ML19045A011
| ML19045A011 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 02/14/2019 |
| From: | David Helker Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML19045A011 (100) | |
Text
200 Exelon Way Exelon Generation Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.90 February 14, 2019 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTN: Document Control Desk Limerick Generating Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353
Subject:
Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b."
References:
- 1. Letter from J. Barstow (Exelon Generation Company, LLC) to U.S.
Nuclear Regulatory Commission, "License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, 'Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b'," dated December 13, 2018 (ADAMS Accession No. ML183478366).
- 2. Letter from V. Sreenivas (U.S. Nuclear Regulatory Commission) to B.
Hanson (Exelon Generation Company, LLC), "Limerick Generating Station, Units 1 and 2 - Supplemental Information Needed for Acceptance of Requested Licensing Action to Adopt Risk-Informed Completion Times in Accordance with TSTF-505, Revision 2 (EPID L-2018-LLA-0567),"
dated January 30, 2019 (ADAMS Accession No. ML19030A147).
In Reference 1, Exelon Generation Company, LLC (Exelon) requested an amendment to the Renewed Facility Operating License Nos. NPF-39 and NPF-85 for Limerick Generating Station (Limerick), Units 1 and 2, respectively.
The proposed amendment would modify Technical Specifications (TS) requirements to permit the use of risk-informed completion times (RICTs) in accordance with the Technical Specifications Task Force (TSTF) Traveler TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF [Risk-Informed TSTF] Initiative 4b" (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18183A493).
In Reference 2, the NRC requested that Exelon provide supplemental information by February 15, 2019 to support the acceptance review of the license amendment request.
The attachment to this letter provides a restatement of the NRC questions followed by our responses.
Exelon has reviewed the information supporting a finding of no significant hazards consideration, and the environmental consideration, that were previously provided to the
License Amendment Request Supplement Adopt TSTF-505, Rev. 2 Docket Nos. 50-352 and 50-353 February 14, 2019 Page2 NRC in Attachment 1 of the Reference 1 letter. Exelon has concluded that the information provided in this response does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92. In addition, Exelon has concluded that the information in this response does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.
In accordance with 10 CFR 50.91 , "Notice for public comment; State consultation,"
paragraph (b), Exelon is notifying the Commonwealth of Pennsylvania of this supplement to the application for license amendment by transmitting a copy of this letter and its attachment to the designated State Official.
This letter contains no regulatory commitments.
If you should have any questions regarding this submittal, please contact Glenn Stewart at 610-765-5529.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 141h day of February 2019.
Respectfully, David P. Helker Manager - Licensing and Regulatory Affairs Exelon Generation Company, LLC Attachment - License Amendment Request Supplement Enclosure 1 - Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process cc: USNRC Region I, Regional Administrator USNRC Project Manager, Limerick USNRC Senior Resident Inspector, Limerick Director, Bureau of Radiation Protection - Pennsylvania Department of Environmental Protection
ATTACHMENT License Amendment Request Supplement Limerick Generating Station, Units 1 and 2 NRC Docket Nos. 50-352 and 50-353 License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b."
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 1 of 97 Docket Nos. 50-352 and 50-353 In Reference 1, Exelon Generation Company, LLC (Exelon) requested an amendment to the Renewed Facility Operating License Nos. NPF-39 and NPF-85 for Limerick Generating Station (Limerick), Units 1 and 2, respectively. The proposed amendment would modify Technical Specification (TS) requirements to permit the use of risk-informed completion times (RICTs) in accordance with the Technical Specifications Task Force (TSTF) Traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF [Risk-Informed TSTF]
Initiative 4b (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18183A493).
In Reference 2, the NRC requested that Exelon provide supplemental information by February 15, 2019 to support the acceptance review of the license amendment request. A restatement of the NRC questions followed by our responses is provided below.
Regulatory Basis This LAR would modify TS requirements to permit the use of RICTs in accordance with TSTF-505, Revision 2.
LAR Attachment 1, Section 1, states:
The methodology for using the risk-informed completion time (RICT) program is described in Nuclear Energy Institute (NEI) 06-09-A, Risk-Informed Technical Specifications Initiative 4b, Risk-Managed Technical Specifications (RMTS) Guidelines, Revision 0, which was approved by the NRC on May 17, 2007 [ADAMS Accession No. ML071200238]. Adherence to NEI 06-09-A is required by the RICT program.
NEI Topical Report (TR) 06-09-A (ADAMS Package Accession No. ML122860402) provides guidance for implementation of a generic TS improvement that establishes a risk management approach for voluntary extensions of completion times for certain Limiting Conditions for Operation (LCOs). The NRC staffs SE, dated May 17, 2007 (ADAMS Accession No. ML071200238), found the guidance in NEI 06-09-A, to be acceptable, with clarifying NRC staff positions, limitations, and conditions. The NEI issued NEI 06-09-A by including the NRC staffs SE in the front of the NEI 06-09 document, but not incorporating the NRC staff positions, limitations, and conditions into the guidance described in the document. Accordingly, NEI 06-09-A could be acceptable for referencing by licensees proposing to amend their TSs to implement RMTS when the NRC staff positions, limitations, and conditions described in the NRC staffs SE dated May 17, 2007, are met.
Limitation and Condition 3 in the NRC staffs safety evaluation on NEI 06-09 dated May 17, 2007 states:
The LAR will provide a discussion of the results of peer reviews and self-assessments conducted for the plant-specific PRA models which support the RMTS, including the resolution or disposition of any identified deficiencies (i.e., findings and observations from peer reviews). This will include a comparison of the requirements of RG
[Regulatory Guide] 1.200 using the elements of ASME [American Society of Mechanical Engineers] RA-Sb-2005 for capability Category II for internal events PRA models, and for other models for which RG 1.200 endorsed standards exist. If additional standards have been endorsed by revision to RG 1.200, the LAR will also provide similar information for those PRA models used to support the RMTS program.
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 2 of 97 Docket Nos. 50-352 and 50-353 RG 1.200, Revision 2, was issued in March 2009 (ADAMS Accession No. ML090410014), and endorsed with comments and limitations, the ASME/ANS (ASME/American Nuclear Society)
Probabilistic Risk Analysis (PRA) Standard ASME/ANS RA-Sa-2009, Addenda to ASME/ANS RA S 2008, Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications.
- 1. Fire PRA supporting requirements that might have been assigned a Capability Category I without any Facts and Observations LAR Enclosure 2, Section 4, states that a full-scope peer review of the fire PRA was performed in November 2011, using the NEI 07-12 Fire PRA peer review process. NEI 07-12 states that,
[i]f the utility chooses to be reviewed against CC [Capability Category] I for a given SR
[supporting requirement], an F&O [fact and observation] need not be written for those SRs if assessed as CC I.
RG 1.200, Revision 2, placed internal fires into the internal hazard category, and endorsed ASME/ANS RS-Sa-2009 Part 4, Technical and Peer Review requirements for At-Power Internal Fires, with comments and limitations.
Therefore, consistent with RG 1.200, Revision 2, and the NRC staffs safety evaluation on NEI 06-09 which describe that a LAR should include a comparison of plant-specific risk models against CCII of the ASME/ANS PRA Standard, provide the following:
- i. A statement confirming that the Limerick Fire PRA used to support this LAR was peer-reviewed against ASME/ANS PRA Standard CCII SRs, or ii. A description of any fire SRs that were assigned a CC I (or not met), but were not provided with an associated peer review F&O, as permitted by NEI 07-12. For each SR assigned only a CC I (or a not met) provide a description of why the SR was not assigned a CC II and disposition the impact of not meeting CC II on this application.
Response
ii. N/A, see response to i.
- 2. Use of Facts and Observation closure process prior to final accepted version LAR Enclosure 2 Sections 3 and 4 state that in July 2016 an F&O closure review was performed by an independent assessment (IA) team on all internal events, internal flooding and fire finding-level F&Os. This July 2016 F&O closure review was a pilot review to develop the process to be detailed in Appendix X to the guidance in NEI 05-04, NEI 07-12, and NEI 12-13 (ADAMS Accession No. ML17086A431). The NRC staff accepted, with conditions, a final version of Appendix X to NEI 05-04, 07-12, and 12-13 in the NRC letter dated May 3, 2017 (ADAMS Accession No. ML17079A427), which differed from the guidance used by the licensee in the July 2016 F&O closure. Therefore, provide the following:
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 3 of 97 Docket Nos. 50-352 and 50-353
- i. A description of the evaluation performed to confirm that the July 2016 IA F&O Closure review is consistent with the Appendix X process as accepted by NRC in the staff memorandum dated May 3, 2017.
ii. The licensee's documented justification and the IA team's documented assessment supporting the classification of each F&O finding resolution for closed F&Os as either a PRA upgrade or PRA maintenance update, as defined in the ASME/ANS RA-Sa-2009 PRA Standard endorsed, with comments and limitations, by RG 1.200, Revision 2.
iii. The IA team's confirmation that for the closed F&Os, the aspects of the underlying SRs in ASME/ANS RA-Sa-2009 that were previously not met, or met at CC-I, are now met or met at CC-II, iv. Alternatively to items i, ii, and iii above, provide all F&Os (i.e., all those that were not closed by any subsequent focused scope peer review) and their proposed resolution or disposition of impact on the TSTF-505 amendment request.
Response
- i. An evaluation was not performed to confirm that the July 2016 IA F&O Closure review is consistent with the Appendix X process as accepted by NRC in the staff memorandum dated May 3, 2017. See Item iv.
ii. See item iv.
iii. See item iv.
iv. The Limerick 50.69 submittal (reference NRC ADAMS ML17179A161) included separate attachments of Peer Review findings that were assessed as either Closed (Attachment 3b in ML17179A161) or Open or Partially Resolved (Attachment 3a of ML17179A161) as of the time of that submittal. Enclosure 1 of this supplement provides the same Peer Review findings that were provided as Attachment 3b of the Limerick 50.69 submittal, including the original Capability Category, which were justified for closure during the 2016 Limerick pilot F&O closure review. Because all of the findings listed in Enclosure 1 have been fully resolved in the current Limerick internal events and internal fire PRA models, Exelon considers these findings no longer relevant to any risk-informed application, including the TSTF-505 amendment request. With resolution of these peer review findings, Exelon considers that the Capability Category II requirements for these internal events and fire PRA supporting requirements are met. These resolutions were reviewed by the NRC as part of the 50.69 LAR and deemed to be acceptable via audit and response to request for additional information (RAI) questions.
The following items were listed in the Attachment 3a of the 50.69 LAR (ref.
ML17179A161) but have been subsequently closed via either an Appendix X closure process or a Focused Scope peer review to support 50.69 implementation.
Finding SR SY-A11-03 SY-A11 HR-A1-01 HR-A1 1-16 FQ-F1 2-8 PRM-B6
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 4 of 97 Docket Nos. 50-352 and 50-353 Finding SR 4-6 HRA-A3 4-30 IGN-A7 4-34 FSS-G1 4-47 FQ-D1 Findings listed in Attachment 3a of the 50.69 LAR (ref. ML17179A161) that have not been subject to an Appendix X closure review, including finding 4-35 (SR FSS-G2),
were provided in Tables E2-1 and E2-2 of the Limerick TSTF-505 LAR. All findings listed in Tables E2-1 and E2-2 have been addressed in the Limerick PRA models.
- 3. Missing discussion and resolution of 50.69 license amendment implementation items On July 31, 2018 (ADAMS Accession No. ML18165A162) the NRC issued license amendments approving requests to implement 10 CFR 50.69 at Limerick Generating Station, Units 1 and 2.
These amendments included the following license condition identifying PRA changes that shall be made prior to implementation of the 10 CFR 50.69 categorization process.
Exelon will complete the implementation items listed in Attachment 2 of Exelon letter to NRC dated April 23, 2018 prior to implementation of 10 CFR 50.69. All issues identified in the attachment will be addressed and any associated changes will be made, focused-scope peer reviews will be performed on changes that are PRA upgrades as defined in the PRA standard (ASME/ANS RA-Sa-2009, as endorsed by RG 1.200, Revision 2), and any findings will be resolved and reflected in the PRA of record prior to implementation of the 10 CFR 50.69 categorization process. of Exelon letter to NRC dated April 23, 2018, included a table listing the implementation items; this table is reproduced below.
Limerick 50.69 PRA Implementation Items Description Resolution
- i. Update the HRA pre-initiators in the The HRA pre-initiators in the internal events internal events PRA model to meet PRA model will be updated to meet Capability Capability Category II of the ASME/ANS Category II of the ASME/ANS RA-Sa-2009 as RA-Sa-2009 as endorsed by RG 1.200, endorsed by RG 1.200, Revision 2. A focused-Revision 2, conduct a focused-scope scope peer review will be conducted of the pre-peer review of the pre- initiator analysis, initiator analysis, and any resulting F&Os will be and resolve any resulting F&Os, as resolved, as indicated in response to RAI 01.a indicated in response to RAI 01.a contained in Exelon letter dated January 19, contained in Exelon letter dated January 2018.
19, 2018.
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 5 of 97 Docket Nos. 50-352 and 50-353 Limerick 50.69 PRA Implementation Items Description Resolution ii. Remove credit for recovery of instrument Credit for recovery of instrument air will be air from the internal events PRA model, as removed from the internal events PRA model, indicated in response to RAI 01.d as indicated in response to RAI 01.d contained contained in Exelon letter dated January in Exelon letter dated January 19, 2018.
19, 2018.
iii. Update the success criteria for main The success criteria for main steam isolation steam isolation valve (MSIV) spurious valve (MSIV) spurious opening will be updated, opening, as indicated in response to RAI as indicated in response to RAI 02.a contained in Exelon letter dated 02.a contained in Exelon letter dated January 19, 2018. January 19, 2018.
iv. Model undesired operator actions in the Undesired operator actions will be modeled in FPRA, conduct a focused-scope peer the FPRA. A focused-scope peer review will be review, and resolve any F&Os, as indicated conducted, and any F&Os will be resolved, as in response to RAI 02.c contained in Exelon indicated in response to RAI letter dated January 19, 2018. 02.c contained in Exelon letter dated January 19, 2018.
- v. Update the FPRA model to model The FPRA model will be updated to model junction box fires consistent with junction box fires consistent with frequently frequently asked question asked question (FAQ) 13-0006, as indicated in (FAQ) 13-0006, as indicated in response response to RAI 2.e contained in Exelon letter to RAI 2.e contained in Exelon letter dated January 19, 2018.
dated January 19, 2018.
vi. Update the FPRA model to incorporate The FPRA model will be updated to transient fires in the multi-compartment incorporate transient fires in the multi-analysis, as indicated in response to RAI compartment analysis, as indicated in 2.f contained in Exelon letter dated response to RAI 2.f contained in Exelon January 19, 2018. letter dated January 19, 2018.
vii. Update the pipe rupture frequencies in the The pipe rupture frequencies will be updated in internal flooding PRA to the most recent the internal flooding PRA to the most recent EPRI pipe rupture frequencies, as EPRI pipe rupture frequencies, as indicated on indicated on page 7 of Exelon supplement page 7 of Exelon supplement letter dated letter dated August 14, 2017. August 14, 2017.
viii. Remove credit for core melt arrest in- Credit for core melt arrest in-vessel at high vessel at high reactor pressure vessel reactor pressure vessel (RPV) pressure (RPV) pressure conditions from the internal conditions will be removed from the internal events PRA model, as indicated on page 7 events PRA model, as indicated on page 7 of of Exelon supplement letter dated Exelon supplement letter dated August 14, August 14, 2017. 2017.
ix. Update the PRA model to account for load The PRA model will be updated to account for shedding when crediting serial operation of load shedding when crediting serial operation high pressure coolant injection (HPCI) and of high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) in loss reactor core isolation cooling (RCIC) in loss of of offsite power (LOOP) and station offsite power (LOOP) and station blackout blackout (SBO) scenarios, as indicated on (SBO) scenarios, as indicated on page 7 of page 6 of the Exelon supplement letter Exelon supplement letter dated August 14, dated August 14, 2017. 2017.
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 6 of 97 Docket Nos. 50-352 and 50-353 Limerick 50.69 PRA Implementation Items Description Resolution
- x. There are several parameters used in the As part of the categorization process for the fire THIEF model that may affect the calculated PRA, in addition to the list of fire PRA time available for manual suppression, and categorization sensitivities specified in NEI 00-therefore, the probability of manual 04, Table 5-3, a sensitivity will be performed in suppression in fire PRA scenarios where which credit is taken for immediate manual manual suppression is credited. Although suppression in scenarios in which manual the impact on the relative importance of suppression is already modeled, as indicated in modeled components is expected to be Exelon letter dated April 23, 2018.
small, there is uncertainty associated with these parameters.
The LARs submitted by Exelon to adopt TSTF-505 and implement a RICT program at Limerick Generating Station, Units 1 and 2, do not provide the status of the 50.69 implementation items described above. Therefore, please:
- i. Confirm that all of the 50.69 implementation items have been completed, or ii. If the 50.69 implementation items listed above have not been completed, describe:
- a. When the 50.69 implementation items are scheduled to be completed and how this schedule supports the proposed review schedule for the TSTF-505 LAR.
- b. How the 50.69 implementation items, which may include additional focused-scope peer reviews which may result in additional F&Os, will be adequately resolved during this LAR review.
- c. How potential changes to the risk profile and the total core damage frequency and large early release frequency resulting from completion of the 50.69 implementation items, will be addressed for these LARs.
Response
- i. All of the 50.69 implementation items listed above have been completed. These items have been incorporated into the FPIE PRA and FPRA Models of record.
These PRA model revisions were completed in 2018. All focused scope peer reviews necessitated by the implementation items listed above have been completed as part of the August 2018 focused scope peer review. All findings associated with the focused scope peer review have been closed in accordance with the Appendix X closure process. Therefore, the LAR reflects resolution of the listed 50.69 implementation items.
ii. Refer to i above.
- 4. Scope of focused-scope peer review(s)
LAR Enclosure 2, Section 3, states that a focused-scope peer review of changes considered upgrades was performed in August 2018 for the internal events and the fire PRA. The LAR did not provide a description of the August 2018 scope of this focused-scope peer review or if any F&Os were generated. Additionally, a number of the 50.69 implementation items involve performing focus-scope peer review(s). Therefore, provide the following:
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 7 of 97 Docket Nos. 50-352 and 50-353
- i. A description of the scope of the August 2018 peer review.
ii. Describe any other focused-scope peer reviews of the internal events, internal flooding or the fire PRA, performed after the most recent full-scope peer review, that have not been described in the TSTF-505 LAR. These focused-scope peer reviews could have been resulted from either addressing the 50.69 implementation items or from performing other changes to the PRA models.
iii. A description of all F&Os resulting from the focused-scope peer reviews listed in items i and ii above, and for each F&O, a disposition of the impact on this application.
Response
- i. The Focused Scope Peer Review included pre-initiators covered by HLR HR-A through HR-D, HR-I, operator response to spurious alarms covered by HLR HRA-A and HRA-E, and fire quantification covered by HLR FQ-A through FQ-F.
ii. No other focused scope peer reviews have been performed beyond those that are listed in the TSTF-505 LAR.
iii. The Focused Scope Peer Review & Finding Level F&O Independent Assessment Report 032362-RPT-10, Rev. 0, Oct. 2018 documents the closure of finding F&Os from the focused scope peer review. The resolved findings are listed in Table 4-1 below. There is, therefore, no impact on the TSTF-505 application from these findings.
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 8 of 97 Docket Nos. 50-352 and 50-353 Table 4-1 August 2018 Focused Scope Peer Review Findings F&O # Basis for Significance Discussion of Issue Possible Resolution Related SR Closure Evaluation (related F&O if applicable) 3-1 FQ-A4 (QU- A mean CDF and mean LERF Although parametric uncertainty Evaluate parametric Status: Resolved, PRA A3) have not yet been developed has been evaluated in the past uncertainty accounting for Maintenance accounting for the state-of- (2016 model documentation), it has the state-of-knowledge correlation (e.g., UNCERT). Basis: Appendix K of the knowledge correlation for the not yet been updated for the 2018 Limerick Generating Station latest Fire PRA model. model. Fire PRA Summary and Quantification Notebook (LG-PRA-021.11, Revision 0b) provides the updated parametric uncertainty results.
Application of the state-of-knowledge correlation is described in Section 3.4 of the Uncertainty and Sensitivity Notebook (LG- PRA-021.12).
Therefore, this SR is MET at CC II or higher.
No PRA Upgrade (re-performed an existing analysis with the same method. No impact to base model results.)
3-2 FQ-B1 Investigation of U2 LERF slower The incorrect gate type was Correct the gate type and Status: Resolved, PRA convergence identified a identified by the utility while requantify the model. If Maintenance modeling error (i.e., U2 gate for responding to a Peer Review the U2 LERF does not converge following model Basis: The LG217A1F0 the Suppression Pool question. correction, enhance the model contains the revised
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 9 of 97 Docket Nos. 50-352 and 50-353 Table 4-1 August 2018 Focused Scope Peer Review Findings F&O # Basis for Significance Discussion of Issue Possible Resolution Related SR Closure Evaluation (related F&O if applicable)
Instrument logic (e.g., see gate documentation to describe gate type for GHEP50000C-GHEP50000C-LPRCL) was an the review made to ensure LPRCL.
AND gate rather than an OR that no significant accident progression sequences for Therefore, this SR is MET at CC gate as in the U1 model). U2 LERF are being missed II or higher.
based on the truncation No PRA Upgrade (simple logic level achieved.
error correction, per Example 6 in the PRA Standard. No significant changes to model results.)
3-5 FQ-F1 (QU- Although sufficient model Two items are identified where Include additional detail in Status: Resolved, PRA F1) review was presented by the additional detail is judged the Fire PRA Maintenance Fire PRA model development warranted to support future users documentation related to top cutsets and top Basis: For comment (1) team, some level of detail was who may not have been part of the accident sequences. For Tables 4-4 through 4-7 of the omitted from the final PRA development team. example, Limerick Generating Station documentation in two areas. (1) Although the top CDF and (1) Add a column to Fire PRA Summary and Improving the documentation LERF cutsets are presented in the Tables 4- 4 through 4-7 in Quantification Notebook could facilitate use by analysts FPRA Summary and which each of the top 10 (LG-PRA-021.11, Revision 0b) not part of the original Quantification Notebook (e.g., cutsets is discussed, provide additional cutset development team in the Table 4-4 through 4-7), there is including the fire- detail for the top future. no discussion as to the scenario induced failures that do contributors to CDF and to details (e.g., fire- induced failures not appear in the cutset. LERF at Unit 1 and Unit 2.
that do not appear in the cutset) (2) Add tables that For comment (2) Section that present the full picture of present the significant impacts. accident sequences, their 4.2 of the Limerick (2) Although accident contribution, and their Generating Station Fire PRA sequence contributors are general description. Summary and Quantification presented in graphical form Notebook (LG-PRA-021.11,
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 10 of 97 Docket Nos. 50-352 and 50-353 Table 4-1 August 2018 Focused Scope Peer Review Findings F&O # Basis for Significance Discussion of Issue Possible Resolution Related SR Closure Evaluation (related F&O if applicable)
(e.g., Figures 4-15 & 4-16), Revision 0b) now includes there is no discussion of what Table 4-4-0 (CDF) and 4- 4-1 these sequences represent. (LERF) that summarizes accident sequences contributing >1% to fire risk, presenting a ready comparison unit to unit.
Additionally, pointers to the Event Tree Notebook and Level 2 Notebook have been added where additional details of sequences are provided.
Therefore, this SR is MET at CC II or higher.
No PRA Upgrade (documentation enhancement only) 3-8 FQ-A4 In review of high CCDP fire One MCR scenario with a high Remove the superseded Status: Resolved, PRA scenarios and discussion with CCDP/CLERP which has been fire scenario from the Maintenance the Fire PRA development team superseded by other refined single-top model.
Basis: Tables B-1 and B-2 of it was determined that one scenarios should be removed from the Limerick Generating high CCDP / CLERP scenario the single-top model. Station Fire PRA Summary
(%F024_MCB07_10C601_648_ and Quantification Notebook Y2) (LG-PRA-021.11, Revision 0b) with a CCDP of 0.348 was now shows this CCDP as 0 included in the model in error.
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 11 of 97 Docket Nos. 50-352 and 50-353 Table 4-1 August 2018 Focused Scope Peer Review Findings F&O # Basis for Significance Discussion of Issue Possible Resolution Related SR Closure Evaluation (related F&O if applicable)
This fire scenario was refined (not modeled) for Unit 1 and and superseded but was Unit 2.
inadvertently not removed Therefore, this SR is MET at from the single top model. CC I-III.
No PRA Upgrade (removing a fire scenario does not involve a new method, similar to Example 6 in the PRA Standard for correcting a logic error. No significant changes to model results.)
3-9 QU-D7 The pre-initiator DXV193DMI is When reviewing importance Develop a detailed HEP for Status: Resolved, PRA risk significant for LERF and measures, one HRA pre-initiator pre-initiator DXV193DMI. Maintenance therefore requires a detailed (DXV193DMI; PRE-INIT - Basis: Section 3.1.15 and HEP per SR HR- D2. RECIRCULATION PUMP SDC PATH Appendix B.22 of LG- PRA-004 RESTORATION ERROR) that uses a Volume 2 provide a detailed screening HEP (1E-02) was found to analysis of pre-initiating event be risk significant for LERF (i.e., human failure event FV=0.00956) and therefore requires DXV193DM and the value is a detailed HEP per SR HR-D2. included in the single top model.
Therefore, this SR is MET at CC II or higher.
No PRA Upgrade (applied existing HRA methods to one more
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 12 of 97 Docket Nos. 50-352 and 50-353 Table 4-1 August 2018 Focused Scope Peer Review Findings F&O # Basis for Significance Discussion of Issue Possible Resolution Related SR Closure Evaluation (related F&O if applicable) pre-initiator, per Example 20 in the PRA Standard. No significant changes to model results.)
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 13 of 97 Docket Nos. 50-352 and 50-353
- 5. Additional justification required by TSTF-505, Revision 2, Table 1 Table 1, "Conditions Requiring Additional Technical Justification," of TSTF-505 Revision 2 contains a list of required actions that may be proposed for inclusion in the RICT Program, but requires additional technical justification to be provided by the licensee.
The following LCOs are proposed to be included in the scope of the RICT program, but are identified in Table 1 as requiring additional justification:
3.3.4.2: End of Cycle Recirculation Pump Trip (EOC-RPT) Instrumentation (mapped to TSTF-505 NUREG-1433 Condition 3.3.4.1.A) 3.7.8: Main Turbine Bypass System (mapped to NUREG-1433 Condition 3.7.7.A)
Consistent with TSTF-505 Revision 2, Table 1 provide:
- i. Justification for the ability to calculate a RICT for the LCOs above, including how the system is modeled in the PRA, whether all functions of the system are modeled, and, if a surrogate is used, why that modeling is appropriate.
Response
TS 3.3.4.2 As indicated in the Enclosure 1 Table E1-1 of the LAR, the EOC-RPT is explicitly modeled in detail in the Limerick PRA and, therefore, a RICT can be calculated. The TS function described in Attachment 1 of the LAR is the PRA modeled function. There are no non-modeled functions for this system. The proposed change to the Action statements for this TS include a note restricting the use of RICT if trip capability is not maintained. Therefore, the LCO meets the listed requirements for inclusion in the RICT program.
TS 3.7.8 The Main Turbine Bypass Valves are modeled in a conservative fashion in the Limerick PRA as noted in Table E1-1 of Enclosure 1 of the LAR. Therefore, the RICT can be calculated for this LCO. The TS function to limit peak pressure in the main steam lines and to maintain reactor pressure within acceptable limits during events that cause rapid pressurization is the PRA modeled function. The combined pressure control function of the turbine control valves and bypass valves while the main turbine is online is not modeled but this is not a mitigation function that would affect risk. Therefore, the LCO meets the listed requirements for inclusion in the RICT program.
Additional Observations While not determined to be sufficiency or completeness of scope items, the NRC staff made the following additional observations during its initial review of this LAR that may, upon additional detailed review, require additional information:
License Amendment Request Supplement Attachment Adopt TSTF-505, Rev. 2 Page 14 of 97 Docket Nos. 50-352 and 50-353
- 1. NUREG-1855 guidance revisions LAR Enclosure 4, Information Supporting Justification of Excluding Sources of Risk not Addressed by the PRA Models, references Revision 1 of NUREG-1855, Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decision Making. LAR , Evaluating Key Assumptions and Sources of Uncertainty, references Revision 0 of NUREG-1855 (ADAMS Accession No. ML090970525). NUREG-1855 most directly supports the evaluation done in Enclosure 9. Revision 1 of NUREG-1855 (ADAMS Accession No. ML17062A466) references EPRI TR-1026511 Practical Guidance on the Use of PRA in Risk-Informed Applications with a Focus on the Treatment of Uncertainty, which includes guidance and generic issues on key assumptions and sources of uncertainty associated with the fire and external hazard PRAs. Therefore, provide the following:
- i. Confirmation that the evaluation of key assumptions and sources of uncertainty provided in LAR Enclosure 9 was done using Revision 1 of NUREG-1855, or ii. A supplement which is consistent with Revision 1, or iii. Justification for why the use of Revision 0 of NUREG-1855 is adequate for this application.
Response
The evaluation of key assumptions and sources of uncertainty provided in LAR Enclosure 9 was done using Revision 1 of NUREG-1855. The reference in Enclosure 9 is incorrect and should be NUREG-1855 Revision 1 consistent with Enclosure 4.
References
- 1. Letter from J. Barstow (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, 'Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b'," dated December 13, 2018 (ADAMS Accession No. ML18347B366).
- 2. Letter from V. Sreenivas (U.S. Nuclear Regulatory Commission) to B. Hanson (Exelon Generation Company, LLC), "Limerick Generating Station, Units 1 and 2-Supplemental Information Needed for Acceptance of Requested Licensing Action to Adopt Risk-Informed Completion Times in Accordance with TSTF-505, Revision 2 (EPID L-2018-LLA*0567),
dated January 30, 2019 (ADAMS Accession No. ML19030A147).
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 15 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
IE-A7-01 IE-A7 Cat II Category II requires a review of RESOLVED.
Now IE-A9 initiating event precursors. There was no documentation demonstrating that Appendix D of the initiating event Cat I this review was performed. notebook contains a listing of all LERs over the ten year period preceding the last PRA update and their disposition in terms of their relevance to PRA initiating events.
IE-D3-01 IE-D3 Cat I/II/III Key assumptions and key sources of RESOLVED.
Cat I/II/III uncertainty are not specifically identified in the documentation by The Summary Notebook includes a element. The summary document comprehensive characterization of key does include a list of key model assumptions and model uncertainty. The uncertainties and includes a number results of that assessment are factored into of sensitivity cases; however, it is not the identification of potentially key clear that it goes far enough to assumptions for applications of the model.
support the intent of the latest requirements. A systematic process should be documented considering each of the standard PRA elements, including appropriate definitions.
It is recognized that EPRI is preparing a product intended to address this issue and Limerick is a pilot plant. A draft of the EPRI uncertainty report
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 16 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) for Limerick was provided which represents the state of the art in this area. When finalized, this document is expected to meet the intent of the supporting requirements.
AS- AS-A5 Cat I/II/III MSIV re-opening is modeled in many RESOLVED.
A5/A6-01 Cat I/II/III of the transient event trees. It is unclear whether this action would be As a result of Finding 86 (FPIE PR) QU-A4-directed via EOPs (either 100 or 101) 01, which questioned credit for FW/PCS or other procedures. This action recovery, credit for re-opening the provides minimal mitigative potential MSIVs was removed during the 2008 due to the timing and equipment update.
necessary for successful operation or restoration of FW and PCS in short term scenarios.
Also, recovery of feedwater is also modeled in transient event trees and fault trees. FW recovery requires MSIV re-opening and provides limited mitigative potential. In the IORV/SORV event tree, both MSIV re- opening and FW recovery are modeled. It is likely that level control issues as well as action timing would prevent MSIV re-
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 17 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) opening for a large spectrum of initiating events in which it is credited.
AS-B3-01 AS-B3 Cat I/II/III Loss of coolant accidents outside RESOLVED Cat I/II/III primary containment are modeled in several event trees. The discussion Section 18 and 19 of the Event Tree Notebook contained in the event tree notebook documents consideration of other impacts of indicates that there are no additional breaks outside containment, and a basis was impacts associated with the breaks of provided for cases where no impacts were RWCU, main steam, HPCI and others expected. There was a discussion of how when the break occurs outside the RHRSW would be failed in the case of an containment. ISLOCA in one of two core spray lines.
AS-B6-01 AS-B6 Cat I/II/III Vapor suppression via manual RESOLVED.
Now AS-B7 actuation of drywell sprays and rapid Cat I/II/III depressurization are each assigned an The two separate actions were combined HEP of 0.1 for medium LOCAs. This into a single action, VHUDS1DXI "FAILURE TO results in a combined HEP for the two CONTROL CONTAINMENT PRESSURE IN actions ("ANDed" together) of 1E-02 MLOCA WITH VS BYPASS," with a common per demand. It is judged that these cognitive. This represents the likelihood that actions should be assigned a high the operators fail to recognize the need to probability of failure given the timing control containment pressure (which fails all of the event sequence, specifically methods) or that they fail to execute the the timing to reach containment control using one of the two available failure. methods. The individual 0.1 screening HEPs were replaced with a detailed analysis to develop an overall HEP that accounts for the
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 18 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) dependencies.
SC/SY- SC-B1 Cat II The success of fire water makeup to RESOLVED.
B1-01 Cat II the vessel to prevent core damage after depressurization needs a rigorous A detailed HRA calculation was performed for analysis. Currently, the fire pump and aligning fire water makeup to the reactor operator action to crosstie fire vessel as documented in FPIE PRA Post protection water to RHR is modeled as Initiator Calculation: A29 (Operator fails to a "super component" with a cross-tie fire water to RHR).
probability of failure of 0.5.
Reportedly, the probability is high to Further discussed in response to RAI 1.d in include the uncertainty as to whether ML18019A091, Response to request for or not the fire protection system can additional information application to adopt actually prevent core damage after 10CFR50.69:
depressurizing the reactor and within The Limerick PRA RHR System Notebook four hours after an initiating event. documents the ability of the fire water system The failure to crosstie fire water to RHR to provide 300 gpm of water to the reactor appears in the third highest frequency vessel when the pressure of the reactor vessel core damage cutset and has a RAW of is 100 psig or less. This confirms that 1.05. Choosing a 0.5 probability of sufficient flow and amount of water is
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 19 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) failure for this event is tantamount to available as assumed for the HRA calculation.
using a screening value. Screening This alternate injection source is modeled as a values should not appear in the success path in the PRA in late scenarios when dominant cutsets. the RPV has been depressurized.
SC/HR- SC-B1 Cat II The HRA calculation for manual RESOLVED.
B1-03 Cat II depressurization for Medium LOCA events (HRA Notebook Calculation A detailed HRA calculation was performed
- 45) credits an available time of 22 for operator failure to initiate emergency minutes based on MAAP run LI0035a. depressurization (medium LOCA, steam MAAP Case LI0035a (Success Criteria break) as documented in FPIE PRA Post Notebook, Table A-1) states that the Initiator Calculation: A14 (AHUSS1DXI, break area is 0.01 ft2 (equivalent to a operators fail to initiate emergency 1.4" diameter line break) for the depressurization (medium LOCA, steam Medium LOCA event. This break size break).
seems more consistent with a Small LOCA event. This same issue exists for A detailed HRA calculation was performed for MAAP Cases LI0031, LI0033, and operator failure to initiate emergency LI0035. depressurization (medium LOCA, water break) as documented in FPIE PRA Post Initiator Using a larger break size (e.g., 4" Calculation A16 (AHUWS1DXI, operators fail to diameter) could significantly decrease initiate emergency depressurization (medium the estimated time available to LOCA, water break).
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 20 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) manually depressurize for Medium LOCA events.
SY-A6-03 SY-A6 Cat I/II/III The HVAC notebook excludes CCF of RESOLVED.
Cat I/II/III EDG fans based on it being included in the EDG CCF values. This may not be Appendix I of the data notebook, Volume 1 true. If HVAC failures were included in Table I-1 defines the equipment the EDG, then HVAC modeling for boundaries. For the EDGs Room heating EDGs is not required at all. and ventilating is not included. Appendix A, Section A.10 of the data notebook, Volume 2 documents the CCF analysis for the EDG ventilation fans. The CCF for failure pairs are included for the fans.
SY-A11- SY-A11 Cat I/II/III The diesel cooling, after a LOOP event, RESOLVED.
01 Now SY-A10 credits ESW and RHRSW. RHRSW has Cat I/II/III two locked closed valves that must be The logic for crediting RHRSW to ESW cross-tie opened and the RHRSW pumps capability is removed in the current model.
manually started in order to establish cooling to the diesels. Early flag events fail this crosstie with operator action WHURSWDX10.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 21 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
However, when the long term flag, XHOSHR, is used the crosstie succeeds 90% of the time. It is inappropriate to credit RHRSW for diesel cooling since, given a LOOP, the diesels auto start and require cooling within a few minutes. RHRSW being available via the crosstie after 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> does not meet the immediate cooling requirement. It is understood that the EDGs will trip on high temperature for LOOP events.
Given this trip occurs, the model should account for the operator action and time involved in reestablishing cooling and restarting the EDGs.
SY-A11- SY-A11 Cat I/II/III Fault tree GEP11423 (typical) is used as RESOLVED.
04 Now SY-A10 the ESW power supply for pump A of Cat I/II/III loop A. This fault tree credits cross The model logic was changed to only credit tying the 4 KV buses. Ultimately, the 4 crosstie actions > 2hrs. See the 4kV system KV cross tying is credited for the ESW notebook.
power when ESW is cooling the diesels.
No credit should be given for 4 KV crossties to power ESW when ESW is cooling the diesels since there is insufficient time to perform this task before the diesels overheat. The
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 22 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) application of the 4KV crosstie should only be used in scenarios where the powered equipment is not needed until the crosstie can be accomplished per the plant procedures. This same concern applies to the 480V loads that are fed from 4KV.
SY-A12b- SY-A12b Now Met The failure of the HPCI minimum flow RESOLVED 01 SY-A13 valve to close will cause a flow Not Met diversion which can challenge the CST The HPCI injection line has a diameter of 14.
inventory. The minimum flow valve The min flow line has an orifice with a failure to close should be modeled and diameter of 1.7. Given these diameters, the water inventory addressed. Note: if flow area is approximately 150sq. in. and the HPCI is operated with elevated flow area of the min flow line is suppression pool temperatures, approximately 4 sq. in. A general assumption switching HPCI suction to the used in many PRAs that has been traditionally suppression pool can cause HPCI to fail accepted is that a flow diversion with area from inadequate lube oil cooling. less than 10% of the main flow path is considered negligible (because of conservatisms in the design basis) without the need to perform a specific analysis.
Therefore, modeling of this flow diversion is not required.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 23 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
SY-A13- SY-A13 Cat I/II/III Spurious operation of instruments and RESOLVED.
01 Now SY-A14 transmitters that can trip a mitigating Cat I/II/III system have not been included in the The data notebook, Table D-1 documents the system fault trees. Note that the ASME failure probability for miscalibration and Standard makes a distinction between spurious operation. The failure probability for miscalibration and spurious operation. spurious operation are two orders of magnitude less than those for miscalibration (spurious operation 1% of miscalibration). SR SY-A14 states "One or more failure modes for a component may be excluded from the systems model if the contribution of them to the total failure rate or probability is less than 1% of the total failure rate or probability for that component, when their effects on system operation are the same." Therefore, excluding the spurious operation failure mode is acceptable.
SY-B8-01 SY-B8 Cat I/II/III A calculation justifying HPCI operation RESOLVED.
Cat I/II/III beyond six hours is needed. It is not adequate to assume that if suppression A best-estimate analysis of room heatup for pool cooling is available HPCI room HPCI was performed (it was also performed cooling is available. for RCIC, although this was not a subject of the Finding).
The calculation (CC-AA-309-1001, Rev. 7, Calc LM- 0400) shows that the room temperatures for each room reach a stable
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 24 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) temperature after a few hours and that temperature is maintained from that point forward by natural processes. In each case, temperature margin against failure is maintained. Therefore, room cooling is not required.
HR-G4- HR-G4 Cat III The assumed time available to RESOLVED.
01 Cat III manually depressurize the RPV for non-ATWS events is assumed to be 55 Appendix A of the HRA Notebook (LG-PRA-minutes, based on the time to core 004, Rev. 3) shows that the time used for time damage (HRA Notebook, Appendix A, available to depressurize (using two valves) is Calculation 33, MAAP Case LI0008). 38.9 minutes. It is stated that this is based on Using the entire time to core damage analysis provided in the SC notebook, section as the time available for manual 3.3.2.
depressurization could be non-conservative. The HRA Notebook states that "Once depressurization starts, steam cooling will prevent core damage, thus depressurization is credited to the point of when core damage is estimated to begin." This statement is judged not to be supported by the Limerick MAAP cases.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 25 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
A similar MAAP case (Case LI0012) indicates that if manual RPV depressurization with 2 SRVs is initiated at 49 minutes (i.e., time to TAF + 30 minutes), core damage would still occur at 54 minutes. MAAP Case LI0012 appears not to support using the entire time to core damage as the time available for manual RPV depressurization. In addition, MAAP Case LI0011 indicates that if manual RPV depressurization with 2 SRVs is initiated at 39 minutes (i.e., time to TAF + 20 minutes), then core damage can be averted.
HR- HR-H3 Cat I/II/III Common cause operator error events RESOLVED.
H3/I1-01 Cat I/II/III are included across system boundaries, but it appears that some cross system The HRA notebook Section 5.2 discusses the combinations are not addressed, but process used to identify the HFE combinations rather are dismissed as risk negligible. that have the potential to be significant risk contributors due to dependency analysis. The process followed, which sets the HEPs to artificially high values so that the combinations come to the top, is typical of current practice across the industry. The
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 26 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) dependency levels are based on consideration of PSFs and implemented in the HRAC, with manual adjustments made based on specific review of the combinations. This process makes no distinction regarding whether or not the dependency is across system boundaries since all HFEs are assigned the same high values, thus all important combinations are captured. Additional details on the analysis of key combinations are provided in Appendix H.
DA-B1-01 DA-B1 Cat II Category II requires usage RESOLVED.
Cat II characteristics to be included in the component grouping. The use of The updated data analysis utilizes maintenance rule data may take this groupings consistent with the available into account for some components, data including the recently implemented however, there is no discussion to generic data from NUREG/CR-6928.
support the extent to which this Section 2.6 and Appendix F of the data requirement is met. notebook provides a description of type codes used in the model.
DA-B2-01 DA-B2 Cat I/II There is no discussion of unique RESOLVED.
Cat I/II components or how outliers (if any) were treated. No specific examples Section 2.6 and Appendix B of the data were found that created an issue, notebook provides a description of plant-however there is no assurance that specific data used in the model. Section B.1 they were evaluated. documents that the plant specific data analysis included consideration for excluding
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 27 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) outliers in the data. That is, infrequently tested/operated components were not included in the plant specific data update group.
DA-C6-01 DA-C6 Met The methods used to determine RESOLVED.
Not Met exposures (demands, runtime, etc.)
were not documented. The reviewer The data notebook was updated to clearly could not validate how demands identify the MSPI as the primary data source were obtained. for demands, runtime, etc., with the Maintenance rule providing functional failure data. Component failure data, demands, and run hours compiled by Limerick system managers was used for some key SSCs that are not within the scope of the Limerick Maintenance Rule Programs data collection and reporting efforts or the Limerick MSPI basis document. The results of the data collection were confirmed with system engineer interviews. See Appendix B of the Data Notebook for details of the discussions held with the system managers.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 28 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
DA-C7-01 DA-C7 Met The methods used to determine RESOLVED.
Not Met exposures (demands, runtime, etc.)
were not documented. The reviewer See DA-C6 disposition.
could not validate how demands were obtained.
DA-C10- DA-C10 Cat II There is no documentation to support RESOLVED.
01 Cat II this requirement. If surveillance test data was not used, then this SR is Section C.4, Table C-4, of the data notebook, "n/a". Otherwise, additional Volume 1 includes details on the basic documentation is needed to events that are calculated using quarterly or determine how surveillance test data bi-annual surveillance interval.
was used as a basis to count component demands to validate that Tables B-3 through B-6 provide the plant the SR is met. specific maintenance rule and MSPI component experience data. The use of this data is sufficient to meet the intent of the SR.
DA-C12- DA-C12 Cat I/II/III Category II requires interviews of RESOLVED.
01 Now DA-C13 maintenance and operations for Cat I/II/III significant basic events. The significant The maintenance data is taken directly from basic events are not specifically the MSPI when possible. In the situations defined although the documentation that reliable estimates for particular indicates that engineering had input. It equipment are not available, interviews with
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 29 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) is likely that engineering used system engineers were performed to maintenance and operations input but generate/confirm the unavailability this is not documented. estimates used in the PRA. During the 2013 PRA Update system manager interviews, system unavailability was discussed with the respective system manager. The change in the unavailability value in comparison to the previous update (2008 PRA Update) was discussed. During this discussion, reasons for the unavailability values increasing or decreasing were provided. These notes are documented in Appendix H of the data notebook, Volume 1.
DA-C14- DA-C14 Cat I/II/III Hardware recoveries are applied to RESOLVED.
01 Now DA-C15 EDG, IA, RHR, RHRSW, and ESW.
Cat I/II/III There was no plant specific data used Appendix G of LG-PRA-010 Data 2013 V1 to determine Mean Time To Repair addresses the hardware recoveries are (MTTR) values and some of the data applied to EDG, IA, RHR, RHRSW, and ESW.
sources (WASH-1400 and IEEE-500) Section G.1 addresses recovery estimates are dated. Standard practice excludes and G.2 addresses repair estimates.
hardware recoveries, especially when Section G.2.1.13 of LG-PRA-010 Data 2013 V1 there is minimal benefit. The summary addresses EDG repair times. Section G.2.2 document indicates about a 1% CDF addresses IA repair time. Section G.2.3 impact due to the hard ware addresses RHR. RRHSW, and ESW repair times.
recoveries. A second recovery term is also applied in the level 2 fault trees Further discussed in response to RAI 1.d in
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 30 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) with very little explanation. ML18019A091, Response to request for additional information application to adopt 10CFR50.69:
The Limerick PRA Data Notebook provides historical information on repair estimates for EDGs and RHRSW / ESW / RHR pumps.
However, the basic events modeling these repairs are set to "T" (True) in the Limerick PRA flag file and are compressed out in the quantification process. Therefore, repair of SSCs modeled by these events is not credited in the PRA model.
The Limerick PRA Data Notebook evaluates the recovery of instrument air only for the purpose of recovering the emergency containment vent. This evaluation is based on judgment, consideration of Limerick accident scenario specifics (MAAP runs), and review of industry studies (EPRI study NSAC-161, WASH-1400). The recovery of instrument air has been included in the model based on this recovery evaluation.
Given that there is uncertainty in the recovery steps that would be taken to recover
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 31 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) instrument air to support containment venting, this event is being set to True in the flag file during the current PRA model update and thus will also be compressed out of the quantification process.
QU-A4- QU-B4 Cat I/II/III The quantification results provide RESOLVED.
01 Cat I/II/III credit for hardware recovery of FW/PCS, ESW, RHRSW, and EDGs Credit for repair of EDGs, and RHRSW, RHR, based on WASH-1400 MTTR models or and ESW pumps was removed from the model other repair models. There appears to as part of the 2008 update. Recovery of be more credit for hardware recovery FW/PCS requires re-opening of the MSIVs.
than in most industry PRAs. (See similar Credit for re-opening the MSIVs was also F&O for supporting requirement DA- removed during the 2008 update.
C14.)
Further discussed in response to RAI 1.d in ML18019A091, Response to request for additional information application to adopt 10CFR50.69:
The Limerick PRA Data Notebook provides historical information on repair estimates for EDGs and RHRSW / ESW / RHR pumps.
However, the basic events modeling these repairs are set to "T" (True) in the Limerick
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 32 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
PRA flag file and are compressed out in the quantification process. Therefore, repair of SSCs modeled by these events is not credited in the PRA model.
The Limerick PRA Data Notebook evaluates the recovery of instrument air only for the purpose of recovering the emergency containment vent. This evaluation is based on judgment, consideration of Limerick accident scenario specifics (MAAP runs), and review of industry studies (EPRI study NSAC-161, WASH-1400). The recovery of instrument air has been included in the model based on this recovery evaluation.
Given that there is uncertainty in the recovery steps that would be taken to recover instrument air to support containment venting, this event is being set to True in the flag file during the current PRA model update and thus will also be compressed out of the quantification process.
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QU-B4- QU-B4 Met There are several cases where basic RESOLVED.
01 Not Met event probabilities exceed 0.1. In some cases, the basic event The issue is addressed by the conversion to probabilities are significantly greater CAFTA, the associated use of TRUEs (.T.) as than 0.1 and occasionally 1.0 is used opposed to 1.0 probabilities, and the upper to represent logic or events that are bound algorithm in CAFTA. Most of the basic no longer used. In these cases, the events that have values greater than 0.1, rare event approximation is not valid. have a probability of 1.0 (not credited HEPs, When used under "OR" gates, this flag events, recovery tags, etc.). These are set treatment can be excessively to .T. in either the flag file or the recovery conservative and potentially invalid. file. Those events that are greater than 0.1 In addition, this treatment can but not 1.0 are mostly Level 2 increase the complexity of model phenomenological basic events in which review since some events that appear there may be little basis to refine the point in the logic are actually not used (i.e., estimate. There are also some HEPs that assigned a failure probability of 1.0). could have a probability greater than 0.1 See also supporting requirements AS- which are refined during the HRA update.
C1 and QU-B8. Other basic events could be fractional multipliers (0.5 of the time pump A is running and 0.5 of the time pump B is running) which are modeled under AND gates. For those 1.0 events that represent logic or events that are no longer used (repair events, etc.), the basic events are set to .T. in the flag file which compresses that particular logic out during quantification.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 34 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
QU-B8- QU-B8 Met There are several cases where logic in RESOLVED.
01 Now QU-B9 the model has been "disabled" via the Not Met use of failure rates of 1.0. Several For those 1.0 events that represent logic or cases are noted as follows: events that are no longer used (repair events,
- LPIC "A" fault tree page 7 etc.), the basic events are set to .T. in the flag models the cross-tie for A&C but the file which compresses that particular logic out HEP values used are 1.0 for all cases. during quantification.
- Accident class IIID event tree contains nodes that are not used since The LPCI A cross tie value for realigning the the conditions for the failure of crossover valve DHU82XDXI was set to 1.0 containment are known prior to in the fault tree and .T. in the flag file.
entering the event tree.
- LPI fault tree (VTR 2), Accident Class nodal basic events not used specifically the gates for early injection are set to .T. in the flag file. The Level 2 and the basic event for operators fail to Notebook provides details on the open RHRSW cross-tie are assigned a containment event trees (CET).
1.0.
- In the event tree notebook, The RHRSW crosstie for injection action page 22-12, gate GBD2532 is an "OR" specific to MLOCA scenarios (JHU073DXI) gate with event HHUFWXDX1 which is which is set to 1.0 and .T. in the flag file.
set to a probability of 1.0.
Basic Event HHUFWXDXI Failure To Isolate This treatment poses several issues. HPCI Injection Through Core Spray Line (ATWS) is set to 1.0 in the model and .T. in the These include the unnecessary flag file.
complexity of the model, difficulty in reviewing the model as well as the
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 35 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) increased potential for misinterpretation of the model. In addition, in certain circumstances the mathematics of Boolean logic may be adversely impacted due to violation of the rare event approximation as well as the generation of non-minimal cutsets.
QU-D1c- QU-D1c Cat II/III In Table 3.5-1 of the PRA Summary RESOLVED.
01 Now QU-D3 Notebook, LERF cutset #3 (2.94E-Cat II/III 9/yr) appears to be non-minimal For those 1.0 events that represent logic or compared to LERF cutset #2 (1.32E- events that are no longer used (repair events, 8/yr). Cutset #2 includes an HEP of etc.), the basic events are set to .T. in the flag 1.0 for RHRSW crosstie injection. A file which compresses that particular logic out secondary failure of 0.223 to during quantification. The modeling continues preclude the RHRSW crosstie is non- to be captured in the CAFTA model for minimal compared to cutset #2. This historical purposes.
leads to a conservative result.
Eliminating this cutset would reduce the LERF by approximately 5%.
QU-D3- QU-D3 Met The PRA Summary Notebook provides RESOLVED.
01 Now QU-D4 a table to compare CDF results to Not Met other Exelon plants. However, the Table 4.6-1 compares the current CDF documentation does not provide any results for all BWR Exelon PRAs as a function discussion for the differences in the of Accident Class. The CDF for Limerick is in results. the middle range for the Exelon BWR plants.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 36 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
Table 4.6-2 provides a detailed contribution breakdown by initiating event. The notes to this table also provide discussion of differences.
The comparison of the Limerick PRA is performed on two levels: The plant system comparison and the model comparison These comparisons allow the insights derived from the uncertainty analysis on a similar plant to assist in the identification of insights on Limerick. The comparison plant used here is a composite or "typical" plant.
The first examination addresses the plant system comparison. Table I.5-3, Critical Safety Functions At Limerick Compared With "Generic" BWR," compares the plant systems and identifies the potential impact on the risk spectrum.
LE-C9a- LE-C9a Cat II/III For Loss of Vapor Suppression events RESOLVED.
01 Now LE-C11 (Level 1 Accident Class 3D), the Level 2 Cat II/III analysis is modeled with a detailed Treatment of vapor suppression failure cases containment event tree. Most industry (Accident Class 3D) now lead directly to a Level 2 PRAs model Loss of Vapor Large, Early Release. Reviewed the Level 2 Suppression core damage events as Fault and Event Trees for the DI, RX, and CZ leading directly to a Large, Early nodes and confirmed that the probabilities
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 37 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
Release for the following reasons: were set to 1.0 which are subsequently set to
- Loss of Vapor Suppression events .T. in the flag files to effectively remove the would cause a rapid pressurization of logic during quantification.
the drywell and result in drywell overpressure. The Level 2 node that addresses the status of the drywell (DI node) should have a probability of 1.0 instead of 0.26. *The failure of the drywell could have a significant impact on the ability for continued RPV injection (e.g., pinching of the injection piping). This would lead to high failure probability for in-vessel recovery (Level 2 RX node). *The Level 2 Containment Intact node (CZ node) should be 1.0 because early containment failure is guaranteed for Loss of Vapor Suppression events.
IF-C3-01 IF-C3 Cat II Failure by spray and submergence RESOLVED.
Now IFSN-A6 were considered for all internal Cat I flooding initiating events. Section 2.2.5 Pipe whip effects were investigated and stated that dynamic effects of pipe determined to not be a concern for piping breaks were considered in the design containing moderate energy water sources.
process and that the effects were not Jet impingement effects were also considered further in the internal determined to not be a concern for piping flooding PRA. No documentation of encapsulated by aluminum lagging. Section
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 38 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) the specific equipment evaluated in 3.4.9 of the internal flood notebook provides the PRA compared to equipment additional information to address pipe whip considered in the design analyses, e.g., and jet impingement concerns. Any damage EQ lists, was documented Since the inflicted on plant equipment due to sprays PRA can credit non-safety-related from a pipe rupture were shown to affect equipment, relying on design basis only those components located within a evaluations to dismiss these dynamic radius of influence of about 16 feet, which effects may credit equipment that implies that whether due to water sprays or cannot withstand the effects jet impingement, equipment located within considered in the design analysis. Also, this radius of influence was considered to be the PRA models may evaluate breaks rendered unavailable.
beyond those of the design basis. Section 3.4.18 addresses pipe whipping due to HELB.
IF-E6-01 IF-E6 Met No quantification of flood-related RESOLVED.
Now IFQU-A7 LERF is performed or documented.
Not Met Section 4.2, Figure 4.2, and Figure 4.4 of the internal flood notebook provide results of flood- related LERF. Flood scenarios that contribute to LERF are quantified. Figure ES-2A and Figure ES- 3B of the summary notebook provide flood-related contributions to total LERF.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 39 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
IF-F3-01 IF-F3 Met Discussion of Issue: Sources of RESOLVED.
Now IFQU-B3 uncertainty and assumptions Not Met associated with the internal flooding The internal flood notebook was updated analysis were not documented in the to include uncertainty and assumptions.
analyses reviewed. Section 2.2 includes assumptions and Appendix G includes uncertainty and sensitivity.
1-1 ES-C1 Met No instrumentation related to the RESOLVED.
Not Met operator actions are identified and modeled in Limerick fire PRA. Instrumentation supporting human failure events is currently explicitly modeled in the This results in a limited amount of Fire PRA. The plant response model has been instrumentation included in the expanded to include explicit logic for the equipment list, consisting of the SSEL instrumentation. The documentation is instruments (Rx Level, Pressure, etc.). available in both the equipment selection Additionally, the FPRA modeling does and plant response model notebooks not fully model the impact of failed instruments. In particular, the HRA is The appropriate instruments have been performed assuming the non-credited assigned and modeled for the corresponding instruments are not available. Overall, human failure events in the HRA analysis.
the resulting HEPs are conservative resulting in an overall estimate of CDF from operator failures that is conservative.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 40 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 1-8 IGN-B5 CC I/II/III Section 1.3.3 of the FIF Notebook RESOLVED.
CC I/II/III describes the assumptions and uncertainty sources. However, these The lognormal distributions from NUREG-2169 uncertainty parameters for fire ignition were used to quantify uncertainty. These frequencies are changed to other distributions are documented in the ignition distribution types from the original (ex: frequency and uncertainty notebooks.
variance to lognormal in the final quantification), but no description is provided for the impact on uncertainty changes.
1-11 HRA-A2 Cat I/II/III Procedures referred for this operator RESOLVED.
Cat I/II/III actions are SE-1 and SE-6 which are dedicated to remote shutdown and The discussion provided in the assessment of alternate shutdown. However, the this HFE in the fire HRA notebook states that operator actions are applied to other credit for the local action is based on a sequences as well as MCR general instruction to try to open the valve, abandonment scenario. and that because of the training given at Limerick the operators would try all means to
- SE-1 or SE-6 is applicable for only open the valve, including locally, even if not when specific condition is provided to specifically stated in the procedure (that is, operators as described in the the operators interpret the instruction "open procedures. the valve" as including local operation if remote operation fails). Some credit in such
- This operator action requires at least an instance is reasonable. The HRA modelling one of multiple cue information. takes credit for the existence of a procedure Without modeling of indication(s), (other than SE-1 and SE-6) that gets the
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 41 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) the HEP should be 1.0. operators to that point during
-for information, note that internal non-abandonment scenarios. In this case, the logic doesn't have a auto signal logic non- abandonment procedure T-102 PRIMARY as well as manual action. CONTAINMENT CONTROL would lead to an instruction calling for the re-alignment. OP-Reviewers key concern raised for SR, LG103- 102-1002STRATEGIES FOR HRA-A2 is the potential unavailability SUCCESSFUL TRANSIENT MITIGATION would of cue information due to fire damage provide for critical parameter monitoring and this concern is not limited to the that would also lead to instructions for re-OA, JHUSPVDX10. Other examples alignment. Thus there are other, non-identified are AHUXTRDXI(-R1) and abandonment procedures that would lead to ZHULVCDXI. the actions.
In case of AHUXTRDXI(-R1), HRA The FPRA was updated to include the credited report (LG-PRA-021.04) presents some cues in the logic model. Appendix D of the of cue information and HEP was equipment selection notebook and Appendix calculated based on the availability of A of the fire HRA notebook provides the indications in the MCR and relied on details regarding which instruments are fact that SSEL has RPV pressure and included for each action. The general level instruments. To support validity of assumption regarding the availability of HEP calculated for AHUXTRDXI (- R1), instruments because the instrument is on the availabilities of cue information SSEL is no longer used. Instrumentation logic (and the applicable power supplies) is included including their dependencies (power, with the operator actions as applicable. Cables interlock) need to be reviewed for are included in the FPRA model such that if a every related scenario or to be included cable is damaged in a given fire scenario then in the logic model. the instrumentation logic would fail.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 42 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
However, it was identified that neither of the above were addressed in the Limerick fire PRA for these example events.
1-15 HRA-A2 Met No discussion is provided in PRA-021- RESOLVED.
(HR-E3) 04 of the FPRA for review and Not Met interpretation of the procedures with The fire HRA Notebook, Appendix D plant operations or training personnel includes a discussion of the operator to confirm that interpretation is interviews conducted that covered the consistent with plant operational and following general areas:
training practices.
- General control room practices
- Operations response in fire events
- Performance Shaping Factors expected in fire events
- Potential undesired operation actions in response to fire-induced instrumentation failures
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 43 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
- Plant procedures and performance shaping factors (PSFs) for post-fire shutdown rom outside the control room In addition, in the detailed HFE analyses contained in Appendix A notes in certain cases additional interviews were conducted to address specific actions where further clarification was deemed necessary. Appendix E of the FPIE HRA notebook contains summaries of interviews conducted in 2004, 2008 and 2013. These included discussions of specific HFEs. Again, Appendix A provides examples where additional interviews were conducted as needed.
1-19 FQ-F1 Met LERF uncertainty distribution is RESOLVED.
(LE-F3) provided in Figure 5-2 and 5-4 for Unit Not Met 1 and Unit 2, respectively. LERF specific assumptions are discussed in Table 3-1 of the uncertainty notebook. An However, LERF specific uncertainty uncertainty matrix for each of the 16 and assumptions or limitations, were NUREG/CR-6850 tasks is provided in Table 3-not provided in the results. For 1, NUREG/CR-6850 uncertainty matrix that example, no discussion of LERF includes LERF assumptions. There is also a sources of uncertainty are more detailed discussion in Section 3.2 of documented in Table 5-1 of the same notebook.
quantification notebook.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 44 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
Additionally, the Limerick fire PRA has no review results of containment isolation system which is a potential source of uncertainty.
2-3 CS-A4 Cat II/III Based on discussion with Limerick risk RESOLVED.
Cat II/III management team, an assumption has been made that instruments were not Instrumentation supporting human failure identified by assuming that safe events is now explicitly modeled in the shutdown analysis ensured that one FPRA. The plant response model has been train of instrument is always available. expanded to include explicit logic for the As a result, the identification of instrumentation. The documentation is instruments was not performed. available in both the equipment selection and plant response model notebooks.
However, such treatment may not be The appropriate instruments have been adequate for multi-compartment assigned and modeled for the corresponding analysis, which could potentially fail human failure events in the HRA analysis.
multiple channels of instruments.
2-5 PRM-A4 Cat II/III A number of excluded fire impact items RESOLVED.
Cat II/III (~400,000) were included in FRANX FireImpact table. However, the The basis for the table was added to the fire technical basis was not evident. scenario development notebook. PAU targets are identified based on walkdown
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 45 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
Additionally, the basis for this table, observations and drawing reviews by including the source of the table qualified Exelon personnel. PAU targets are information, is not provided. included in the scenario reports in Appendix A of the fire scenario development notebook.
Finally; the scenario report includes a This walkdown data is then entered into the list of excluded events and targets, but ARCPlus' Fire PRA module software where does not include the listing of events in the data is maintained. ARCPlus' Fire PRA the FireImpact table. module software develops the FRANX file which includes the inputs to the FireImpacts table. It is noted that per the FRANX users manual, FRANX uses the table to store the excluded targets.
The ARCPlus' software is a software product in which the code was verified to correctly populate the FRANX tables.
2-7 CS-A6 Cat I/II/III The self-assessment indicates that the RESOLVED.
Cat I/II/III requirement of CS-A6 is met by the follows: The cable selection methodology identified Circuit failure modes associated with in NUREG/CR-6850, specifically in Section 3.3 the effects of de-energizing as a result of the notebook, and states that, for FPRA of the operation of overcurrent selected components, cables that can result protective devices was considered in the overcurrent protective device when performing circuit analysis to find responding to a hot short should be additional cables. included. A review of Specification NE-294, However, no discussion in Section 4 of Exelon Specification for Post-Fire Safe
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 46 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
LG-PRA-021.03, Model Development Shutdown Program Requirements, Section Notebook is included. Table F-1 is not 5.4, determined that for FSSD cable, the evident either. same methodology was applied.
2-11 PRM-C1 Met There is no evidence that plant RESOLVED.
(SY-A4) walkdowns and interviews with Not Met knowledgeable plant personnel (e.g., The MSO process is documented in a series engineering, plant operations, etc.) to of locations. Appendix B of equipment confirm that the systems analysis selection notebook provides the results of correctly reflects the as-built, as- the expert panel assessment of the MSOs operated plant. The MSO expert panel and the disposition as to whether or not the reviewed the Limerick-applicable MSO MSO would be modeled in the FPRA. There scenarios. However, the model is a series of detailed individual technical changes for MSO scenarios in final evaluations for the MSOs that provide FPRA models have not been confirmed details about the assessment of each MSO.
by plant walkdowns and interviews Where the disposition is that the MSO needs with knowledgeable plant personnel. to be modeled in the FPRA, the technical evaluation includes appendices for the MSO Fault Tree, P & IDs, MSO Component Circuit Analysis Data Sheets and MSO Component Circuit Analysis Marked Up Schematics The plant system engineers, who qualify as "knowledgeable individuals" with respect to this SR, were directly involved in the
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 47 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) development of these technical assessments. Their involvement meets the intent of the SR.
2-12 PRM-B12 Cat I/II/III In the Unit 1 CCDP cutsets for 026_F0A RESOLVED.
Cat I/II/III scenario, 3 initiating event (IE) flags were set to some values that add up to The initiating event treatment has been 100%. However, in this cutset file, fully updated since the peer review.
there is another significant IE flag Currently, there is an event tree that map
$VLP, which contributes to more than fire scenarios to the corresponding tree in 20% CDF. the fault tree. The revised approach of using the fire initiating event decision tree (FIEDT)
The treatment with IE flags does not allows the fire induced initiating event logic seem to be appropriate. to propagate through the appropriate event tree sequences. Therefore, there is a mapping of components to the specific initiating event that triggered in each scenario.
The treatment is documented in the Fire PRA PRM notebook LG-PRA-021.55 Section 4.2 and Appendix D (the decision tree is
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 48 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) described in detailed in Appendix D).
Evaluated as PRA maintenance in response to RAI 3.i in ML18019A091, Response to request for additional information application to adopt 10CFR50.69.
2-14 PRM-A4 Cat I/II/III Section 11.0 of the Fire Scenario RESOLVED.
Cat I/II/III Notebook (LGPRA-021.05) documents the conditional plant trip probabilities. The conditional trip probabilities were This treatment is not consistent with removed from the model. Opposite unit the ES/CS task results. Once a fire scenarios with no impact result in a manual scenario is developed, the fire is shutdown. This represents a small assumed to have resulted in a plant conservatism in the fire risk.
trip, either due to immediate plant response or manual shutdown per Tech Spec. A conditional trip probability should not be applied. For example; in the EDG room, the model shows a loss of the EDG, loss of the AC bus and loss of the DC bus. A plant shutdown would be required, and a conditional probability of trip should not be credited. Additionally, the conditional probability is applied for scenarios in the main control room; which would likely result in a shutdown
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 49 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) for a challenging fire.
As for the impact to the other unit, detailed fire modeling and plant response procedures should be evaluated to determine whether the other unit would be tripped or not.
2-15 PRM-C1 Cat I/II/III A number of CCF BE probabilities were RESOLVED.
(SY-B1) listed in ASM-02 and ASM-03 Cat I/II/III notebooks. The current version of the Data Notebook contains this and other CCF type code data However, the calculation methods and that were added for the fire PRA. Data data sources for generating CCF basic Notebook, Rev 2, Volume 1 Table D-1 provides events and failure probabilities are not the parameters and source for the documented. independent failure of the type code. Data Notebook, Rev 2, Volume 2 provides the CCF For example, MV HF type code used parameters and source (either a generic for the new CCF event is not source reference or a type-code specific documented in the FPIE DA calculation in Appendix A) for the CCF type notebook. codes.
2-19 PRM-C1 Met The sources of model uncertainty and RESOLVED.
(AS-C3) related assumptions for the added or Not Met modified system models, the added Table 3-1 and Section 3.2.14 of uncertainty MCRAB event tree with respected to notebook provide a discussion of the accident sequences, success criteria sources of model uncertainty. Model were not documented. uncertainty is generally considered to be
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 50 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) those things that are not (cannot) be addressed through parametric uncertainty analysis (e.g., assumptions used where another equally valid assumption could have been. Section E.5 of the plant response model notebook provides additional sources of uncertainty specific to MCRAB.
2-21 FSS-A6 Cat I/II LG-PRA-021.05, Fire Scenario RESOLVED.
Cat I/II Notebook, Appendices A and B document the fire scenarios. At least The conditional plant trip probability has been one scenario is defined for each main completely removed from the Fire PRA model.
control board where more than one No fire scenario receives credit for conditional function is failed. trip probability in the model. In the specific case of the main control room, a fire in either In the FRANX model, some MCR fire a Unit 1 or Unit 2 electrical cabinet or main scenarios have a severity factor to control board that results in abandonment account for the conditional trip conditions is modeled as a plant trip for both probability. However, inside these MCR units given that the operators will be leaving fire scenarios, MCRAB sequences are the MCR to shutdown both units using the embedded (by setting IE flag $RSP to a remote shutdown methods value for the specific MCRAB scenario).
Therefore, this treatment is not appropriate for the MCRAB scenarios.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 51 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 2-24 FSS-C6 Cat I/II A number of cabinet fires were RESOLVED.
Cat I/II evaluated with scenario-specific non-suppression probabilities that account The use of the Mathcad calculation has been for target damage times based on the replaced in the current version of the FPRA thermal response of the damage with the use of the Fire Modeling Workbook target. This method is documented in approach, which is described in detailed in Appendix E of LG-PRA-021.05, Fire the fire modeling treatments notebook. The Scenario Notebook. Table 10-2 workbook approach was reviewed for documented the resulted non- selected fire scenarios to ensure that the fire suppression probabilities based on the growth for both the ignition source and Mathcad calculations. Appendix E secondary combustibles is correctly documented the assumptions and a implemented in the analysis and that the sample of the calculation. However, time to target damage has been updated.
the detailed calculations have not been The fire modeling workbook approach formally documented and verified. calculates time to target damage using the THIEF model (which is documented in The process to use this method has Supplement 1 to NUREG 1805) with not been developed to ensure representative cable properties.
consistent use and results. Evaluated as PRA maintenance in response to RAI 3.i in ML18019A091, Response to request for additional information application to adopt 10CFR50.69.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 52 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 2-27 FSS-F1 Cat III LG-PRA-021.07, Exposed Structural RESOLVED.
Cat III Steel Analysis, documents the consideration of unprotected structural Table 1.1-1 of the structural steel notebook steel. Section 1.1 documents the provides the basis for the assumption that assumptions used in this analysis. more than one structural steel member is Assumption 3 states that failure of required before threat of building collapse.
more than one structural steel The basis includes the following: "the member is required before threat of building design is performed in accordance building collapse is challenged. The with ACI and AISC design codes. These basis supporting this assumption is industry codes contain provisions that engineering judgment. Due to the ensure ductile behavior of members and significance of this assumption (all their connections. The scenario involving the scenarios were screened out), the loss of a single column results in localized technical basis should be enhanced to damage and loss of function (excessive include some civil engineering design deformations), but not likely collapse.
information. However, a failure of two or more major vertical steel columns engages a larger portion of the building and would likely exceed the capacities of adjacent floor, beam, and column members."
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 53 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 2-28 FSS-F1 Cat III LG-PRA-021.07, Exposed Structural RESOLVED.
Cat III Steel Analysis, Table 2-1, includes the walkdown results. PAUs 93 and 106 The structural steel notebook documents are AIR COMPRESSOR AREA, EHC that fires in PAUs 93 and 106, involving lube POWER UNIT AREA, AND TURBINE oil storage tanks, are included in the LUBE OIL STORAGE TANK AREA. structural steel analysis. Appendix A of the However, these two PAUs were fire scenario development notebook screened by stating that high hazard documents that catastrophic scenarios sources were not identified in PAU and including collapse of the turbine building are therefore walkdowns for structural included in the PRA.
steel were not performed.
This does not seem to be appropriate.
2-29 FSS-F3 Met A qualitative assessment has been RESOLVED.
Not Met performed for area in which a high hazard source and structural steel has A quantitative assessment of the risk that been identified. However, the includes a collapse of the turbine building quantitative assessment of the risk of has been included. As shown in the SS the selected fire scenarios including notebook (Section 4), the FSS notebook collapse of the exposed structural steel (Appendix A) and the Summary and was not performed. Quantification notebook (Tables B-1 and B-2), structural steel scenarios that collapse the turbine building are quantified in the FPRA.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 54 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 2-30 FSS-H10 Met Walkdowns to develop the fire RESOLVED.
Not Met scenarios was performed. However, the walkdown process has not been The walkdown notebook provides guidance documented, i.e. formal walkdown when performing walkdowns for plant procedure has not been used which partitioning, fire ignition frequency, and fire describes the purpose of each scenario selection.
walkdown conducted, dates, Scenario summary reports are included in participants and results. Appendix A of the FSS notebook. The F&O response indicates that additional details are Per the SR note: Typical walkdown maintained in the ARCPlus' software.
results may include the purpose of each walkdown conducted, dates and participants, supporting calculations (if any), and information gained. This was not documented as a part of the FPRA.
3-2 PP-B7 Met Confirmatory walkdowns were not RESOLVED.
Not Met performed to confirm the conditions and characteristics of the credited Section 3.2.7 of the plant partitioning partitioning elements. According to the notebook documents that confirmatory response to question 03-05 walkdowns were conducted in October 2015.
'Confirmatory walkdowns were not Appendix B gives a description of each barrier.
performed to confirm the conditions and characteristics of the credited partitioning elements. The use of Fire Areas, as defined in the regulatory fire protection program, was judged to
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 55 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) provide assurance that the conditions and characteristic of credited partitioning elements are as stated in the Fire Safe Shutdown Analysis (FSSA).'
3-3 SF-A1 Met The scenario walkdowns documented RESOLVED.
Not Met in the 1995 IPEEE only report identifying scenarios where flammable Section 3 and 4 of the seismic fire gas or liquid storage vessels could interactions notebook were reviewed, and create a significant fire hazard due to a sections 3.1.1 and 4.1.1 discuss unique seismic event. Investigation of other interactions. These sections reference new unique fire scenarios is not walkdowns that were performed.
documented. Additionally, the Seismic PRA walkdown notebook includes discussion of observed interactions and the walkdown checklists include a specific section to check for these interactions.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 56 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 3-5 SF-A3 Met Review of Appendix I of the Limerick RESOLVED.
Not Met Fire Scenario Notebook indicates that spurious operation of the fire The seismic fire interactions notebook, Section suppression systems is conducted 4.1.3 addresses this finding. An assessment however common cause failure of was performed of potential common cause these systems is not addressed. failures of the fire suppressions systems in the Review of the 1995 IPEEE Seismic/Fire plant. The assessment concluded that there Interaction reflects this as well; were no significant vulnerabilities in this common cause failure of fire regard.
suppression systems is not addressed.
3-6 SF-B1 Met The Seismic Fire Interaction Analysis is RESOLVED.
Not Met based on the 1995 IPEEE. Accordingly, this analysis is 16 years old and should As noted, while originating in SF-B1 the finding be revisited to ensure accuracy of the exists because of the Findings on SF-A1 to SF-information contained. In addition, this A5 (the documentation is incomplete because analysis does not satisfy all of the the analyses for those SRs was not adequately requirements of ANS RA-Sa-2009 for performed). The documentation has been Seismic Fire Interaction Analysis. This updated.
results in analysis and documentation that does not satisfy the intent of the Seismic Fire Interaction Analysis.
3-8 FSS-C2 Cat II/III Time dependent growth curves are RESOLVED.
Cat II/III used to describe fire growth in profiles in risk significant contributors in The fire modeling treatments notebook scenarios that are investigated using lists the detailed fire scenarios defined for detailed fire modeling methods such as the risk significant rooms.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 57 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
CFAST and the Expansion of Generic Fire Modeling Treatment technique The fire modeling treatments notebook, described in Section 10 of the Fire Section 3.3 describes the heat release rate Scenario Notebook. Additional detailed growth profile implemented in the fire fire modeling is required and planned modeling analysis, which is consistent with the for some risk significant scenarios. guidance in Appendix G of NUREG/CR-6850.
This level of modeling has not been provided for all risk significant PAUs.
3-12 FSS-A1 Cat I/II/III During conduct of the Peer Review RESOLVED.
Cat I/II/III walkdown several locations were identified that would have been Walkdowns were conducted in areas in which expected to have been selected as bounding transients were not included to transient scenarios because of low identify potential pinch point locations. New cable trays or cable trays penetrating transient scenarios were added to address the the floor. Discussion in the field specific examples from the F&O, as indicated that some of these locations documented in the fire scenario selection were not selected as transient notebook, Appendix A. Transient scenarios scenarios. Examples of such locations have expanded from 168 transient scenarios include cable tray installations along in the peer review model to 283 transient the south wall of PAU 025, low cable scenarios in the current model (excluding full trays located between column lines room scenarios), indicating that many new M5 and N5 and K18 to K91 in PAU 94, transient scenarios were added.
and cable trays located above storage areas in PAU 107 at column line N39.2.
These examples are simply
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 58 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) representative and are not expected to be inclusive of all potential scenarios.
3-14 FSS-A1 Cat I/II During conduct of the Peer Review RESOLVED.
Cat I/II walkdown target selection for fire scenarios was challenged in several Section 3.2.3.1 of the fire scenario locations. This was performed by development notebook documents that reviewing the targets found in the target set identification is based on plant field against the Scenario Definition walkdowns and drawing reviews. The target Report Targets using the appropriate set for each scenario is listed in Appendix A ZOI information from Appendix C of of the notebook. Missing targets identified the Fire Scenario Report. This exercise during the peer review were related to a new was fully conducted for two initiators; system that had been added after the FPRA PAU 0107: T01-2 and PAU 013 F0E1- 2. targets had been identified. Walkdowns were performed to identify additional targets to be This exercise was conducted to validate added. The particular examples of targets selection of the targets listed and to missed were corrected.
determine if any potential risk relevant targets were missed. Because Fire PRA The FPRA is now maintained in the raceway data was used during target ARCPlusTM Fire PRA module software. To selection it was expected that raceway ensure new targets are not excluded, when
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 59 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) targets would be found in the field that new targets are added to the ARCPlusTM were not listed as targets. Field software the targets are then included for all identified targets that were not listed scenarios for the locations the targets are in the Scenario Definition Report located. The analyst then must perform the Targets were listed for later necessary analysis/walkdowns to manually disposition. exclude the targets as applicable. This was the process used during this update and will Seven potential targets were identified be used to maintain and update the FPRA for PAU 0107: T01-2. Of these, one was moving forward.
determined to be potentially risk relevant but not included in the target Exelon procedure CC-AA-102, Design Input selection for this scenario. and Configuration Change Impact Screening, is the process used to identify if a Seven potential targets were identified modification will have an impact on the fire for PAU 013: F0E1-2. Of these, two risk. If it is determined that a modification were determined to be potentially risk may impact the fire risk a URE is created to relevant but not included in the target track the modification to ensure the FPRA is selection for this scenario. This scenario appropriately updated.
involved a medium voltage Switchgear HEAF; the risk relevant cables were Additionally, the FPRA maintenance and captured in the scenario by their update procedure requires review of endpoints in the cabinet. Details of the modifications for impact on the FPRA.
target raceways that are not included in these scenarios are provided in the response to question LGS-99-06.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 60 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 4-1 ES-A1 Met The Limerick FPRA modeling does not RESOLVED.
Not Met include identification of equipment whose failure, including spurious Induced initiating event logic to propagate operation, caused by an initiating fire through the appropriate event tree would contribute to or otherwise cause sequences. Therefore, there is a mapping of an automatic trip, a manual trip per components to the specific initiating event procedure direction, or would invoke a that triggered in each scenario.
limiting condition of operation (LCO) The treatment is documented in the plant that would necessitate a shutdown. response notebook, Section 4.2 and Appendix D
Table 3-1 of the Model Development calculation provides the results of a comparison of the CDF (CCDP) given an initiating event in comparison to a turbine trip followed by a loss of the system. The differences are shown as small for all listed Initiating Events.
However, the discussion does not include any comparison of CCDPs for various fire scenarios (with equipment failed, or a discussion on the expected timing and thermo hydraulics following each event. As a result, although the difference for the base CCDP may be small, the impact for specific fire scenarios may be much larger. A
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 61 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) question asked about the top 10 scenarios indicated a small difference in most of the top 10 scenarios, if modeled differently. In almost all cases, the existing modeling is slightly non-conservative. For example, the top scenario would have a CCDP of 9.72E-02 versus 9.67E-02 (in the existing model), if modeled as a loss of RECW or loss of FW.
Additionally, the verification performed to model the results in Table 3-1 are produced by basically setting CCF values to true to model the impact of system failures. These failure events do not have any cables assigned. As a result, there does not appear to be documentation that all of the equipment that is included in the initiating event modeling are mapped with specific cable routing performed.
As clarified in the note, the Initiating Events modeled in the FPRA are basically expected to be modeled in
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 62 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) the same manner that initiating events are modeled under the IE requirements in Section 2. Without specific identification of equipment that can cause an initiating event, this requirement cannot be met.
4-2 ES-A5 Met The FPRA model did not include RESOLVED.
Not Met potential initiating events that were identified in the MSO expert panel The initiating event treatment has been review. For example, MSO scenario 2ai updated since the peer review. Now a fire was not considered for FPRA modeling, initiating event decision tree (FIEDT) is used due to credit for Level 8 trip. Appendix I that allows the fire induced initiating event of the model development calculation logic to propagate through the appropriate lists this as not applicable to Limerick. event tree sequences. Therefore, there is a However, an overfeed can occur at mapping of components to the specific Limerick, with the TD FW pumps. As a initiating event that triggered in each result, no review of the number of scenario.
MSOs required to cause the scenario The treatment is documented in the was performed. plant response model notebook, Section 4.2 and Appendix D (the decision tree is described in detailed in Appendix D).
The MSO scenarios have been incorporated into the PRA model using a systematic process that includes a comprehensive review of the generic MSO list from both a
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 63 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
PRA and deterministic perspective. The documentation is available in both the equipment selection and plant response model notebooks. The appropriate MSO scenarios have been included in the plant response model. A disposition for each scenario, including those screened from the plant response model, is available. The specific scenario listed in the finding as an example, i.e., scenario 2ai, is currently modeled in the FPRA.
Evaluated as PRA maintenance in response to RAI 3.i in ML18019A091, Response to request for additional information application to adopt 10CFR50.69.
4-8 FSS-G6 Cat II/III The Battery Room Fires assume a RESOLVED.
Cat II/III 69kw HRR for batteries, per Table 11-
- 1. However, the analysis does not NUREG/CR-6850 states that bin 19, misc.
include the possibility of a hydrogen hydrogen fires, does NOT include battery fire, as defined in the Misc. Hydrogen rooms. Therefore, the finding that Fires bin. The HRR and damage zone miscellaneous hydrogen fires bin need to be for these fires is discussed in included in battery rooms is not in agreement NUREG/CR-6850, N.2.4. with NUREG/CR-6850.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 64 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
Failure to include Hydrogen Fires in the battery rooms affects the Ignition Frequency Calculation, the fire modeling as well as the Multi-Compartment Analysis from these compartments.
4-9 FSS-G2 Met The MCA notebook includes both RESOLVED.
Not Met qualitative and quantitative screening criteria. The quantitative screening No quantitative screening is performed on the criteria used for the MCA is set at 1E- multi compartment scenarios that survived 07/year. See the MCA notebook, the qualitative screening step. That is, there is Section 4 for a discussion on screening. no longer the screening of multi This is applied for screening of MCA compartments based on a threshold value. If a sequences, where the ignition multi compartment combination is frequency, severity factor, non- determined to survive qualitative screening, a suppression and CCDP are applied. As scenario is developed, quantified and maintained as a risk contributor in the FPRA applied, the contribution of screened model. This process is documented in section PAUs can be significant, especially if the 3.3 of the multi-compartment notebook.
CCDP is near 1.0 as it is for many of the MCA scenarios.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 65 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 4-11 CS-A2 Cat II LG-PRA-021.03 Section 4 includes a RESOLVED.
Cat II discussion of the cable selection process and analysis using NE-0294. The complete fire PRA equipment list is Once the equipment and cables are included in Appendix A of LG-PRA-021.52, the selected, the process involves the Equipment Selection report. Table A-1 identification of all cables and circuits, includes a "CODE" column in which some Fire including hot shorts, which would PRA basic events are designated as CODE N2, affect equipment. which indicated that the basic event is not connected to a Fire PRA component ID However, the documentation of the because the specific equipment does not components with no cables due to have cables in the Fire PRA.
primary component mapping is not clear in the FPRA documentation. For many of these components, the cables are included with a Fire PRA ID, such as a primary component, that represents the failure. Primary components are identified in the Comments column in Table A-1 of LG-PRA-021.52.
Similarly, Table C-1 of LG-PRA-021.52 provides disposition of safe shutdown equipment and identifies if cables are mapped to another component. These relationships are also included in Table A-1 of the CS notebook (LG-PRA-021.53), in which a sub-component, if applicable, is listed in the
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 66 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
INDMS column.
4-16 FSS-C4 Cat II The low voltage cabinet Severity RESOLVED.
Cat II Factors were applied to Inverters in the FPRA. Per the guidance in the draft This finding is related to the application of the methodology, the severity factor severity factors following a draft methodology should only be applied to cabinets that was not consistent with the guidance in containing no power components, and Chapter 8 of NUREG/CR-6850. This only low power instrumentation, methodology has been removed from the relays, etc. model and no longer used.
The Fire PRA has been updated to apply severity factors consistent with the guidance in NUREG/CR- 6850 as described in the Fire Modeling Treatments notebook LG-PRA-021.07.02. Currently, severity factors are applied to electrical cabinets that are not modeled as high energy or low energy arcing faults. That is, high and low energy arcing fault scenarios do not credit severity factors
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 67 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) as calculated following the methodology in Chapter 8/Appendix E of NUREG/CR-6850 (i.e., a severity factor of 1.0 is applied).
4-17 FSS-C4 Cat II The Electrical Cabinet Severity Factors RESOLVED.
Cat II are applied in a few locations in the FPRA. However, the approach is not The use of the Unreviewed Analytical yet reviewed by the Industry FPRA Method and the Expansion of Generic Fire methods panel. As a result, use of Modeling Treatment technique has been these severity factors is considered an replaced in the latest version of the Fire PRA Unreviewed Analytical Method. with the use of the Fire Modeling Workbook approach, which is described in detailed in the Fire Modeling Treatments notebook LG-PRA- 021.07.02.
The workbook approach was reviewed for selected fire scenarios to ensure that the fire growth for both the ignition source and secondary combustibles is correctly implemented in the analysis and that the time to target damage has been updated from the unreviewed analytical method. The fire modeling workbook approach calculates
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 68 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) time to target damage using the THIEF model (which is documented in Supplement 1 to NUREG 1805) with representative cable properties.
Evaluated as PRA maintenance in response to RAI 3.i in ML18019A091, Response to request for additional information application to adopt 10CFR50.69.
4-18 PRM-B2 Met A review of the FPIE Peer Review F&Os RESOLVED.
Not Met related to FPRA did not include a review of all F&Os (including The plant response model notebook, Appendix suggestions) from the FPIE Peer C provides a disposition of the internal events Review. SR lists exceptions and peer review items. Internal events PRA peer deficiencies. Note that suggestions in review suggestions have been incorporated the internal events could be more into the PRA (i.e., there are no open important to the FPRA in some cases. suggestions) 4-19 PRM-B2 Met An assessment of the FPIE PRA was not RESOLVED.
Not Met provided against Addendum A of the standard as part of the FPRA An assessment of the internal events PRA documentation. against Addendum A has been performed and is documented in the roadmap notebook.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 69 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 4-21 PRM-C1 Met The Main Control Room Abandonment RESOLVED.
(AS-A3) (MCRAB) event tree is developed using Not Met the existing Limerick process, allowing A check was made of the basis for the time for explicit modeling of systems, available for actions from the RSP in the operator actions, and key safety HRA. The action to depressurize from the functions. The event tree is shown in RSP (AHUX1RDXI- FRA, OPS FAILS TO Figure 3-25 of ASM-03. Key Safety DEPRESSURIZE AT RSP PER SE-1) has an Functions are listed in 3.1.1.13.1. available action time of 38.9 minutes, based However, the ASM-03 discussion does on T/H run LI0010. The conditions of this run not clearly document the success are loss of all injection and one LPCI train criteria for each key safety function. For available, and while based on the non-example, on page 3-12 of the Limerick abandonment condition is the same as for PRA Event Tree Notebook, success MCRAB, so not additional run would be criteria for depressurization using ADS required.
includes a full discussion of timing (via MAAP), systems required, components A similar check was made for the action to required (2SRVs), expected operator utilize RCIC from the RSP (RHURSPDXI-FRA, actions, etc. This type of discussion is OPERATOR FAILS TO USE RCIC FOR RPV not provided for the MCRAB event LEVEL CONTROL FROM RSP). The time tree. available to perform this action was 45 minutes, however it was noted that the T/H run supporting this action was also LI0010, which as noted was for depressurization and LPI. Subsequently, the PRA team stated that a more representative run was LI0014, which shows that core damage has not
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 70 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) occurred by 45 minutes with no injection and no action (LI0001 shows the same thing), but neither shows the precise case where RCIC is started at 45 minutes although it could be implied that this would be successful. The PRA team ultimately provided a set of plots for the case where RCIC was started at 45 minutes, which conclusively shows that CD is averted.
4-23 PRM-C1 Cat I/II/III MCRAB Event tree uses existing FPIE RESOLVED.
(AS-A9) success criteria and T-H analysis. This Cat I/II/III was not confirmed in the A review and spot check was conducted of documentation as applicable to the how the T/H runs were used to support the new event tree development. success criteria for MCRAB actions. In general, the use of internal events and/or fire non-abandonment T/H runs for MCRAB actions is appropriate when the scenario details match closely enough. The use of the runs is adequately documented in the HRAC file.
Further discussed in response to RAI 2.d in ML18019A091, Response to request for additional information application to adopt 10CFR50.69:
The thermal-hydraulic analysis for in-Main Control Room (MCR) accident sequences and
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 71 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
Main Control Room Abandonment (MCRAB) postulated sequences are not different for the fire PRA. The differences are in the operator action response. The fire PRA human reliability analysis for MCRAB operator actions include distinctions accounting for the differences in timing to accomplish credited operator actions for the differing scenarios (i.e., non-MCRAB and MCRAB). Specifically, the MCRAB credited operator actions include additional timing delays for the diagnosis, decision, and execution to establish the credited systems for MCRAB postulated scenarios based on procedures and operator interviews. The time available for operator actions, rather than the system window, is the difference between non-MCRAB and MCRAB sequences. Therefore, the terms in general and closely enough in the F&O resolution were used to indicate that the thermal-hydraulic calculations are appropriate with the understanding that the timing to initiate certain functions differ between non-MCRAB and MCRAB scenarios. These timing differences were addressed in the human reliability analysis.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 72 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 4-25 PRM-C1 Met The FPRA documentation did not RESOLVED.
(LE-C12) include any review of significant Not Met accident progress sequences (with Reviewed Section 4 of the Summary and respect to fire) to determine operator Quantification Notebook (LG-PRA actions or engineering analysis that 021.11). Several reviews were performed could be included in the FPRA that and the significant contributors to LERF could reduce LERF. were reviewed, including review of top cutsets.
4-26 FSS-C4 Cat II The FPRA FSS report page 6-1 lists that RESOLVED.
Cat II All Motor Control Centers (MCC) have been treated as closed, sealed and The F&O response indicates that the latest robust in which damage beyond the guidance in FAQ 14-0009 has been applied ignition source was not postulated. Per and damage beyond the MCC is postulated.
the electrical cabinet FAQ 043, MCCs This was corroborated by Section 3.5 (Table are never considered sealed, based on 3-3) of LG- PRA-021.07.01, in which the two events in the EPRI DB where fire severity factor of 0.043, based on qualified propagated from the MCCs. MCC, thermoset target cables, and target Additionally, the ERIN supplemental distance of 0.5 ft is listed as an input. In report and the GE BWROG report addition, the FSS notebook (Appendix A) and shows a rough severity factor of 0.1 to the Summary and Quantification notebook 0.2 for MCCs, meaning some (Tables B-1 and B-2) include scenarios percentage of fires will get out of the involving sealed MCCs that propagate (for MCCs. example 027_00B131_L_Y). In the F&O response, no justification is provided for crediting qualified MCC and thermoset cables, however, the peer review
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 73 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) assessment was "Met Cat 1-2" for FSS-C5 (JUSTIFY that the damage criteria used in the Fire PRA are representative of the damage targets associated with each fire Scenario),
based on the plant using damage criteria for thermoset cables.
The PRA team provided documentation indicating that cables at Limerick are thermoset.
Evaluated as PRA maintenance in response to RAI 3.i in ML18019A091, Response to request for additional information application to adopt 10CFR50.69.
4-31 PRM-13 Met Most new FPRA components are based RESOLVED.
(DA-C2) on existing FPIE parameters, where Not Met plant specific data was performed. The current version of the Data Notebook However, new failure probabilities and contains this and other CCF type code data parameters in the FPRA do not have that were added for the fire PRA. Data plant specific data reviews in the FPRA. Notebook, Rev 2, Volume 1 (LG-PRA-010)
For example, a new type code not in Table D-1 provides the parameters and the FPIE is included in the FPRA: MV source for the independent failure of the HF. Additionally, other events not type code. Tables B-3 through B-6 provide using the generic type code should be the plant specific maintenance rule and MSPI reviewed for possible plant specific component experience data.
data review.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 74 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 4-32 HRA-C1 Met The FPIE HEP KHUSPPDX10 was RESOLVED.
Not Met based on an alarm response, and is now a procedural driven action from As regards the issue that certain actions FSSG-3022 in the FPRA. However, the should be modeled as being implemented action for failure to perform the without full indications and alarms, the procedural step for the control room indications for HFEs evaluated using detailed action is not included in the HEP. modeling are now included in the model directly and their failure fails the action (see Action JHUSPVDX10 was based on the Finding 1-11) unless there are alternative FPIE HRA, but as implemented in the alarms available.
FPRA (without full indication or alarms available), the operator action should This latter case is addressed generically include a non-proceduralized diagnosis through cue delay (see Finding 4-41), which is of the failure of SPC based on rising SP applied whether or not the primary temperature. This operator action step instruments are lost. Therefore, the issue of is not included in the FPRA analysis for non-proceduralized diagnosis due to loss of this action. indications or alarms is directly addressed in the modeling, and there is no credit given for These are just examples. It appears the non-proceduralized case. In addition, for there are other HEPs with similar CBDTM, the fire HEP is developed assuming issues; where the FPIE operator actions there is no alarm (Pcb is changed from are different (different procedures, "alarm" to monitor.)
different actions) for the FPRA.
A utility comment was provided and All significant (F-V > 0.005 or RAW>2) are reviewed by the peer review team. The evaluated using detailed modeling, as are comment included an argument that many of the non-significant ones, but there
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 75 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) inclusion of the modeling of the are non-significant ones that use screening procedural step was a matter of HEPs. These may not have the analyst preference. However, review of instrumentation modeled.
the standard indicates that both diagnosis and performance HEPs are On the surface this appears to be required to be modeled. On the second questionable because if the action; the comment noted that the instrumentation was modeled then in actual manipulation of the valve was certain scenarios the HEP would be not proceduralized, since local effectively 1.0.
manipulation of an MOV can be accomplished without explicit Also, the contention that CC II for SR HRA-C1 procedural direction. Although this implies instrumentation availability does not may be true; local operator action have to be considered if a screening HEP is failure should be considered in the used is incorrect. However, setting the HEP overall HEP. Since these were just to 1.0 is essentially the definition of RAW -
examples (F&O disposition should look how important is the HFE versus not at other similar HEPs), and given the crediting the action (HEP=1), so it can be more complete modeling will result in concluded that not including the the HEPs changing, the F&O was instrumentation when the HFE RAW is less retained. than 2 should not be significant.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 76 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 4-36 FSS-G4 Met In the MCA, the barrier failure RESOLVED.
Not Met probability assigned to each scenario is based on the worst case barrier The MCA notebook indicates that "The MCA failure probability. However, the barrier failure probability classification is NUREG/CR-6850 approach as well as determined by the summation of all previous approaches guides analysts applicable barrier types. In the case of a to sum up the failure probability for particular barrier containing more than one each possible failure path. For of the same element (e.g., more than one example, if there is a door and a fire door), only one failure probability is applied wall with penetrations, the barrier for that element." This was confirmed by failure probability is the sum of the identifying the credited barriers listed in MCA two individual rates. interaction matrix (Appendix A), identifying the barrier failure probability values from Table 3-1 for each barrier, summing the applicable values and comparing to the BFP value in the FSS notebook, Appendix A, for the particular scenario.
4-37 HRA-D1 Met Recovery Actions are included in the RESOLVED.
Not Met Table 2-1 listing of the HRA notebook.
This table includes the recovery events At the on-site review the FPRA team produced already indicated in the Fire Response their hand-written notes from the cutset Procedures. reviews. These notes contained comments about HRA actions to add credit for recovery The process to include actions was actions. These actions were then assigned to performed using an iterative process; the HRA lead to develop the necessary HFEs adding actions when needed to and HEPs. The actions identified were found in
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 77 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) address the risk significant sequences. the FHRA Notebook (LG- PRA-021.09) and incorporated in the model. It is suggested that However, a review of the existing PRA the cutset review notes should be results, including the LERF results, did incorporated into the documentation.
not include a complete review of cutsets for possible recovery actions that can restore the functions, systems, or components to provide a more realistic evaluation of significant accident sequences.
4-40 HRA-A2 Cat I/II/III Several operator actions are included RESOLVED.
Cat I/II/III in the FPRA that appear to be crediting local action of MOVs where LG-PRA-021.52 was reviewed. Table B-1 is 92-18 protection is not present. As a a compilation of the disposition of MSOs.
result, spurious operation of the 5K is the generic MSO for 92-18 valves.
valve may occur, bypassing the limit The comments column states "MOVs with and torque switches, resulting in the the 9218 concern are not recovered in the valve motor or stem failure. As a FPRA."
result, local action may not be possible, given the spurious Table A-1 contains the basic event operation continues for some time. disposition for the equipment selected for the fire PRA. A number of valves were identified as having a potential 92- 18 issue, and the comment column for each states "Mapped for 92-18 potential." A spot check was done of the modeling approach in
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 78 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
CAFTA/FRANX for these valves. The gate structure was such that the valve failed without any recovery credit for certain fire scenarios. In addition to the valve failing, it was noted that the recovery action was also mapped in FRANX such that it was listed as "affected equipment" that was failed in certain fire scenarios.
4-41 HRA-B1 Cat I/II In many cases, the delay time assumed RESOLVED.
Cat I/II for diagnosis of an action for Fire is adjusted by 2 minutes from the FPIE LG-PRA-021.09 Appendix D discusses the timing. Review of several events operator interviews and presents the case indicates that since the procedural for applying a two-minute time delay. As guidance is much different in the case explained in that document, the two of the fire, and the actions may no minutes applies only to account for cue longer be driven by alarm response, delay. The delay appears to be primarily the 2 minute time delay is related to the need for the operators to inappropriate. This is especially consider secondary indications to confirm applicable for actions where the alarm plant status because primary indications may or indications are not on the SSEL. be giving false readings and also for general distraction due to the fire. It is not intended Review of a Limerick operator during to account for other delays that affect the peer review on local actions during execution.
fire in the cable room may not occur until an hour. However, the FPRA Also, it was noted that the indications are now models these basically as 14 minutes modeled directly in the fire PRA (see
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 79 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) based on 2 minutes longer than the discussion above under F&O 1-11) and failed FPIE modeling. indication will fail the action, the adjusted HEP for the fire PRA is only applied when there is sufficient information available for the diagnosis, so in this case the two minute delay is in line with what has been used in other fire PRAs for adjusting T-delay - it is neither generally conservative nor generally optimistic and so represents a reasonable assumption (and a source of uncertainty).
4-44 HRA-E1 Met Uncertainty bounds for each HEP are RESOLVED.
(HR-I3) provided in Attachment A of the HRA Not Met Notebook. The FQ notebook Table 5-1 Table 3-1 and Section 3.2.14 of LG-PRA-includes one item on general HEP 021.12 provide a discussion of the uncertainty (HEPS are highly sources of model uncertainty. Model uncertain), but does not include any uncertainty is generally considered to be discussion on related specific Limerick those things that are not (cannot) be FPRA assumptions or sources of addressed through parametric uncertainty. For example, without uncertainty analysis (e.g., assumptions tracing much of the non-SSEL used where another equally valid instrumentation, the treatment for assumption could have been used).
recovery actions and non-SSEL indicated HEPs is very conservative. While the list is relatively short and it could be Additionally, the modeling of fire argued that there are other items that could impacts, including the time delay be considered to constitute HRA model assumptions, additional stress factors uncertainty (for example, the selection of the
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 80 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) and other modeling methods applied quantification model used as opposed to provides additional uncertainty that another acceptable model), these are may be considered. judgement calls by the analyst. What cannot be disputed is that sources of model uncertainty were considered and identified, which is what is required.
4-45 FSS-C1 Cat II Some risk significant scenarios involve RESOLVED.
Cat II full room burnout. For example, PAU 43W top scenario for LERF. LG-PRA-021.11 (Summary and quantification) indicate that the top contributors for CDF and LERF do not include full room burnout scenarios. For example, Figures 4-5 through 4-7 show that the top scenarios for CDF and LERF are the Remote Shutdown Panels, switchgear HEAFs, transient fires, MCA oil fire, and electrical panel fires.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 81 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 4-48 HRA-C1 Met HEP for control room abandonment RESOLVED.
Not Met for an area 25 fire is modeled using a screening value of 0.1 with no detailed Area 25 is the AER. The AER is not an modeling of credited equipment. abandonment area, and so MCRAB does not apply. The 0.1 value was a screening CCDP applied in the absence of detailed fire modeling, and no abandonment credit is applied.
Detailed fire modeling has now been done for the AER, and examining the FRANX file shows that there are well over 100 fire scenarios in the AER (as opposed to only a single scenario in the model that was peer reviewed).
Those scenarios are now treated in the same way as other scenarios in the plant fire model
- specific equipment fails as the result of fire impacts and the same HEPs are applied as appropriate. A spot check was made in the FRANX file that showed that the scenarios had cable impacts mapped. A spot check was made in the integrated fault tree (with fire scenarios inserted) and it was seen that the AER scenario impacts were modeled for each
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 82 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) impact alongside other scenarios that had the same impact.
4-51 FQ-F1 Met Limerick fire PRA model was RESOLVED.
(QU-B1) quantified in two forms: CAFTA and Not Met FRANX. FTREX was used as a Reviewed Appendix G, "Model Quantification quantification Engine. Limitations" of LG-PRA-021.11, "Summary and Quantification Notebook." Limitations However, the FPRA documentation with referenced code versions are provided does not discuss the method-specific in Appendix G. Appendix G summarizes the limitations and features that could some of the potential critical limitations that impact the results. may influence the FPRA model quantification and its application related to the use of the CAFTA suite of codes. A discussion of the limitations associated with using FRANX for the FPRA model development process is also provided.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 83 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 4-52 FQ-F1 Cat I/II/III Review of significant sequences was RESOLVED.
(QU-D1) performed and documented in the Cat I/II/III quantification notebook. However, the Section 4.2.7 of the Summary and review to show the logic of the cutsets Quantification Notebook documented or sequences is correct was not review.
documented. Table 4-4 and Table 4-5 summarize the top 10 CDF cutsets from quantification of the Additionally, a review of the results of Unit 1 and Unit 2 Single-Top Fire PRA model, the PRA for modeling consistency respectively. Table 4-6 and Table 4-7 (e.g., event sequence model's summarize the top 10 LERF cutsets from consistency with systems models and quantification of the Unit 1 and Unit 2 success criteria) and operational SingleTopFire PRA model, respectively.
consistency (e.g., plant configuration, procedures, and plant specific and The cutsets were reviewed for industry experience) was not included reasonableness and were determined to in the FPRA documentation. make logical sense. The review of the cutsets indicates that the results are consistent with A review of the results to determine the system models and associated success that the flag event settings, mutually criteria, and that the flag event settings, exclusive event rules, and recovery mutually exclusive event rules, and recovery rules yield logical results was also not rules yield logical results.
documented. As part of the final cutset review, multiple cutsets were selected at random for each A review of a sampling of decade that is relevant in the cutset file nonsignificant accident cutsets or (both CDF and LERF).
sequences to determine they are Also, the bottom cutsets for CDF and LERF,
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 84 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) reasonable and have physical meaning respectively, were reviewed in order to was not performed. identify the non-significant cutsets.
A review of the importance of These cutsets were evaluated in a similar components and basic events to way as the ones documented in Tables 4-4 determine that they make logical through 4-7, but are not documented in this sense was not documented in the notebook.
FPRA quantification notebook. These cutset reviews for CDF and LERF evaluated top cutsets, as well as cutsets The above should be provided also for randomly chosen in the cutset file. Cutset LERF (See LE-F SRs). searches were also performed to look for particular type of scenarios (e.g., MCR abandonment, MSOs) that were often nonsignificant cutsets. Changes were identified based on these cutset reviews and incorporated into the final fire model.
The details of these reviews are not documented in the PRA notebooks, but at the on-site review the FPRA team produced their hand-written notes from the cutset reviews. These notes demonstrated that the cutset reviews sufficient to support these confirmations were conducted, that issues were identified, and that actions were assigned to address the issues. However, the
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 85 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) cutset review notes were not incorporated into the PRA documentation.
4-53 FQ-F1 Met The quantitative definition used for RESOLVED.
(QU-F6) significant basic event, significant Not Met cutset, and significant accident The FPRA uses definitions consistent sequence was not referenced or with the standard per Section 3.5 of the provided in the FPRA documentation. summary and quantification notebook:
Significant Basic Event: A basic event that contributes significantly to the computed risks for a specific hazard group. For internal events, this includes any basic event that has an FV importance greater than 0.005 or a RAW importance greater than 2.
Significant Cutset: One of the set of cutsets resulting from the analysis of a specific hazard group that, when rank ordered by decreasing frequency, sum to a specified
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 86 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) percentage of the core damage frequency (or large early release frequency) for that hazard group, or that individually contribute more than a specified percentage of core damage frequency (or large early release frequency).
For this version of the Standard, the summed percentage is 95% and the individual percentage is 1% of the applicable hazard group.
Significant Accident Sequence: One of the set of accident sequences resulting from the analysis of a specific hazard group, defined at the functional or systematic level, that, when rank-ordered by decreasing frequency, sum to a specified percentage of the core damage frequency for that hazard group, or that individually contribute more than a specified percentage of core damage frequency. For this version of the Standard, the summed percentage is 95% and the individual percentage is 1% of the applicable hazard group.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 87 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 5-1 PP-C2 Met The analysis is good in identifying RESOLVED.
Not Met those locations outside the PA but within the OCA; however, it is silent in As stated in the F&O, the documentation at terms of those locations that were the time of the peer review did not include a screened from further consideration. comprehensive listing of structures in the GAB and those that were qualitatively screened.
To resolve the F&O the plant partitioning report and qualitative screening report were revised. The plant partitioning report includes a comprehensive listing of structures in the licensee controlled area included as part of the GAB. Then, the qualitatively screening report provides a comprehensive listing of those structures screened.
For example, PAUs ADMIN (Admin. Tower) and BLR (Boiler Building) are identified in Figure 4-1, which shows the GAB, and also listed in Table 4-1 of the QLS notebook, which indicates that they are screened because "This PAU does not contain PRA equipment, cables, and a fire in the PAU does not result in a required manual or automatic plant trip or a manual shutdown based on
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 88 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
Technical Specifications."
5-2 ES-A5 Met It does not appear that all spurious RESOLVED.
Not Met operations were appropriately dispositioned. For example, generic The MSO scenarios have been incorporated scenarios 5a, 5d, 5f, were into the PRA model using a systematic dispositioned as pending; however, no process that includes a comprehensive analysis of the MSO applicable to review of the generic MSO list from both a these scenarios were identified. PRA and deterministic perspective. The documentation is available in both the equipment selection and plant response model notebooks (LG-PRA-021.52 and LG-PRA- 021.55).
The appropriate MSO scenarios have been included in the plant response model. A disposition for each scenario, including those screened from the plant response model, is available. The specific scenarios listed in the finding, i.e. 5a, 5d, 5f, are no longer pending
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 89 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) and have been either added to the model or dispositioned. A similar comprehensive approach has been applied to all the MSO scenarios.
5-3 ES-A6 Cat II It does not appear that all spurious RESOLVED.
Cat II operations were appropriately dispositioned. For example, generic The MSO scenarios have been scenario 4u was dispositioned as not incorporated into the PRA model using a applicable to Limerick because it is a systematic process that includes a COP issue. Actually, 4u is not a COP comprehensive review of the generic MSO issue, but rather a containment list from both a PRA and deterministic isolation issue, and therefore perspective. The documentation is applicable to Limerick. available in both the equipment selection and plant response model notebooks (LG-PRA-021.52 and LG-PRA-021.55).
The appropriate MSO scenarios have been included in the plant response model. A disposition for each scenario, including those screened from the plant response model, is available. The specific scenarios listed in the finding, i.e. 4u, is appropriately dispositioned.
A similar comprehensive approach has been applied to all the MSO scenarios.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 90 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 5-7 IGN-A7 Cat I/II/III A consistent methodology was used to RESOLVED.
Cat I/II/III determine ignition frequencies. The method applied uses a 0.1 weighting The Ignition Frequency Notebook (LG-PRA-factor, which is not included in the 021.56), Section 3.1.8, explains the method generic approach referenced in used for calculating transient ignition NUREG/CR-6850. Note that the frequencies. A weighting factor of 0.1, ranking of 1 is listed as a minimal level noted by the peer review finding, is no in NUREG/CR-6850. longer used for calculating the ignition frequencies.
The method used is based on NUREG/CR-6850 and FAQ 12-0064, in which ignition frequencies are calculated using influence factors for maintenance, hotwork, storage, and occupancy. The method documented in LG-PRA-021.56 (Section 3.1.8, Appendix D) is consistent with the guidance in FAQ 12-0064 and therefore the F&O is resolved.
Evaluated as PRA maintenance in response to RAI 3.i in ML18019A091, Response to request for additional information application to adopt 10CFR50.69.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 91 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 5-10 FQ-1 Met Significant contributors corresponding RESOLVED.
(LE-F1) plant damage states (accident classes)
Not Met are required in accordance with FQ- E1, Reviewed Section 4 of LG-PRA-021.11.
but this information was not provided in Significant contributors to LERF are discussed the FPRA documentation. in LG-PRA- 021.11 (Summary and Quantification Notebook):
Section 4.2.1, Figures 4-1 through 4-4, provide Physical Analysis Unit (PAU) contributions for CDF and LERF.
Section 4.2.2, Figures 4-5 through 4-8, provide fire scenario contributions for CDF and LERF.
Section 4.2.6, Figures 4-15 through 4-16, provide CDF accident sequence contributions for LERF In Figure 4-15 and 4-16 for LERF contributors by sequence for Unit 1 and Unit 2, the sequences represent containment event tree end states. The containment event trees include nodes for the various LERF contributors which include those listed in Table 2-2.8-9 of the Standard.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 92 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) 5-12 FMU-C1 Met The FPRA configuration control process RESOLVED.
Not Met is documented by Exelon fleet procedure ER-AA-600-1061. Section The current revision of the FPRA maintenance 2.5 describes the process for assessing and update procedure, ER-AA-600-1061 pending changes to the model of includes explicit provision for evaluation of the record (MOR). These reviews are cumulative impact of outstanding changes.
performed on a case-by-case basis, and the independent impact on the model is determined. The procedure is silent in terms of assessing the 'cumulative' impact of multiple changes. Exelon comment on this F&O is as follows:
"Although the procedure does not specifically mention cumulative impacts, the intent of the statement that includes "evaluate the impact of pending changes to the FMOR" is considered to implicitly include the cumulative nature of the pending changes. This is consistent with the guidance established for control and update of the internal events PRA. This issue was discussed with the reviewer near the end of the peer review.
"Although the peer review team agrees that more experienced PRA
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 93 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) professionals will understand the implicit requirement; less experience PRA professionals may not understand the requirement. As a result; the F&O remains a finding.
6-2 CS-C2 Cat I/II/III The input version of the cable routing RESOLVED.
Cat I/II/III database and related inputs are not provided in the references. Inputs Section 4.1 of the cable selection notebook were used from Appendix R, MSO discusses the sources for the data in Table A-1.
resolution project, and ES related Fire Table A-1 identifies the source for each cable PRA Tasks. This information is fed on to FPRA component. FPRA data is contained in other tasks such as scenario the cable selection notebook tables. INDMS development and quantification. data and MSO data were derived from references 4 and 7, respectively, in Section 5.0 of the cable selection notebook. These references include dates to identify the input version of the data.
6-3 SF-A4 Met The Seismic - Fire Interactions results RESOLVED.
Not Met is found in LG-PRA-021.05 Appendix I
- Seismic Fire Interactions. The seismic fire interactions notebook, Section 4.1.4 addresses the first part of the finding.
Impact on post-earthquake response An assessment was performed that by the plant is not addressed. (SR SF- identified the extent to which needing to A4) enter procedure SE-8 (Fire) would affect the
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 94 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) execution of the already entered procedure The report does not address the SE-5 (Earthquake). The section does note storage and placement of firefighting some limitations in these areas, which are equipment nor are the brigade access assessed as minor.
routes addressed. (SR-SF-A5)
Section 4.1.5 addresses the second part of the finding. An assessment was performed that identified the extent to which the brigade training prepares the brigade to deal with earthquakes access routes and how the earthquake can affect the equipment. The section does note some limitations in these areas.
6-5 FSS-D3 Met Limerick uses a bounding approach for RESOLVED.
Not Met the initial treatment of fire scenarios using a generic fire modeling The summary and quantification notebook calculation and the information and documents the risk significant PAUs. The fire further information documented in the modeling treatments notebook lists the generic treatments notebook. detailed fire scenarios defined for these rooms. The fire modeling treatments One PAU was treated with additional notebook describes the fire modeling analysis, fire modeling (4kV Emergency which is consistent with the current industry Switchgear room) with the CFAST fire guidance.
modeling summarized in the scenario workbook Appendix E. However, a number of other PAUs have results
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 95 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) that are significant contributors to overall unit fire risk (e.g. PAU 025, Auxiliary Equipment Room). These PAUs/Scenarios could benefit from additional fire modeling.
6-6 FSS-D4 CAT I/II/III Limerick uses a bounding approach for RESOLVED.
CAT I/II/III the initial treatment of fire scenarios using a generic fire modeling The F&O response indicates that the CFAST calculation and the information and analysis is no longer being used in the further information documented in the switchgear HGL analysis, so the F&O is no generic treatments notebook. longer applicable. Inputs used for HGL calculations in the FMT notebook and the The fire modeling tools include CFAST input files for CFAST used in the Main Control as used to create the Generic Fire Room Abandonment notebooks are provided.
Modeling Treatments (including supplements) and the Main Control Abandonment Analysis.
Technical basis is provided in the treatments/tools above.
The detailed fire modeling was performed for the Switchgear Room
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 96 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC) fires and the results documented in the scenario development report Attachment G. The basis for a number of inputs was explicitly provided; however, the basis for some of the CFAST inputs was not explicitly provided. For example, a spreadsheet was developed to create the input deck for the CFAST model. The spreadsheets and input deck were not available to the peer team to check.
References:
LG-PRA-021.05, Generic Fire Modeling Treatment, Supplement to Generic Fire Modeling Treatment -
Hot Gas Layer, MCRAB Analysis.
6-7 FSS-D7 Met Generic estimates per NUREG/CR- RESOLVED.
Not Met 6850 are used and the system is operational during plant operation per Section 3.8 of the fire modeling treatments plant procedures. notebook documents that the fire protection detection and suppression No evidence was found to indicate a system impairments review. This included a review for outlier was performed. review of the fire protection health report Also, scope of risk relevant fire performance indicator worksheet for suppression and detection systems multiple years. No major failures of systems not identified. were identified.
License Amendment Request Supplement Enclosure 1 Adopt TSTF-505, Rev. 2 Page 97 of 97 Docket Nos. 50-352 and 50-353 Enclosure 1 Peer Review Findings Resolved and Justified for Closure by Limerick 2016 Pilot Closure Process Finding Supporting Current Finding Number Requirement(s) and Capability Resolution Description Original Capability Category Category Assessment (CC)
The scope of the FP systems (i.e. a list of all the credited systems, not just risk-relevant areas) is identified in Table 3-1 of the fire modeling treatments notebook.