ML14142A104
| ML14142A104 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 05/21/2014 |
| From: | Mahesh Chawla Division of Operating Reactor Licensing |
| To: | Smith K Entergy Nuclear Operations |
| References | |
| MF0382 | |
| Download: ML14142A104 (13) | |
Text
NRR-PMDAPEm Resource From: Chawla, Mahesh Sent: Wednesday, May 21, 2014 1:44 PM To: Smith, Keith E (ksmit21@entergy.com); Amy Hazelhoff (ahazelhoff@enercon.com); MIKSA, JAMES P (jmiksa@entergy.com)
Cc: Hamzehee, Hossein; Fields, Leslie; Robinson, Jay; ONeal, Daniel; Wall, Scott; Carlson, Robert
Subject:
Request for Additional Information - PRA - Palisades - NFPA 805 LAR - MF0382 Attachments: Palisades Followup PRA RAIs final LCF Revised.docx By letter dated December 12, 2012 (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML12348A455), as supplemented by letters dated February 21, September 30, October 24, December 2, 2013, and April 2, 2014 (ADAMS Accession Nos. ML13079A090, ML13273A469, ML13298A044, ML13336A649, and ML14092A126 respectively), Entergy Nuclear Operations, Inc. (ENO or the licensee) submitted a license amendment request (LAR) to revise Facility Operating License No. DPR 20 for Palisades Nuclear Plant. The LAR would permit transition of the fire protection licensing basis from Title 10 of the Code of Federal Regulations (10 CFR), Section 50.48(b), to 10 CFR 50.48(c), "National Fire Protection Association Standard NFPA 805" (NFPA 805). The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed to complete the review, as per the attached file.
Please arrange a teleconference for clarifications, if needed to discuss this request, but no later than two weeks from today. The licensee should provide a list of any RAIs they wish to discuss during the clarification call prior to the call so the appropriate staff members/contractors can be present during the call. Moreover, the staff is requesting responses to these RAIs as soon as reasonably achievable but no later than 60 calendar days from the date of receipt of this email. Thanks Mahesh Chawla Project Manager Phone: 301-415-8371 Fax: 301-415-1222 mahesh.chawla@nrc.gov 1
Hearing Identifier: NRR_PMDA Email Number: 1303 Mail Envelope Properties (Mahesh.Chawla@nrc.gov20140521134400)
Subject:
Request for Additional Information - PRA - Palisades - NFPA 805 LAR - MF0382 Sent Date: 5/21/2014 1:44:22 PM Received Date: 5/21/2014 1:44:00 PM From: Chawla, Mahesh Created By: Mahesh.Chawla@nrc.gov Recipients:
"Hamzehee, Hossein" <Hossein.Hamzehee@nrc.gov>
Tracking Status: None "Fields, Leslie" <Leslie.Fields@nrc.gov>
Tracking Status: None "Robinson, Jay" <Jay.Robinson@nrc.gov>
Tracking Status: None "ONeal, Daniel" <Daniel.ONeal@nrc.gov>
Tracking Status: None "Wall, Scott" <Scott.Wall@nrc.gov>
Tracking Status: None "Carlson, Robert" <Robert.Carlson@nrc.gov>
Tracking Status: None "Smith, Keith E (ksmit21@entergy.com)" <ksmit21@entergy.com>
Tracking Status: None "Amy Hazelhoff (ahazelhoff@enercon.com)" <ahazelhoff@enercon.com>
Tracking Status: None "MIKSA, JAMES P (jmiksa@entergy.com)" <jmiksa@entergy.com>
Tracking Status: None Post Office:
Files Size Date & Time MESSAGE 1528 5/21/2014 1:44:00 PM Palisades Followup PRA RAIs final LCF Revised.docx 63717 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Recipients Received:
REQUEST FOR ADDITIONAL INFORMATION VOLUNTARY FIRE PROTECTION RISK INITIATIVE ENTERGY OPERATIONS, INC.
PALISADES NUCLEAR PLANT DOCKET NO. 50-255 Probabilistic Risk Assessment (PRA) RAI 01.e.01 The response to PRA RAI 01.e, in the letter dated December 2, 2013, Agencywide Documents Access and Management System (ADAMS) Accession No. ML13336A649, stated that the primary coolant pump (PCP) seal failure model used the methodology presented in WCAP-15749-P, Revision 1, Guidance for the Implementation of the Combustion Engineering Owners Group (CEOG) Model for Failure of Reactor Coolant Pump Seals Given Loss of Seal Cooling (Task 2083), December 2008. This topical has not been endorsed by the NRC.
Describe whether the PCP seal failure is the same for both the compliant and the post-transition PRA models such that the impact of this model on the change in risk estimates is minimal. If the PCP seal model differs between the compliant and post-transition PRA models, or if the model has a substantive impact on the change in risk estimates, provide a summary of the method and the quantitative results that are used in the PRA.
PRA RAI 01.f.01 The response to PRA RAI 01.f in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649 indicates that the circuit analysis of identified instrumentation for dominant operator actions has been completed and will be incorporated into the transition fire PRA risk results, which is to be provided in response to PRA RAI 30.
- a. Discuss what is meant by dominant relative to RG 1.200s, An Approach For Determining The Technical Adequacy Of Probabilistic Risk Assessment Results For Risk-Informed Activities, definition of a significant basic event and whether these non-dominant actions are assumed to be failed in the fire PRA.
- b. If not assumed to be failed, justify this treatment by discussing the risk significance of the credited non-dominant operator actions on the transition risk results.
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PRA RAI 01.h.01 In the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, the response to PRA RAI 01.h, subsection 3) Justifications for Assumptions Identified as Non-Conservative in the licensees analysis describes that the treatment of location in the dependency analysis differs from the guidance in NUREG-1921, EPRI/NRC-RES Fire Human Reliability Analysis Guidelines, Draft Report for Comment. NUREG-1921 guidance does not negate the possibility of success of all subsequent actions after failure of an action in the main control room as stated in the RAI response but does state that there would be high dependence between all actions.
Simply stating that the approach is not realistic is not sufficient justification to deviate from the NUREG. It also appears that the timing decision branch of Figure 6-1 of NUREG-1921 is not utilized by the dependency analysis for sequential actions due to this deviation.
Provide a time and distance justification for each set of control room actions considered to be in different locations or conform to the accepted method. Identify the final approach used in the response to PRA RAI 30.
PRA RAI 01.h.02 The dependency analysis described in response to PRA RAI 01.h does not indicate that a minimum value was utilized for the joint probability of multiple human failure events (HFE) and the response. The statement, e.g., for zero dependence, the conditional human error probabilities (HEP) is equal to the independent HEP implies that joint HEPs may take on any value. Section 6.2 of NUREG 1921 addresses the need to consider a minimum (floor") value for the joint probability of multiple HFEs. Each value less than the floor value should be individually justified.
Considering this guidance, describe and justify that joint HEP values that appear in fire PRA cutsets including any values less than the floor value. If a HEP floor for cutsets was not used consistent with NUREG-1921 (i.e., 1E-5 with justifications for lower values), provide updated risk results as part of the aggregate change-in-risk analysis requested in PRA RAI 30, which is consistent with NUREG-1921 guidance.
PRA RAI 01.j.01 The response to PRA RAI 01.j in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, indicates that damage beyond the ignition source is not postulated for several 480V motor control center (MCCs). Per Section 6.5.6 of NUREG/CR-6850, EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities: Volume 2: Detailed Methodology, postulated fires originating in all cabinets above 440V are considered potentially challenging and propagation outside of the cabinet should be evaluated.
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Provide updated risk results, as part of the aggregate change-in-risk analysis requested in PRA RAI 30, following this or other accepted guidance. If other guidance is used, describe the method used.
PRA RAI 01.k.01 The response to PRA RAI 01.k, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, indicates that main control room (MCR) abandonment is only postulated for those fires resulting in a loss of MCR habitability; however, the response to PRA RAI 03, in the letter mentioned above, states that the RAI Response Fire PRA Model will include additional scenarios that model MCR abandonment due to equipment damage, with control being transferred to other locations, such as the alternate shutdown panel.
If the intent is to credit MCR abandonment due to loss of control, provide a description of the method and its technical justification. Include an explanation of the supporting analysis, work performed, and process followed in the technical justification.
PRA RAI 01.l.01 The response to PRA RAI 01.l, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, indicates that the core damage frequency (CDF) and large early release frequency (LERF) associated with MCR abandonment scenarios are calculated using multiple scenarios. Provide the range of conditional core damage probability (CCDPs) and conditional large early release probability (CLERPs) that have been developed. In addition, explain how the process and the range of estimates developed relate to the MCR abandonment scenario bins below:
- a. Scenarios where the fire fails few functions aside from MCR habitability and successful shutdown is relatively uncomplicated by the fire scenario.
- b. Scenarios where the fire could cause some recoverable functional failures or spurious operations that complicate the shutdown.
- c. Scenarios where the fire induced failures cause great difficulty for shutdown by failing multiple functions and/or causing complex spurious operations.
PRA RAI 01.mm.01 The response to PRA RAI 01.mm, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, indicates that key assumptions and sources of uncertainty were identified.
Provide a table that describes these key assumptions and sources of uncertainty that assesses their impact on the NFPA 805 application.
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PRA RAI 01.q.01 The response to PRA RAI 01.q, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, states that the time delay method will replace the damage accrual method originally employed by the fire PRA. Note that in Section H.1.5.2 of NUREG/CR-6850, the failure times reported in Table H-8 assume steady-state fire exposure conditions and are therefore, not applicable for use in calculating exposure conditions that evolve over time.
Provide a technical justification for how the time delay method accounts for pre-heating of targets that occurs at heat fluxes prior to reaching the peak heat flux for the fire being analyzed including those below the target damage threshold, and those not already taken into account by Table H-8.
Provide updated risk results as part of the aggregate change-in-risk analysis requested in PRA RAI 30 that appropriately account for pre-heating or that conservatively do not credit the time delay associated with the pre-heating period.
PRA RAI 01.r.01 The response to PRA RAI 01r, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, states that a one-minute time delay will be applied for credited automatic detection systems.
- a. How is the probability of failure of automatic detection included in the PRA?
- b. If the automatic detection fails, is manual detection then credited?
- c. When manual detection is credited after automatic detection fails, is the 15 minute delay used?
- d. If a logical scenario of detection failure, manual detection with 15 minute delay, and attempted manual suppression is not included in the PRA. Evaluate the impact on the results of not including this scenario or add it to the PRA.
PRA RAI 01.y.01 The response to PRA RAI 01.y, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, appears to indicate that the barrier failure probability is defined by the most limiting barrier (e.g., non-rated barrier, door, damper, or wall) and not the sum of the types of barriers present.
Demonstrate that the impact on the results is not significant or provide updated risk results as part of the aggregate change-in-risk analysis requested in PRA RAI 30, summing the barrier failure probabilities for each type of barrier present per NUREG/CR-6850.
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PRA RAI 12.01 The ASME PRA standard calls for a focused scope peer review for PRA upgrades, where PRA upgrade is defined in the standard as:
The incorporation into a PRA model of a new methodology or significant changes in scope or capability that impacts the significant accident sequences or the significant accident progression sequences.
The response to RAI 12 states, the detailed HEP methodology was reviewed by the peer review and has not been changed. As such, a focused scope review of the HEP analysis is also not warranted. The response to RAI 23.e states, the use of NUREG-1921 methods for screening, scoping and detailed HEP values constitutes data and methods not included in the fire PRA peer review. However, these data and methods are considered acceptable for use.
- a. Clarify these conflicting statements considering that using data and methods acceptable for use is unrelated to the need for a peer review.
- b. Describe the method that will be used to ensure that any PRA upgrade will be peer reviewed.
PRA RAI 17.b.01 The response to PRA RAI 17.b, in the letter dated December 2, 2013 ADAMS Accession No. ML13336A649, states that the plant-wide main control board (MCB) frequency is apportioned to each of the three MCB sections based on the length of the MCB sections. Appendix L of NUREG/CR-6850 assigns the MCB frequency to each scenario.
Provide updated risk results as part of the aggregate change-in-risk analysis requested in PRA RAI 30, applying the full Bin 4 frequency to each MCB scenario postulated per Appendix L of NUREG/CR-6850.
PRA RAI 20.01 The response to PRA RAI 20, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, indicates that the fire PRA model being updated in response to RAIs will use the fire ignition frequencies from NUREG/CR-6850 Supplement 1 and that the use of the original NUREG/CR-6850 frequencies is not expected to yield risk results that exceed the risk acceptance guidelines in RG 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis. Updated risk results will be provided in the aggregate analysis requested in PRA RAI 30. Utilizing the updated fire PRA used to respond to PRA RAI 30, confirms that the risk results of the sensitivity study based on NUREG/CR-6850 ignition frequencies, consistent with Footnote 10 of Supplement 1 to NUREG/CR-6850, continue not to exceed the RG 1.174 risk acceptance guidelines.
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If the guidelines are exceeded:
- a. Discuss what is exceeded;
- b. Describe the fire protection, or related, measures that will be taken to provide additional defense-in-depth; and,
- c. Discuss whether there are conservatisms in the analysis, and if so, the risk significance of the conservatisms.
PRA RAI 23.01 The response to PRA RAI 23, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, states that, the RAI Response Fire PRA Model will be quantified to provide updated Attachment W values as required for the LAR submittal once all issues that impact quantification have been identified and resolved via the RAI process. Section 3.2.5 of RG 1.205 states that risk decreases may be combined with risk increases for the purposes of evaluating combined changes in accordance with Regulatory Positions 2.1.1 (1.1 in RG 1.174 revision 2) and 2.1.2 (1.2 in RG 1.174 revision 2) of RG 1.174. Accordingly, both individual and cumulative risk effects should be evaluated.
Given that the submitted application represents a change that combines risk increases with risk decreases, provide and explain the total increase in CDF and LERF from unresolved fire area variances from deterministic requirements (VFDRs) (i.e., those that will be incorporated into the post-transition licensing basis), and total decrease in CDF and LERF from modifications beyond compliance (i.e., unrelated to VFDRs and included to reduce risk).
PRA RAI 23.a.01 Table PRA RAI 23.1, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, in the response to PRA RAI 23, summarizes how the change in risk values will be estimated. The staff was unable to complete its review of the methods because the parameters defined and used in the response are not included in the guidance documents.
Furthermore, it appears that the values in LAR Table W-2 would change considerably using Table PRA RAI 23.1 and no new values were provided.
- a. Define protection of individual VFDR components beyond those protected by Modifications required for compliance and provide some examples.
- b. Summarize modeling simplifications that result in conservative risk estimates in the compliant plant and/or the post-transition plant.
- c. Provide a detailed explanation for the large risk offset (i.e., 4.5E-4/5.7E-5) obtained from the beyond compliance modifications. As part of this explanation, characterize the top 6
five cutsets from the two dominate scenarios for each of the two fires areas (excluding the MCR) that have the most negative change in risk value for the transition from the compliant to the post-transition plant . Provide this information for both CDF and LERF and for both the compliant plant and the post-transition plant (i.e., a total of 40 cut-sets for CDF and 40 for LERF).
PRA RAI 23.c.01 The response to PRA RAI 23c, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, indicates that additional exceptions to those modeling mechanisms discussed in the response to PRA RAI 23b were employed (e.g., those cases for which the PRA model lacks sufficient resolution to model the VFDR or those that utilize surrogate basic events or HFEs to estimate/bound the change in risk in lieu of manipulating components or actions directly associated with the VFDR); however, the discussion of these exceptions is limited to a reference provided in the licensees analysis.
Provide a discussion of these exceptions and how the delta risk is determined for each.
PRA RAI 28.a.01 The response to PRA RAI 28a, in the letter dated December 2, 2013, ADAMS Accession No. ML13336A649, states that the aggregate impact of employing scoping values for the HFEs as provided in NUREG-1792, Good Practices for Implementing Human Reliability Analysis (HRA) that are not risk significant is an increase in (internal events) CDF by a factor of 1.8; however, the response does not address the impact on the fire PRA.
- a. Provide the impact of employing NUREG-1792 scoping values on the fire risk estimates demonstrating that they are insignificant for both the transition and the self-approval change in risk guidelines values;
- b. Otherwise, provide updated risk results as part of the composite change-in-risk analysis requested in PRA RAI 30, using scoping values consistent with the guidance in NUREG-1792, and indicate what values will be used in post-transition fire risk evaluations.
PRA RAI 30 Section 2.4.3.3 of the NFPA 805 standard incorporated by reference into 50.48(c) states that the probabilistic safety assessment (PSA) (PSA is also referred to as PRA) approach, methods, and data shall be acceptable to the authority having jurisdiction (AHJ), which is the NRC. RG 1.205, Risk-Informed, Performance-Based Fire Protection for Existing Light-Water Nuclear Power Plants, identifies NUREG/CR-6850, NEI 04-02, Revision 2, Guidance for Implementing a Risk-Informed, Performance-Based Fire Protection Program Under 10 CFR 50.48(c), and the ongoing FAQ process as documenting acceptable to the staff for adopting a fire protection program consistent with NFPA 805.
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The NRC staff identified several methods and weaknesses that were used in the fire PRA. RAIs were provided about these methods and weaknesses and the responses have been reviewed.
The staff notes that the justification does not seem to be complete (e.g., credit for control power transformers is not supported by experiments). Also, in some instances, aspects of the Fire PRA model may have been incomplete at the time of the LAR submittal, but subsequently completed in response to an RAI. All these methods are included in the list below:
- PRA RAIs 01.a and 03 (i.e., F&O CS-A9-01) regarding integration of the completed supplemental cable analysis into the fire PRA model
- PRA RAIs 01.c and 03 (i.e., F&O CS-C1-01) regarding integration of the cable routing data verification results into the fire PRA model
- PRA RAI 01.h (as clarified by PRA RAI 01h.02) regarding minimum (floor") values for the joint probability of multiple HFEs
- PRA RAI 01.dd regarding use of guidance in NUREG-1921 for screening, scoping and detailed human error probabilities
CDF, LERF, CDF and LERF) reflecting propagation of parametric uncertainty, accounting for the state of knowledge correlation
- PRA RAI 07 regarding the treatment of transient and fixed ignition sources in the cable spreading room
- PRA RAIs 08 and 11 regarding the development of scenarios for self-ignited cable fires and cable fires due to hot work
- PRA RAI 13 regarding identified inconsistencies in the generic frequencies assigned to Bins 24 and 26
- PRA RAI 17.a regarding the treatment of the complete back panel of sub-enclosure 1 as electrical cabinets
- PRA RAI 17.b (as clarified by PRA RAI 17b.01) regarding apportionment of the MCB frequency to MCB sections
- PRA RAI 17.d regarding treatment of fire propagation for MCB and electrical panels in the MCR, addressing both adjacent and non-adjacent panels as well as considering the impact on time-to-abandonment calculations
- PRA RAI 28a.01 regarding pre-initiator scoping values for HFEs Changes that may impact fire-affected components The responses to the following Fire Modeling (FM) RAIs appear to have caused changes that may impact the fire-affected components for a variety of fires. The aggregate change-in-risk evaluation should include the potential impact of changes in:
- FM RAI 01.c regarding wall and corner effects of transient fires on MCR abandonment times and implementation of NUREG/CR-6850 abandonment criteria
- FM RAI 01.e regarding thermal plume and hot gas layer effects on ZOI determination
- FM RAI 01.f regarding impact of secondary and intervening combustibles on ZOI determination
- FM RAI 01.g regarding the flame spread, fire propagation and HRR estimates associated with cable trays
- FM RAI 01.k regarding non-cable secondary combustibles
- FM RAI 01.l regarding horizontal and vertical cable tray propagation
- FM RAI 04 regarding fire models used outside their limitations PRA Methods and weaknesses still under review:
The following methods and weaknesses have been identified, but the NRC Staff review is continuing with additional RAIs and further supporting information has been requested.
Alternatively, any of these methods and weaknesses may be replaced with a method or model previously accepted by the NRC by modifying the Fire PRA model.
- PRA RAI 01.f.01 regarding instrumentation (including associated cable tracing) for HFEs credited in the fire PRA
- PRA 01.h.01 regarding treatment of location in the dependency analysis
- PRA RAI 20.01 regarding NUREG/CR-6850 fire ignition frequencies sensitivity analysis 10
FM Methods and weaknesses still under review:
The following methods and weaknesses have been identified for which the NRC Staff review is continuing with additional FM RAIs that may cause changes that impact the fire-affected components for a variety of fires:
- FM RAI 01.01 regarding structural steel analysis
- FM RAI 07 regarding time of fire propagation to adjacent cabinets
- a. For each method (i.e., each bullet) above, explain how the issue will be addressed in 1) the final composite analysis results provided in support of the LAR, and 2) the PRA that will be used at the beginning of the self-approval of post-transition changes. (This includes all items listed above including changes that may impact fire affect components; PRA methods and weaknesses still under review, and FM methods and weaknesses still under review)
- b. Provide the results of a composite analysis that shows the integrated impact on the fire risk (CDF, LERF, CDF, LERF) after the methods and weaknesses have been replaced. As the review process is concluded, additional changes to replace any method or weakness still under review may be required. In this composite analysis, for those cases where the individual issues have a synergistic impact on the results, a simultaneous analysis must be performed. For those cases where no synergy exists, a one-at-a-time analysis may be done.
If the impact on the change in risk from transition is negligible, a quantitative evaluation is unnecessary.
- c. As committed in the responses to PRA RAIs 23 and 26, respectively, provide updated Attachments W (including all tables, e.g., CDF and LERF insights), and Attachment S to the LAR.
PRA RAI 31 The responses to several PRA RAIs (e.g., 01.g, 01.cc, and 03) are contingent on the development of a new all-inclusive fire response procedure. Describe if there is an Implementation Item in table S-3 that addresses the development and implementation of this procedure. If not, describe the method that will be used to ensure development of the procedure.
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