ML17160A263
| ML17160A263 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 06/05/2017 |
| From: | Mark D. Sartain Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 17-079A | |
| Download: ML17160A263 (31) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 June 5, 2017 United States Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C. 20555 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 ASME SECTION XI INSERVICE INSPECTION PROGRAM PRA INFORMATION TO SUPPORT PROPOSED Serial No. NAPS/DEA Docket Nos. License Nos. 10 CFR 50.55a 17-079A RO 50-338 NPF-4 NPF-7 INSERVICE INSPECTION ALTERNATIVES N1-14-NDE-010 AND N2-14-NDE-005 By letter dated March 27, 2017, Virginia Electric and Power Company (Dominion Energy Virginia) submitted proposed inservice inspection (ISi) alternatives N1-14-NDE-010 and N2-14-NDE-005 for North Anna Power Station (NAPS) Units 1 and 2, respectively.
The proposed alternatives would extend the interval for reactor vessel nozzle welds, Category 8-F pressure retaining welds from 10 years to 20 years in accordance with WCAP-17236-NP-A, Revision 0, Risk-Informed Extension of the Reactor Vessel Nozzle lnservice Inspection Interval.
Dominion requested approval of the proposed alternatives by March 1, 2018. In a May 22, 2017 telecon, the NRC requested information regarding the technical adequacy of the PRA Model used to prepare proposed ISi alternatives N 1-14-NDE-010 and N2-14-NDE-005 be submitted to support review and approval of the proposed Reactor Vessel Nozzle Weld Examinations Extensions.
Attachment 1 provides Dominion Energy Virginia's response to NRC's request for PRA information to support alternatives N1-14-NDE-010 and N2-14-NDE-005 for NAPS Units 1 and 2. A table of Supporting Requirements that were not met for Capability Category II during the North Anna Power Station (NAPS) 2013 Full Peer Review and a table of Findings from the NAPS 2013 Full Peer Review are included in Attachment
- 1. If you have any questions, please contact Ms. Diane Aitken at (804) 273-2694.
Sincerely, Mark Sartain Vice President Nuclear Engineering and Fleet Support This letter contains no NRC commitments.
Attachments Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions Page 2of2 1. North Anna PRA Model Technical Adequacy Assessment cc: U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Avenue, NE Suite 1200 Atlanta, GA 30303-1257 Mr. J. E. Reasor, Jr. Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd. Suite 300 Glen Allen, Virginia 23060 NRC Senior Resident Inspector North Anna Power Station Mr. James R. Hall NRC Senior Project Manager-North Anna U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, Maryland 20852-2738 Ms. K. R. Cotton-Gross NRC Project Manager-Surry U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, Maryland 20852 ATTACHMENT 1 Serial No. 17-079A Docket Nos. 50-338/339 Page 1 of 29 NORTH ANNA PRA MODEL TECHNICAL ADEQUACY ASSESSMENT VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
NORTH ANNA POWER STATION UNITS 1 AND 2 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 2 of 29 North Anna PRA Model Technical Adequacy Assessment , A review has been performed to assess the technical adequacy of the NAPS-R07e PRA model used to prepare proposed ISi alternatives N1-14-NDE-010 and N2-14-NDE-005.
North Anna PRA model NAPS-R07e is an interim model revision of NAPS-RO? PRA model with an effective date of June 17, 2016 which was used to support this assessment..
North Anna PRA Model Notebook MC.1, Rev. 3 documents the R07e PRA model changes and quantification results. PRA Model Notebooks are used to review and approve interim changes to Dominion Energy Virginia PRA models between issuances of PRA Models of Record. PRA models are maintained and updated under a PRA configuration control program in accordance with Dominion Energy Virginia procedures and ASME/ANS PRA standard requirements.
Plant changes are reviewed, including physical and procedural modifications and changes in performance data, and the PRA model is periodically updated to reflect such changes. The NAPS-RO? PRA model underwent a full scope peer review led by Westinghouse in 2013. During the peer review, the North Anna model was reviewed against the requirements in ASME/ANS PRA standard, RA-Sa-2009 and Reg. Guide 1.200, Rev. 2. The review inCluded a total of 316 numbered supporting requirements (SRs) for internal events and internal flooding in nine technical elements and 10 configuration control SRs. Eleveri of the SRs were determined to be not applicable (N/A) to the North Anna PRA. 292 SRs were rated as SR Met, Capability Category (CC) II, or greater. Three SRs were rated as Category I and 20 SRs were Not Met. In the course of this review, 72 Facts and Observations (F&Os) were prepared, including 35 suggestions, 35 findings, and 2 best practices.
The 2013 peer review team concurred with the closure of peer review F&Os that were generated prior to the 2013 peer review. Therefore, this assessment does not consider peer review F&Os generated prior to the 2013 peer review. The SRs that did not meet CC II in the 2013 Peer Review were reviewed for their impact to this application (proposed ISi alternatives N1-14-NDE-010 and N2-14-NDE-005).
Table 1 contains the results of this review. All SRs not listed in Table 1 were concluded to meet CC II or higher by the 2013 Peer Review. Based on the result of the review of PRA Standard SRs, the CC 11 SRs that were not met have no impact on this application and no additional sensitivity studies are required to be performed.
SR AS-A10 AS-86 AS-C1 DA-82 DA-C14 DA-08 HR-03 HR-G3 HR-G6 HR-13 IE-A6 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 3 of 29 Table 1 -NAPS R07e Supporting Requirements:
CCII Not Met CC II ,, Met? Impact to Application None. This issue has been resolved in the PRA model that was No used to support this application.
None. A review was performed to evaluate coincident maintenance that would include identification of dependencies among plant No alignments. ,No such dependencies were identified.
None. This SR was considered Not Met due to a need to enhance documentation.
A documentation enhancement that would facilitate emergent risk informed applications will not significantly No impact the quantifications performed to support this application.
None. This issue has been resolved in the PRA model that was No used to support this application.
None. This issue has been resolved in the PRA model that was No / used to support this application.
None. This issue has been resolved in the PRA model that was No used to support this application.
None. This SR was considered Not Met due to a need to enhance documentation related to following the guidelines of NUREG-0700.
The North Anna PRA uses the HRA Calculator software which adheres to the guidelines of NUREG-0700.
Clarification to the basis of adherence to NUREG-0700 will not impact the quantification of LOCA sequences which was performed to support No this application.
None. This SR was considered Not Met due to a need to enhance documentation.
The documentation of quality of operator training for HFEs will not significantly impact the quantification of LOCA No sequences which was performed to support this application.
None. This SR was considered Not Met due to a need to enhance documentation.
An additional survey to review HEP consistency will not significantly impact the quantification of LOCA sequences No which was performed to support this application.
None. This SR was considered Not Met due to a need to enhance documentation.
The documentation of additional sources of uncertainty will not significantly impact the quantification of LOCA No sequences which was performed to support this application.
None. This issue has been resolved in the PRA model that was No used to support this application.
SR IE-C3 IFPP-83 IFQU-A6 IFSN-A10 IFSN-A14 IFSN-A16 IFSN-AS IFSO-AS IFSO-83 LE-G1 QU-8S -----------------
Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions Attachment 1 -Page 4 of 29 Table 1 -NAPS R07e Supporting Requirements:
CCII Not Met CC II Met? Impact to Application None. The application only quantified LOCA sequences.
There is no impact to the application from this SR not meeting Capability No Category 11. None. The application only quantified LOCA sequences.
There is no impact to the application from this internal flooding SR not No meeting Capability Category II. None. The application only quantified LOCA sequences.
There is no impact to the application from this internal flooding SR not No meeting Capability Category II. None. The application only quantified LOCA sequences.
There is no impact to the application from this internal flooding SR not No meeting Capability Category 11. None. The application only quantified LOCA sequences.
There is no impact to the application from this internal flooding SR not No meeting Capability Category II. None. The application only quantified LOCA sequences.
There is no impact to the application from this internal flooding SR not No meeting Capability Category II. None. The application only quantified LOCA sequences.
There is no impact to the application from this internal flooding SR not No meeting Capability Category 11. None. The application only quantified LOCA sequences.
There is no impact to the application from this internal flooding SR not No meeting Capability Category 11. None. The application only quantified LOCA sequences.
There is no impact to the application from this internal flooding SR not No meeting Capability Category II. None. This SR was considered Not Met due to a need to enhance documentation.
Development of a peer review SR road map will No not impact the quantifications performed to support this application.
None. This issue has been resolved in the PRA model that was No used to support this application.
SR SY-C1 \ Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 5 of 29 Table 1 -NAPS R07e Supporting Requirements:
CCII Not Met CC II Met? Impact to Application None. This SR was considered Not Met due to a need to enhance documentation.
Enhancement of the dependency matrix documentation will not significantly impact the quantifications No performed to support this application.
Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 6 of 29 The 'Finding' level F&Os identified during the 2013 Peer Review were reviewed for their impact on this application.
The results of the 'Finding' review is documented in Table 2. The table includes 'Finding' level F&Os from the peer review on the North Anna PRA model that were open. Some of these F&Os have been resolved in interim model revisions since the peer review. The findings that remain unresolved were reviewed for their impact on their potential impact on the quantification of LOCA sequences that were performed to support this application.
The review of open peer review findings determined that none of the findings have an impact on this application or require additional sensitivity studies to be performed.
F&O AS-A10-01 AS-B6-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 7 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
Differences in transient initiating event group are not clearly described impact of the loss of condenser vacuum which affects steam dump capability and operability of main feed water and the This PRACC item was spurious SI which challenges PORV open. Loss of addressed in the NAPS-condenser vacuum is not explicitly modeled and is R07d interim model None. This issue has been treated as a transient with MFW, which affect steam update as documented in resolved.
dump capability and main feedwater.
Spurious SI NAPS PRA Model event increases RCS pressure and subsequently Notebook MC.1, Rev. 2. open a PORV when operator fails to terminate the SI. Basis for Significance:
General transient event tree logic should capture the differences.
Discussion:
No discussion could be identified in the Unresolved.
AS calculation and supporting information with respect to plant configurations and maintenance A review was performed to evaluate practices creating dependencies among various coincident maintenance that would system alignments.
PENDING -confirm this to be the include identification of case when reviewing system notebooks. (Ref. dependencies among plant Assessment of NAPS Peer Review F&Os -TPJ.xlsx) alignments.
No such dependencies Basis for Significance:
System alignments could have were identified.
an impact on the risk profile if unique plant configurations or maintenance practices are used.
F&O AS-C1-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 8 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
Accident sequence analysis is a key Unresolved.
element of PRA to integrate many other elements of PRA, but accident sequence notebook needs to improve for further application and update. For This is a documentation issue. A instance, operator actions are generally described documentation enhancement that without specific governing procedures and basic would facilitate emergent risk event name modeled in HRA. Observations in AS-C2 informed applications will not provide more specific examples.
Observations in AS-significantly impact the C1-02 and AS-C2-01 and 02 provide more specific quantifications performed to examples.
Basis for Significance:
This would facilitate support this application.
emergent risk informed applications using documents with better traceability.
F&O AS-C2-01 DA-82-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 9 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
- 1. Inconsistent documentation for Unresolved.
mitigation tops with designators (e.g., -LATE, -EARLY, etc.). Additionally, some of the mitigation top discussions are inappropriate for the initiator being discussed OR the cross reference to the applicable mitigation top discussion is invalid. For example, for the LOOP initiator, the BAF mitigation This is a documentation issue. top discusses the failure of MFW, even though MFW Increased gate name consistency is not used in the LOOP event tree. and the improvement of traceability between an accident sequence 2. Accident sequence notebook does not include a analysis and HRA analysis will not description of the accident progression for each impact the quantifications sequence or group of similar sequences.
performed to support this application.
- 3. Operator action is described in the accident sequence notebook, but there is limited timing information and no link with HRA information.
Basis for Significance:
This would improve traceability of accident sequence model and facilitate further risk informed applications.
Outliers with zero demands are included in groups This PRACC item was with frequently-tested components.
addressed in the NAPS-R07d interim model None. This issue has been update as documented in resolved.
NAPS PRA Model Notebook MC.1, Rev. 2.
I F&O DA-C14-01 DA-DB-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions Attachment 1 -Page 1 O of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
Coincident maintenance events for intersystem events have not been looked at. Need to This PRACC item was evaluate historical maintenance schedules to detect addressed in the NAPS-patterns of typical maintenance combinations and R07d interim model then add these identified coincident maintenance update as documented in None. This issue has been events to the model. Basis for Significance:
These resolved.
events could have an impact on the annual risk NAPS PRA Model Notebook MC.1, Rev. 2. results. Some plants have experienced a significant NAPS-DA.6 revised. impact to their results form including such events in the model. Discussion:
No discussion of evaluation of the impact of plant modifications on the data could be found in any of the below: This PRACC item was -GARD on Data (2061, 2063) addressed in the NAPS-R07d interim model -Data Calculation and Supporting Analyses update as documented in None. This issue has been NAPS PRA Model resolved.
-SY .3 System Notebooks Notebook MC.1, Rev. 2. NAPS-DA.2, Rev 6 issued. Therefore this SR is considered to be Not Met Basis for Significance:
This item could change the results from the PRA.
F&O DA-DB-02 HR-D3-01 HR-G2-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 11 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
No discussion of evaluation of the impact of plant modifications could be found in any of the This PRACC item was below: addressed in the NAPS--GARD on Data (2061, 2063) R07d interim model update as documented in None. This issue has been -Data Calculation and Supporting Analyses NAPS PRA Model resolved.
Notebook MC.1, Rev. 2. -System Notebooks Basis for Significance:
Data NAPS-DA.2, Rev 6 could be impacted by a plant mod and effect risk issued. results Discussion:
The additional NRC notes adds a Unresolved.
This is a documentation issue. The requirement for adherence to NUREG-0700, Human-North Anna PRA uses the HRA System Interface Design Review Guidelines.
The Calculator software.which adheres basis for stating that no cases were identified where to the guidelines of NUREG-0700.
the quality is lacking needs to reference NUREG-Clarification to the basis of 0700 as the process for validating the quality of the adherence to NUREG-0700 will not man-machine interface.
Basis for Significance:
impact the quantification of LOCA Additional NRG requirement to go from Cat. I to Cat. sequences which was performed to 11. support this application.
Discussion:
Dependency not assessed for recoveries This PRACC item was credited in post-initiators using the CBDTM method. addressed in the NAPS-Basis for Significance:
Potential to underestimate R07d interim model None. This issue.has been human error probabilities.
update as documented in resolved.
NAPS PRA Model Notebook MC.1, Rev. 2.
F&O HR-G3-01 HR-G6-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 12 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
Cat. II requires an evaluation of the Unresolved.
This is a documentation issue. The quality of operator training on the HFE of interest, documentation of quality of including whether the training is classroom training or simulator training and the frequency of such training.
operator training for HFEs will not The frequency field in the HRA Calculator was not significantly impact the filled out for the NAPS post initiator HFEs. Basis for quantification of LOCA sequences Significance:
Provides documentation for the quality which was performed to support of operator training for the HFE of interest.
this application.
Discussion:
HR-G6 requires a check of the Unresolved.
consistency of the post-initiator HEP quantifications.
The instructions are to review the HFEs and their final HEPs relative to each other to check their This is a documentation issue. An reasonableness given the scenario context, plant additional survey to review HEP history, procedures, operational practices, and consistency will not significantly experience.
HR.2 states that an operator survey, impact the quantification of LOCA which collects operator response times, was sequences which was performed to performed to meet this requirement.
However, the support this application.
surveys do not really check the consistency of the HEP quantifications.
Basis for Significance:
Confirm that quantifications are reasonable.
F&O HR-G7-01 HR-13-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 13 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
There were some cases of unanalyzed dependency combinations found in the cutsets of This PRACC item was cutset file U1-CDF-Avg Maintenance-R07.cut.
addressed in the NAPS-Examples include cutsets 3119, 22480, 22642, R07d interim model None. This issue has been 22643, 22868, 23050. The applicable truncation update as documented in resolved.
limits used in the dependency analysis need to adjust NAPS PRA Model to eliminate unanalyzed combos in the cutsets. Basis Notebook MC.1, Rev. 2. for Significance:
Some cutsets may have higher failure probabilities than presently quantified.
Discussion:
NAPS _HR.1, HR.2, HR.3 section 2.3 and Unresolved.
HR.4 section 5 addresses assumptions and This is a documentation issue. uncertainties.
Only source of model uncertainty listed documentation of additional is lack of ERO credit which in reality can be sources of uncertainty will not accounted for using the recoveries available in the significantly impact the The HRA calculator.
NUREG/CR-1278 lists sources of quantification of LOCA sequences uncertainty which could be referenced.
Basis for which was performed to support Significance:
Need better documentation of sources this application.
of uncertainty.
F&O IE-A6-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 14 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
Common cause and routine system alignments are generally appropriately considered for complicated safety system initiating event fault trees. However, for other systems (notably, electrical systems) there is no discussion or evidence of a review for initiators due to common cause of electrical systems nor due to routine system This PRACC item was alignments.
GARD NF-AA-PRA-101-204C identifies that transformers, battery chargers, and inverters are addressed in the NAPS-candidates for common cause. These common R07d interim model cause failures are modeled in the core damage update as documented in resolved.
mitigation fault trees. However, these common NAPS PRA Model cause failures are not considered as initiating events, Notebook MC.1, Rev. 2. particularly for RSST 4KV transformers, vital inverters, and 125VDC battery chargers.
Also, for example, unavailability of a backup battery charger may drive a plant shutdown given loss of the normally operating charger.
F&O IE-A6-01 (cont'd.)
IE-C1-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 15 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application In addition, could not find a discussion of why common cause blockage of service water travelling screens was not considered.
Basis for Significance:
IE-A6 CAT II requires a systematic evaluation of initiating events, including events resulting from multiple failures resulting from common cause or from routine system alignments.
Notebook IE.1 says that due to the independency of busses, the loss of more than one bus at a time is assessed as negligible frequency, however this statement does not consider common cause. No evidence of a systematic evaluation is evident. Discussion:
Plant specific-only data is used for some Unresolved.
initiating events. Initiating event SPUR-SIS has only The application only quantified one failure, but there is no justification for not LOCA sequences.
There is no incorporating generic data. Basis for Significance:
impact to the application from Initiating event SPUR-SIS uses plant-specific data, findings related to non-LOCA but not justification made that there is adequate initiating events. plant-specific data to characterize the parameters.
F&O IE-C3-01 IFPP-B1-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions
- Attachment 1 -Page 16 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
Many recovery actions are credited in Unresolved.
The application only quantified SSIE fault trees. No discussion or analysis was LOCA sequences.
There is no found to justify these credits. Basis for Significance:
impact to the application from SR IE-C3 requires justification for credited recoveries findings related to non-LOCA in initiating events. These recoveries are also used initiating events. in the post-initiating event mitigation tree. Discussion:
It is suggested to add an overall site Unresolved.
layout drawing into the IF .1 A notebook with the other individual building level layout drawings to aid in reader understanding of the buildings' relationships to each other and a table of such buildings and their disposition in the flooding study (i.e. include/retain, This is a documentation issue. The screened, etc.) prior to or in conjunction with the quantification performed to support Appendix R information being used as a . this application only included LOCA study input. Basis for Significance:
Deemed a fmdmg sequences, so there is no impact to for document enhancement due to the inability to the application from this internal perform as detailed a review as could be possible flooding finding. given documentation updates. The flooding notebooks seem to present the results more so than the starting point through the endpoint with some discussion given in Section 2.1 of the IF .1 A notebook related to using Appendix R information and the overall process.
F&O IFPP-83-01
-. Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 17 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
No discussion is given in the various Unresolved.
internal flooding notebooks with regard to the plant partitioning process or conclusions as what sources of uncertainty may be present or may have been introduced as part of the partitioning task. Assumptions are given in Section 2.3 of the IF.1 B notebook related to flood area definitions; though no discussion of their potential impacts to the analysis are given. Sources of uncertainty related to the The application only quantified flooding initiating events pipe mode are included in LOCA sequences.
There is no Section 6.0 of the IF.2 notebook and repeated in impact to the application from this Section 2.0 of the QU.4 notebook (with no other internal flooding related uncertainties added in this internal flooding finding. QU.4 notebook) while Section 5.0 of the IF.3 notebook indicates that sensitivities related to internal flooding are contained in the QU notebooks, though only sensitivity cases related to HEP and CCF values were noted which contained the overall internal flooding events in the sensitivity case model quantifications.
Basis for Significance:
The SR was . deemed 'not met' thus a finding level is appropriate.
F&O IFQU-A6-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 18 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
While the flooding-specific HFEs are Unresolved.
developed with detailed assessments, several of the noted items in the SR were not accounted for. Items noted from review of SR IFQU-A6: (b) The impact of the flooding on cues that the control room uses for a non-flooding HFEs is not discussed in the supporting spreadsheet of the internal flooding The application only quantified HRA notebook for internal events HFEs used in the LOCA sequences.
There is no flooding analysis.
impact to the application from this (a) The impact of the flooding on additional workload internal flooding finding. and stress in the control room uses for a non-flooding HFEs is not discussed in the supporting spreadsheet of the internal flooding HRA notebook for internal events HFEs used in the flooding analysis.
In addition, the stress levels for the flooding-specific events were evaluated at low stress levels, which is inconsistent with the intent of the SR. ..
F&O IFQU-A6-01 (cont'd.)
IFQU-A9-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 19 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application In addition, there appears to be inconsistent timings for the HEPs defined between the HRA calculator inputs and the NOTEBK-PRA-NAPS-IF.2 for time to perform the action (which is usually 1 minute less than the time to damage) being noted in the NOTEBK-PRA-NAPS-IF.2 notebook and the time to damage being used in the HRA calculator.
This slight difference is not expected to cause significant changes, but should be reviewed for consistency and updated as needed. Basis for Significance:
The SR was deemed 'not met' thus the level of finding is appropriate.
Discussion:
One internal flooding source system, Unresolved.
firewater, was noted as not always failed when its The quantification performed to piping is the flooding source. Credit of the alternate pump cooling from firewater is still possible under support this application only flooding initiating events from firewater piping. Basis included LOCA sequences, so for Significance:
Revision of the PRA model is there is no impact to the application required, thus a level of finding is deemed from this internal flooding finding. appropriate.
F&O IFQU-81-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 20 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
Several internal flooding HRA Unresolved.
documentation inconsistencies were noted during review. Examples include: -the HRA notebook NOTEBK-PRA-NAPS-HR.10 and the internal flooding notebook NOTEBK-PRA-NAPS-IF.2 do not list the same set of flooding-specific HFEs This is a documentation issue. The -all of the HFEs listed in the HRA notebook application only quantified LOCA NOTEBK-PRA-NAPS-HR.10 do not appear in the sequences.
There is no impact to PRA model, event REC-FLD-ABSWLL appears as a the application from this internal flag event flooding finding. -the internal flooding notebook NOTEBK-PRA-NAPS-IF.2 presents HFE HEP-ISO-TBSWLL which is not contained in the HRA calculator which does contain event REC-FLD-TBSWLL, however, neither event appears in the PRA model. Basis for Significance:
Information is needed in the flooding/HRA notebooks, thus a finding rather than a small item that would warrant a suggestion.
_J F&O IFSN-AS-01 IFSN-AB-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 21 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
The critical height of all PAA-related Unresolved.
SSCs is not given in an easy to identify single location such as the table listing of PAA-related SSCs within the various internal flood areas. In The application only quantified addition, the critical height is not always defined in LOCA sequences.
There is no the other sections of the internal flooding notebooks impact to the application from this such as walkdowns or area scenario discussions, internal flooding finding. only for the end-state important SSCs. Basis for Significance:
SR requires spatial location of SSCs which was not consistently done. Discussion:
Assumptions of doors failing without Unresolved.
allowing water accumulation may be a beneficial The application only quantified failure for the flood room/area where the accumulation would not occur due to the assumption LOCA sequences.
There is no of the door failing open immediately.
Basis for impact to the application from this Significance:
Potential non-conservatism without internal flooding finding. significant analysis to ensure treatment is okay.
F&O IFSN-B2-02 IFSO-A4-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 22 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
The included pipe break flow rates do not Unresolved.
always include a calculation for the full diameter break size, and in addition, there is no consideration of pump run out flow rate comparison to the calculated break flow rate in the various internal The application only quantified flooding notebooks.
Also, the flooding flow rate used LOCA sequences.
There is no to determine the consequential impacts for each impact to the application from this flooding area should be listed in the area scenario internal flooding finding. discussions.
Basis for Significance:
Information is
- needed in the flooding notebooks, thus a finding rather than a small item that would warrant a suggestion.
Discussion:
Inadvertent actuation of fire protection Unresolved.
system outside of Aux Building not modeled or The application only quantified screened.
Inadvertent actuation of fire protection LOCA sequences.
There is no system inside of Aux Building not discussed.
Basis impact to the application from this for Significance:
SR specifically calls for inadvertent internal flooding finding. actuation to be considered.
F&O IFSO-AS-01 IFSO-B3-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 23 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
The capacities of various sources are Unresolved.
limited by an assumption that all flood isolations could be performed within 60 minutes. No basis is given for this assumption, and the potential of all scenarios using a purely assumptive basis for such inherent screening of potential impacts should also model non-isolated scenarios for the same pipe break source. Also, the treatment is inconsistent with The application only quantified an IF HFE that is evaluated past 60 minutes. LOCA sequences.
There is no impact to the application from this internal flooding finding. This F&O applies to the following SRs: IFSO-B1, IFQU-A6, IFQU-AS, IFSN-A9, IFSN-A15, IFSN-A16, IFSN-A10, IFSN-A14, and IFSN-B2. Basis for Significance:
This assumption greatly impacts the risk from internal floods. REC-FLD-IRR has available time of 84 minutes, yet still analyzed for failure probability.
Discussion:
There is no uncertainty analysis related Unresolved.
This is a documentation issue. The to flood sources. Basis for Significance:
Missing application only quantified LOCA uncertainty analysis.
SR unmet. sequences.
There is no impact to the application from this internal flooding finding.
F&O LE-G1-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 24 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
There is no adequate roadmap that Unresolved.
facilitates peer review of the Level 2/LERF documentation.
This is exacerbated by the significant reliance on historical documents going back to the original IPE report. Basis for Significance:
There are several dated self-assessment documents.
For LE, about 1 /3 of the SRs do not have any This is a documentation issue. discussion of how the SR is met and where the Development of a peer review SR documentation can be found. Moreover, because of the conversion of the Volume numbers (e.g. LE.2 to road map will not impact the LE.1 ), there is additional confusion added for LE. .quantifications perlormed to Many of the referenced sections in the self-support this application.
assessment (e.g., Section 5.4.1 of LE.1 (old LE.2)) appear to no longer exist. Finally, unlike the other technical elements that have completely revised the analysis, the Level 2 relies significantly on historical documents including the 20 year old IPE, SM-1243 and SM-1464.
F&O QU-B5-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 25 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
Section 3.2 of fleet wide PRA procedure NF-AA-PRA-28 describes method to break the circular logic appropriately and table 3 in SY.2 attachment lists circular logic break gates, but further review of the logic indicates the circular logic is not handled properly.
This PRACC item was A Gate 2-EP-CB-12A-LC "NO ELECTRIC POWER addressed in the NAPS-125 V DC BUS 2-1 (U2 ESGR) (CIRC LOGIC R07c interim model None. This issue has been update as documented in resolved.
BREAK)" is modeled under EOG 2H. The 125V DC NAPS PRA Model power supply with circular logic break is supplied Notebook MC.1, Rev. 1. power only from battery under LOOP condition which is required the EOG. However the battery power is ANDed with battery charger failures as below: 2-EP-CB-12A-PS-LC AND 2-BY-BC-2-1-FAIL 2-BY-BC-2C-l-FAIL 2-BY-B-2-1 Basis for Significance:
Improper breaking of circular logics would result in improper accident sequence evaluation.
F&O QU-88-01 QU-F5-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 26 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
NASP PRA developed logic to eliminate mutually exclusive situations to correct cutsets containing mutually exclusive events. However a mutually exclusive logic "U 1-EVENTS-NO-AUTO-This PRACC item was PRZ-PRES-NX" may delete LOSC sequence addressed in the NAPS-because the logic produces U12-LOSS-SW-R07c interim model None. This issue has been EVENTS*LOSCS combination.
This logic seems to update as documented in resolved.
delete LOSCS logic associated with total loss of SW NAPS PRA Model event which results in loss of RCP seal cooling and Notebook MC.1, Rev. 1. injection.
Basis for Significance:
Incorrect mutually exclusive logic deletion may result in improper accident sequence evaluation.
Discussion:
Quantification code limitations are stated Unresolved.
This is a documentation issue. as being contained in the user manuals to the various inclusion of specific software software codes and there is no discussion provided limitations in Dominion PRA The in the .NOTEBK-PRA-NAPS-QU.1 or QU.2 Documentation will not impact the notebooks.
Basis for Significance:
Finding based on quantifications performed to need for actual information in the notebook(s).
support this application.
F&O SC-81-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 27 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
The large break LOCA success criterion used in the PRA appears to be inconsistent with the Chapter 14 UFSAR analysis.
Basis for Significance:
For large LOCA, NAPS SC.1 R 3, Section 5.2.2, Table 5.2-2 shows for the injection phase that 2/2 accumulators on intact loops and 1 of 2 LHSI pumps This PRACC item was are needed. The basis is stated to be the UFSAR. addressed in the NAPS-However, the large break LOCA analysis in Chapter R07d interim model None. This issue has been 14/15 of the UFSAR is based on the most limiting update as documented in resolved.
single failure, typically, an emergency diesel NAPS PRA Model generator.
The UFSAR thus may credit charging Notebook MC.1, Rev. 2. flow (of the order of 650 gpm). Therefore, the success criterion that is assumed in the PRA may be a smaller set of equipment than the analysis on which it is supposedly based, without justification for excluding the charging pump.
F&O SY-A14-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 28 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
There was no evidence that plugging of manual valves was considered for instances where an exposure time is valid. For example, if a manual valve is normally open in a standby train, it is susceptible to plugging over an exposure time between system alignment rotations (could be every 2 weeks). Applying an exposure to the manual valve plugging failure data may result in a failure probability higher than check valve fails closed failure probability This PRACC item was (which is currently modeled).
This could be a addressed in the NAPS-significant contributor for RHR HX and pump manual R07d interim model None. This issue has been valves that could have a very long exposure rate update as documented in resolved.
between tests or alignments Basis for Significance:
NAPS PRA Model The generic assumption about plugging of manual Notebook MC.1, Rev. 2. valves does not provide evidence that plugging was considered over the exposure time for the standby trains. The system notebooks did not seem to provide any sort of modeling notes on this topic either. If using the SY-A 15 screening, it should be documented that this case meets SY-A 15. This could be a significant contributor for RHR HX and pump manual valves that could have a very long exposure rate between tests or alignments.
F&O SY-C1-01 Serial No. 17-079A Docket Nos. 50-338/339 PRA Info for NAPS 1 and 2 RV Nozzle Weld Examinations Extensions -Page 29 of 29 Table 2 -NAPS R07e 'Finding' Level F&Os Summary of Finding Resolution Impact on Application Discussion:
The dependency matrix appears to Unresolved.
address dependency for front-line systems and mechanical support systems, but appears incomplete This is a documentation issue. The for electrical support systems. For example, no examples identified are modeled dependency is listed for 125VDC panel 2-BY-B-2-11 correctly but the associated or MCC 2-EP-MCC-2A 1-2. In some instances the documentation requires additional support system gate is provided, in other instances detail. The improvement of the only the system name is provided.
Basis for dependency matrix documentation Significance:
This issue made it difficult to assess the will not significantly impact the completeness of the dependency analysis.
This issue quantifications performed to made it difficult to assess the completeness of the support this application.
identification of the systems needed to provide or support the safety functions contained in the accident sequence analysis.