant s~ecific basis.
IE-C10 IE-C10-01, MET, Closed Discussion: If fault-tree modeling is IE fault trees were evaluated and This was a combination of one used for initiating events, CAPTURE.within the initiating event documentation was added to Section documentation issue Structure, System fault tree models all relevant combinations of events involving 4.2.3 of Cale B.1 to address the IE fault - and is resolved.
or Component the annual frequency of one component failure combined with tree documentation discussed above. There is no impact (SSC) failure with the unavailability (or failure during the repair time of the first on the ILRT the unavailability of component) of other components. Extension Risk other SSCs. Anal sis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Basis for Significance: Use of plant specific information in the Internal Events Fault Trees (!EFT) was not evident.
There was no discussion in the !EFT. Use of plant specific information in the IEFT was not evident. There was no discussion in the IEFT documentation regarding the treatment of common cause events. There is no discussion of how the 24-hour and 365-day exposure intervals are factored into the model.
There is no discussion of whether the success criteria used for the mitigating fault trees are applicable (or not) for the IEFT.
The Common Cause Failure (CCF) treatment in the !EFT should be described in order to verify that the appropriate exposure intervals are applied based on equipment rotational practices.
Possible Resolution: Evaluate and document the !EFT success criteria. Expand the !EFT documentation to address the all of above issues.
IE-C14 IE-C14-01, NOT Closed Discussion: In the ISLOCA frequency analysis, INCLUDE the Table C.4. 7-5 of Cale C.4. 7 Revision 9 This is resolved; no MET, following features of plant and procedures that influence the lists the containment penetrations and model change was Interfacing System ISLOCA frequency: (a) configuration of potential pathways disposition regarding their potential as necessary. There is Loss of Coolant including numbers an ISLOCA pathway was developed. A no impact on the Accident (ISLOCA) and types of valves and their relevant failure modes and the set of screening criteria were developed ILRT Extension Risk frequency existence, size, and positioning of relief valves (b) provision of consistent with the SR requirement. Analysis.
protective interlocks (c) relevant surveillance test (d) the These criteria were used explicitly to capability of secondary system piping. screen each potential ISLOCA pathway.
The unscreened ISLOCA flow paths are Basis for Significance: There is no systematic review of all consistent with what modeled in containment penetrations performed for or in the ISLOCA RISKMAN.
calculation. All penetrations that are screened out need to be Also, impact of Surveillance test was justified, yet this process was not evident in the documentation. added to the documentation.
Review of relevant surveillance test procedures is needed to meet this SR. other requirements specified in SR IE-C14 must also be evaluated and documented.
Possible Resolution: Create a table of all containment penetrations and disposition their potential as an ISLOCA pathway. Impact of surveillance test procedures should be explicitly documented. Explanation of RISKMAN treatment of ISLOCA quantification should be documented. Document all requirements of the SR.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension IE-C15 IE-C15-01, NOT Closed Discussion: CHARACTERIZE the uncertainty in the initiating Parametric uncertainty for IE This is resolved.
MET, event frequencies and PROVIDE mean values for use in the frequencies is given in H.1.6 as Range There is no impact Associated SR: IE- quantification of the PRA results. Factors (Error Factors) for LOCA IEs on the ILRT C1 and alpha/beta values for gamma Extension Risk (MET), uncertainty Basis for Significance: No discussion of uncertainty distributions. Analysis.
associated with IEs. parameters for IEFT was located in Calculation Files C.10 and H.1.6. This is required to meet SR IE-C15 and is necessary to document the process used to calculate the IE frequencies per SR IE-C1.
Possible Resolution: Provide a discussion of uncertainties (preferably in Calculation H.1.6).
IE-D1 IE-D1-01, NOT Closed Discussion: The DCPP PRA documentation is not written in References to PLG-0637 as the basis This was a MET, . manner that facilitates PRA applications, upgrades, and peer have been taken out and information documentation issue Associated SRs: review. In great part, this is probably due to the fact that this has been included in the new and is resolved.
IE-D2 documentation heavily references the original DCPP PRA calculation revisions for system There is no impact (NOT MET), IE-D3 documents, especially PLG-0637. This mak~s it difficult to notebooks, initiating event notebooks, on the ILRT (NOT MET), AS-C1 understand details of the model, difficult to confirm that the event tree notebooks, and other PRA Extension Risk (NOT MET), SY-C1 model addresses PRA requirements, and difficult to update and development documentation. Analysis.
(NOT MET), DA-E1 use it for PRA applications. This finding applies to elements IE, (NOT MET), QU-F1 AS; SY, DA, QU, LE, IFPP, IFSO, IFSN, and IFQU.
(NOT MET), LE-G1 (NOT MET), IFPP- Basis for Significance: The DCPP PRA documentation is not 81 (NOT MET), written in manner that facilitates PRA applications, upgrades, IFS0-81 (NOT and peer review. In great part, this is probably due to the fact MET), IFSN-A5 that this documentation heavily references the original DCPP (MET), IFSN-81 PRA documents, especially PLG-0637. This makes it difficult to (Nor MET), IFQU- understand details of the model, difficult to confirm that the 81 (MET) model addresses PRA requirements, and difficult to update and use it for PRA applications.
Possible Resolution: In the summary document, Calculation file B.1, describe each aspect of the model development, referencing supporting calculations. And, these supporting calculations should provide additional details of the analysis to the level of documentation to demonstrate that all SRs are met.
This approach, in essence, suggests abandoning the heavy reliance on PLG-0637, which does not meet many requirements of the PRA Standard and creating a set of "living" PRA documents that fully meet these requirements. This would not only eliminate the need to "patch" deficiencies of the PLG-0637 Revision 3 Page 43of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension documentation but also provide a means to much more easily document model updates - thereby facilitating use of the model and document in future risk applications.
IE-D2 IE-02-01, NOT Closed Discussion: DOCUMENT the processes used to select, group, Re IE-A3: Section 4.2.1 of Cale B.1 This is resolved.
MET, and screen the initiating events and to model and quantify the Revision 1 references to Cale H.1.6, There is no impact Associated SRs: initiating event frequencies, including the inputs, methods, and which discusses use of plant-specific on the ILRT IE-A3 (MET), IE- results. For example, this documentation typically includes: experience. Extension Risk A 10(MET), (a) the functional categories considered and the specific Analysis.
IE-B3(CC-ll), IE- initiating events included in each Re IE-A 10: Section 6.2 of Cale B.1 C2(MET), IE- Revision 1 describes the potential for C3(MET), IE- Basis for Significance: IE-A3: CALCULATION FILE B.1 the loss of Instrument Air system as a C4(MET), IE-CB should reference Tables H1 .6-5, 6, 7, and B to demonstrate dual unit initiator.
(MET), IE-C9 compliance with SR IE-A3.
(MET), IE-C10 Re IE-B3: The Total Loss of (MET), IE-C12 IE-A 10: The DCPP PRA documentation does not describe the Condensate Flow initiator was moved (MET), IE-D1 (NOT potential for the loss of IA as a dual Unit initiator. from PLMFW to TLMFW as MET), documented in Table 4.4 of Cale B.1 documentation IE-B3: Table 4-3 of Calculation File B.1: indicates that the Revision 1. Cale H.1.6 Revision 8 also TOTAL Loss of Condensate Flow was subsumed into the reflects this change.
Partial Loss of Feedwater initiator. This is inappropriate. DCPP PRA personnel agreed and indicated that this is an editorial Re IE-C2: In Attachment 2 of Cale H.1.6 error. This should be corrected. Revision 8 clearly states "freeze date" for the Unit 2 IE data.
IE-C2: Table H.1.6-5 of Calculation File H.1.6 states that the Unit 1 IE data is updated through March Re IE-C3: Recovery actions credited in 31, 2009; however, no "freeze date" is provided for the Unit 2 IE the system fault trees used for initiating data. This date should be provided. events (e.g., Top Event AI for loss of the ASW or Top Event ex for loss of all IE-C3: Credited recovery actions should be documented. CCW system) are documented in Success Criteria section of the system IE-C4: Calculation File H.1.6 does not provide details notebooks such as D.2.6 for the ASW associated with generation of mean and uncertainty parameters system and D.2.7 for the CCW system.
associated with the generic data (from NUREG/CR-692B) nor does it provide any details on the Bayesian calculations. This Re IE-C4: Tables H.1.6-2 and H.1.6-8 information should be documented (preferably in Calculation provide details of the distribution H.1.6) in order to facilitate future updates. parameters associated with the generic data, DCPP experience, and Bayesian IE-CB, IE-C9, IE-C10, and IE-C11: There updated results.
is insufficient documentation describing the construction of the
!EFT. This includes a lack of documentation regarding the Re IE C-8, IE-C9, IE-C10, IE-C11: IE treatment of CCF, how the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and 365 day exposure fault trees are discussed in detail in the Revision 3 Page 44of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension intervals are factored into the model, the success criteria used applicable system notebooks (i.e for for the IEFT, and the use of plant specific information in the Loss of CCW initiator, Cale D.2.7).
assessment of recovery actions used in the IEFT. CCFs are discussed in H.1. Recovery actions are discussed in C.8. Cale 8.1 IE-C12: A detailed discussion comparing the DCPP PRA IE discusses the System Initiator frequencies with generic data sources and explaining Quantification Methodology in Section differences is not documented. This is required to demonstrate 7.2.4.
r that SR IE-C12 is met.
Re IE-C 12: Section H.1.6. 7 of Cale Possible Resolution: Revise documentation to address the H.1.6 Revision 8 discusses comparison above issues. of the DCPP plant specific IE freguencies with generic data.
AS-B3 AS-83-01, NOT Closed Discussion: This .SR states, "For each accident sequence, A new system notebook, 1.1 Revision 0 This is resolved .
MET, . IDENTIFY the phenomenological conditions created by the was created to document the review of There is no impact Associated SRs: accident progression. phenomenological conditions for all on the ILRT AS- 83 (NOT Phenomenological impacts include generation of harsh initiating events for their impacts on the Extension Risk MET), SY-A18 environments affecting temperature, pressure, debris, water success of the system or function. Analysis.
(MET), SY- A21 levels, humidity, etc. that could impact the success of the (MET), SY-A23 system or function under consideration ... " Based on this review, the following (MET), SY- 814 model changes were made.
(MET), Basis for Significance: Based on a review of accident Credit was conservatively removed for phenomenological sequence documents, there does not appear to be a review of the Instrument Air System (IA) for Main conditions created phenomenological conditions created by each accident Steam- Line Break and Feedwater-Line by accident sequence. Environmental Qualification (EQ) Program Break (Outside of Containment) progressions documentation was provided, however, there may be non- initiators in the PRA model as their safety-related components that are affected by an accident impacts could not be verified.
sequence that were not reviewed/included for the accident impact on the functionality of the component. Credit was also removed for the operator action to make-up to the Possible Resolution: Include a sequence level review of RWST in the event of an Interfacing phenomenological conditions and include those that affec~ the System LOCA (ISLOCA) due to success of systems/functions in the accident sequence potentially high radiation conditions in analyses. areas that operators need to enter to eerform necessa~ actions.
AS-B7 AS-B7-01, Closed Discussion: This SR requires the modeling of time-phased Current time phased recovery in Section This was a MET, time-phased dependencies. G.4.1.1 of Cale G.4 uses correct battery documentation issue dependencies depletion times. Section D.2.1.2.4.1 of and is resolved.
Basis for Significance: Time-phased dependencies were Cale D.2.1.2 Revision 1O was revised to There is no impact found to be modeled in the accident sequences (e.g., AC power correct inconsistency between Cale G.4 on the ILRT recovery and DC battery depletion). However, the and D.2.1.2. Extension .Risk documentation has inconsistencies that need to be resolved. Anallsis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension One example of an inconsistency is that the battery depletion time in documents G.4 and D.2.1.2 are not the same (5.75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br /> vs.12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />).
Possible Resolution: Ensure that PRA documentation reflects the actual times used in the model and that PRA documentation is consistent.
AS-C2 AS-C2-01, NOT Closed Discussion: This SR requires the documentation of processes Documentation related finding This was a MET, used to develop accident sequences. associated with accident sequence documentation issue Documenting documentation. and is resolved.
processes used to Basis for Significance: AS-A11-01 and AS-87-01 identify Refer to disposition for F&Os AS-A11- There is no impact develop accident issues related to the documentation of the accid~nt sequence 01 and AS-87-01. on the ILRT sequences analyses. Extension Risk Possible Resolution: Improve the accident sequence Analysis.
documentation to accurately reflect what is modeled.
SC-A1 SC-A1-01, NOT Closed Discussion: This SR states "USE the definition of "core The definition of core damage . This is resolved.
MET, damage" provided in Section 1-2 of this Standard. If core dependent on collapsed water level was There is no impact Associated SR: SC- damage has been defined differently than in Section 1-2, (a) removed from the documentation. on the ILRT A2 (NOT MET), IDENTIFY any substantial differences from the Section 1-2 MAAP runs were updated using the Extension Risk definition of core definition (b) PROVIDE the bases for the selected definition." core damage definition of > 1800°F Analysis.
damage peak fuel temperature.
Basis for Significance: Based on the information in E.16, Revision 0, two definitions of Core Damage are used in the Prior to this update, core uncovery was DCPP Internal Events. The first definition, Peak Node used as the end point in the timing temperature >1800°F is a valid success criterion, and meets the analysis for the HRA. The use of core definition in Section 1-2 of the Standard. However, the second uncovery vs. peak clad temperature of criterion of "the time until the water level is collapsed below the 1800°F results in a slightly conservative top of active fuel" is not a valid definition since the definition of time available for the HFE. Converting Core Damage as written in Section 1-2 requires the the collapsed water level uncovery of consideration of uncover and heat-up, and this definition does fuel criteria to Peak Control not consider heat-up. Additionally, it is not valid to have two Temperature (PCT) of 1800°F would not separate definitions for the same end state. adversely affect the timing requirements.
Possible Resolution: Remove the second definition of Core Damage, and do all analyses and timings using the Peak Node tem~eratures >1800°F.
SC-A4 SC-A4-01, NOT Closed Discussion: This SR states "IDENTIFY mitigating systems that Cale B.1 was revised to include an This is resolved.
MET, are shared between Units, and the manner in which the sharing evaluation of two shared system Diesel There is no impact shared systems is performed should both Units experience a common initiating Fuel Oil (DFO) and Instrument Air (IA) on the ILRT between Units event (e.g., LOOP)." systems in Section 6.2 of ~evision 1. Extension Risk Anal sis.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review--Facts and Observations SR 2009 ASME/ANS Status Impact on ILRT Finding/Observation Disposition Cat II Requirement Extension Basis for Significance: A review of the documentation did not reveal where shared systems were identified and discussed with respect to how they were credited in dual Unit scenarios.
Discussion with DCPP personnel identified that there are not many shared systems at DCPP and they are not typically credited. However, the identification of which systems are shared between the Units, and how they are credited is not documented anywhere. For example, no discussion on the DG Fuel Oil transfer system is provided, although it is a known shared system. Therefore it is not possible to verify that a shared system is not inadvertently credited in the analyses during dual Unit scenarios.
Possible Resolution: Document which systems in the PRA are shared systems at DCPP, and discuss how they are credited in the Internal Events PRA, including how they are credited during dual Unit initiators. Verify that the shared systems are modeled consistent with their availability during dual Unit initiators.
SC-AS SC-AS-01, NOT Closed Discussion: This SR states: SPECIFY an appropriate mission PG&E reviewed the fire and internal This is resolved.
MET, time for the modeled accident sequences. For sequences in events accident sequences, success There is no impact
_mission time which stable plant conditions have been achieved, USE a criteria and associated thermo-hydraulic on the ILRT minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Mission times for individual (TH) runs for various non-LOCA and Extension Risk SSCs that function during the accident sequence may be less LOCA sequences (MAAPs 13-04, 13- Analysis.
than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> as long as an appropriate set of SSCs and 06, 13-07, 13-08) to verify that a stable operator actions are modeled to support the full sequence plant condition could be achieved for a mission time. For example, if following a LOCA, low pressure minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The injection is available for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, after which recirculation is review included verification whether required, the mission time for LPSI may be 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and the individual SSCs can support the mission time for recirculation may be 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />. For sequences minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> as in which stable plant conditions would not be achieved by 24 currently credited in the PRA models.
hours using the modeled plant equipment and human actions, PERFORM additional evaluation or modeling by using an The review concluded that for scenarios appropriate technique. Examples of appropriate techniques where a stable hot shutdown condition include: was desired, the Condensate Storage (a) assigning an appropriate plant damage state for the Tank (CST) inventory would be sequence; depleted in less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> unless (b) extending the mission time, and adjusting the affected additional secondary inventory was analyses, to the point at which conditions can be shown to made available. The PRA model at the reach acceptable values; or time of the internal events peer review (c) modeling additional system recovery or operator actions for did not contain the equipment or the seguence, in accordance with reguirements stated in the operator actions necessary to assess Revision 3 Page 47of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status _ Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Systems Analysis and Human Reliability sections of this whether a stable state was reached Standard, to demonstrate that a successful outcome is using Auxiliary Feedwater (AFW) achieved. cooling along. For the Internal Events model, long-term AFW cooling is Basis for Significance: Notebook E.16, Revision 0 states "A cr~dited only if the Closed Loop 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time is assumed sufficient to obtain a stable Residual Heat Removal (RHR) cooling plant condition, either hot standby or cold shutdown after an is not available. In the Fire PRA, only initiating event has occurred." This SR requires verification-that long-term AFW cooling is credited; a safe, stable endpoint is obtained, and specifies using a Closed Loop RHR cooling is not minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. No discussion could be credited.
found that verified that each accident sequence actually reached a safe stable state at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> could be identified. For Small LOCA (SLOCA) sequences, a RCS leakage and injection by itself.is Possible Resolution: Each accident sequence needs to be not sufficient to cooldown and bring the reviewed to ensure that the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time is valid to RCS pressure to the RHR entry reach a safe stable state, and this review needs to be condition. These sequences require documented. For any accident sequence that is identified that AFW cooling to reduce the RCP does not reach a safe, stable state at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the time to pressure and temperature prior to reach a safe, stable state needs to be identified, and the model depletion of the Refueling Water updated accordingly. If R_HR entry conditions are met prior to 24 Storage Tanks (RWST) and switch-over hours, then entry into shuf down cooling (use of RHR for long to the RHR Containment Recirculation.
term heat removal) needs to be included in the accident The results of the TH runs for various sequence, or a valid reason for not modeling RHR needs to be sizes of small LOCA show that the provided. existing CST volume is sufficient to support such secondary cooling function. Therefore a supplemental secondary inventory supply within 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time is not required to mitigate Internal Events or fire induced SLOCA sequences.
For Medium and Large LOCA (MLOCA and LLOCA) sequ~nces, the TH runs indicate that the RCS is rapidly depressurized and the additional cooling via the AFW is not necessary.
- Therefore a make-up to the CST within 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time is not required to mitigate MLOCA or LLOCA sequences. _
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension As discussed above, supplemental secondary-inventory is required for non-LOCA scenarios in order to maintain a stable hot shutdown condition for a minimum of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The Fire and Internal Events models are updated to incorporate .additional inventory requirements by adding the equipment necessary to align alternate AFW water supply sources and an operator action based on the existing Operating Procedures. (AR PK 10-01 and OP D-1:V).
For LOCA scenarios, Residual Heat Removal (RHR) is required and modeled within the FPRA to reach a stable end state. In order to ensure that a stable end state is reached in the fire analysis, the FPRA model was updated to include a required supplemental water supply to AFW for non-LOCA scenarios.
SC-A5 SC-A5-02, NOT Closed Discussion: This SR states: SPECIFY an appropriate mission Reviewed success criteria and verified This is resolved.
MET, time for the modeled accident sequences. For sequences in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is acceptable Looked at MAAP There is no impact mission time which stable plant conditions have been achieved, USE a runs. on the ILRT minimum mission time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Mission times for individual Extension Risk SSCs that function during the accident sequence may be less E.16 Rev 1 Documentation revised to Analysis.
than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, as long as an appropriate set of SSCs and include some text of this review:
operator actions are modeled to support the full sequence MAAP Cales were reviewed (MAAP 13-mission time. For example, if following a LOCA, low pressure 06, 13-07, 13-08) and run past 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> injection is available for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, after which recirculation is to verify that a safe stable state was required, the mission time for LPSI may be 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and the achieved. RHR entry conditions were mission time for recirculation may be 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />. also reviewed for the applicable accident sequences.
For sequences in which stable plant conditions would not be achieved by 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> using the modeled plant equipment and For LOCA scenarios, Residual Heat human actions, PERFORM additional evaluation or modeling by Removal (RHR) is required and using an appropriate technique. Examples of appropriate modeled within the FPRA to reach a techniques include: stable end state. In order to ensure that a stable end -state is reached in the fire Revision 3 Page 49of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension (a) assigning an appropriate plant damage state for the analysis, the FPRA model was updated sequence; . to include a required supplemental (b) extending the mission time, and adjusting the affected water supply to AFW for non-LOCA analyses, to the point at.which conditions can be shown to scenarios.
reach acceptable values; or (c) modeling additional system recovery or operator actions for A new Top Event "AWR" representing the sequence, in accordance with requirements stated in the long term availability of the AFW supply Systems Analysis and Human Reliability sections of this water is modeled. Associated event Standard, to demonstrate that a successful outcome is trees (i.e., Fl RELTREE and SLTREE) achieved. and their split fraction rules and event.
Basis for Significance: Several accident sequences were Update: A new Top Event "AWR" identified where RHR entry conditions were met prior to representing long term availability of the 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, but RHR was not required for success in the accident AFW supply water is modeled.
sequence. If RHR is not questioned, then the end state may not Associated event trees (i.e., LATETREE
- be stable since heat removal via the SGs will be diminished as and SLTREE) and their split fraction decay heat lowers, and RHR will be required to maintain rules and event tree structures were temperatures long term. modified to incorporate the new top event. PRA Cales C.4.2 and E.2 were Possible Resolution: Ensure that all accident sequences are updated to reflect the above changes.
modeled to the actual safe, stable end state. If RHR entry conditions are met prior to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, then entry into shut down cooling (use of RHR for long term heat removal) needs to be included in the accident sequence, or a valid reason for not modeling RHR needs to be provided.
SC-83 SC-83-01, NOT Closed Discussion: SR SC-83 states "When defining success criteria, Additional MAAP runs were performed This is resolved.
MET, USE thermal/hydraulic, structural,. or other analyses/evaluations to define new LOCAbreak size (MAAP There is no impact Associated SRs: appropriate to the event being analyzed, and accounting for a 13-03 Rev 0). on the ILRT SC- 81 (CC-11), lE- level of detail consistent with the initiating event grouping (HLR- Extension Risk 84 (MET), 1E-C1 IE-B) and accident sequence modeling (HLR-AS-A and HLR- SLOCA < 2.75" Analysis.
(MET), 1E-C13 (CC- AS-B)." 2.75" < MLOCA < 6" I/II), LOCA break LLOCA > 6" sizes Basis for Significance: The current success criterion for LOCAs is based on plant capabilities and system responses. SLOCA and MLOCA frequencies were The specific break sizes associated with the transitions between updated and documented in H.1.6 Rev the LOCA definitions have not been adequately justified. Based 8.
on PRA12-14, several MAAP analyses have been performed to verify the equipment needed to successfully respond to the Cale E.16 Revision 1 (Success Criteria) break size (runs are done for 1, 2, 3, 5, 7, 12, and 16 breaks), incorporated these changes.
but no runs could be found to validate the transition points between the break sizes. Per the requirement, thermal hydrauli~ evaluations are required at a level of detail to support Revision 3 Page 50of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension the definitions/break sizes so that the appropriate initiating event frequencies can be determined.
Possible Resolution: Perform additional thermal hydraulic analyses to determine the actual LOCA break sizes where the success criteria changes (e.g., break size above which Charging is not sufficient, break size where Containment Spray is first required, etc.). Once the new break sizes are determined, determine the correct Initiating Event frequency associated with the newly defined break ranges.
SC-83 SC-83-02, NOT Closed Discussion: This SR states "When E.16 updated (Revision 1) to include This is resolved.
MET, defining success criteria, USE thermal/hydraulic, structural, or ISLOCA MAAP Calculation with a 2.75" There is no impact Associated SR: SC- other analyses/evaluations appropriate to the event being break for success criteria. To be on the ILRT 81 (CC-II), verify analyzed, and accounting for a level of detail consistent with the consistent with the updated SLOCA Extension Risk Small Loss of initiating event grouping (HLR-IE-B) and accident sequence success criteria (previously a break size Analysis.
Cooling Accident modeling (HLR-AS-A and HLR-AS-B)." < 2.0", but now< 2.75"), the lower break (SLOCA) size via size limit for ISLOCA of 2.75" was MAAP Basis for Significance: In Calculation E16, Revision 0, (which analyzed.
is not referenced anywhere in the discussion of ISLOCAs in the body of the E16 Calculation), the MAAP analysis referenced for According to MAAP case HR-OL-01 b, the success criteria validation is based on an 8 inch ISLOCA, the flow rate from a -2.75" break at 570 F and not on a 2 inch ISLOCA. The use of an 8 inch break size is immediately following a LOCA is inappropriate because the required equipment and timing approx. 4660 GPM (MAAP break associated with responding to a 2 inch break would be flowrate of 166381 LB/HR with density significantly different than the required equipment and timing of 5.9478 lb/gal).
associated with an 8 inch break.
For a 2" break, case HR-OL-01 a, the Additionally, the E16 Calculation implies that the RHR pumps break flowrate is approx. 2470 GPM are unavailable due to a lack of suction from the sump, but the (MAAP break flowrate of 880045 L13/HR ISLOCA Calculation (which is not referenced anywhere in the with density of 5.9478 lb/gal).
E16 Calculation), C.4.7 Revision 8, makes an assumption that the RHR pumps would be unavailable since they would be Top Event SM was changed to reflect subjected to extreme pressures/temperatures. The assumption 2.75" break size and leak rate. Sections that the RHR pumps would be unavailable during all ISLOCA E.10.4.3 and E.10.5.3 of Cale E.10 sequences is overly conservative compared to industry norms Revision 10 reflects this change.
for modeling ISLOCAs, and compared to the modeling at similar power plants. This assumption should be re-evaluated to be more realistic and in-line with current industry practices.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Possible Resolution: Perform additional MAAP analyses of smaller ISLOCA sizes to verify that the success criteria specified is valid, and update as appropriate.
SC-84 SC-84-01, MET, Closed Discussion: This SR states "USE analysis models and The success criteria from the design This is resolved.
define Large Break computer codes that have sufficient capability to model the basis analysis is consistent with the There is no impact Loss of Coolant conditions of interest in the determination of success criteria for MAAP based success criteria and a on the ILRT Accidents CDF, and that provide results representative of the plant. A review of this non-MAAP based Extension Risk (LBLOCAs) qualitative evaluation of a relevant application ot'codes, models, accident analysis shows that the current Analysis.
or analyses that has been used for a similar class of plant (e.g., PRA model success Criteria is Owner's Group generic studies) may be used. USE computer appropriate.
codes and models only within known limits of applicability."
Basis for Significance: The MAAP code is used in support of all LOCA break sizes at DCPP. However, the MAAP code has known limitations with respect to its modeling of large LOCAs, and is not a valid code to use for determining success criteria for LBLOCAs. Although the limitations of the MAAP code are included in the MAAP 4 Users Guide, they are not summarized anywhere in the DCPP analyses, so it is not clear that the limitations of the code were considered when developing the DCPP success criteria.
Possible Resolution: Define the success criteria for LBLOCAs based on the criteria in the FSAR or on a specific analysis using a computer code that is capable of evaluating LBLOCAs such as CENTS, RETRAN, or RELAP.
SC-84 SC-84-02, MET, Closed Discussion: This SR states "USE analysis models and Conditions in Table E.16-3, and the MC This is resolved.
AlWT definition computer codes that have sufficient capability to model the top event of Attachment 4 of Cale E.16 There is no impact conditions of interest in the determination of success criteria for (Revision1) were updated to be on the ILRT CDF, and that provide results representative of the plant. A consistent with the current model, and Extension Risk qualitative evaluation of a relevant application of codes, models, Attachment 8. The basis for the change Analysis.
or analyses that has been used for a similar class of plant (e.g., in Unfavorable MTC threshold from -7 to Owner's Group generic studies) may be used. USE computer -5.5 is explained in the Rev 7 notes of codes and models only within known limits of applicability." E.11 which updates "the MTC issue based on new information for cycle 10, Basis for Significance: The discussion in E.16, Revision 0, which begins on Unit 1 in March, 1999.
associated with the Anticipated Transient Without Trip (ATWT) The fuel constitution for cycle 10 is scenarios of concern and the success criteria for A TWT is not substantially different than cycle 9 with consistent. Table E.16.2 identifies 12 AlWT scenarios, but the respect to the value being used for top success criteria developed does not clearly consider each of event MC. The new MC value is .01,
- these AlWT scenarios. *Section E.16.5.6 states that the using a threshold of -5.5 pcm per Revision 3 Page 52of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension success criteria for AlWT is developed for the following criteria degree F instead of-7 pcm per degree and the success criteria is discussed in detail in Attachment 8: F. This is consistent with new analysis and the cycle 10 fuel loading AlWT 1 - Turbine Trip Successful, Power Level> 80%, MTG< characteristics to ensure that RCS
-7 pcm/For Turbine Trip Successful, Power Level< 80%, MTG pressure does not exceed 3200 pounds.
> -7 pcm/F The system transient analysis, reactor AlWT 2 -Turbine Trip Successful, Power Level> 80%, MTG> and Westinghouse fuel engineers have
-7 pcm/F been consulted and documentation has AlWT 3 - Turpine Trip Successful, Power Level< 80%, MTG< been provided from Westinghouse to
-7 pcm/F PG&E concurrent with this change." -
ATWT 4-Turbine Trip Fails AR0445958 But Attachment 8 is not based on these criteria. Attachment 8 evaluates:
- 1. Turbine trip within 30 seconds; 100% power; MTG< -5.5 pcm/°F.
- 2. Turbine trip within 30 seconds; 80% power; MTG > -5.5 pcm/°F.
- 3. Turbine trip within 30 seconds; 100% power; MTG> -5.5 pcm/°F.
- 4. Turbine trip within 1 minute; 80% power; MTG < -5.5 pcm/°F.
- 5. No turbine trip.
- 6. Main feedwater lost.
- 7. Turbine trip and reactor coolant pump coastdown.
None. Core melt assumed if these events combined with a failure to trip.
Calculation File C.4.6, Revision 9, states that the basis for the MTG of-7pcm/F could not be identified, but no definitive answer as to the basis for the -5.5 was provided either. The actual criteria for DCPP specific AlWT conditions needs to be defined, justified, and evaluated for system response required to mitigate theATWT.
Possible Resolution: Determine what the DCPP AlWT definition is (DCPP specific pcm/F values) and determine the actual system level success criteria required to mitigate the various AlWT accident sequences.
SC-85 SC-85-01, MET, Closed Discussion: This SR states "USE analysis models and The impact of not crediting feed and This is resolved.
crediting PORVs for computer codes that have sufficient capability to model the bleed for small LOCA scenarios was There is no impact Revision 3 Page 53of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension depressurization conditions of interest in the determination of success criteria for determined to be approximately 1E-8/yr on the ILRT when AFWnot CDF, and that provide results representative of the plant. A CDF (Reference 36). Although the risk Extension Risk available qualitative evaluation of a relevant application of codes, models, benefit for this credit is' not significant, it Analysis.
or analyses that has been used for a similar class of plant (e.g., could contribute some risk benefit in Owner's Group generic studies) may be used. USE computer certain configurations, such as an AFW codes and models only within known limits of applicability." pump being inoperable. Therefore, the DCPP PRA model has been updated to Basis for Significance: In Calculation File 8.1, Revision 0, ensure that small LOCA scenarios there is a documentation of a comparison of success criteria for correctly credit the use of feed and DCPP to the success criteria at similar plants. One outlier was bleed when appropriate.
noted. This outlier is that the success criteria for a small LOCA without AFW available is assumed to result in core damage at
References:
- 1. PG&E PRA Calculation DCPP, but the use of PORVs to depressurize and cooldown is File PRA 13-13, Rev 0, "Small LOCA credited at similar plants. The basis for not crediting the use or Feed and Bleed" PORVs at DCPP for depressurization and cooldown is not documented, and discussions with plant PRA personnel did not identify any reason that the PORVs could not be credited at DCPP. Since the PORVs appear to be a valid option at DCPP, they should be credited in these accident sequences.
Possible Resolution: Update the accident sequence progression for Small LOCAs and include credit for using the PO RVs to depressurize and cooldown for those sequences where AFW is not available, or justify not crediting it. If the Emergency Operating Procedure (EOP) network uses the PORVs for this application, it should be credited in the PRA.
SC-C2 SC-C2-01, NOT Closed Discussion: The process followed for developing the success Removed the collapsed water level This is resolved.
MET, not clear
- criteria for each accident scenario is not clearly documented. definition of Core Damage and now use There is no impact process of For example, there are two definitions of core damage used, the Peak Node temperature of greater than on the ILRT developing the basis for the timing of human actions is not clear (two criteria 1B00°F. Extension Risk success criteria used - but nothing showing why both are acceptable), the Analysis_.
limitations of the software used for the success criteria is not The use of collapsed water level is documented, etc. conservative for HRA timing evaluation.
In addition, the conse.rvatism is limited Basis for Significance: The overall process used to develop due to the short amount of time the DCPP success criteria, including identification of the between uncovery of active fuel and supporting engineering bases, inputs, methods, and results is peak clad temperature of 1800°F.
not clearly documented. Particular items noted include:
Limitations of computer codes There are two definitions of core damage used in the DCPP- addressed in SC-84-01. Impact of and there should only be one. (See F&O SC-A1-01)
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension ATWT success criteria addressed in The calculations used to support the success criteria for various SC-84-02.
accident sequences is not always clearly identified - for example, the basis for the A TWT success criteria is not clear, and the discussion in the E.16 Report uses two difference criteria for pcm/F. (See F&O SC-84-02)
The limitations associated with the computer codes used in support of the success criteria are not documented in the DCPP calculations or reports.
The bases for establishing the time available for human actions is suspect since some of the HRAs are based on a core damage of 1800°F, while others are based on a core damage definition of "water below top of active fuel" - the use of 2 different definitions of core damage is incorrect, plus there is no discussion as to when/how it was determined which timing to use for which operator action - should base the time available for all operator actions on the core damage definition of 1800° F peak clad temperature.
Possible Resolution: Update the documentation to specifically address the elements identified in the SC SR. At a minimum, the list provided in SC-C2 should be reviewed, and the applicable items listed in the SR should be clearly documented in the Success Criteria calculation/document.
SC-C3 SC-C3-01, NOT Closed Discussion: This SR states: Document the sources of model PRA Calculation 8.1 (Revision 1) and This was a, MET, uncertainty and related assumptions (as identified QU-E1 and C.10 (Revision 5) documents the documentation issue Associated SRs: QU-E2) associated with the development of success criteria. assumptions and uncertainties and is resolved.
IE- D3 (NOT MET), There is a similar requirement to document sources of associated with each technical elements There is no impact SY- C3 (NOT uncertainty and assumptions for the other elements of the PRA o(different hazard groups. As on the ILRT MED, as well. suggested in this F&O, these Extension Risk Documenting \
documents have been updated by Analysis.
source of Basis for Significance: A review of many of the PRA systematically reviewing PRA uncertainties elements identified that there was not summarization of the development documents (e.g., system sources of uncertainty or assumptions associated with the notebooks, success criteria notebook, individual PRA element. The documentation of these items is event-tree notebooks, etc.).
required by the standard, and these items should be used as the basis for determining which sensitivity studies need to be performed for the PRA.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Possible Resolution: Go through each of the individual PRA element reports and calculations and identify and summarize the sources of uncertainty and the assumptions associated with the element being documented. These sources of uncertainty and assumptions should then be used as the basis for determining what sensitivity studies need to be performed for the DCPP PRA.
SY-A4 SY-A4-01, NOT Closed Discussion: PERFORM plant walkdowns and interviews with DCPP PRA models were prepared by This is resolved.
MET, knowledgeable plant personnel (e.g., engineering, plant industry and in-house experts in 1988. There is no impact walkdown and operations, etc.) to confirm that the systems analysis correctly Per the PRA configuration control on the ILRT interview reflects the as-built, as-operated plant. programs (i.e., TS1.NR3 and AWP E- Extension Risk Basis for Significance: Based on discussion with DCPP PRA 028), DCPP PRA has been updated as Analysis.
personnel, neither plant walkdowns nor interviews with needed to reflect the as-built and as-knowledgeable plant personnel were performed to confirm that operated plant (e.g., review of the the systems analysis correctly reflects the as-built, as- operated procedure changes, design changes, plant. This is required for CC-111111. equipment reliability, etc.).
Possible Resolution: Perform walkdowns and interviews.
The models and their technical )
elements have been continuously refined and/or corrected for errors through their uses in applications.
Many different talk-th roughs of accident scenarios have been performed since the original development of the PRA that confirm the accuracy of the accident response model.
Attachment 1 to HRA Calculation G.2, "Human Action Analysis - Failure Likelihood and Range Factor Calculation, Revision 6 dated November 2012 document the operator and training personnel interviews that were conducted the fall of 2012 to review PRA initiators and consider whether any initiators or initiating event categories had been omitted. The similar operator interviews were documented in Attachment 3 of Cale H.1.6 Revision 8.
Revision 3 Page 56of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension In addition, new MAAP runs (documented in PRA12-13 "MAAP HRA Cases") were performed and the human error probabilities (HEPs) were updated to reflect the 'new timing. It is not likely the current models including Internal Events and Fire still contain gross model errors or assumptions which result in significant deviation from the as- builUas-operated plant condition or configuration.
Numerous walkdowns performed for the Fire and Seismic PRAs have been performed within the last 5 years and no evidence that the systems analysis differs from the as-built, -as-operated lant was noted.
SY-A16 SY-A16-01, NOT Closed Discussion: In the system model, Pre-initiators review was performed and This is resolved.
MET, INCLUDE Human Factors Engineering (HFEs) that cause the pre- initiator HFEs were identified in G.1 There is no impact Associated SR: / system or component to be unavailable when demanded. Rev 2. All newly identified miscalibration on the ILRT HR-A1 (NOT These events are referred to as pre-initiator human events. and misposition HFEs were included in Extension Risk MET), (See also Human Reliability Analysis, 2-2.5.) the PRA model. Analysis.
modeling of pre-initiators Basis for Significance: Review of the AFW system fault tree indicates that no pre-initiator HFEs are modeled. Given that the AFW is a standby system, at least one pre-initiator HFE (e.g.,
failure to restore pump after maintenance or testing) is expected to be in the model. Related SR HR-A1 and F&O HR-A1-01.
Possible Resolution: Either model the pre-initiator and others like it in other standby systems and trains or justify and document whi'. it is not needed.
SY-A20 SY-A20-01, NOT Closed Discussion: INCLUDE events representing the simultaneous Simultaneous unavailability of This was a MET, simultaneous unavailability of redundant equipment when this is a result of redundant safety- related equipment documentation issue unavailability of planned activity (see DA-C14). due to planned activity is excluded from and is resolved.
redundant SSCs consideration. This is consistent with TS There is no impact Basis for Significance: Per discussion with DCPP PRA 3.0.3 restrictions for safety-related on the ILRT personnel, simultaneous unavailability of redundant safety- equipment. Extension Risk related eguiEment due to Elanned activit~ is excluded from Anal~sis.
(
Revision 3 Page 57of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Stat~s Finding/Observation Disposition Impact on ILRT Cat II Requirement Extension consideration. This is consistent with Technical Specification Examination_ of the 12-week rolling (TS) 3.0.3 restrictions for safety-related equipment. This MOW matrix at DCPP did not identify assumption is. reasonable. However, this approach is not any planned, repetitive activity which documented. In addition, this assumption is probably not would cause coincident unavailability appropriate for non-safety equipment, whose unavailability is due to maintenance for redundant not restricted by TS. An example of this is multiple IA equipment (both intra-system and compressors concurrently out of service. intersystem). Calculation or modeling of coincident maintenance unavailability Possible Resolution: Either account for allowed simultaneous was therefore unnecessary.
of redundant equipment or document justification of it is not modeled. The above justification was included in Section H.1.2 of PRA Calculation H.1 Revision 1.
SY-A23 SY-A23-01, Closed Discussion: DEVELOP system model nomenclature in a The AFW basic events were renamed to This is resolved.
MET, consistent consistent manner to allow model manipulation and to represent be consistent with system/component There is no impact system model the same designator when a component failure mode is used in failure mode nomenclature used on the ILRT nomenclature multiple systems or trains. throughout the PRA model. ~xtension Risk Analysis.
Basis for Significance: Based on discussion with DCPP PRA The changes are documented in PRA personnel, consistent system/component failure mode Cale E.2 Rev 12.
- nomenclature is used in all system notebooks, except the AFW notebook.
This occurred as a result of a modeling oversight.
Possible Resolution: Correct condition for AFW and document system/component failure model nomenclature.
SY-B3 SY-B3-01, NOT Closed Discussion: ESTABLISH common Common Cause failure of Safety Inject This was a MET, cause failure groups by using a logical, systematic process that (SI) system components is modeled and documentation issue CCF groups considers similarity in common cause groups are defined and is resolved.
(a) service conditions within the model. The review comment There is no impact (b) environment is that the common cause groups are on the ILRT (c) design or manufacturer not documented in the system Extension Risk (d) maintenance notebook. Analysis.
JUSTIFY the basis for selecting common cause component Documentation was revised for all groups. systems to specifically list the common cause that is modeled.
Candidates for common cause failures include, for example:
(a) motor-operated valves (b) pumps (c) safety-relief valves Revision 3 Page 58of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (d) air-operated valves (e) solenoid-operated valves (f) check valves (g) diesel generators (h) batteries (i) inverters and battery charger U) circuit breakers Basis for Significance: No documentation was found for the Common Cause Failure (CCF) group definition. for the SI top event. DCPP PRA staff indicated that this is a known gap. For other systems, CCF groups appear to generally be defined inside of RISKMAN files but not in the documentation.
Possible Resolution: Close gaps in CCF group definitions and basis in all system notebooks.
SY-88 SY-88-01, NOT Closed Discussion: IDENTIFY spatial and environmental hazards that The IEPRA incorporated the results of This was a MET, may impact multiple systems or redundant components in the room heat-up calculations and system documentation issue Associated SR: SY- same system, and ACCOUNT for them in the system fault tree success dependency on HVAC. The* and is resolved.
814 (MET), spatial or the accident sequence evaluation.* results of room heat-up calculations There is no impact and environmental provide a basis for operator action on the ILRT hazards impacting Basis for Significance: No discussion of room heatup and timing or to demonstrate that a loss of Extension Risk multiple SSCs dependence on HVAC could be found in the sampled system cooling would not impact modeled Analysis.
notebooks. No discussion of spatial and environmental SSCs. A SSC requiring cooling is dependencies could be found in the sampled system considered failed if the cooling is not notebooks. After discussions with DCPP personnel, we available due to failure of the HVAC identified additional documentation not provided earlier that was SSC and if operators fail to establish available to potentially address these gaps. However, the alternate ventilation/cooling within the SN8s do not have this discussion nor references and therefore time estimated based on the room heat-the PRA does not meet this SR. up calculations.
Possible Resolution: Provide a discussion of spatial and Documentation of the effects of room environmental dependencies in each system notebook. heatup is available and references plant Incorporate any impacts from these considerations on SSCs in specific room heatup calculations.
the system notebooks documentation as well in the models. These results are not reiterated within the individual system notebooks but system modeling is consistent with the room heatue calculations.
SY-810 SY-810-01, Closed Discussion: MODEL those systems that are required for PG&E performed a systematic This is resolved.
NOT MET, initiation and actuation of a system. In the model quantification, evaluation of modeling of permissives There is no impact INCLUDE the ~resence of the conditions needed for automatic and interlocks in the Internal Events on the ILRT Revision 3 Page 59of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension modeling of actuation (e.g., low vessel water level). INCLUDE permissive PRA (IEPRA) and documented in PRA Extension Risk permissive and and lockout signals that are required to complete actuation Cale 14-01, Rev 1. Analysis.
interlocks logic. The evaluation includes identification and modeling of (1) those systems that Basis for Significance: The treatment of permissive and are required for initiation and actuation interlocks could not be located in the system notebooks. of a system, (2) the conditions needed for automatic actuation (e.g., low vessel Possible Resolution: Model permissive and interlocks and water level), and (3) control features document in system notebooks. (e.g.;protection and control permissive, lock-out signals, and component interlocks that are required to complete actuation logic, as required in the Supporting Requirement (SR) of Section 2 of AMSE/ANS RA~SA-2009 Standard.
Based on the results of the review, permissive and interlocks of the following SSCs are included in the Internal Events model; 8701/8702, 8982A/B, and 9003A/B, 8804A/B.
SY-815 SY-815-01, Closed Discussion: INCLUDE operator interface dependencies To address this F&O, the DCPP This is resolved.
NOT MET, across systems or trains, where applicable. procedures were reviewed to identify There is no impact intersystem realignment and calibration activities for on the ILRT operator Basis for Significance: A review of several system notebooks all systems and components including Extension Risk dependency indicate that DCPP did include human actions that had the any dependencies between activities Analysis.
potential to impact multiple trains of a given system and components. This review was (miscalibration) and actions from one system that could impact performed in order to be consistent with the function of another system. the ANS/ASME Standard supporting requirements and is documented in Possible Resolution: Close gap. revision 2 of PRA calculation G.1.
As a result of this review, additional pre-initiator HFEs were identified in standby systems and were quantified using the EPRI HRA Calculator THERP module.
Although pre-initiator dependency across Trains was identified due to misposition and included in the DCPP HFEs, none of the HFEs involved miscalibration across systems or trains.
Revision 3 Page 60of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension SY-C2 SY-C2-01, NOT Closed Discussion: DOCUMENT the systems analysis in a manner SY-A22: 'Cale File E.17 Rev 0 states the This was a MET, that facilitates PRA applications, upgrades', and peer review. following: "No credit is taken for documentation issue Associated SRs: Basis for Significani;e: SY-A22: Based on discussion with component or system operability for and is resolved.
SY- A22 (CC-II), DCPP PRA personnel, credit for system operability is taken only beyond design rated capabilities unless There is no impact SY-81 (MET), SY- if design capabilities are not exceeded. supported by appropriate testing, on the ILRT 83 (NOT MET), This modeling assumption should be documented in the system engineering analysis or operational Extension Risk SY-86 (MET), notebooks. data." Analysis.
SY-87 (CC-II), SY- SY-81: NUREG/CR-5485 for CCF is not referenced in the 89 (MET), SY-811 documentation related to modeling intra-system common cause SY-81: NUREG/CR-5485 for CCF is (MET), failures. now referenced in H.1 Rev 1 documentation SY-86: The need for the HVAC system support is not discussed SY-B6/B9: Room Heat-ups and thermal in the SI system notebook. This and other system notebooks fragilities are explained in E.16.5.8 of should be reviewed and, if appropriate, revised to describe the Success Criteria Notebook. The HVAC dependencies. original analysis for mission time ventilation requirements - Appendix A of SY-87: Success criteria and timing is not discussed in the PLG-0637 was added to E.16. This system notebooks. Success criteria are provided but references document shows that only the SSPS are not provided. For example, a reference or basis for the and the 480V switchgear are vulnerable assumed time for high pressure recirculation of 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> is not to loss of ventilation during the mission provided in the high pressure system notebook. Similarly, no time. All other systems which normally discussion of the potential for and effects of room heat-up in use ventilation systems do not need system notebooks reviewed. This information should be them to operate within the mission time.
documented in the system notebooks. New revisions of these notebooks put the ventilation requirement more SY-89: References need to be added to the system notebooks prominently in the main body under the to describe HVAC dependency. heading, "Support Systems."
SY-811: Gaps were found in the system notebooks regarding Furthermore, these new revisions the discussion of available inventories of air, power, and cooling contain references to PLG-0637 (where to support the mission time. the ventilation requirement is determined).
Possible Resolution: Ensure that all system notebooks address the above issues and that the system models address SY-87: *All system notebooks were these issues appropriately. ., reviewed for mission times and timing success criteria, and the following changes were made:
- The Success Criteria section for E.4 "ECCS high pressure system" Rev10 has been completely rewritten with Revision 3 Page 61 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension references to 6-hour and 18-hour mission times removed. No model change is required since a 24-hour mission time was previously used, and continues to be used.
- D.2.1.2 "125Vvital DC system" Rev10 has the following text added to the Success Criteria section: "A 2-hour mission time is considered sufficient because transfer to the startup power source or the diesel generators is automatic and nearly instantaneous; and in the case that human action is required to restore the 4kV busses, 21 minutes is the time it takes for operators to manually perform the transfer according to the analyses done for ZHEAC1 and ZHEAC2 found in the HRA Calculator Report (Reference 35)."
- References were added to D.2.8 "AMSAC System"
- Cale E.11 Revision 11 - Top Event RS Success Criteria was revised to remove timing criteria and state that the top event is not credited in the current model.
- The success criteria in E.3.4.3 was revised for top events OB, OBS, and PO such that there is no explicit requirement for the PO RVs to remain open for six hours.
- Reference to G.4 Electric Power Recovery Model was added to D.2.1.5 Rev 12 Diesel Generator Systems and D.2.1.6 Rev 11 Diesel Transfer System to help justify the 6-hour mission time for non-seismic Revision 3 Page 62of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Rev,iew - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension events in the Success Criteria Subsection.
SY-811: Section E.16.5.10 was added to Success Criteria Notebook Cale E.16 Revision 1 which includes discussion about available inventories of air, power, and cooling to support mission times.
HR-A1 HR-A1-01, NOT Closed Discussion: Supporting requirements HR-A1 and A2 discuss To address this F&O, OCPP procedures This is resolved.
MET, the identification of pre-accident HRA based on whether the were reviewed to identify realignment There is no impact Associated SRs: procedure or practice involves realignment (A 1) or calibration and calibration activities. This review on the ILRT HR-A2 (NOT (A2). Per the standard, these criteria should be performed was performed in order to be consistent Extension Risk MET), SY-A16 before going to the screening method performed in Attachment with the ANS/ASME Standard Analysis.
. (NOT MET), pre- 4. supporting requirements HR-A1 and initiator HRAs HR-A2. This review is documented in Basis for Significance: Some potential pre-accident HRAs revision 2 of PRA calculation G.1.
could be screened too early.
As a result of this review, additional pre-Possible Resolution: Review the procedures and practices initiator HFEs were identified for against whether it involves realignment or calibration. inclusion into the PRA model and were quantified using the EPRI HRA Calculator TH ERP module. These new HFEs were incorporated into the PRA model.
HR-A3 HR-A3-01, MET, Closed Discussion: Pre-initiator HRA screening criteria 30 could Screening criterion 30 was faulty in that This is resolved.
preinitiator HRAs remove restoration errors prematurely. If a system or train is it included system or component There is no impact automatically actuated following an event, then a restoration automatic actuation. As the F&O on the ILRT error of manual valves in the flow path could be missed. correctly points out, a system may be Extension Risk Examples include mis-positioning of a valve in the standby automatically actuated without changing Analysis.
CCW pump train if it receives an automatic start signal on low the position of the component in header pressure and misposition of a valve in SI pump train if question. To address this F&O, all of the the valve does not automatically open on an ESFAS signal. screening criteria, including criterion 30, were reviewed and revised as Basis for Significance: Mispositioned events could be missed necessary to ensure that the criteria in the modeling. applied specifically to the component being operated/calibrated. The OCPP Possible Resolution: Review the process for identifying pre- procedures were then reviewed against accident HRAs. the new criteria to identify realignment and calibration activities. This review is Revision 3 Page 63of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT'Extension Table A-1 Internal Events PRA Peer'Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension documented in revision 2 of PRA calculation G.1.
HR-C3 HR-C3-01, Closed Discussion: HR-C3 states "INCLUDE the impact of To address this F&O, the DCPP This is resolved.
NOT MET, miscalibration as a mode of failure of initiation of standby procedures were reviewed to identify There is no impact consideration systems." While the pre-accident HRA document discusses the realignment and calibration activities. on the ILRT of mis- reasons for not including common miscalibration, the PRA This review was performed in order to Extension Risk calibration Standard requires inclusion of miscalibration events. be consistent with the ANS/ASME Analysis.
Standard supporting requirements and Basis for Significance: The exclusion of the miscalibration is documented in revision 2 of PRA contradicts to the requirement. calculation G.1 ~
Possible Resolution: Include the consideration of As a result of this review, new pre-miscalibration. initiator mis-calibration HFEs were identified and were quantified using the EPRI HRA Calculator TH ERP module.
These new HFEs were incorporated into the PRA model.
HR-D3 HR-D3-01, Closed Discussion: The detailed pre-accident HFEs in Section New sections (G.1.4.3.1.6, G.1.4.3.2.6, This is resolved.
CC-I, pre- G.1.3.3 do not discuss the quality of procedures, administrative and G.1.4.3.3.6) dealing with procedure There is no impact initiator HFEs controls, or Man-Machine Interface (MMI) requirements in and human- machine interface quality on the ILRT performing the assessments. has been added to G.1 Rev. 2. Extension Risk Analysis.
Basis for Significance: The quality of procedures, administrative controls, and human-machine interface reviews are required to meet CC-11/111 requirements in HR-D3.
Possible Resolution: Address the issues identified in this F&O.
HR-E1 HR-E1-01, ME;T, Closed Discussion: This SR States: When identifying the key human The basis for significance is incorrect. No issues were Associated SR: SY- response actions REVIEW: The DCPP PRA does credit operator identified. There is A17 (MET), (a) the plant-specific emergency operating procedures, and actions that manually start pumps and no impact on the crediting manual other relevant procedures (e.g., AOPs, annunciator response operate valves when the automatic ILRT Extension Risk verification steps procedures) in the context of the accident scenarios signal fails. Data variable ZHEOS1 Analysis.
when auto failed (b) system operation such that an understanding of how the addresses tbe manual start of ESF system(s) functions and the human interfa'ces with the system is pumps and the operation of ESF valves obtained. on failure of the SSPS signal.
Additionally the DCPP PRA credits the Basis for Significance: Currently, there are no operator manual start and/or alignment of actions associated with starting pumps or aligning valves even standby equipment upon failure of the when the EOP network specifically states "Verify" pump started running train. Basic events CCOP2, or "Verify" valve open/closed. In the event the automatic signal aligning the backup CCW heat Revision 3 Page 64of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Req'uirement Extension fails to start the pump or align the valve, credit should be taken exch?nger on failure of the running for the Operator backing up the automatic signal. CCW heat exchanger and CVHE1, transferring to the unselected control Possible Resolution: Review the EOP/AOP Procedure room ventilation sub train, are two network and identify those pumps/valves whose desired examples.
function is "Verified" by the Operators, and add an Operator action to perform the action given failure of the automatic signal. A review was performed to verify that no manual recovery for failure of an automatic signal that could be credited was missed. In order to avoid unnecessary complexity in the PRA model, the scope of the review was limited to risk significant basic events.
The risk significant basic events were reviewed in conjunction with the emergency operating procedures (EOPs) to determine if any additional manual recoveries of automatic signal failures could be found. No additional operator actions were identified that could mitigate the failure of an automatic signal for risk significant components. Therefore, no change to the DCPP PRA model is required.
HR-E3 HR-E3-01, CC-I, Closed Discussion: This SR States: TALK THROUGH (i.e., review in Operator interviews were re-performed This was a consistent detail) with plant operations and training personnel the and documented in the G.2 Rev 7 HRA documentation issue interpretation procedures and sequence of events to confirm that database for each applicable operator and is resolved.
of procedures interpretation of the procedures is consistent with plant action. There is no impact observations and training procedures. on th.e ILRT Many different talk-through of accident Extension Risk Basis for Significance: Attachment 1 of Calculation G.2, scenarios have been performed since Analysis.
Revision 6, summarizes the talk through performed with original development of the PRA that Operations and Training personnel. However, there is no confirm the accuracy of the accident discussion on how the specific scenarios discussed were response model. Attachment 1 to selected, the questions posed to the Operators, the entire Calculation G.2 identifies the scenario sequence of procedures followed in the response to the types that were discussed with four accident sequence, etc. Additionally, all that is contained in separate operators and with training, Attachment 1 is a summary of the PRA interpretation of the talk- including the procedure path that would through, but the actual Operator interview sheets are not be followed. The interviews focused on included. the key scenarios such as LOCA, loss of AFW, and SGTR that are known to Revision 3 Page 65of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Without having the basis for why the scenarios discussed were be risk-significant. It is common when selected, it is not possible to ensure that the most risk- conducting operator interviews to significant, or important Operator actions were discussed. consolidate scenarios to maximize the Additionally, without the Operator Interview sheets it is not benefit of the limited time available with possible to verify what the operators/trainers said, and that the the operators. In addition, routine responses were taken in context. procedure reviews are performed in order to ensure that procedure changes Possible Resolution: Provide the basis for the accident have not changed the as-built plant sequences discussed, and ensure that the list includes all risk response.
significant operator actions. Find the actual Operator Interview sheets, and include them with the report. For any risk significant operator actions that Operator Interview sheets cannot be found, perform an additional Operator interview, including documentation of the interview, to ensure that the interpretation of the procedures is correct.
HR-E4 HR-E4-01, CC-I, Closed Discussion: This SR States: USE simulator observations or Simulator observations were performed This is resolved.
confirming talk-through with .operators to confirm the response models for on 3/27/2014 for response models and There is no impact response models scenarios modeled. a statement is inserted in Section 5 of on the ILRT via simulator Cale G.2 Revision 7. Extension Risk observations or Basis for Significance: Attachment 1 of Calculation G.2, Analysis.
talk-through Revision 6, summarizes the_ talk through performed with Operations and Training personnel. However, there is no discussion associated with confirming that the response models (i.e., MMP runs) used to support the PRA are realistic.
Additionally, no documentation of the use of simulator observations to confirm the response models can be found.
Possible Resolution: Category I does not require using simulator observations or talk-through with operators to confirm the response models. However, to get to a Category 11/111, a confirmation of the response models, either using simulator observations of operator talk-through, is required.
HR-G5 HR-G5-01, CC-II, Closed Discussion: The required time to complete actions used in the Operator interviews were re-performed This is resolved.
Associated SRs: HRA Calculator for is documented in Calculation File G.1 HFE and documented in Section 5, There is no impact HR- E3 (CC-I), HR- datasheets. These datasheets generally indicate that this time Attachment 1 and HRA database of on the ILRT E4 (CC-I), is based on operator interviews. This meets SR Category II. Cale G.2 Rev 7 for each applicable Extension Risk verification of the However, because for other HFEs, not basis for the required operator action. Response times were Analysis.
time estimates in time is provided. F&O HR-B5-01 documents this deficiency. verified via interviews.
HRA via observation of Basis for Significance: The basis for the required time to complete actions used in the HRA Calculator for is not Revision 3 Page 66of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension simulators or walk- documented in Calculation File G.1 or in the HRA Calculator through file. In order to fully meet SR HR-G5 to Category II, these times should be based on either walk-throughs, talk-through, or simulator observations.
Possible Resolution: Perform the required walkthroughs, talk-through, or simulator observations* and revise the time
- estimates, if necessary. Document these in the HRA Calculator and Calculation File G2.
HR-G6 HR-G6-01, MET, Closed Discussion: Section 7.2 of Calculation Correction: The HFEs referred in this This was a combining identical File G2 documents several checks performed to check the F&O should be read as ZHEF04 and documentation issue HF Es reasonableness of the HEPs of the post initiator HF Es relative ZHEF05 and is resolved.
to each other. This is considered adequate for the SR to be There is no impact met. A review of the final set of HFEs indicates that two appear ZHEF05 is the HEP for 1 normal power on the ILRT to be essentially identical; these have the same HEPs: ZHFE04 source unavailable. Extension Risk and ZHFE05. These two should be combined into one HFE, Analysis.
since the use of both could adversely affect the HRA ZHEF04 is the HEP for both normal dependence analysis and the impact of the state of knowledge power sources unavailable.
correlation in the quantified results. This is documented in F&O HR-G6-01. ZHEF05 is the HEP for operator action to align a backup power supply to the Basis for Significance: A review of the final set of HFEs Diesel Fuel Oil Pump when one of the indicates that two HFEs appear to be essentia.lly identical; these normal power sources is unavailable.
have the same HEPs: ZHFE04 and ZHFE05. These two ZHEF04 is similar except used in cases should be combined into one HFE, since the use of both could where both normal power sources are adversely affect the HRA dependence analysis and the impact unavailable. These HFEs are similar but of the state of knowledge correlation in the quantified results. not identical Possible Resolution: Combine HFEs ZHFE04 and ZHFEO The two HEPs never appear in the into a single HFE. same cutsets because of the mutually exclusive house event impacts used in the top event split fractions.
Because they do not appear in the same cutsets, the dependency between two HFEs is immaterial. The current model is adequate and no model changes are needed.
In order to address the reviewer's concern, some documentation changes were made to clarify the diesel fuel oil Revision 3 Page 67of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension modeling. Table 7 .1 of Cale G.2 Revision 7 and Section D.2.1.6.5.5 of Cale D.2.1.6 Revision 11 were updated to include better descriptions of the HEPs. Riskman data descriptions were also updated to avoid confusion.
HR-G7 HR-G?-01, Closed Discussion: Section C.9.8 (Human Error Probability (HEP) A detailed Internal Events model HRA This is resolved.
NOT MET, \ Dependency Study) and Attachment 7 of Calculation dependency was performed and There is no impact HFE C.9 document the DCPP PRA post initiator HFE dependency documented in PRA Cale G.3, Revision on the ILRT dependencies analysis. This document discusses a review of dependence 0. Changes to the Internal Events model Extension Risk between actions, but does not list a set of operator actions that were identified and incorporated to Analysis.
were evaluated or how the dependence between actions is DC03.
dependent.
Basis for Significance: DCPP personnel discussed the process used to identify and evaluate HRA dependencies; however, the process does not seem to provide a thorough means for identifying and accounting for dependent human actions.
Possible Resolution: Evaluate the dependency of HFEs according to the requirements of the SR.
HR-H2 HR-H2-01, Closed Discussion: This SR States: CREDIT All HFEs were re-reviewed. The minor This is resolved.
MET, staffing level operator recovery actions only if, on a plant-specific basis, the change to non-Operations staffing There is no impact assumed in HRA following occur: levels does not impact existing HFEs. on the ILRT (a) a procedure is available arid operator training has included Extension Risk the action as part of crew's training, or justification for the Analysis.
omission for one or both is provided (b) "cues" (e.g., alarms) that alert the operator to the recovery action provided procedure, training, or skill of the craft exist (c) attention is given to the relevant performance shaping factors provided in HR-G3 (d) there is sufficient manpower to perform the action.
Basis for Significance: Calculation G.2, Revision 6, discusses the "normal" staffing levels at the plant and implies that these are the staffing levels used in the analysis. A review of the HRA calculator files shows that the staffing levels listed in the HRA calculator include electricians, Instrument & Controls (l&C),
Health Physics (HP), and Chemistry personnel in addition to the Operations staff. Based on discussions with DCPP personnel, the non-Operations personnel are not on-site 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, 7 days Revision 3 Page 68of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension a week, but are available via call-in - so they should not be credited for shorter term responses. Additionally, minimum Operations staffing levels should be used when evaluating the post-initiator recovery actions.
Possible Resolution: Identify what the minimum Operations staffing levels are, and ensure that the HRA failure/success probabilities are based on these manpower levels. Additionally, ensure that non-Operations personnel are not credited as being available immediately - but account for the time that will be reguired to call them in.
DA-C1 DA-C1-01, NOT Closed Discussion: This SR requires the use of recognized sources The DCPP PRA Data Update This is resolved.
MET, for generic data for component failure rates, common cause calculation (PRA Cale H.1, Revision 1) There is no impact use of the latest failures, and off-site power recovery. included a reference to NUREG/CR- on the ILRT industry 5485 for CCF methodology and NRC's Extension Risk documentation for Basis for Significance: It is evident from the data analysis "CCF Parameter Estimations, 2010 Analysis.
SSC failure rate, (Calculation File H.1) that the latest generic data (NUREG/CR- Update" for the updated CCF factors.
CCF, and offsite 6928) is used for component failure rates and probabilities; power recovery however, it is not evident that recognized sources are utilized The Electric Power Recovery Model for common cause failures and off-site power recovery. calculation (G.4 Revision 9) included a reference to INEEUEXT-04-02326 for Possible Resolution: Ensure that the latest industry the AC power recovery probability data.
documentation is utilized for the listed generic data and reference them in the DCPP data ~ackage.
DA-C4 DA-C4-01, Closed Discussion: This SR states, "When evaluating maintenance or Cale H.1 Rev 1 (Section H.1.5.2 and This was a NOT MET, other relevant records to extract plant-specific component H.1.5.3) documents detailed basis for documentation issue Associated failure event data, DEVELOP a clear basis for the identification component failure identification. Also, and is resolved.
SR: DC-C3 (NOT of events as failures. Cale B.1 Rev 1 Section 9.2.2 contains .a There is no impact MET), basis summary of this. on the ILRT for identification DISTINGUISH between those degraded states for which a Extension Risk of an event as failure, as modeled in the PRA, would have occurred during the Added the below text to H.1.5.3 and Analysis.
a failure mission and those for which a failure would not have occurred included a table for screened out (e.g., slow pick-up to rated speed). failures in Table H.1-7:
INCLUDE all failures that would have resulted in a failure to The remaining records were reviewed perform the mission as defined in the PRA." by the PRA group to eliminate er:itries that were not considered valid for the Basis for Significance: There was no evidence found in the purposes of this calculation. This data documentation that a clear basis for the identification of includes degraded states for which a events as failures was developed. Also, no evidence was found failure would not have occurred during that degraded states were distinguished as being PRA Revision 3 Page 69of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension applicable or not. Possible Resolution: Document the the PRA mission time and retaining evidence and the basis for the identification of events as those that would have occurred.
failures.
DA-C5 DA-C5-01, Closed Discussion: No discussion is documented on how failure The failure events of the "2009 Failure This is resolved.
NOT MET, events were re-reviewed for inclusion. In reviewing the data Events" spreadsheet of the "H1 Comp There is no impact documenting provided in the Integrated Relational Data System (IRDS) Failure Tables Rev 1.xls" workbook on the ILRT evaluation of failure
- spreadsheet, only one case was found where the same were reviewed and it was found that Extension Risk events component was failed twice on consecutive days. there were two separate failure events Analysis.
for the S-44/E-44 super component on Basis for Significance: Without documentation, it cannot be consecutive days (11/26/2005; determined if these were both counted as failures. This SR is 11/27/2005). One of the events was covered under the Maintenance Rule methodology. screened out from further analysis, leaving one event to represent both.
Possible Resolution: Expand documentation to reference this methodology. Calculation File H.1 - Documents methodology for H.1 was updated to include the review of plant failure events occurring close in time as one or methodology used in removing these multiple events. types of repeat failures.
DA-C6 DA-C6-01, MET, Closed Discussion: In Data Notebook H.1, Component Operating Data analysis was reviewed and PMT This is resolved.
removing post- Experience section, it states that "the failure rate determination demands were removed from the count. There is no impact maintenance from requires the total number of demands (for demand failure One Data variable (ZTPATS, Turbine on the ILRT demand counts variables) or the total operating hours (for fail-to-run (operate) Driven AFW Pump Failure to Start) was Extension Risk variables) for the prescribed updating period. These updated and new variable was included Analysis.
calculations are based on the number of components, number in the current FPRA model.
of surveillance tests and maintenance events, and operating hours of the reactor and other systems." In addition, multi tables A change in the failed-to-start in H.1 provided maintenance and test demands, durations and probability of the Turbine Driven AFW other plant specific information based various plant data (TDAFW) impacts both the Internal sources. However, certain post- maintenance tests were Events and Fire model. This change included; these should not be accounted for as per SR. was included as part of the routine data update performed in 2014.
Basis for Significance: Per SR requirement, it should not account for post-maintenance tests as stated in the SR.
Possible Resolution: Remove post-maintenance from demand countin .
DA-C10 DA-C10-01, Closed Discussion: Per review and discussion with DCPP personnel, Documentation was added to Section This was a NOT MET, No no document to prove this SR was met. H.1.5.1 of Cale H.1 Revision 1: documentation issue document and is resolved.
Basis for Significance: It needs to demonstrate this SR was Credit is taken for successful demands There is no impact
- met as specified in the SR. from surveillance tests by mapping the on the ILRT ZT-variables to applicable surveillance Extension Risk test procedures and reviewing the test Analysis.
Revision 3 Page 70of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/~bservation Disposition Cat II Requirement Extension Possible Resolution: Perform the items required for this SR procedures themselves. Tables of the and document them. Unit 1 and Unit 2 demands are shown in the "Tables_ALL_With_Summary_2013_Up date;xlsm" spreadsheet. This also contains comments on the failure mode for these surveillance tests. Component failure modes are not broken down into sub-elements or causes.
DA-C14 DA-C14-01, Closed Discussion: It does not appear that a search for instances of Examined the 12-week rolling MOW_ This was a NOT MET, coincident maintenance 'was performed since there is no matrix at DCPP and did not identify any documentation issue Associated reference tci it in Data Notebook H.1. planned, repetitive activity which would and is resolved.
SR: SY- cause coincident unavailability There is no impact A20 (NOT Basis for Significan*ce: Need to assess routine activities for due to maintenance for redundant on the ILRT fl!IET), planned multiple component unavailable or document that Maintenance equipment (both Extension Risk Rule practices do not allow for routine instances of multiple intra-system and intersystem). Analysis.
trains or equipment being unavailable. Calculation or modeling of coincident maintenance unavailability was Possible Resolution: Perform this review or document that therefore unnecessary.
coincident maintenance on redundant trains is not performed.
Validate by, review of data. The above statement was added in Section H.1.2 of Cale H.1 Revision 1.
DA-C16 DA-C16-01, Closed Discussion: No documentation for explaining the disposition of Section H.1.6.4 of Cale H.1.6 Revision 8 This is resolved.
MET; plant specific LOOP events could be identified in the Initiating documents the treatment of DCPP There is no impact disposition of Events document provided to the reviewers. specific LOOP event. on the ILRT plant specific Extension Risk LOOP events Basis for Significance: Such documentatiQn is necessary to Specifically, one LOPPC Diablo Canyon Analysis.
meet the SR requirement.
- event on 5/15/2000 removed from generic data and classified as a plant _
Possible Resolution: Close gaps in documenting the specific LNVEL event (See Attachment dispositioning of PS LOOP events in development of basis for 2 of H.1.6 for Unit 1).
IE fre uenc .
DA-D4 DA-D4-01, - Closed Discussion: No documentation found in Data Calculation for The Bayesian updating is done using This is resolved.
CC-11/111, following related to the Bayesian Update- tests to ensure that the Riskman Data Module. Throughout There is no impact Associated SR: DA- the updating is accomplished correctly and that the generic - the process, Riskman shows the analyst on the ILRT E 1 (NOT MET), parameter estimates are consistent with the plant-specific a plot of the prior distribution, and a plot Extension Risk tests and check of .application include the following: of the prior distribution together with the Analysis.
_data updates (a) confirmation that the Bayesian updating does not produce a posterior distribution. Riskman also posterior distribution with a single bin histogram shows various stats for these (b) examination of the cause of any unusual (e.g., multimodal) distributions such as the mean, median, posterior distribution shapes and range factor. This process helps, the Revision 3 Page 71of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (c) examination of inconsistencies between the prior distribution analyst determine if the update and the and the plant-specific evidence to confirm that they are distributions are valid and make sense.
appropriate (d) confirmation that the Bayesian updating algorithm provides The Bayesian update checks for all meaningful results over the range of values being considered failure rates and all initiating events (e) confirmation of the reasonableness of the posterior were added as an attachment to the distribution mean value Data Update file (H.1 ). The Bayesian updates for flooding frequencies and Basis for Significance: Finding F&O is because that much of maintenance events were also checked the SR requirement is not present. using the same criteria, but the screen shots from those Bayesian updates Possible Resolution: Provide documentation for the were not included here. All distributions, performances of these tests and checks as recommended in including priors and posteriors, with the Standard. their plots and statistics are stored in the Riskman files.
DA-D6 DA-D6-01, CC-Ill, Closed Discussion: Update use of references in Data calculation. A reference to NUREG/CR-5485 was This was a documenting added in Section H.1.1 of Cale H.1 documentation issue method and Basis for Significance: Per conversation with DCPP staff, Revision 1. and is resolved.
references in data NUREG/CR-5485 was used for CCF methodology; however this There is no impact calculation is not li!)ted as a reference or in discussions in the calculation. on the ILRT Extension Risk Possible Resolution: Update Data calculation clearly / Analysis.
discussing the methodolog}'. used and correct references.
DA-D8 DA-D8"01, NOT Closed Discussion: No documentation of analysis done on impact on Evaluation of DCN impacts are made as No issues were MET, data of design changes (such as recirculation sump screen part of the design change process and identified. There is Documenting Design Change Notices (DCNs), or new charging pump DCNs) documented during the design change no impact on the evaluation of could be found in the data calculation. process using a task via associated ILRT Extension Risk design changes on design change tracking SAPN. For Analysis.
impact on data Basis for Significance: Assessing the data is part of the SR example, the conclusion of the requirement. assessment performed for the new charging pump concluded that the pump Possible Resolution: Include documentation of analysis should be added to the model.
performed to evaluate impact on data for DCNs incorporated in th_e PRA model in the Data calculation. On a routine basis as part of model maintenance, all design changes since the last model update are re-reviewed again for im~acts on the model.
DA-E2 DA-E2-01, NOT Closed Discussion: Documents provided to peer review team do not In general, all PRA documentation is This was a MET, facilitate review. Additional questions and uncontrolled backup updated to .include all information in a documentation issue Associated SR: DA- materials such as spreadsheets had to be obtained to get a single calculation file without external and is resolved.
D5 ~CC-llll, traceable basis for the Data Calculation. There is no imeact Revision 3 Page 72of117
54006-CALC-01 Evaluation of Risk Significance* of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension documentation attachments or spreadsheets, including on the ILRT Basis for Significance: The peer review team felt the lacking data calculation files. Extension Risk of documentation as required by the SR is significant. Analysis.
System and component boundaries are Possible Resolution: Improve the documentation as required described in the system calculations.
by SR and consider every detail of the requirements stated in the SR. The model used in the actual PRA model is listed in the C.9 (Quantification of CDF and LERF). This is done only in this C.9 as not all calculations are required to be updated or revised for each model release.
Sources for data is listed in H.1 Title of H.1 includes time period used for data.
Uncertainty is in PRA Cale C.10.
QU-C2 QU-C2-01, NOT Closed Discussion: Based on discussion with DCPP personnel, the A detailed Internal Events model HRA This is resolved.
MET, HFE human action dependencies are not evaluated with a minimum dependency was performed and There is no impact dependency default value to prevent underestimating risk. documented in PRA Cale G.3, Revision on the ILRT
- 0. Changes to the Internal Events model Extension Risk Basis for Significance: The issue identified in this F&O either Analysis. -
were identified and incorporated to needs to be performed or justified with alternative means to DC03.
ensure proper consideration of risk contributions.
Possible Resolution: It needs to justify adequate risk contributions are considered.
QU-04 QU-04-01, CC-I, Closed Discussion: The Category II requirements for this SR, Resolved and documented in Section This was a comparison to other "COMPARE results to those from similar plants and IDENTIFY C.9.8.6 of Calculation C.9 Revision 13 documentation issue similar plants causes for significant differences. For example, Why is LOCA a by performing a more in-depth and is resolved.
large contributor for one plant and not another?" comparison with other Westinghouse 4- There is no impact loop plants. on the ILRT Basis for Significance: DCPP has performed and documented Extension Risk a comparison to other similar plants for the CDF results. Analysis.
However, in order to meet this requirement to Category II, a further level of comparison is required.
Possible Resolution: Justification and/or actions are needed to assess the difference, especially significant differences of modeling assumptions and treatment with similar ~lant.
QU-F2 QU-F2-01, NOT Closed Discussion: This SR provides several details of items The results of quantification and risk This was a MET, expected to be seen in the quantification documentation. insights of the base model (i.e., Model documentation issue and is resolved.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASMEIANS Impact on ILRT SR Status FindinglObservation Disposition Cat II Requirement Extension Associated SR: Basis for Significance: Items listed in this SR were not located of Record) are documented in Cale C.9 There is no impact QU- F1 (NOT in the documentation (e.g., item b). Also, issues identified in Revision 13 and C.10 Revision 5. on the ILRT MET), other QU SRs point out details that should be documented in Extension Risk documentation the quantification package. Analysis.
Possible Resolution: Improve the documentation for the quantification calculation.
QU-F6 QU-F6-01, NOT Closed Discussion: This SR states, "DOCUMENT the quantitative The following statement was added to This was a MET, definition used for significant basic event, significant cutset, Section C.9.7 of Cale C.9 Revision 13: documentation issue documenting significant accident sequence. If other than the definition used and is resolved.
definition of in Part 2, JUSTIFY the alternative." "Significant sequences are defined as There is no impact significant being the top 95% contributors to a on the ILRT Basis for Significance: Although the quantitative definition for specific hazard group and having an Extension Risk significant accident sequence is given in the DCPP individual contribution of 1% to that Analysis.
documentation, there was no definition for significant basic hazard group."
event located.
Basic Event importance (RAW) to CDF Possible Resolution: Provide the necessary definitions in and LERF are shown in Attachments 16 DCPP documentation. and 17 of C.9, respectively. Significant Basic Events are those defined as having a RAW importance greater than 2.0.
LE-C2 LE-C2-01, NOT Closed Discussion: This SR states: INCLUDE realistic treatment of As documented in PRA Cale 14-02 It is stated that the MET, modeling of feasible operator actions following the onset of core damage Revision 0, all SAMG procedures were addition of operator operator actions consistent with applicable procedures, e.g., EOPs/SAMGs, reviewed. No additional human actions actions would not be following the onset proceduralized actions, or Technical Support Center guidance. would be worthwhile to credit in the worthwhile to add; of core damage PRA due to credit already being taken however, additional Basis for Significance: The current LERF analysis states that as part of core damage mitigation and actions could be there are no post-core damage operator actions available or due to high uncertainty and non- credited in the FPRA credited. However, a review of plant procedures identified that prescriptive actions in the procedures. that would reduce there are several SAMG procedures available that do include LERF. Treatment is post-core damage actions that need to be reviewed and conservative for credited as applicable. overall LERF. While reduction in LERF Possible Resolution: Review the SAMG procedures, and any would lead to an other available post-core damage procedures, and credit the increase in Class 3b, available actions as appropriate. the change is expected to be small, and there is significant margin for L':.LERF to the u er Revision 3 Page 74of117
54006-CALC-01 EYaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension level ofRG 1.174 Region II (see Section 5.2.4).
Therefore, the ILRT analysis is not adverse! affected.
LE-D7 LE-D7-01, CC-II, Closed Discussion: This SR states: PERFORM containment isolation As documented in Cale E.8 Revision 8, This is resolved.
realistic _ analysis in a realistic manner. INCLUDE consideration of both a systematic evaluation of containment There is no impact containment the failure of containment isolation systems to perform properly penetrations was performed and on the ILRT isolation analysis and the status of safety systems that do not have automatic documented in a separate spreadsheet. Extension Risk isolation provisions. A set of screening criteria were Analysis.
developed consistent with the Basis for Significance: For the containment isolation, there is requirement of this SR, and consistent no documentation readily available that shows a traceable basis with large early release definition. Each for the list of Configuration Identification (Cl) valves that are containment penetration is dispositioned present in the model and the systematic disposition of all of the explicitly using this set of screening containment penetrations that are not in the model. criteria.
Possible Resolution: Provide a systematic evaluation of all FCV-253/254 was moved to top event containment penetrations to arrive at the list of valves that are CP top due to 2" break size being used present in the Cl model. as boundary for large release. Also, identified that 8100/8112 and 8149A/B and 8149C and 8152 that were scoped into CP.
LE-E2 LE-E2-02, Closed Discussion: This SR states: USE realistic parameter PG&E has an existing calculation for 2 Using a small MET, definition of estimates to characterize accident progression phenomena. and 4 inch containment bypass sizes. containment L.ERF with 3" Using the same methodology as this isolation size is not Opening Basis for Significance: Calculation N.2, Revision 0 states existing calculation, a 3 inch size was conservative for "Using the Westinghouse Owners Group Definition for Large evaluated and determined to be an ilLERF but is Early Release Frequency (LERF) in WCAP-16378 a acceptable size for LERF purposes. conservative for total containment leak rate analysis would show that an equivalent LERF. While pipe break diameter that would result in a large release is about However, DCPP has decided to reduction in LERF 3." However, no actual calculation verifying this expected break conservatively use 2" for containment would lead to an size can be located. bypass size. As documented in increase in Class 3b, Resolution section of F&O LE-D7-01, the change is Possible Resolution: Perform and document a calculation containment isolation analysis was re- expected to be verifying that the 3 inch break size is accurate for the DCPP performed based on greater than 2" small, and there is LERF related containment leak rate. definition of the large release path in significant margin for Cale E.8 Revision 8. ilLERF to the upper level ofRG 1.174 Re ion II see Revision 3 Page 75of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Section 5.2.4). There is no impact on the ILRT Extension Risk Anal sis.
LE-F2 LE-F2-01, MET, Closed Discussion: This SR states: REVIEW contributors for This F&O has no impact on the ILRT This was a review of LERF reasonableness (e.g., to assure excessive conservatism have Extension Risk Analysis. The F&O is documentation issue sequences for not skewed the results, level of plant-specificity is appropriate related to documentation of the baseline and is resolved.
reasonableness for significant contributors, etc.) LERF results, and identified outdated There is no impact results and assumptions. The seal on the ILRT Basis for Significance: The LERF contributors were re- LOCA split fractions were confirmed to Extension Risk reviewed for reasonableness, but the quantification report (C.9, not have changed since the Level 2 Analysis.
Revision 11) discussion does not reflect the latest LERF analysis was performed, so there are no quantification cutsets, Additionally, there is an assumption in the model updates required to address this N.2, Revision 0 notebook that states "It is assumed that the issue. Reviewing and documenting the conditional core damage probability for different seal LOCA most current results and assumptions sizes is the same. This assumption may not be correct but is for LERF would not impact the adopted in the.absence of information at a more detailed level calculations of risk changes for the ILRT from the Level 1 PRA." The Level 1 RCP Seal LOCA model is Extension Risk Analysis.
now developed to a detailed enough level to get the actual Conditional Core Damage Probabilities (CCDPs), so this assumption needs to be remov~,d and the actual composition of HANNS and HANNI PDS (fraction of sequences which are seal LOCAs) needs to be used.
Possible Resolution: Update Section C.9.9.1.B of the C.9 report to reflect the current LERF cutsets and insights. Revise the N.2 calculation and RCP Seal LOCA PDS split fractions to ensure that the actual RCP Seal LOCA CCDPs are used to reflect the correct split fractions.
- LE-G3 LE-G3-01, NOT Closed Discussion: This SR states: DOCUMENT the relative C.9 Rev 13 has contributions (along This was a MET, documenting contribution of contributors (i.e., plant damage states, accident with discussion) to LERF as well as documentation issue LERF calculation progression sequences, phenomena, containment challenges, CDF. and is resolved.
containment failure modes) to LERF. There is no impact on the ILRT Basis for Significance: Although the LERF model has been Extension Risk quantified and the cutsets are available to determine the relative Analysis.
contribution of contributors, this information is not documented in the LERF calculation, and the information in the quantificati,0n calculation does not reflect the latest results, and does not include all the types of contributions discussed in this SR.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-1 Internal Events PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Possible Resolution: Update the quantification calculation (C.9) or the LERF calculation (N.2) with the information required b this SR.
LE-G5 LE-G5-01, NOT Closed Discussion: This SR states: IDENTIFY limitations in the The DCPP PRA model includes a This was a MET, limitations in LERF analysis that would impact applications. complete Level 2 detailed analysis. documentation issue the LERF analysis There are currently no general and is resolved.
-Basis for Significance: The limitations in the various portions limitations in the LERF analysis that There is no impact of the analyses that would impact applications are not identified would impact applications. Any special on the ILRT or discussed. case limitations impacting an application Extension Risk are specifically identified on a case-by- Analysis.
Possible Resolution: Identify and discuss the limitations of the case basis.
various analyses that would impact applications.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension IFSO-A6 IFSO-A6-01, Closed Discussion: The walkdown reports include spray sources Attachment E.1 Revision 1 of Section 7 This was a MET, spray near the equipment and states that the equipment is spray of the Internal Flooding PRA Calculation documentation issue prptection protected. However, the documentation does not discuss what F.4 Revision 1 documents the spray and is resolved.
is credited as spray protection and what the limitations of that target component screening process. There is no impact protection are. For instance, is there a source that could spray For spray susceptible mitigating on the ILRT on the equipment where the spray protection would not be equipment where there is a spray Extension Risk effective? source in the area, whether the Analysis.
equipment is protected is determined Basis for Significance: Without documenting how spray and documented in Table E.1-1, based protection is credited, the plant may change or remove it on insight gained in the internal flooding without the PRA analysts understanding that the internal floods PRAs performed in the industry, field analysis is negatively affected. walkdown, and/or DCPP plant database regarding equipment environment Possible Resolution: Where spray protection is credited, qualifications. For components not include the source and limitations of the spray protection. screened in Table E.1.1, a field walkdown is performed to collect information for quantitatively modeling the spray scenarios. These are documented in sections E.1.2 and E.1.3 for Unit 1 and 2, respectively. The newly identified spray scenarios are included in Appendix E of Section 7, Revision 1 of the Internal Flooding PRA Report.
IFSN-A3 IFSN-A3-01, Closed Discussion: Reviewed associated notebooks and For infinite flood sources, and large This was a NOT MET, auto attachments, no evidence for each flood area and for each flood sources, auto and/or operator documentation issue and/or operator source the applicable and relevant either auto and/or operator responses to terminate or contain a and is resolved.
responses responses was identified if it has the probability to terminate or flood are considered. For infinite flood There is no impact contain a flood propagation. sources, considerations were provided on the ILRT in resolution to IFSN-A 10-01. For Extension Risk Basis for Significance: Such proper identification is not just example, to terminate flood due to the Analysis.
to meet this SR but it also would enable to properly meet other Circulating Water pipe break, credit was SRs and model development and risk insights. taken for the automatic pump trip feature based on float switch mounted Possible Resolution: Identify per SR requirements. on the condenser pit walls. For large flood sources such as fire water pipe break with water source from raw water storage reservoir, HFEs were developed for operator actions to terminate the flood. See Appendix G of Section 9, Revision 1 of the Internal Flooding PRA Report, and Section 10:
Revision 3 Page 78of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Revision 1 of the Internal Flooding PRA Report for development of these HFEs.
For other flood sources, scenario modeling including modeling of plant response is developed on a flood area and/or scenario specific basis. For example, for flood sources with limited source inventory (e.g., chilled water pipe breaks), termination of flooding would occur if the source system is de leted.
IFSN-A8 IFSN-AB-01, Closed Discussion: This SR requires the identification of drain lines Section 7.3, Revision 1 of the Internal No issues were MET, drain line paths and back flow through drain lines involving failed check Flooding PRA Report documents the identifi.ed. There is and back flow valves, pipe and cable penetrations, etc., as stated in the SR. identification of propagation pathways at no impact on the paths Currently it is stated that drains were no credited. This does DCPP. Due to the open layout design ILRT Extension Risk not eliminate the need for the identification. To meet this SR it and numerous openings in different Analysis.
needs to review drain drawings to identify the path or credit elevations of the Auxiliary Building and past drain line studies explicitly. Cable trays, etc. Turbine Buildings (e.g., open stairways and grate-covered floor openings),
Basis for Significance: Did not identify as required by the floods originating in one level is standard SR. These conditions could be screened out later, expected to propagate freely to the but need to be identified first as specified by this SR. basement of the building. There is a subsection in section 7.3 discussing Possible Resolution: Identify accordingly. drainage system; backflow of water is not a significant issue in the Auxiliary Building because of the physical layout of the building. There are large open areas outside the pump rooms, and the pump rooms are elevated above the pipe tunnel, where water would collect.
There is also a subsection in section 7.3 discussing unsealed cable tray/conduit and pipe penetrations. For the cases in which pipe penetrations are not sealed, other significantly larger propagation pathways are present; one example is Containment Penetration Area El 115',
the gap along the containment wall is a much larger propagation pathway than pipe penetrations through the floor. As a response to this F&O, in water level Revision 3 Page 79of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension rise timing estimation for nominal flood originated at Fuel Handling Building El.
100' (the corridor area 31, the AFW pump room 3-Q-1, or 3-Q-2), drain flow through floor drains and then drain lines to the Auxiliary Building sump is estimated, as documented in Section 7, Revision 1 of the Internal Flooding PRA Re ort.
IFSN-A9 IFSN-A9-01, Closed Discussion: No calculations were provided to the review Flood calculations were performed for No issues were NOT MET, flood team that shows the flooding rates and the time to equipment selected areas where bounding identified. There is depth and damage. The calculations are needed to determine assumptions were too severe and more no impact on the propagation propagation beyond the initial flood area. detailed analysis was required, ILRT Extension Risk including flood areas with limited Analysis.
Basis for Significance: Calculations for flood areas with a drainage paths and large flood source large capacity are needed to show that the flood does not capacities. The calculations consider propagate without some action to mitigate the flood. flood rates, flood propagation through door gaps, opening between rooms and Possible Resolution: Perform flood calculations to show floor drains. The flooding depth (level flooding depth and propagation to other areas. If older rise) timing is evaluated in these calculations exist that show the flooding depth and calculations, as documented in propagation, review and revise these to meet the current PSA Appendix E of Section 7, Revision 1 of standard requirements. the Internal Flooding PRA Report.
IFSN-A10 IFSN-A10-01, Closed Discussion: Table 4-1 lists the flood source capacities for The size of infinite flood sources, No issues were MET, size of flood each water source, but subsequent evaluations ot the flooding Circulating Water, Auxiliary Saltwater identified. There is sources scenarios do not mention the impact of emptying that source and Firewater from the raw water no impact on the on the flood depth in the areas or the subsequent propagation reservoir, were included in the flood ILRT Extension Risk of infinite water sources to various other areas without scenario development along with the Analysis.
operator action to isolate the flood. flood area, source, flood rate, SSC damage and operator actions. System Basis for Significance: The size of the flood source is not design and plant flood mitigation really considered beyond the initial scoping of the flood features were considered for these sources. infinite sources, which are documented in Section 7.3 of Revision 1 of Section 7 Possible Resolution: To determine the true impact of of the Internal Flooding PRA Report.
flooding, include the size of the flood source and what could be For the Circulating Water Turbine flooded if infinite sources, such as circulating water and ASW Building flood the automatic pump trip are not isolated. feature based on the float switches mounted on the condenser pit walls is credited and modeled. For the ASW flood in the CCW heat exchanger room Revision 3 Page 80of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension it is concluded that it is not credible to postulate a flood propagation scenario that would cause damage to the emergency diesel generators and offsite power based on the limited flood rate, the ASW pumps tripping terminates the flood and numerous control room alarms. Operator actions to isolate the raw water reservoir are credited and modeled for flood scenarios in the Auxiliary, Fuel Handling and Turbine Buildings. If these credited operator actions and automatic trip functions are failed additional SSCs are assumed to be dama ed.
IFSN-A11 IFSN-A11-01, Closed Discussion: The impact of large flooding sources in areas For the Turbine Building flood This is resolved.
NOT MET, multi- that could impact both Units has not been considered. For scenarios, ASW and Circulating Water There is no impact Units effect instance, Circulating Water and ASW are considered infinite piping failure is assumed to cause a on the ILRT sources since they take suction from the ocean. The Turbine dual unit trip. ASW and Circulating Extension Risk Building is a large open area that contains the turbines for both Water pipe breaks in the intake Analysis.
Units. However, a possible duel Unit scram due to a very structure causing dual unit trip are not large flood in these areas was not considered. Similarly, the considered credible scenarios (see Intake structure contains SSCs for both Units that could also Appendix E of Section 7, Revision 1 of result in a dual Unit scram due to a pipe break in a large the Internal Flooding PRA Report.). In source such as ASW. response to this F&O, pipe failures in Auxiliary Building flood areas that are Basis for Significance: The impacts of floods effecting multi- shared between the two units are Units must be considered. included in the flood initiator frequency count for both units (as documented in Possible Resolution: Update the flood analysis to consider Appendix G of Section 9, Revision 1 of large floods impacting multi-Units. the Internal Flooding PRA Report).
IFSN-A12 IFSN-A12-01, Closed Discussion: Based on the discussion of building features, it The scenarios in Appendix E of This is resolved.
MET, screening appears that flooding scenarios are screened or assumed not Section 7, Revision 1 of the Internal There is no impact of flood scenarios to propagate bas~d on drains, curbs and barriers between Flooding PRA Report were reviewed. on the ILRT rooms. This screening implicitly assumes that the leak is Additional propagation scenarios Extension Risk smaller than the drain capacity and/or that the operators take previously screened in Revision O were Analysis.
action to reduce or stop the flow before water backs up into the identified and scoped in with flood room and fails additional equipment or propagates beyond the source capacity and propagation paths room. Table E-1 in the flooding document discusses screening considered in characterization and of numerous flooding scenarios for propagation. The quantification of the flood scenarios. In propagation screenings do not look at accumulation on the addition, select human failure events Revision 3 Page 81 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-2 Internal Flooding PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension area where the water is going and whether equipment in that (HFE) were developed to model the area would be impacted due to flood or whether the flood flood isolation for large flood sources could propagate beyond the se9ond flood area to another area such as Firewater from the raw water and damage equipment. reservoir. Failure of these HFEs result Basis for Significance: Many flooding scenarios are in additional PRA equipment damage qualitatively screened by making undocumented assumptions beyond the original source flood area, and suppositions and thus prematurely screening these such as both RHR pumps being flooding scenarios. The propagation dqes not appear to damaged whenever the 54' pipe tunnel consider source capacity and spread beyond the second area. in the Auxiliary Building is flooded Large flooding sources can propagate to several rooms beyond its capacity volume.
IFPP-A5 IFPP-A5-01, Closed Discussion: Walkdown documentation in Section 5 of the Walkdowns were performed in response This was a MET, walkdown Internal floods report has a lot of blank fields associated with to IFSO-AB-01 for spray screening and documentation issue documents the flooding sources in the areas. The equipment list is modelling, and to IFSNA12-01 for and is resolved.
generally complete but appears to be a download of the propagation scenarios. For the few There is no impact Appendix R Safe Shutdown Equipment list. Therefore, it is instances where additional pipings are on the ILRT difficult to determine if all flooding sources in a zone have been identified, the Section 5 walkdown table Extension Risk identffied and is difficult to know what sources have been is updated. The process of identifying Analysis.
included or not. equipment list is discussed in detail in Section 3.3 Rev 0 and Rev 1. It Basis for Significance: Hard for a reviewer or regulator to involves using multiple information determine that all flood scenarios have been properly sources as a starting point, such as IPE dispositioned. internal flooding, current fire PRA, and current internal events PRA. A Possible Resolution: Improve the documentation to address comprehensive review of the initially the concerns identified in the F&O. compiled list of components was performed to identify those equipment which can be damaged by flooding effects and whose damage would affect the accident initiation and/or mitigating functions.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension PP-C2 PP-C2-01 (2008), Closed No explicit justification for the exclusion of locations Attachment 3 was added to PRA Cale F.3.1 This was a NOT MET, exclusion within the licensee controlled area is provided in the to identify all of the permanent buildings on documentation of areas FPRA documentation. Because the global boundary the site and to address the potential fire issue and is encompasses all of the Fire Hazards Analysis (FHA) effects in order to justify their inclusion or resolved. There is areas, and adds certain areas not included in the FHA, exclusion from the Global Plant Analysis no impact on the this is unlikely to be a problem. Boundary. ILRT Extension SR PP-C2 calls explicitly for providing this Further discussion is provided in Section 4 of Risk Analysis.
documentation. Since it has not been done, this SR is F.3.1.
not met. During the 2010 peer review, the (Note: This F&O was generated during the January 2008 PP SR, PP-C2 was reviewed and judged to review. be met.
ES-B1 ES-B1-02 (2008), Closed The intent of ES-B1 per Discussion 2 is that it is iterative. This F&O has been resolved by additional The exclusion of CC I, need to verify The analysis does not demonstrate that excluded analysis. The risk significance of excluded systems from the the basis of components are revisited to determine if the systems and equipment has been Fire PRA is excluding low system/component should be added due to importance documented in the uncertainty and sensitivity conservative for importance SSC of risk. Reference Section 7.7.1.c and Section 3.2 for analysis to justify the firial set of SSCs the ILRT valid systems and components considered. Discussion 2 of credited in the fire PRA. application. The ES-B1 reviews the importance of using an iterative With this F&O resolved, along with additional other part of this approach to validate the assumptions made in the initial F&Os ES-B1-03 (2008) and ES-B1-01 F&O is related to review of components to include. Even though systems (2010), SR ES-B 1 is judged to be met at documentation.
such as Main Feed I Condensate are not important to the Capability Category II based on the Therefore, there is internal events model, they may be important to specific verification of low risk importance of excluded no adverse impact fire areas once initial results are reviewed. Reference SSCs. The 2010 peer review identified a on the ILRT Section 7. 7 .1.c and Section 3.2 for systems and similar finding (see ES-B1-01 (2010) below), Extension Risk components considered. but concluded that SR ES- B1 is met at Analysis.
Add step to process to review the assumptions and Capability Category II.
determine if systems /components originally excluded due to significance should be added.
(Note: This F&O was generated during the January 2008 review.
ES-B1 ES-B1-03 (2008), Closed The component selection considers spurious operations This F&O has been resolved by additional This is closed.
CC I, not including a including MSOs that could affect system operation. The analysis and model updates. A sensitivity There is no impact recovery action for result of this review is the failure of associated analysis was performed and documented to on the ILRT potentially significant components without consideration for recovery. For evaluate the risk significance of EOP and Extension Risk scenario, specifically example, spurious operations of equipment that could post-fire recovery actions. Important actions Analysis.
the drain-down of cause a loss of Refueling Water Tank (RWST) inventory have been added to the fire PRA model.
the RWST results in a loss of the RWST for the purposes of With this F&O resolved, along with additional injection and subsequent recirculation. This results in a F&Os ES-B1-02 (2008) and ES-B1-01 loss of primary inventory control function and heat (2010), SR ES-B1 is judged to be met at Caeabili!l Cate~o~ II. The 2010 eeer review Revision 3 Page 83of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension removal (feed and bleed). This is showing as being concluded that SR ES-81 is met at Capability conservative and significantly affecting results. Category II.
From discussion #2: Ultimately the selected equipment and the resulting FPRA plant response model must be sufficiently complete that the objectives with respect to level of detail, realism, and accuracy as stated in Table 1-1 of this standard are met consistent with the intended capability category.
Evaluate significance of not including recovery actions and equipment and include where appropriate.
(Note: This F&O was generated during the January 2008 review.
ES-81 ES-81-01 (2010), Closed Calculation F.3.2 does not explicitly include a step to This F&O has been resolved by additional The exclusion of CC II, need to verify review the assumptions used to exclude components or analysis. The risk significance of excluded systems from the the basis of systems that were excluded to verify that these systems and equipment has been Fire PRA is excluding low components can remain excluded based on risk documented in the uncertainty and sensitivity conservative for importance SSC significance. The DCPP response indicates that the analysis to justify the final set of SSCs the ILRT' valid uncertainty of excluded components and systems is credited in the fire PRA. application. The addressed in F.3.15. With this F&O resolved, along with additional other part of this A review of Calculation F.3.15 does not indicate any F&Os ES-81-03 (2008) and ES-81-01 F&O is related to discussion of the uncertainty of the exclusion of (2010), SR ES-81 is judged to be met at documentation.
components or systems based on risk significance under Capability Category II based on the Therefore, there is Section 3.3.2 of the calculation. verification of low risk importance of excluded no adverse impact SS Cs. The 2010 peer review identified a on the ILRT Basis for Significance: The iteration to validate that the Extension Risk assumption to exclude components or systems needs to similar finding (see ES-81-01 (2010) below),
but concluded that SR ES- 81 is met at Analysis.
be performed to ensure that the model is not excessively conservative to meet a Capability Category II. Capability Category II.
Possible Resolution: Perform a sensitivity analysis of components or systems that were excluded during the ES task to confirm that they are not risk significant.
(Note: This F&O was generated during the December 2010 review).
ES-82 ES-82-01 (2010), Closed MSO review does not appear to evaluate and disposition This F&O has been resolved by additional This F&O has documentation the effects of multiple spurious operations on calculations reviews and model updates. The qualitative been resolved by inconsistencies and to support the success criteria in the FPRA. This includes screening criteria used to evaluate the impact additional reviews
.errors in MSO system success criteria such as multiple flow diversion of MSOs on the function success criteria was and model documentation. paths and timing associated with manual actions. CC-II supplemented by additional reviews to updates. There is needs to consider the effect on two sEurious oEerations confirm there were no situations in which the no imEact on the Revision 3 Page 84of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension per train and the effect on the system success criteria. effects of coincident MSOs would impact ILRT Extension Multiple spurious operations may affect the success system success criteria. As a result, MSO of Risk Analysis.
criteria for the train in either required system pressurizer power- operated relief valves performance functions and/or supporting manual actions. (PORVs) was considered as requiring Not performing this review could have impact on system mitigation as a medium-break instead of a success and HRA. Review multiple operational effects on small-break LOCA.
calculations that support system and train success. The 2010 peer review concluded that SR ES-(Note: This F&O was generated during the January 2008 B2 is met at Capability Category Ill.
review.
CS-A2 CS-A2-03 (2008), Closed A review of Appendix R circuits has not been completed DCPP Action Request A0414724 addressed This is closed.
CC Ill, incomplete to find potential circuit failures that could lead to the this issue in November 2000 in response to There is no impact circuit analysis for bypass of MOV torque and limit switches. Where NRC IE Notice 92-18. on the ILRT the bypass of MOV damage to MOV is possible, credit for manual actions to During the 2010 peer review, SR CS-A2 was Extension Risk torque and limit credit operation of the valves need to be removed. Credit judged to be met at CC-II but a new F&O CS- Analysis.
switches. for valve operation could be taken when valve positioning A2-01 was added. Refer to F&O CS-A2-01 may not be available due to physical valve damage. (2010) for details.
Review existing circuit analysis for MOVs where shorts could bypass the torque and limit switch and determine if valve damage could occur. If so, validate that manual actions to recover the valve position are not credited in the FPRA.
(Note: This F&O was generated during the January 2008 review).
CS-A2 CS-A2-01 (2010), Closed F&O: In response to NRC IE Notice 92-18, a review of This F&O has been resolved by additional This is closed.
CC II, expand NRC safety-related MOVs was performed in Evaluation AR analyses. Action request (AR) A0414724 There is no impact IN 92-18 to MOVs A0414724. A review should be conducted to confirm that documented the review of MOVs credited in on the ILRT required to support MOVs from the internal events PRA that are credited in the Appendix R analysis to address NRC Extension Risk the manual actions the FPRA, but are not included in the above evaluation Information Notice 92-19. Additional review of Analysis.
in the FPRA. are added to that evaluation. If not, then credit for the fire PRA identified additional MOVs not in manual operation of the affected MOVs should be the scope of AR A04J 472d. These MOVs removed from the FPRA. have been evaluated for this failure mode to Basis for Significance: This action is required to meet the ensure that manual operation of the MOV is SR. The evaluation AR A0414724 only addressed MOVs not improperly credited, and the that are credited for Appendix R Safe Shutdown. Any documentation has been revised to reflect new MOVs credited from the internal events PRA for the the additional evaluations.
FPRA have not necessarily been evaluated for With this F&O resolved, SR CS-A2 is judged mechanical damage resulting from a stalled condition, to be met at Capability Category II. (The and may not be capable of manual operation.
Revision 3 Page 85of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Possible Resolution: See text of F&O above. 2010 peer review concluded that SR CS-A2 (Note: This F&O was generated during the December is met at Capability Category II.)
2010 review).
CS-A? CS-A?-01 (2008), Closed Components added associated with ISLOCA Sequences This F&O has been resolved by a model The current Fire NOT MET, 3-Phae in Table 7-4 of the Component Selection Calculation did update. Cables associated with isolation PRA model is hot short not appear to have 3-Phase Hot Short Analysis in the valves where spurious actuation due to three- conservative for circuit analysis. This includes CVCS valves 8112 and phase hot shorts could result in an ISLOCA the ILRT 8100, and RHR valves 8701 and 8702. have been verified in the model, and extension Requirement not met for major ISLOCA pathways. additional cables for valves identified have application.
Add in to the analysis the cable impact and analysis for been added. NUREG/CR-7150 guidance Therefore, there is valves mentioned above, and ensure the impact is recommends screening of 3-phase proper no adverse impact modeled in the PRA. polarity hot shorts; therefore, the current Fire on the ILRT (Note: This F&O was generated during the January 2008 PRA model is conservative for the ILRT Extension Risk review). extension application. Analysis.'
The 2010 peer review concluded that SR CS-A? is met.
CS-A10 CS-A 10-01 (2008), Closed The Assumptions for Guaranteed failure (GF) in the This F&O has been resolved by additional This is resolved.
NOT MET, potential Impact Matrix for the 50 or so components not traced has analysis. The risk significance of excluded There is no impact high CDF impact of resulted in conservatism in the CCDP for the FPRA systems and equipment has been on the ILRT the assumptions of results. The present CCDP for a baseline PRA run is a documented in the uncertainty and sensitivity Extension Risk guaranteed failure of factor of 40. higher than the internal events, which may in analysis to justify the final set of SSCs Analysis.
non-traced SSCs. part be due to assumptions on the GF issue. This results credited in the fire PRA.
in a significantly too high.GDF for Fire for all scenarios, With this F&O resolved, along with additional and may be one of the main contributors to the overall F&Os ES-81-03 (2008) and ES-81-01 high GDF initially estimated. A review of Cale (2010), SR ES-B 1 is judged to be met at 134Draft.doc and the Impact matrix was performed. In Capability Category II based on the general, all components id~ntified in the component verification of low risk importance of excluded selection process were traced, and the tracing results are SS Cs.
in the impact matrix. However, many of the components The 201 O peer review concluded that SR CS-that were listed as credited under Component Selection were actually not traced and assumed failed, as A 10 is met at Capability Category Ill.
identified as a Guaranteed Failure in the Matrix. A review of th~ FDS1 results was performed, with the lowest FDS1 CCDP of 5.3E-05. This is about a factor of 40 higher than the reactor trip CCDP (1.4E-06). What this indicates is that between the assumptions in the equipment selection task IA, MFW, Containment Spray not credited) and the components not traced in the Cable Revision 3 Page 86of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension Selection, the CCDP for the FPRA is a factor of 40 too high.
Review the FDS1 results for several scenarios, and determine the assumptions that are most affecting the results. Based on this review, perform cable routing and circuit analysis needed to remove the assumptions, and re-run the FDS1 results. Once a baseline FDS1 result is similar to the internal events PRA CCDP (with the HEP set back to the original internal events PRA results), then the remaining assumed component failures can likely remain .. This may need to be looked at again for multiple initiating events and for higher CCDP events where the assumed failures can become important for certain scenarios.
(Note: This F&O was generated during the January 2008 review.
CS-A11 CS-A 11-01 (2008), Closed In discussions with the PRA staff, there were several This F&O has been resolved by a This was resolved NOT MET, lack of components, where Appendix R basis was used to documentation update. The cables bya documenting the determine the cable routing, without specific cable/circuit associated with the 480 V switchgear HVAC documentation basis for assumed review and routing. This includes Cable Room, Battery and damper were analyzed and traced. The update. There is cable routing, room, and 480 VAC switchgear room dampers (which remaining assumed cable routing were no impact on the Associated SRs: - results in a loss of Heating Ventilation and Air reviewed and the documentation updated to ILRT Extension CSC3, FSS-E4. Conditioning (HVAC)). This event is important in the document the basis for the routing Risk Analysis.
PRA, as evidence by the baseline results analysis assumptions provided by DCPP, which shows this to be the number 1 The 2010 peer review concluded that SRs scenario due to an increased HEP event for non- CS-A 11 and CS-C3 are not applicable.
recovery of loss of HVAC. Due to the failure to document the use of the Appendix R basis for the cable routing, a finding was developed to add this documentation to the PRA. Without the documentation, it is not possible to determine where the cable tracing results come from for these components. Additionally, these components are always assumed failed for fires in areas where the component cables are assumed to be located.
Add the documentation for components not specifically traced into the PRA, and the basis for the resulting routing. This can then be input into the uncertainty results discussion, including the fire modeling (FSS) uncertain .
Revision 3 Page 87of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (Note: This F&O was generated during the January 2008 review.
PRM-A4 PRM-A4-01 (2008), Closed Uncertainty and Sensitivity and Analysis (Task 15) have Note: This SR in 2007 Standard has been This is resolved.
NOT MET, not been performed yet. This item could not be verified. deleted from 2009 Standard. There is no impact incomplete Once the FPRA model becomes stable, perform Task 15 PRA Cale F.3.15 has been prepared on the ILRT Uncertainty and to account for uncertainties and sensitivities. documenting the Uncertainty and Sensitivity Extension Risk Sensitivity analysis. (Note: This F&O was generated during the January 2008 Analysis. Analysis.
review.
PRM- PRM-813-01 (2008), Closed DCPP has not reviewed accident progression beyond
- This F&O has been resolved a model update. This is resolved.
813 NOT MET, core damage considering fire failures. It is recommended The LERF model for fires has been There is no impact incomplete that DCPP perform this review and docu.ment it. completed and documented. on the ILRT quantification of In reviewing the draft report, DCPP contested this finding The 2010 peer review team concluded that Extension Risk LERF model, and said that they had performed a screening review the SR PRM-814 is met. Analysis.
Associated SRs: containment penetrations to identify potential sources of PRM-814. fire-induced containment isolation failures. DCPP provided a copy of Calculation F.3.3.1, Rev. 0, dated June 6, 2006, documenting this review. A subsequent review of this document indicated that DCPP had performed a thorough review of all containment penetrations using a documented set of screening criteria. As a result of this review, DCPP retained 59 penetrations for further evaluation as potential sources for containment isolation failure:
However, at the time of the review, as discussed in Table 4-13, the quantification was still in process and there was not enough information or documentation to determine the extent to which fire-induced containment isolation failures had been incorporated into the model and addressed in the final quantification. This finding stands until DCPP has completed the quantification and*
documented the results and the final model. However, based on the additional information provided, it seems likely that DCPP will meet this requirement when they have completed the quantification.
(Note: This F&O was generated during the January 2008 review.
PRM- PRM-815-01 (2010), Closed F&O:. F.3.2 states that "The possibility of multiple open Revision 1 to Calculation F.3.2.1 has been This is resolved.
815 MET, lack of pathways (<3") should also be considered." A review of changed such that Section 4 and Attachment There is no impact the remaining small isolation pathways shows that the
- 1 now include the dispositioning of non- on the ILRT likelihood of combined events leadin~ to a eathwa~ >3~' is screened containment eenetrations .based on Revision 3 Page 88of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension documenting low very low and could likely be screened. However, this is the size of equivalent opening gi~en multiple Extension Risk probability of not documented. pathways. Analysis.
multiple Basis for Significance: All new fire-related LERF open pathways . pathways that were identified in F.3.2.1 have not been leading to greater formally dispositioned and docum_ented.
than 3" opening, Associated SRs: Possible Resolution: The PRM documentation should be PRM-C1 updated to disposition all potential LERF pathways applicable to the FPRA that were identified in F:3.2.1.
(Note: This F&O was generated during the December 201 O review).
PRM-C1 PRM-C1-02 (2010), Closed F&O: F.3.5, Section 6.4.2.1(Step4) states: "It is This F&O has been resolved by a model The newRCP MET, modeling of assumed in the model that the installation of the high update. The RCP seal model was modified seal modelling is new low leakage temperature RCP seals has the benefit excluding the based on the vendor guidance documents to based on the RCP RCP seals. possibility of an RCP Seal LOCA on loss of cooling to the include both human error and random failure seals to be seals." This was verified in the rules (Appendix I) which modes. installed. The Fire have split fraction SEO (with a value of 0.0), as the first PRA model rule in SE, set to be default as success (i.e., SEO= 1). results presented However, neither the Flowserve N-9000 nor the new in this report are Westinghouse shutdown seal (SOS) are guaranteed to based on this not develop a Seal LOCA in the event of loss of seal model, which injection and thermal barrier cooling. Both seal types provides require an operator action to trip the RCPs (not modeled reasonable in DCPP FPRA) and both seals have a nominal failure estimates of Fire rate (e.g., on the order of 1E-3) even when the RCPs are PRA CDF and successfully tripped (not modeled in DCPP FPRA). LERF for this Basis for Significance: RCP seal LOCA can be a application.
significant contributor to fire CDF in PWRs, even with Therefore, there is newer seals (either- N-9000 or Westinghouse SOS). no impact on the ILRT Extension Assuming that no operator action is required and that the Risk Analysis.
seal cannot fail (i.e., failure probability= 0.0) may significantly affect the results and/or insights of the FPRA.
Possible Resolution: Add modeling for RCP seal failure, including the need for operator action to trip the RCPs.
WCAP-16175 provides guidance and values for RCP seal failure rates for N-9000 seals. If Westinghouse SOS seals are expected to be installed, Westinghouse should Revision 3 Page 89of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension be able to provide approximate failure rates and required operator timing.
(Note: This F&O was generated during the December
- 2010 review .
PRM-D1 PRM-D1-01 (2008), Closed Documentation for the Plant Response model has This F&O has been resolved by completion This is resolved.
NOT MET, the PRM portions in draft and other portions not complete. This is of the plant response model documentation. There is no impact report is in draft form due to the current status of the project with the plant The 2010 peer review concluded SR PRM- on the ILRT response model undergoing updates. C1 is met. Extension Risk Once the model becomes stable, update F.3.5 with how Analysis.
the model was developed and updated the PRA model documentation as necessary to account for model changes used to acc~unt for FPRA evaluation capability.
(Note: This F&O was generated during the January 2008 review).
FSS-A5 FSS-A5-01 (2008), Closed For many compartments, target sets associated with high This F&O has been resolved by a model This is resolved.
NOT MET, risk compartments and ignition sources has not been update. Since the initial peer review in 2008, There is no impact incomplete completed. A review of fire compartment 388-100 was the fire PRA scenarios have been completed on the ILRT development of performed to evaluate the adequacy of the scenario and documented. The 2010 peer review Extension Risk detailed fire selection method. This is not in line with the intent of this identified an industry best practice for this Analysis.
scenarios requirement as provided in Discussions #1 and 2. High element.
risk compartments not evaluated in a level of depth The 2010 peer review concluded SR FSS-A5 sufficient to understand the results. is met at Capability Category Ill.
FSS-A6 FSS-A6-01 (2008), Closed The main control room analysis is not complete. This This F&O has been resolved by completion This is resolved.
NOT MET, item could not be verified. of the MCR analysis. The fire modeling of the There is no impact incomplete the fire (Note: This F&O was generated during the January 2008 MCR has been performed and documented. on the ILRT modeling of the Main review). The 2010 peer review concluded SR FSS-A6 Extension Risk Control Room is met at Capability Category I/II. Analysis.
MCR FSS-81 FSS-81-01 (2008), Closed Scenarios that require MCR abandonment/reliance on This F&O has been resolved by a model and This is resolved NOT MET, MCR ex-control room operator actions have not been documentation update. The control room since the RAI 03 abandonment developed. MCR abandonment criteria is identified in abandonment criteria are consistent with model, which analysis, Associated Main Control Room Fire Risk Analysis but not justified NUREG/CR-6850, and this is documented incorporated the SRs: FSS-82. based on review of draft Main Control Room Fire Risk with the RAJ 03 model. The RAJ 03 model revised MCR Analysis. MCR abandonment criteria identified but includes the risk contribution of MCR abandonment justification not provided as required in the SR. abandonment in the Fire PRA CDF and model, is used in
'Complete fire scenario development and evaluation MGR LERF. the external scenarios and scenarios that reguire either MCR events sensitivi~.
Revision 3 Page 90of117-1'
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension D
Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension abandonment or ex-control room operator manual With this F&O resolved, FSS-81 is judged to Therefore, there is actions. be met. no impact on the (Note: This F&O was generated during the January 2008 ILRT Extension review}. Risk Analysis.
FSS-C2 FSS-C2-01 (2008), Closed For Capability Categories II & Ill, a time-dependent This F&O has been resolved with a model This is resolved.
CC I, lack of time assessment of heat release rate is called for scenarios update. Time dependent HRRs have been There is no.impact dependent heat important to risk. In the compartments for which scenario developed and implemented using the t2 fire on the ILRT release rate development was examined, heat release rates for most growth, peak, and decay per NUREG/CR- Extension Risk components (e.g., cabinets) were constant with time. 6850. Analysis.
Time-dependent heat release rates were assessed in at The 2010 peer review concluded SR FSS-A6 least some cases for target cables. The scenarios is met at Capability Category 11/111.
examined are important contributors to risk. To achieve Capability Category II or Ill, time dependent assessment of the heat release rates is required.
More detailed assessment of the heat release rates may contribute to reducing the assessed frequencies for these scenarios and compartments.
(Note: This F&O was generated during the January 2008 review).
FSS-C5 FSS-C5-01 (2008), Closed A technical basis is needed 1to justify the use of damage The F&O has been resolved with a model This is resolved.
CC I/II, justification. temperatures for qualified cable when a limited amount update. The fire modeling of all fire areas There is no impact for the use of of non-qualified cable is installed in the plant. Use of containing thermoplastic cables (or cables of on the ILRT damage criteria of damage temperatures for qualified cables may be non- unknown material which are assumed to.be Extension Risk qualified cable for conservative for targets that include nonqualified cables. thermoplastic) were updated, and now Analysis.
non-qualified cable. Pursue identification of nonqualified cable routes or considers appropriate damage criteria for develop severity factors that may be applied to targets unqualified cables.
that may: include nongualified cables.
FSS-C5 FSS-C5-01 (2010), Closed NOTE: This finding was identified in 2008 review and re- The F&O has been resolved with a model This is resolved.
CC I/II, treatment of identified in 2010 review. update. The fire modeling of all fire areas There is no impact thermoplastic cables F&O: DCPP fire modeling reports indicate that the containing thermoplastic cables (or cables of on the ILRT damage/ignition temperature at DCPP is based on unknown material which are assumed to be Extension Risk thermoset cabling which was concluded from thermoplastic) were updated, and now Analysis.
performance of PRA calculation F.3.6.1, which considers appropriate damage criteria for established that all raceways and conduit at DCPP unqualified cables.
contain thermoset cabling. This review identified less than 1% (350 cables) of plant cables as being thermoplastic and 5.19% (2,229 cables) of cables were constructed of unknown materials based on this it was Revision 3 Page 91 of 117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension concluded that thermoset damage criteria should be applied to all fire modeling targets and self-ignited cable fires need not be considered. While this information clearly demonstrates that most cables at DCPP are qualified a very small percentage is non-qualified and those cables could damage/ignite at lower non-qualified cable damage temperatures.
Basis for Significance: A very limited set of non-qualified cables exist in the plant which should be evaluated using lower damage/ignition temperatures. If these cables are present in a fire scenario for which fire modeling was performed use of damage criteria for qualified cable may be non-conservative.
Possible Resolution: Identify the routing of cables with un-qualified or unknown cable construction. Screen such cables which are located in areas where no fire modeling was performed or the cables are routed in conduits. In cases where such cables are routed in cable trays in risk-significant areas reevaluate the treatment of targets where these cables are routed.
(Note: This F&O was generated during the December 201 O review .
FSS-C8 FSS-C8-01 (2008), Closed Fire Wrap is not discussed in the fire area analysis This F&O has been resolved with a model This is resolved.
NOT MET, treatment performed for the PRA, and the technical justification for update and documentation update. There is no impact of fire wrap credited wrap is not provided as required by FSS-C8. Credited fire wrap in each fire area and fire on the ILRT Provide a description of when fire wrap is credited, a list scenario is documented in the risk modeling Extension Risk of fire areas and components where it is credited and workbook . Analysis.
.reference to the technical justification for the fire wrap The 2010 peer review concluded SR FSS-C8 qualifications in the FPRA. Additionally, provide is met.
documentation of the wrap effectiveness, including the maintenance of the wrap (no mechanical damage) and the review of the wrap against direct flame impingement from a high hazard ignition source.
(Note: This F&O was generated during the January 2008 review.
FSS-03 FSS-03-01 (2008), Closed Fire modeling is not complete. Spreadsheets have been This F&O has been resolved by completion This is resolved.
CC I, fire modeling is completed for eight areas and one CFAST model is of fire modeling and documentation. There is no impact not completed for all completed based on submittal to Peer Review. on the ILRT Revision 3 Page 92of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations r 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension screened areas Complete Fire Modeling Task and documentation to The 2010 peer review concluded SR FSS- Extension Risk satisfy this. SR.
- 03 is met at Capability Category Ill. Analysis.
(Note: This F&O was generated during the January 2008 review).
FSS-D? FSS-D?-01 (2010), Closed F&O: To meet Capability Category II, it should be This F&O has been resolved by additional This is resolved.
CC I, use of plant demonstrated that the system has not experienced
- review with no model change required. A There is no impact specific data for outlier behavior relative to system unavailability. A review review of plant-specific maintenance and on the ILRT suppression and of data and results of Calculation M-1079 indicates that testing data for fire suppression and Extension Risk detection systems the plant smoke detector unavailability is similar to the detection systems was performed and results Analysis.
generic unavailability. There does not.appear to be a documented. It was concluded that these similar review performed for the heat detectors or the fire systems have not experienced outlier suppression systems. behavior compared to the generic data Basis for Significance: The analysis currently meets applied in the fire PRA.
Capability Category I. This finding discusses the gap that With this F&O resolved, SR FSS-D? is needs. to be addressed to meet Capability Category II for judged to be met at Capability Category II.
this Supporting Requirement.
Possible Resolution: Perform a review of plant-specific maintenance and testing data for fire suppression and other fire detection systems in order to characterize the unavailability ofthese systems to confirm that here are no outliers.
(Note 1: Tliis F&O was generated during the December 2010 review).
(Note 2: After the issue of the draft peer review report, PG&E requested that the peer review team revisit this F&O. The review team caucused and decided that the F&O will stay as originally written. The PG&E's request and the review team's conclusions are documented in Appendix C).
FSS-08 FSS-08-01 (2008), Closed The effectiveness of the fire detection and suppression This F&O has been resolved by a This is resolved.
MET, suitability of systems is included in the fire modeling spreadsheets; documentation update. The effectiveness of There is no impact detection and however evidence of an evaluation of the suitapility of the automatic detection and suppression on the ILRT suppression systems , detection and suppression systems and specific features systems has been evaluated during Extension Risk that may impact these systems was not identified. walkdowns and inspections, and has been Analysis.
This information *is contained to some degree in the FHA included in revised documentation.
- but specific discussion in the fire modeling calculations should be included. SR requires specific discussion of suitability of detection and suppression systems and Revision 3 Page 93of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension specific analysis unit features that may impact these systems. Include write-up in fire modeling calculations to discuss these attributes.
(Note: This F&O was generated during the January 2008 review).
FSS-09 FSS-09-01 (2008), Closed Qualitative analysis of the smoke analysis is included in This F&O has been resolved by completion This is resolved.
CC I, incomplete individual fire modeling spreadsheets; although the of the smoke damage analysis; no model There is no impact smoke damage approach used is good, this activity is not yet complete. change was required. The smoke damage on the ILRT analysis Smoke analysis has been performed for smoke transport analysis was completed with no new risk- Extension Risk through bus ducts. This analysis needs to be completed significant scenarios identified. Smoke Analysis.
for all affected compartments. damage was evaluated based on the Complete smoke damage analysis for all affected guidance in Appendix T of NUREG/CR-6850.
compartments. The 2010 peer review concluded that SR 1(Note: This F&O was generated during the January 2008 FSS-09 is met at Capability Category 111111.
review).
FSS- FSS-010-01 (2008), Closed Confirmatory walkdowns have not been performed to This F&O has been resolved by a This is resolved.
010 NOT MET, verify that as-built plant conditions or detection, documentation update. Confirmatory There is no impact confirmatory suppression, etc. have been characterized appropriately walkdowns have been performed for fire on the ILRT walkdown of for each analyzed fire scenario. The site has high scenarios per the fire modeling procedure Extension Risk detection and confidence in the accuracy of drawings and initial and documented in the fire modeling Analysis.
suppression system walkdowns used to establish fire scenario parameters workbooks.
not done are accurate; however the information gath~red has not The 2010 peer review concluded that SR been validated. FSS-010 is met at Capability Category 111111.
Perform confirmatory walkdowns to validate fire model inputs.
(Note: This F&O was generated during the January 2008 review.
FSS- FSS-011-01 (2008), Closed Confirmatory walkdowns have not been performed to This F&O has been resolved by a This is closed.
011 NOT MET, confirm that the combinations of fire sources and target documentation update. Confirmatory There is no impact confirmatory sets appropriately represent the as-built plant conditions. walkdowns have been performed for fire on the ILRT walkdown of fire (Note: This F&O was generated during the January 2008 scenarios per the fire modeling procedure as Extension Risk source and targets review). documented in the fire modeling workbooks. Analysis.
not done The 2010 peer review concluded that SR FSS-Of1 is met with a new finding - refer to F&O FSS-011-01 (below).
FSS- FSS-011-01 (2010), Closed F&O: Fire modeling for some of the electrical cabinets DCPP committed to install the incipient OCPP committed 011 MET, crediting the (i.e., Cabinets PK109, RAR, RFWM, RG, detection system in SSPS room and Cable to install the inCiEient detection RNASB/RNARA/RNARB, RN01, RNP1, RNP2, & SEreadin9 Rooms of both Units ~SAPN inciEient detection Revision 3 Page 94of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension system for some of RTFW) located in Fire Compartment 7A include credit for 50365080). It is anticipated that all of the Fire system in SSPS electrical cabinets in incipient detection which is not yet installed. PRA related modifications will be completed room and Cable the Cable Spreading Basis for Significance: Incipient detection has not been prior to the next scheduled Type A tests for Spreading Rooms Room installed accordingly credit for this system does not Units 1 and 2 in the first quarter of 2019 and of both Units reflect current plant conditions., Crediting this detection 2018, respectively (see Section 5.3.1 for (SAPN may mask risk associated with these cabinets. details). The fire areas for the detection 50365080).
system were selected based on risk insights Therefore, this is Possible Resolution: The incipient detection sysJem from the FPRA model being developed as closed, and there should be installed as planned or the scenarios that part of NFPA 805. is no impact on credit this system should be revised to eliminate credit The modeling methodology of crediting and the ILRT for incipient detection.
incorporating the incipient detection system Extension Risk (Note: This F&O was generated during the December (in-cabinet) in the FPRA model followed FAQ Analysis.
2010 review).
08-0046 and is documented in Rev 3 of the Fire Modeling Procedure (EPM-DPFP-001),
Section 8.4.2.
At DCPP the incipient detection system will be installed only in the SSPS and CSR rooms, which are not continuously occupied.
It is not used in an area-wide application or in the Main Control Room.
FSS-E1 FSS-E1-01 (2010), Closed F&O: During conduct of the peer review walkdown in The suggestion F&O has been resolved with This is closed.
MET, validating type compartment 7A it was noted that both heat and smoke a model update. See F&O FSS-CS-01 (2008) There is no impact of detection system detection is provided in the area. This compartment is above. on the ILRT (smoke or heat) protected with a C02 fire suppression system which is Extension Risk credited in the Cable credited for the FPRA. The documentation contained in Analysis.
Spreading room the fire modeling report does not address whether this system is cross-zoned or not. Typically such a system would require activation of one heat or two smoke detectors to activate the C02 system. The fire modeling
- was predicated on activation of a single heat detector which is likely accurate for this system however the system function should be validated and accurate modeling of system response should be documented.
Basis for Significance: Fire modeling parameter needs to be validated.
Possible Resolution: Validate fire detection and suppression system operation and ensure proper modeling.
Revision 3 Page 95of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (Note: This F&O was generated during the December 2010 review).
FSS-E2 FSS-E2-01 (2010), Closed F&O: The basis for the establishment of a fire This F&O has been resolved by additional This is resolved.
MET, use of generic suppression system unavailability factor of 0.01 is not review with no model change required. A There is no impact unavailability for the clear. Documentation included in Section 5.8 of the fire review of plant-specific maintenance and on the ILRT suppression system modeling reports indicates that this value was adopted testing data for fire suppression and Extension Risk based on a lack of plant-specific information and that this detection systems was performed and results Analysis.
value equates to 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> of exposure per year. The documented. It was concluded that these report indicates that the value is based on an estimate of systems have not experienced outlier maintenance activities however no additional detail is behavior compared to the generic data provided. applied in the fire PRA.
Basis for Significance: The rationale used to justify the With this F&O resolved, SR FSS-E2 is use of this unavailability factor is not provided. judged to be met at Capability Category II.
Possible.Resolution: The write-up provided as rationale for this unavailability factor should be expanded to discuss why the 0.01 value is representative or bounding of DCPP fire suppression system unavailability.
(Note 1: This F&O was generated during the December 2010 review).
(Note 2: After the issue of the draft peer review report, PG&E requested that the peer review team revisit this F&O. The review team caucused and decided that the F&O will stay as originally written.).
FSS-E3 FSS-E3-01 (2008), Closed The Fire Modeling and accident sequence analysis does This F&O has been resolved by a This is resolved NOT MET, fire not include a characterization of uncertainty, either documentation update. The uncertainty and the modeling uncertainty qualitative or quantitative. associated with fire modeling has been uncertainty Provide a quantitative characterization of uncertainty identified and characterized in the analysis does not factors in the fire modeling and sequence analysis, for documentation. affect Fire PRA significant fire scenarios, per FSS-E3. The 2010 peer review concluded that SR values used in the ILRT Extension (Note: This F&O was generated during the January 2008 FSS-E3 is met at Capability Category Ill.
Risk Analysis.
review).
Therefore, there is no impact on the ILRT Extension Risk Anal sis.
FSS-F1 FSS-F1-01 (2008), Closed Exposed Structural Steel Analysis/Review has not been This F&O has been resolved by a This is resolved.
NOT MET, exposed performed. documentation update. The exposed There is no impact structure steel on the ILRT Revision 3 Page 96of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension analysis not done Perform Exposed Structural Steel Analysis per FSS-F1 structural steel analysis has been completed Extension Risk to F3. and documented. Analysis.
(Note: This F&O was generated during the January 2008 The 2010 peer review concluded that SR review). FSS-FI is met at Capability Category I/II.
FSS-G1 FSS-G1-01 (2008), Closed Multi-Compartment Analysis has not be performed. This F&O has ~een resolved by a This is resolved.
NOT MET, multi- Complete Analysis for Multi-Compartment Scenarios for documentation update. The multi- There is no impact compartment FSS-G1 to G6. compartment analysis has been completed on the ILRT analysis was done. and documented. Extension Risk (Note: This F&O was generated during the January 2008 Analysis.
review). The 201 O peer review concluded that SR FSS-G1 is met.
FSS-H1 FSS-H1-01 (2008), Closed Documents reviewed are in-progress and at various This F&O has been resolved by completing This is resolved.
NOT MET, lack of levels of completion. Fire modeling is currently in- the analysis and documentation .. Fire There is no impact documentation of the process; the detailed fire modeling analyses have not modeling has been completed and on the ILRT detailed fire been fully documented. Documentation of uncertainty documented in detailed fire modeling Extension Risk modeling, analysis, multi-compartment analysis and fire scenario workbooks. Analysis.
Associated F&Os: confirmatory walkdowns is required. See F&O FSS-E3-01 (2008) (above) for SR H2 through H10. Complete analysis and accompanying documentation. completion of the uncertainty analysis.
(Note: This F&O was generated during the January 2008 See F&O FSS-G1-01 (2008) (above) for review). completion of the multi-compartment analysis.
The 2010 peer review concluded that SR FSS-H1 is met.
FSS-H4 FSS-H4-01 (2008), Closed The input values for each modeling tool used is This F&O has been resolved by completing This is resolved.
MET, incomplete documented in the corresponding attachment to Cale. the analysis and documentation. Fire There is no impact detailed fire File No. 3.11 a; however because the detailed fire modeling has been completed and on the ILRT modeling and modeling task has not been completed satisfaction of this documented in detailed fire modeling Extension Risk documentation of fire SR is not complete. workbooks. Analysis.
modeling inputs. Complete Fire Modeling Task and documentation to satisfy this SR.
(Note: This F&O was generated during the January 2008 review).
FSS-H5 FSS-H5-01 (2008), Closed The fire modeling output results for each analyzed fire This F&O has been resolved by completing This is closed.
CC I, incomplete scenarios are documented in the respective Calculation the analysis and documentation. Fire There is no impact detailed fire File No. 3.11 a attachments; however the completed modeling has been completed and on the ILRT modeling analyses and documentation are not finalized. No documented in detailed fire modeling Extension Risk and parametric evidence of uncertainty evaluations was identified. Fire Analysis.
uncertaint:,: modelin9 results are documented for com~leted Revision 3 Page 97of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension analyses/scenarios; documentation of remaining workbooks. The results of the parameter scenarios must be performed. Parameter uncertainty uncertainty was performed and documented.
evaluations should be conducted to achieve CC-II. The 2010 peer review concluded that SR Complete and document results for remaining scenarios FSS-H5 is met at Capability Category II, with including parameter uncertainty evaluations. a new finding; see FSS-H5-01 (2010) below.
(Note: This F&O was generated during the January 2008 review.
FSS-H5 FSS-H5-01 (2010), Closed F&O: The documentation in the Risk Modeling This F&O has been resolved by a This is resolved.
CC II, lack of Workbooks (Attachment 2 of the Detailed Fire Modeling documentation update. The risk modeling There is no impact documenting the Reports) does not clearly identify the cause of the target workbooks have been revised to identify the on the ILRT cause of the target damage (i.e., heat effects, smoke). Section 5.8 of the cause of target damage. Extension Risk damage, Associated report does discuss the impact of smoke damage, and Analysis.
SRs: FSS-D9 discussions with the analyst indicate that smoke damage is a consideration and can be the cause of target damage. However, the analysis results do not differentiate, and so it cannot be easily determined if target damage is due to smoke.
Basis for Significance: Needed to meet the SR.
Possible Resolution: Document fire modeling output results for each analyzed fire scenario in a manner that facilitates FPRA applications, upgrades, and peer review.
(Note: This F&O was generated during the December 2010 review).
IGN-A4 IGN-A4-01 (2008), Closed DCPP documented their review of plant-specific fire This F&O has been resolved by a This is closed.
CC II, possible experience between 1996 and 2006 in Attachment 10 to documentation update. The two DG fires There is no impact Bayesian update for F.3.6. As stated in Section 5.3, "Based on the review of have been further reviewed and additional on the ILRT Diesel Generator fire the plant fire events and the facts that: ( 1) there was no justification for not using the plant-specific Extension Risk frequency or provide unusual pattern in the fire events, (2) no common-cause experience has been documented. The use Analysis.
justification, problem was identified for two fire events associated with of generic fire frequency data without a Associated SRs: the Diesel Generators, and (3) there were only a small Bayesian update has been specifically IGN-B4. number of "potentially challenging" fire events in last 10 addressed as a source of uncertainty.
years of plant operation, it is decided that a plant-specific update of the generic fire frequencies is not warranted."
However, the two Diesel Generator fires in 20 plant years translate to a rough fire frequency of about 1E-1/plant year. This is approximately an order of magnitude greater than the generic frequency. DCPP should consider either performing a Bayesian update for the Diesel Generator fire frequency or providing a more Revision 3 Page 98of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension detailed justification of the basis for not performing the Bayesian update. If DCPP does not perform the update, they should add this to their list of epistemic sources of uncertainty. (Note: This F&O was generated during the January 2008 review).
QNS-81 QNS-81-01 (2008), Closed Compartments with risk below the screening criteria and This F&O has been resolved by a This is resolved.
NOT MET, lack of the risk results are not documented in F.3.5. It is not documentation update. The documentation There is no impact documenting the possible to verify that all fire areas/compartments was confirmed to list the fire compartments on the ILRT screened fire areas, identified in the plant partitioning have been analyzed. with risk below the screening criteria, Extension Risk Associated SRs: Add a list of all fire areas/compartments analyzed to the including both GDF and LERF. Analysis.
QNS-D1 results in F.3.5, including those below the 1E-07/year The 2010 peer review concluded that SR GDF. QNS-81 is met.
(Note: This F&O was generated during the January 2008 review).
QNS-81 QNS-81-02 (2008), Closed Screening Results as supplied in F.3.5, Step 6.2 do not This F&O has been resolved by a This is resolved.
NOT MET, lack of provide LERF results. LERF results are part of the documentation update. The documentation There is no impact LERF screening screening criteria (and criteria for determining additional was confirmed to list the fire compartments on the ILRT results, Associated modeling for Diablo) identified in Section 5.2. Without with risk below the screening criteria, Extension Risk SRs: QNS-D1 LERF results, some fire areas may not be analyzed, including both GDF and LERF. Analysis.
even though LERF results are too hig.h. Perform and The 2010 peer review concluded that SR document the LERF results in Section 6.2 of F.3.5 for QNS-81 is met.
screened and unscreened fire areas/compartments.
(Note: This F&O was generated during the January 2008 review).
CF-A1 CF-A1-02 (2008), Closed Circuit Failure Probabilities in Attachment 2 are This F&O has been resolved by a model This is resolved.
CC I, circuit failure incorrectly combined when there are multiple cables in a update. The circuit failure mode probability There is no impact probability estimate fire area. For example, two cables with a spurious calculations have been revised to properly on the ILRT involving dependent/ operation probability of 0.1 each are added as 0.1 + combine multiple cable failure probabilities. Extension Risk independent circuits 0.1*(1-0.1) = 0.19. In most cases, when the first cable is The 2010 peer review concluded that this SR Analysis.
(e.g., off-schemeor damaged (and does not spuriously actuate), the was met at Capability Category I with a new interlock circuits) grounding of the cable will blow the fuse of the finding F&O CF-A1-01 (2010).
component. Damage to the second cable will have no impact on the component and should not be considered in the probability calculation. Discussions with the NUREG/CR-6850 authors indicate thatthe write-up on this issue is confusing in NUREG/CR-6850, but the interpretation in Diablo FPRA is not correct for most circuits. Most Com[:!onents include multi[:!le com[:!onents Revision 3 Page 99of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension in each fire area. This means that on average, the spurious operation probabilities used are conservative by a factor of 2.
Use the bounding generic spurious operation probability for each component in each fire area as a starting point.
For components with off-scheme or interlock circuits, which are supplied from an independent power supply should be considered additive. Other circuits should be considered dependent and not additive.
(Note: This F&O was generated during the January 2008 review).
CF-A1 CF-A1-01 (2010), Closed F&O: Detailed circuit failure analyses have been This F&O has been resolved with a model This is resolved.
CC I, detailed circuit performed and documented. However, only a few of the update. The circuit failure probabilities were There is no impact failure calculation circuit failure probability calculations make use of the updated for basic events yvith risk reduction on the ILRT based on specific methodology provided in FAQ 080047. A substantial worth (RRW) values greater than 1.05 for fire Extension Risk circuit configuration number of risk significant components (based on RRW) CDF and LERF employing the FAQ 08-0047 Analysis.
for risk significant need to have circuit failure probabilities updated, since methodology.
components using
- the current calculations are conservative. Additionally, With this F&O resolved, PG&E judges that appropriate method for probabilities with more than two events, the equations SR CF-A 1 is now met at Capability Category (e.g., FAQ 08-047) in Attachment 2 should be checked. For example, with 3 111111, based on consideration of the specific events A, B and C, the exclusive OR calculation should circuit configuration for risk-significant be: A+ B + C - A*B - A*C - B*C + A*B*C components.
Basis for Significance: CC 11/111 requires that risk-significant events have circuit failure calculations performed based on the specific circuit configuration and appropriate method (FAQ 08-0047).
Possible Resolution: Review the risk rankings for fire induced failures and spurious events. Calculate the conditional failure probabilities for these events based on the specific circuit configuration and accounting for the method discussed in FAQ 080047.
(Note: This F&O was generated during the December 2010 review).
CF-A2 CF-A2-01 (2008), Closed Uncertainty values and distribution types for the circuit This F&O has been resolved with a This is resolved.
NOT MET, failure probabilities was not provided in the analysis files, documentation update. The documentation There is no impact .
Uncertainty values CF tables or in RISKMAN. was revised to add a discussion on on the ILRT and distribution
- The CF values are from NUREG/CR6850, Chapter 10. distribution types and uncertainty values for Extension Risk types for the circuit Use of these and an assumed distribution can be used to the circuit failure probabilities. Analysis.
Revision 3 Page 100of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Cat II Requirement
- Status Finding/Observation Disposition Extension failure probabilities characterize the uncertainty for each spurious operation The 2010 peer review concluded that SR CF-was not provided. probability. When spurious operation probabilities are A2 is met.
combined, the riew uncertainty may need to be estimated. *
(Note: This F&O was generated during the January 2008' review).
- HRA-A3 HRA-A3-01 (2010), Closed' Section 6.4 of Calculation File No. F.3.12, "Post-fire This F&O has been resolved by additional This CC II, basis for Human Reliability Analysis" states that the FPRA review and update of the documentation. The documentation screening undesired screened all undesired actions in response to spurious screening basis for all annunciators and issue is resolved.
actions in response annunciators [and indications]. The basis for screening indications was reviewed and confirmed to be There is no impact to spurious many spurious or erroneous indications .is either acceptable. The specific examples identified on the ILRT annunciators inadequate or not provided in the FPRA documentation. were corrected in the documentation. Extension Risk Examples: Analysis.
- F.3.2, Attachment 7 identifies 6 alarms that could result in operator taking action without any other cues. The actions taken in response to these spurious annunciators were determined to be recoverable, and were screened based on the fact that the recovery action was estimated to be less than 5E-2. There is no basis for Why this screening level is appropriate.
- There are some adverse actions listed in F.3.12 Table C-4 that do not appear to be discussed or dispositioned anywhere else (e.g., E-1, steps 14, 16, and 17).
- There are many alarm responses in Attachment 7 of F.3.2, (pages 18, 19 and 20), which do not require verification, but had been screened out without proper basis.
- The screening disposition for several operator actions in F.3.12 Table C-2 does not appear to be complete. For spurious RWST level indication, the screening disposition states that the spurious indication "Could be screened" based on redundancy, but there is an open-ended "However. .. " at the end of the disposition.
There are other examples in Table C-2 where the screening criteria are not definitive, as the disposition states "Could be screened ... " (e.g., E-0, Steps'26 and Revision 3 Page 101 of 117 ,
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension 27). The screening criteria should be stated explicitly, as opposed to suggested with the phrase 'could be.'
HRA-81 HRA-81-01 (2008), Closed The validity of the actions as they were defined and This F&O has been resolved by additional This is resolved.
MET, additional evaluated for the internal events PRA has generally be evaluations and model updates. A review There is no impact instrumentation considered appropriately as they are carried over into the was conducted of operator actions to identify on the ILRT beyond that explicitly FPRA. The availability of indications, context for the additional equipment or cables to be Extension Risk addressed in the actions, etc., has been assessed in modifying the evaluated; this included the feed-and-bleed Analysis.
internal events PRA existing analyses to apply for fire scenarios. action.
(e.g., RCS pressure One potential exception was encountered. The HFEs and temperature relating to failure to initiate feed-and-bleed cooling (e.g.,
indications in event ZHEOB1_0) account for indications relating to support of Bleed and steam generator level. These indications provide the Feed operation. cues for initiating feed-and-bleed cooling. The procedure includes a caution and instructions for maintaining RCS conditions (pressure and temperature) within bounds to ensure adequate heat removal but not excessive cool down. For the internal events, this control function is not addressed; it is implicitly taken to be successful. There are sufficient indications of RCS conditions and the time available is such that this is probably adequate. For some plants, at least, this control function can be critical to the long-term success of the action. For the DCPP fire analysis, the availability of only equipment and cables associated with steam-generator levels have been addressed for this HFE. If control is required and if instruments needed to support control could be affected by fires in particular compartments\ this is not being tracked. This is an element of the manner in which the HFEs are addressed as they are adapted from the internal events PRA to the fire analysis that needs to be considered. It is expected to affect a very small number of HFEs.
This event should be evaluated to determine if additional equipment and cables should be addressed. A review should be made of other HFEs for which additional instrumentation beyond that explicitly addressed for internal initiators (and therefore captured for the fire analysis) is credited.
Revision 3 Page 102of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Obseniation Disposition Cat II Requirement Extension (Note: This F&O was generated during the January 2008 review).
HRA-C1 HRA-C1-01 (2008), Closed R-1736044-1728, Dated August 10, 2007, documents The internal events HRA was updated in This is closed.
NOT MET, open the results of the Diablo Car:iyon focused scope Peer 2012 and included review and resolution of There is no impact F&Os from the Review of HRA. This document contains a number of the previous F&Os. Results of the updated on the ILRT focused peer review Facts and Observations documenting specific issues internal event HRA were incorporated into Extension Risk of HRA in 2007 affecting the application of the methodology in general the fire HRA. Analysis.
and some specific HFEs. These F&Os have not been The 2010 peer review concluded that SR resolved for the Level 1 HRA as yet. There was no HRA-C1 is met at Capability Category II with indication that DCPP had reviewed these issues for any a new finding F&O HRA-C1-01 (2010).
impact on their fire HRA. Several of these new F&Os were reviewed to determine if any of identified issues had the potential to influence the fire HRA and to determine if the impacted HFEs had carried over to the Fire HRA. In the limited spot-check, two such HFEs, ZHEF04 and ZHOE1, were identified. They are associated with the new F&Os, HR-F2-1, HR-G3-2 and HR-G3-3. The issues identified in these F&Os could be influenced by fire conditions. There is no indication that DCPP had reviewed these issues in preparing the fire HRA. There is some indication that the DCPP's methodology for developing screening HEPs may, at least in part, cover some of the issues. Note that for ZHECV1, one of the other HFEs referenced one of the fire variants for this HFE, ZHECV1_0, but only the base case was quantified in the HRA course. Furthermore, Table 2 and Table A-1 contain the base case value and the _o case value.
DCPP needs to review the F&Os in H1736044-1728 to determine if any of the issues could be influenced by a fire and if so any of the impacted HFEs carried over into the FPRA were. DCPP should then identify how they addressed these issues in the fire HRA.
(Note: This F&O was generated during the January 2008 review).
HRA-C1 HRA-C1-02 (2008), Closed HFEs adapted from the internal events PRA have been This F&O has been resolved by completion This is closed.
NOT MET, no evaluated for general fire conditions, using bounding of the detailed analyses for the important There is no impact detailed analyses parameters for some elements of the analysis. operator actions modeled in the fire PRA. on the ILRT address in Revision 3 Page 103of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension conditions Additional cause-based mechanisms (in the cause-based The 2010 peer review concluded that SR Extension Risk associated with a decision-tree method that forms the basis for assessing HRA-C1 is met at Capability Category II with Analysis.
specific fire scenario. the s;ognitive contribution in their HRA approach) have a new finding F&O HRA-C1-01 (2010).
been considered to account generally for fire conditions.
For example, branch points different from those for the equivalent HFE in the internal events PRA are selected for cases in which the fire scenario implies that a partial set of indications would be available In addition, the recovery factors internal to the cause-based assessment have been set to 1.0, rather than retained at the values assessed for the HFE in the internal events PRA. The execution assessment has also been modified, both to remove this internal recovery and to increase the execution time. For HFEs reflecting actions identified from the fire response procedure, a screening assessment has been performed. No detailed analyses of HFEs have been completed, either to address conditions associated with a specific fire scenario, or to adjust further the factors treated as bounding in the analysis. This process is planned as the fire quantification progresses, but clearly has not been completed. Moreover, it would appear likely that at least some HFEs would need to be treated using a time-reliability correlation, because the cause-based approach may not adequately capture time constraints. It is not clear that this is planned at the current time.
The detailed assessment of fire scenarios will need to be supported by detailed treatment of HFEs. The detailed assessment will need to be completed for fire scenarios that contribute to core-damage frequency. Moreover, it is likely that additional methods will need to be applied to assess HFEs corresponding to time constrained actions.
(Note: This F&O was generated during the January 2008 review).
HRA-C1 HRA-C1-01 (2010), Closed F&O: Human action dependencies have been accounted This F&O has been resolved by completion This is closed.
CC II, HRA for in the FPRA. The internal events HRA (from which of the fire PRA HRA dependency analysis. There is no impact dependency analysis the Fire HRA events were developed) dependency on the ILRT analysis is complete, and only four new fire-specific Extension Risk events have been added. The final check for de~endent Anal:z'.sis.
Revision 3 Page 104of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS St t Impact on ILRT SR Finding/Observation .Disposition Cat II Requirement a us Extension operator actions (quantification of the FPRA with HEPs set to a high value) has not been completed.
Basis for Significance: The evaluation with all HEPs set to a high value will ensure that no dependencies have been overlooked.
Possible Resolution: Check for dependent HFEs in the FPRA model by quantifying it with HEPs set to a high value.
(Note: This F&O was generated during the December 2010 review).
HRA-D1 HRA-01-01 (2008), Closed No recovery analysis beyond the HFEs included initially This F&O has been resolved by a model This is closed.
NOT MET, recovery in the model has yet been identified. For example, some update. A review of the dominant scenarios There is no impact actions for risk scenarios that appear to be contributing include loss of and areas was conducted, and appropriate on the ILRT significant fire offsite power independent of the fire effects. recovery actions were added to the model. Extension Risk scenarios Consideration of the recovery of offsite power has not yet Screening analyses were initially Analysis.
been made. Consideration of recovery will be necessary incorporated followed by detailed analyses in conjunction with the definition and assessment of for the important operator actions modeled.
detailed fire scenarios. The 2010 peer review concluded that SR The recovery analysis will need to be performed as the HRA-01 is met at Capability Category II.
sequence quantification progresses from bounding to detailed.
(Note: This F&O was generated during the January 2008 review).
HRA-E1 HRA-E1-01 (2008), Closed F.3.12, the fire HRA analysis report contains a set of The internal events HRA was updated in This is closed.
NOT MET, open assumptions (see page 3 of 1167). The first assumption 2012 and included review and resolution of There is no impact F&Os from 2007 is "The internal events PRA and HRA are complete and the previous F&Os. Results of the updated on the ILRT focused HRA peer in compliance with the ASME PRA Standard [1] Category internal event HRA were incorporated into Extension Risk review II as endorsed by Reg. Guide 1.200 ". However, R- the fire HRA. Analysis.
1736044-1728, Dated August 10, 2007, documents the The 2010 peer review concluded that SR results of the Diablo Canyon focused scope Peer Review HRA-C1 is met at Capability Category II with of HRA. This document contains a number of Facts and a new finding F&O HRA-C1-01 (2010).
Observations documenting specific issues affecting the application of the methodology in general and some specific HFE. These F&Os have not been resulted for the Level 1 HRA as yet. Based on these F&Os, several of the RA-Sb-2005 HRA SRs are identified as being not met. Thus, it cannot be uneguivocally stated that the Revision 3 Page 105of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension DCPP HRA is in full compliance with the ASME PRA Standard.
DCPP needs to address/resolve the new F&Os in R-1736044-1728, Dated August 10, 2007.
(Note: This F&O was generated during the J.anuary 2008 review).
HRA-E1 HRA-E1-02 (2008), Closed Documentation of the initial (screening or bounding) This F&O has been resolved by completion This is closed.
NOT MET, methods has been completed, but the manner in which of the detailed HRA analyses and There is no impact uncertainty analysis more detailed assessments will be performed is not yet documentation of uncertainty considerations. on the ILRT documented. The detailed assessments of HFEs and of The 2010 peer review concluded that SR Extension Risk recovery actions are not yet documented because the HRA-E1 is met. Analysis.
analyses have not 1been performed. Documentation of assumptions and sources of uncertainty has also not yet been done. Documentation currently is limited to the methods used for the general treatment of HFEs as they are adapted to the FPRA, and for the screening analysis of HFEs associated with actions identified from the fire response procedure.
Documentation of the detailed treatment of HF Es, of recovery analyses, and of the assumptions and uncertainties will need to be developed.
(Note: This F&O was generated during the January 2008 review).
SF-A1 SF-A1-01 (2010), Closed F&O: Diablo Canyon Calculation F.3.13, Rev. 0 covers This F&O has been resolved by a This is closed.
MET, clarify which Seismic-Fire interaction. This calculation uses a part of documentation update. The documentation There is no impact areas were the IPEEE submittal as the basis to conclude that all fire was revised to demonstrate the areas on the ILRT considered in the scenarios resulting from an earthquake are identified and considered in the IPEEE walkdown were Extension Risk IPEEE walkdown qualitatively analyzed. The IPEEE submittal bases much consistent with the global plant analysis Analysis.
of these conclusions on a walkdown. While the boundary (GPAB) considered in the current identification of seismically-induced fires appears to be fire PRA, and that the conclusions reasonable, the IPEEE does not provide sufficient adequately support the seismic-fire documentation of what areas were considered and what interaction analysis.
areas were screened out. At present, there does not appear to be sufficient documentation to support the conclusions relating to this SR in the calculation.
Basis for Significance: The SR is judged to be met, even though this supporting information is needed to meet the SR. The reguired information is needed to fully meet the Revision 3 Page 106of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension SR. Note, however, that item this item does not impact the results of the FPRA.
Possible Resolution: It is recommended that either the supporting data for the IPEEE plant walkdown be reviewed to provide more bases for identifying seismic-fire interaction scenarios, or another walkdown be done and documented to identify seismically induced fires in support of this SR.
(Note: This F&O was generated during the December 2010 review).
SF-A3 SF-A3-01 (2010), Closed F&O: The SR SF-A3 requires assessment of the This F&O has been resolved by a This is resolved.
MET, no clear potential for common-cause failure of multiple fire documentation update. The documentation There is no impact conclusion that SR suppression systems due to the seismically-induced was revised to disposition CCF of fire on the ILRT SF-A3 is met. failure of supporting systems. Diablo Canyon Calculation protection systems due to a seismic event as Extension Risk F.3.13, Rev. 0 addresses seismic-fire interaction. Section not credible. Analysis.
6.2 addresses SR SF-A3. While there is a lot of supporting information in this section, there is no.clear conclusion made that this SR is met. There needs to be a clear conclusion drawn that the SR is met based on the supporting information.
Basis for Significance: Even though the review team concluded that this SR is met, this item is needed to meet the SR.
Possible Resolution: Rewrite Section 6.2 of the Calculation F.3.13 to draw the conclusion that SR SF-A3 is met.
(Note: This F&O was generated during the December 2010 review).
SF-A5 SF-A5-01 (2010), Open F&O: Diablo Canyon Calculation F.3.13, Rev. 0 covers Update to the training program is being The status of MET, TQ1.DC12 Seismic-Fire interaction. In this calculation it was noted tracked by a plant action item, and will be training has no needed to be revised that a Notification SAPN 50294777 (Task 23) has been closed when SAP Notification50294777, impact on created to revise TQ1 .DC12 to include fire brigade Task #23 is implemented fully. The status of calculations of risk training to cope with a seismically-induced fires and training has no impact on calculations of risk changes associated system, ~quipment, communications and changes associated with the ILRT Extension associated with brigade ac_cess logistics. This recommendation needs to Risk Analysis. the ILRT be implemented in order to meet this SR. The review Extension Risk team is judging this SR to meet, however, an F&O has Analysis.
Therefore, there is Revision 3 Page 107of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension been written to require implementation of this no impact on the recommendation .. ILRT Extension Basis for Significance: The SR is judged to be met Risk Analysis.
assuming that_this recommendation is being implemented.
Possible Resolution: Implement the suggested recommendation.
(Note: This F&O was generated during the December 2010 review).
FQ-B1 FQ-B1-01 (2008), Closed The sequence quantification is in process but is in a This F&O has been resolved by completion This is closed.
NOT MET, complete preliminary state. It does not yet meet the requirements of quantification of the fire PRA model and There is no impact quantification and of FQ-B 1, FQ-01, FQ-E1 and FQ-F1. Completion of the the associated documentation. on the ILRT document the quantification process is obviously essential for the fire The 2010 peer review concluded that SR FQ- Extension Risk results, Associated analysis. - 81 is met with on new F&O FQ-B1-01 (2010). Analysis.
SRs: FQ-C1, FQ-D1, It is expected that the quantification process will be FQ-E1, and FQ-F1. carried through consistent with the manner in which it has been started.
(Note: This F&O was generated during the January 2008 review).
FQ-B1 FQ-81-01 (2010), Closed F&O: The FPRA does not achieve convergence: at the This F&O has been resolved by a model This is closed.
MET, truncation current truncation level of 1E-8. below the scenario _ update. The truncation level in the fire PRA There is no impact analysis, Associated frequency. Establishing a proper truncation level is model is documented to demonstrate on the ILRT F&Os: FQ-F1-01. required by QU-B2 and QU-83 (the QU-8 SRs are convergence. Extension Risk referenced in FQB1). The FPRA truncation is discussed Analysis.
in F.3.5, Appendix S; the increases in GDF and LERF by lowering the truncation one order of magnitude are 12%
and 24%, respectively.
Basis for Significance: A proper truncation level is required to ensure that quantification results properly reflect the risk contributors, and that significant sequences and/or contributors are not eliminated. The increases in GDF and LERF by lowering the truncation frequency by one order of magnitude are greater than 5% (QU-B3 requirement).
Possible Resolution: Use lower truncation limit or address model issues which may be causing convergence problem.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension (Note: This F&O was generated during the December 2010 review).
UNC-A1 UNC-A 1-01 (2008), Closed The FPRA shall identify key sources of CDF and LERF This F&O has been resolved by completion This is resolved.
NOT MET, uncertainties, including key assumptions and modeling of the uncertainty and sensitivity analyses There is no impact uncertainty analysis approximations. These uncertainties shall be and documentation. on the ILRT not done, Associated characterized such that their impacts on the results are The 2010 peer review concluded that SR Extension Risk SRs: UNC-A2, understood. Uncertainty and sensitivity analysis have UNC-A1 is met with one new F&O UNC-A1- Analysis.
UNCA3 not completed yet, Items could not be verified for SRs 01 (2010).
UNC-A1, UNC-A2 & UNC-A3 therefore, assumed as not met.
Once the FPRA model becomes stable, perform the CDF and LERF uncertainties, including key assumptions and modeling approximations.
(Note: This F&O was generated during the January 2008 review).
MU-A1 MU-A1-01 (2008), Closed DCPP has an Administrative Procedure for Control of the This F&O has been resolved by updating the This is closed.
MET, update PRA PRA, TS3.NR1. While this procedure is written at a administrative procedures to address There is no impact administrative relatively high level, but appears to focus primarily on the changes in PRA technology and industry OE. on the ILRT procedures .to internal events PRA. DCPP intends to use this process The 2010 peer review concluded that SR Extension Risk include fire for control of the maintenance and update of the FPRA. MU-A 1 is met. Analysis.
considerations, In general, the process in TS3.NR1 appears to be Associated SRs: applicable for the FPRA but it should be modified to MUA2, MU-81 specifically address fire specific issues.
through 84, MU-C1, For this review, TS3.NR1 was reviewed against the MU MU-E1, MU-F1 SRs which are based on Section 5 of RA-Sb-2005 with the assumption that the words "FPRA" are inserted for "PRA" and assuming that DCPP will update the process to specifically address the FPRA and any unique _aspects thereof.
DCPP should update TS3.NR1 to specifically address the FPRA and any unique aspects thereof. In particular, TS3.NR1 and appropriate plant process and procedures should be updated to require monitoring changes to the Fire Protection Program and evaluating any plant changes that impact the Fire Protection Program for potential impact on the FPRA. Section 5.4, PRA Software should also be modified to explicitly call out any codes such as Modular Accident Analysis Program Revision 3 Page 109of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Impact on ILRT SR Status Finding/Observation Disposition Cat II Requirement Extension (MMP), the HRA Calculator or fire modeling codes that are not are ready controlled under other QA requirements.
(Note: This F&O was generated during the January 2008 review).
Update from PRA RAI 1.m: F&O MU-A 1-01 (2008) observes that the PRA administrative procedure focuses on internal events, and therefore needs to be updated to address the FPRA per the guidance in the PRA Standard. F&O MU-A2-01 (2008) observes that the licensee's procedure does not require monitoring changes in PRA technology and industry experience.
The disposition to these F&Os explains that "DCPP Procedures AWP E-028 and TS3.NR1 will provide the overall program of the PRA model maintenance and upgrade." Though implementation Item S-3.26 of the LAR commits to new pli:int administrative procedure AWP E-028 for scheduling updates and controlling associated models and files, there does not appear to be a process for updating the applicable administrative procedures. It is not clear whether improvements to the applicable administrative procedures have been performed yet. Explain whether the cited improvements to the administrative procedures have already been performed or are.included in an existing implementation item listed in LAR Attachment S, Table S-3. If the cited improvements have not yet been made and are not described in an existing implementation item, then discuss the method to ensure that the cited improvements in FPRA procedure TS3.NR1 will be made before it is used as a basis in self-approval of post-transition changes.
MU-A2 MU-A2-01 (2008), Closed DCPP has an Administrative Procedure for Control of the This F&O has been resolved by.updating the This is closed.
NOT MET, include PRA, TS3.NR1. This procedure does not explicitly administrative procedures to address There is no impact monitoring, require monitoring changes in PRA technology and changes in PRA technology and industry OE. on the ILRT reviewing changes in industry experience. The 2010 peer review concluded that SR Extension Risk PRA technology and Update Section 5.1.3 of TS3.NR 1 to explicitly require MU-A2 is met. Analysis.
industry OEs monitorin1:1/reviewin1:1 chan1:1es in PRA technololi!;t and Revision 3 Page 110of117
54006-CALC-01 Evaluation of Risk Significance of Perma,nent ILRT Extension Table A-3 Fire PRA Peer Review - Facts and Observations 2009 ASME/ANS Status Impact on ILRT SR Finding/Observation Disposition Cat II Requirement Extension industry experience on an every other Unit 2 outage basis.
(Note: This F&O was generated during the January 2008 review).
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement The seismic peer review was performed against a draft version of the Diablo Canyon seismic PRA model, which used updated hazard and fragilities analyses. As noted, the current seismic PRA model, which uses the existing hazard analysis and fragilities, is proposed to be used for the ILRT Extension; therefore, the F&Os for the seismic hazard model (SHA) and seismic fragility model (SFR) elements do not apply to the model proposed to be used.
SPR-81 SPR-81-01, MET, Open Observation: The human action analysis is carried forward from the This F&O is judged to have no significant basis for delay time internal events is adjusted based on time delay defined in Attachment 1, impact on the ILRT Extension Risk in seismic HRA Evaluate Seismic Event Mitigation Strategies (Task 2). The delay times Analysis. The seismic HRA is rel.atively are generic for all actions and it is not clear how they were defined. The unimportant, and any increase in HEP refined results for the first 3 ranges seem to be overly refined given the values would not have a significant impact experience database. Further, a task analysis for the additional work on seismic risk.
load in response to the seismic event was not documented Basis for Significance: It is believed that the seismic influence is considerable with relation to operator stress particularly with regard to higher accelerations. The timing consideration is one factor to address due to delayed responses occurring as operators recover from the effects of the seismic event. The current timing impacts the OCR/TRC method but does not appear to influence the C8DTM method. Given that the internal analysis already assumes a high stress level the net result is that the proceduralized actions are effectively insensitive to seismic effects which seem unrealistic and controlled by the methods selected.
Possible Resolution: A re-evaluation of the actions with regard to the seismic evaluation and considerations with regard to the methods selected and perform a reasonableness assessment of the results. In any case the rationale for the generic time and the changes in delay time by acceleration range needs to be sufficiently documented to provide adequate support the final approach.
SPR-81 SPR-81-02, MET, Open Observation: The model for lower acceleration credits the restoration of This F&O has no impact on the ILRT diesel mission time the diesel generators. The assessment appears to assume the same Extension Risk Analysis. The DG recovery conditions and timing as found in the internal events analysis assuming a is only credited for non-seismic failures for 6-hour mission time. This appears to be inconsistent with the general lower acceleration earthquakes. No diesel guidance for the study that the EDGs are to function for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> due to recoveries are credited for scenarios in the impact of the seismic event on the offsite grid which the components suffer a seismic Basis for Significance: The use of the internal events analysis is based failure; therefore, the impacts of the seismic on a convolution using experience data for all causes of offsite power event on the recovery action will be loss and is not consistent with the situation being addressed. Use of this . minimized. The failure probability and basis value for seismic is not appropriate. was reviewed and confirmed to be correct for seismic events.
Possible Resolution: Revise the assessment to be based on 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
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54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review- Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement SPR~81 SPR-81-03, offsite Open* Observation: The fragility for the offsite power is based on DCL-90-205 This F&O will be resolved by additional power fragility which examines the seismic capacity for the 230kV switchyard. It does review and model update if required. The not address external impacts of transmission lines to the site or potential current SPRA model provides a reasonable for other failures that would occur beyond DCPP. estimate of the seismic CDF and LERF for Basis for Significance: The typical value for the median capacity for the purposes of the ILRT extension risk offsite power is on the order of 0.3g mpga (0.7 MSA) and it would be analysis.
expected that a probability of failure at DCPP would exceed that found for most plants due to the awareness of seismic impacts. The documentation indicates a performance of 1.4g MSA (ZOSPWR). The first seismic range is from 0.2g MSA to 1.25 MSA and the associated probability (SOP1) is 0.0144. Given that the capacity should cross 0.5 somewhere over this range, the calculated value appear to understate the probability. Further the next range is up to 1. 75g MSA with an average value of 5.37E-01. Overall the range appears to be under predicting the likelihood of a loss of offsite power.
Possible Resolution: Review the method and determine if the calculation is accurate.
SPR-82 SPR-82-01, NOT Open Observation: The current HFE basis appears to not include any impacts This F&O has no significant impact on the MET, operator gained from operator interviews related to how the seismic event would ILRT Extension Risk Analysis. The seismic interviews in HFE impact timing or other stress factors necessary to adjust the internal HRA is relatively unimportant, and any basis events HFE for seismic. The basis for selecting generic time delays used increase in HEP values would not have a to modify time delay does not appear to be based on any consideration significant impact on seismic risk.
for timing and the complexity of the scenario. It also appears to have little impact on the assessed unreliability for the seismic-specific events.
Basis for Significance: The time windows and cues would be altered based on the seismic event. Following any significant seismic event staff will be involved in verification activities which may delay subsequent activities modeled in the PRA and slow response. Stress may also be present for larger seismic events as the operations staff will have increased workload restoring the plant following the event.
Possible Resolution: Re-baseline the timing for events addressed (counted) in the SPRA using additional operator discussions and considering as a minimum the impact of higher accelerations in terms of work load.
SPR-82 SPR-82-02, NOT Open Observation: No dependency assessment has been developed for the This F&O has no significant impact on the MET, seismic HRA seismic PRA at this point. ILRT Extension Risk Analysis. The seismic dependency HRA is relatively unimportant, and any Revision 3 Page 113of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement Basis for Significance: The current assessment does not account for increase in dependent HEP values would dependence between postulated operator actions as is required by back not have a significant impact on seismic reference HR-G7. risk.
Possible Resolution: Define the HFE combinations in the seismic PRA and complete the assessment for dependence in keeping with the standard.
SPR-83 SPR-83-01, NOT Open Observation: The standard requires defined criteria and documentation This F&O has no impact on the ILRT MET, no of the screening process. The DCPP SPRA does define the criteria for Extension Risk Analysis. Because the acceleration the screening (SS Cs with capacity >11 g); however, there is no original seismic PRA model was developed screening criteria description of*usage of a systematic process for screening SSCs for the concurrent with the internal events PRA DCPP SPRA model. model, no screening was used. Updating Possible Resolution: Add documentation that considers and the documentation to better describe this dispositions all plant equipment for inclusion in the SPRA model, and process will not impact the calculations of clearly provide a documented basis for the final SEL for which the risk changes for the ILRT Extension Risk fragilities are developed and used in the SPRA quantification. Provide a Analysis.
list of the screened out SS Cs in a table so that this process is understood by future reviewers.
SPR-88 SPR-88-01, NOT Open Observation: The model includes a recovery of the Emergenc/'f:Jlesel The diesel generator recovery referenced MET, EOG Generators (EOGs) following a seismic event with an intensity where by the reviewer is only credited for non-recovery they did not fail due to seismic considerations but rather. due to random seismic failures for lower acceleration failures. The analysis appears to utilize the same analysis as utilized in earthquakes. No diesel recoveries are the internal events analysis without alteration and is based on a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> credited for scenarios in which the duration. components suffer a seismic failure Basis for Significance: The use of a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> duration would be therefore the impacts of the seismic event inconsistent with the ground rules applied in the seismic model and on the recovery action will be minimized.
would understate the probability of failing to restore onsite sources. It is The diesel basic events in the seismic also not considered appropriate to include non-seismic experience for model use a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time.
higher accelerations due to resources being displaced to address other plant issues. The standard curves found in most the literature are not considered appropriate.
Possible Resolution: Review the existing assessment and ensure that the EOG recovery is consistent with the need to provide onsite power for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. If EOG recovery is retained, it should be adjusted to reflect the impact that increasing severity and the potential for aftershocks are addressed.
SPR-89 SPR-89-01, CCI, Open Observation: No time or task analysis seems to be developed or This F&O has no significant impact on the*
time-motion study documented to provide the basis on an individual action to demonstrate ILRT Extension Risk Analysis. The seismic Revision 3 Page 114of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement the ability to perform the action and to estimate not only initial delay but HRA is relatively unimportant, and any delays in diagnosis and implementation. increase in HEP values would not have a Basis for Significance: The current assessment only captures in a very significant impact on seismic risk. The time general basis the initial delay and does not provitje any delay impact for delay used in the seismic HRA was based resources being diverted or delayed to do on scenario specific interviews with Operations personnel; therefore, it is expected that these values are valid, and therefore additional documentation may be needed to resolve this F&O.
SPR~B11 SPR-811-01, MET, Open Observation: Table 1 in PRA Calculation F.6 includes a number of This F&O has is judged to have no seismically induced failure modes that would result in loss on inventory with the potential for significant impact on the ILRT Extension floods flood impacts that go beyond the local seismic failure. For example, Risk Analysis. The unconditional seismic Containment Spray Pump failure mode is line break, loss of contents. failure probability for SSCs that could result These failure modes should be considered during the seismic-induced flooding was reviewed to estimate the flood walk down. impact of this issue. In all cases, the total Basis for Significance: Equipment failure modes include a number of unconditional failure probability for these potential flood sources. types of SSCs (piping, tanks, etc.) was less than 1 E-06. Therefore, the potential impact Possible Resolution: Examine the potential for expanded damage from of additional seismically induced flooding is seismically induced flood during the walk down. not significant. Therefore, resolution of this F&O is judged not to significantly impact the calculations of risk changes for the ILRT Extension Risk Analysis.
SPR-C1 SPR-C1-01, MET, Open Observation and Basis for Significance: The DC SPRA model reflects This F&O has no adverse impact on the chattering of solid the as-built, as-operated plant with some exceptions. These include the ILRT Extension Risk Analysis.
state relays conservatism assumption related to the solid state protective relays on Conservatisms in the seismic response of
- the 4kV breakers and the updated charging pump. components will not adversely impact the Possible Resolution: Evaluate the impact of the solid chatter of relays calculations of risk changes for the ILRT and the charging pump. Extension Risk Analysis.
SPR-E1 SPR-E1-01, MET, Open Observation: Due to the definition of the hazard bins, the failure fragility This F&O has no adverse impact on the expand number of probability for offsite power (SOP) has a value of 0.014 in the first bin and ILRT Extension Risk Analysis. The issue is bins to allow for a 0.54 in the second bin. The discrete bins do not provide a good how the initiator binning is used to credit better fragility representation of the offsite power fragility curve in this range. While . operator recovery actions. Because the representation RISKMAN properly handles this in the fragility calculation with the use of upper bin boundary was used in developing 1OD-bin representation of the fragility curve in each initiator bin, the use operator actions and not bin midpoint of the mid-point may not accurately reflect the range of plant conditions values, the operator actions are for HRA and recovery. conservative for a given range of Revision 3 Page 115of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement Basis for Significance: Due to the range of the first bin compared to acceleration. If additional binning is added, the change in fragility for offsite power, it is possible that the first bin is it is possible that more credit could be non-conservative for the upper portion of that bin. taken for a recovery action at lower Possible Resolution: Expanding the number of bins would allow for a accelerations. Therefore, resolution of this better representation of fragility in discrete bins. F&O would not to adversely impact the calculations of risk changes for the ILRT Extension Risk Analysis.
SPR-E1 SPR-E1-02, MET, Open Observation: In the definition of the hazard bins, the last bin represents This F&O has no impact on the ILRT expand bins 3 to 4g median acceleration. However, at this level, the conditional Extension Risk Analysis. Redefining the covering hazard probability of large early release (CLERP) is still well below 1.0. The hazard bin to ensure LERF importance can above 4.0g current model accounts for this by assuming that the value of CLERP for be assessed has no impact on the earthquakes above 4g is 0.1, and applying this residual to the LERF calculations of risk changes for the ILRT results outside the RISKMAN model. While this may be a reasonable Extension Risk Analysis.
assumption with regard to the total LERF value, it results in loss of information regarding the relative importance of LERF contributors ..
Basis for Significance: This approximation results in loss of information regarding the contributors to LERF.
Possible Resolution: Expand the number of hazard bins, with bins that represent the hazard above 4.0 g. The last bin should be chosen so that the CLERP value is close to 1.0.
SPR-E1 SPR-E1-05, MET, Open Observation: The RISKMAN event tree ELECPWR appears to have an This F&O will have no significant impact on error in ELECPWR error in the rules for top event DH, specifically split fraction set DH1 SB to the ILRT Extension Risk Analysis. A review DH63SB. These use the macro SEISB when they should be using of the error concluded that it will not impact "SEISA + SEISB." the results of the seismic PRA, and Basis for Significance: This error will likely not be important to the therefore will not impact the calculations of results because it represents the lower acceleration bins. In addition, this risk changes for the ILRT Extension Risk was the only error identified in the seismic-related rules that were re- Analysis.
reviewed.
Possible Resolution: Correct the error and verify that the error was not important to the results.
SPR-E5 SPR-E5-01, NOT Open Observation: PRA Calculation C.9 provides point estimates for CDF This F&O has no impact on the ILRT MET, no and LERF, but does not address uncertainty distributions. Extension Risk Analysis. Seismic uncertainty Basis for Significance: The SR requires estimating or addressing parametric uncertainty analysis does not distribution uncertainty distributions for CDF and LERF. impact the quantitative results and will not provided impact the calculations of risk changes for Possible Resolution: Use RISKMAN Monte Carlo tools to calculate the ILRT Extension Risk Analysis.
uncertainty distributions for CDF and LERF.
Revision 3 Page 116of117
54006-CALC-01 Evaluation of Risk Significance of Permanent ILRT Extension Table A-4 Seismic PRA Peer Review - Facts and Observations SR 2009 ASME/ANS Status Finding/Observation ILRT Disposition Cat II Requirement SPR-F1 SPR-F1-01, NOT Open Observation: The SPRA documentation says in a number of places that This F&O has no impact on the ILRT MET, modeling of the SPRA takes no credit for cross ties between Units following a seismic Extension Risk Analysis. The issue was cross ties between event (e.g., Page 2 of Attachment 2 to F.6). However, the RISKMAN reviewed and it was determined that the Units event tree model does not guarantee failure of all cross-tie options for model appropriately addresses availability seismic events. As a result, it is not clear that the model is consistent for opposite unit equipment. Therefore, with the documentation. resolution of this F&O will not impact the Basis for Significance: Potential inconsistency between documentation calculations of risk changes for the ILRT and model. Extension Risk Analysis.
Possible Resolution: Either revise the Event Tree models so that it is assured that no credit is taken for cross-ties or provide justification for specific cross-ties (for example, at low acceleration levels where independent hardware failures dominate, cross-tie options may be appropriate).
SPR-F1 SPR-F1-02, NOT Open Observation: The current documentation includes references to PLG- This F&O has no impact on the ILRT MET, roadmap 0637, but it is not clear how much of that 1988 document is still valid and Extension Risk Analysis. Clarification of between current relied on. documentation will not impact the documents and Basis for Significance: Unclear what current documentation is. calculations of risk*changes for the ILRT PLG-0637 Extension Risk Analysis.
Possible Resolution: Provide a roadmap from current documentation (e.g., Calculation F.6) back to specific sections of PLG-0637 that are still current.
SPR-F1 SPR-F1-05, NOT Open Observation: Page 22 of PRA Calculation F.6 implies that shutdown This F&O has no impact on the ILRT MET, document seals are inclµded in the model. While it is understood that these may be Extension Risk Analysis. The current future plant mods added in the future, the documentation should reflect the as-built plant. seismic PRA model does not include credit Basis for Significance: Documentation is not consistent with as-built for these seals. The documentation issue plant.
- identified by this F&O does not impact the calculations of risk changes for the ILRT Possible Resolution: Remove this reference to shutdown seals. Extension Risk Analysis.
SPR-F3 SPR-F3-01, NOT Open Observation: Some modeling uncertainties and assumptions are This F&O has no impact on the ILRT MET, complete identified throughout the documentation. However, no complete Extension Risk Analysis. Improving the sources of model documentation of sources of model uncertainty and assumptions was documentation of model uncertainty and uncertainty and identified. assumptions will not impact the calculations assumptions Basis for Significance: This is required by the SR. of risk changes for the ILRT Extension Risk Analysis.
Possible Resolution: Analyze and document the sources of model uncertainty and assumptions in the plant response model.
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