ML18151A467

Response to Request for Additional Information Regarding License Amendment Request to Revise Integrated Leak Rate Test (Typed a) and Type C Test Intervals

ML18151A467
Person / Time
Site:	Millstone
Issue date:	05/24/2018
From:	Mark D. Sartain Dominion Energy Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
18-230
Download: ML18151A467 (36)

Text

Dominion Energy Nuclear Connecticut, Inc.

Rt 156, Rope Ferry Road, Waterford, CT 06385 ~ Dominion Dominion Energy.com MAY 2 4 2018 ~ Energy U.S. Nuclear Regulatory Commission Serial No.18-230 Attention: Document Control Desk NRA/WDC RO Washington, DC 20555 Docket No. 50-336 License No. DPR-65 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO REVISE INTEGRATED LEAK RATE TEST (TYPE A) AND TYPE C TEST INTERVALS By letter dated October 4, 2017 Dominion Energy Nuclear Connecticut, Inc.

(DENG) requested a license amendment in the form of changes to the Millstone Power Station Unit 2 {MPS2) Technical Specifications (TSs) for facility Operating License DPR-65. This proposed amendment would allow DENG to extend the Type A primary containment integrated leak rate test (ILRT) interval for MPS2 to 15 years and the Type C local leak rate test interval to 75 months, and incorporates the regulatory positions stated in RG 1.163.

In an email dated May 17, 2018, the NRG transmitted a request for additional information (RAI) related to the LAR. The RAI contained six questions.

Attachment .1 to this letter provides DENC's response to question RAl-06.

Attachment 2 provides an updated MPS2 PRA model quality summary. DENG plans to submit the response to the remaining RAI questions, RAl-01 through RAl-05, by June 18, 2018.

Should you have any questions in regard to this submittal, please contact Wanda Craft at (804) 273-4687.

Sincerely,~ t_ _

1 uJlJJU~ -

Mark D. Sartain Vice President - Nuclear Engineering & Fleet Support STATE OF CONNECTICUT COUNTY OF NEW LONDON The foregoing document was acknowledged before me, in and for the County and State aforesaid, today by Mark D. Sartain, who is Vice President - Nuclear Engineering & Fleet Support of Dominion Energy Nuclear Connecticut, Inc. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this~ '1' Ii day of tl"II! y ,2018.

My Commission Expires: ft ffl... 3o. ~O ~I TIMOTHY F. OLSOWY NOTARYPUBLIC NY COMMISSION EXPIRES APR. 30, 2021

Serial No: 18-230 Docket No. 50-336 Page 2 of 2

Attachment:

1. Response to Re_quest for Additional Information Regarding License Amendment Request to Revise Integrated Leak Rate Test (Type A) and Type C Test Intervals - RAl-06

2. MPS2-R05g PRA Model Quality Summary Commitments made in this letter: None cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 R. V. Guzman Senior Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 C2 Rockville, MD 20852-2738 NRG Senior Resident Inspector Millstone Power Station Director, Radiation Division Department of Energy and Environmental Protection 79 Elm Street

• Hartford, CT 06106-5127

Serial No.18-230 Docket No. 50-336 ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO REVISE INTEGRATED LEAK RATE TEST (TYPE A) AND TYPE C TEST INTERVALS- RAl-06 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

Serial No.18-230 Docket No. 50-336 Attachment 1, Page 1 of 6 By letter dated October 4, 2017 Dominion Energy Nuclear Connecticut, Inc. (DENC) submitted a license amendment request (LAR) in the form of changes to the Millstone Power Station Unit 2 (MPS2) Technical Specifications (TSs) for facility Operating License DPR-65. The proposed amendment revises MPS2 TS 6.19, "Containment Leakage Rate Testing Program," by replacing the reference to Regulatory Guide (RG) 1.163 (September 1995) with a reference to Nuclear Energy Institute (NEI) topical report NEI 94-01, Revision 3-A and the limitations and conditions specified in NEI 94-01, Revision 2-A, as the implementing documents used to develop the MPS2 performance-based leakage testing program in accordance with 10 CFR 50, Appendix J, Option B.

This proposed amendment would allow DENC to extend the Type A primary containment integrated leak rate test (ILRT) interval for MPS2 to 15 years and the Type C local leak rate test interval to 75 months, and incorporates the regulatory positions stated in RG 1.163.

In an email dated May 17, 2018, the NRC transmitted a request for additional information (RAI) related to the LAR. The RAI contained six questions. This .

attachment provides DENC's response to RAl-06.

' Background In. the safety evaluation (SE) issued on June 25, 2008 (ADAMS Accession No. ML081140105), the U.S. Nuclear Regulatory Commission (NRG) staff found the methodology in NE/ 94-01, Revision 2, and EPRI Report No. 1009325, Revision 2, acceptable for referencing by licensees proposing to amend their TSs to permanently extend the ILRT interval to 15 years, provided certain conditions are satisfied.

Condition 1, set forth in Section 4.2 of the SE for EPRI Report No. 1009325, Revision 2, states that the licensee should submit documentation indicating that the technical adequacy of their probabilistic risk assessment (PRA) is consistent with the guidance in Regulatory Guide (RG) 1.200, relevant to the ILRT extension application. Revision 2 of RG 1.200 endorses, with clarifications and qualifications, the American Society of Mechanical Engineers/American Nuclear Society (ASMEIANS) PRA Standard RA-Sa-2009.

The information provided in the LAR is not sufficient for the NRG staff to reasonably determine that the licensee's PRA is consistent with the guidance in RG 1.200, Rev. 2, and therefore, cannot assess the technical acceptability of the licensee's PRA for use in support of this application. The following requests for additional information (RA/s) outline the information needed for the NRG staff to complete its review:

RAl-06 The licensee submitted over 100 open F&Os from various peer reviews and self-assessments. During the week of March 19-23, 2018, the licensee conducted an F&O

Serial No.18-230 Docket No. 50-336 Attachment 1, Page 2 of 6 closure review as well as a focused-scope peer review for the MPS2 PRA model, which may have closed a significant number of open F&Os. If the licensee intends to supplement its application with the F&O closure results in order to reduce the amount of open F&Os that the NRG would need to review, then provide the following clarifications with respect to implementation of the Appendix X, F&O closure process:

DENC Response A Facts and Observations (F&O) closure review and a focused scope peer review of the MPS2 PRA model were recently completed which resulted in a significantly reduced number of F&Os remaining open in reference to the MPS2-R05g PRA model.

Clarification is provided below with respect to implementation of the Appendix X F&O closure process. An updated list of open F&Os and their impact on the LAR is also provided. Since the MPS2-R05g model is an update to the MPS2-R05e model used to support the LAR, additional supporting information is provided to reaffirm the conclusions presented in the LAR. The additional information provided for the MPS2-R05g model includes a summary which demonstrates the technical adequacy of the PRA in accordance with Regulatory Guide (RG) 1.200, Rev. 2, and verification that the risk metrics associated with the ILRT extension remain acceptable.

a) Clarify whether a focused-scope peer review was performed concurrently with the F&O closure process. If so, provide the following:

DENC Response A focused-scope peer review was performed concurrently with the F&O closure process.

i. Summary of the scope of the peer review.

DENC Response The scope of the 2018 focused scope peer review is described in the PRA quality summary for the MPS2-R05g model. See Table 2 of Attachment 2.

ii. Detailed descriptions of any new findings generated from the peer review and their disposition for the application.

DENC Response Detailed descriptions of the new findings from the 2018 focused scope peer review and their dispositions are provided in the MPS2-R05g PRA model quality summary. See Table 3 of Attachment 2.

Serial No.18-230 Docket No. 50-336 Attachment 1, Page 3 of 6 b) Confirm that the licensee provided the closure review team a written assessment and justification of whether the resolution of each F&O, within the scope of the independent assessment, constitutes a PRA upgrade or maintenance update, as defined in ASMEIANS RA-Sa-2009, "Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications, Addendum A to RA-S-2008," as endorsed by RG 1.200 Revision 2.

DENC Response A written assessment and justification of whether the model changes associated with the resolution of each F&O constitute a PRA upgrade or maintenance update, as defined in ASME/ANS RA-Sa-2009, was provided to the closure review team.

c)Section X.1.3 of the Appendix X guidance includes the following five criteria for selecting members of the closure review team:

i. Every member of the independent assessment team should be independent of the PRA associated with the F&Os being reviewed, per the criteria of "independent" in the ASMEIANS PRA Standard. These members may be contractors, utility personnel, or employees of other utilities, and may include members of peer review teams_ that previously reviewed the models being assessed.

DENC Response Each member of the independent assessmen*t team was independent per the criteria in the ASME/ANS PRA Standard, having neither performed nor directly supervised any work on the PRA being reviewed, and each team member signed a reviewer affirmation statement to certify their independence.

ii. Every member of the independent assessment group should meet the relevant peer reviewer qualifications as stated in the ASMEIANS PRA Standard for the technical elements associated with the F&Os being reviewed.

DENC Response The peer review qualifications, as stated in the ASME/ANS PRA Standard, were met for every member of the independent assessment group.

• 1. The team members collectively represented expertise in all the technical elements of a PRA.

Serial No.18-230.

Docket No. 50-336 Attachment 1, Page 4 of 6

2. Each member had knowledge and experience in the technical elements to which the SRs/F&Os being reviewed belong, and each member was independent.

3. Each peer reviewer was knowledgeable of the methodologies and approaches used in the PRA element assigned for review, as demonstrated by each individual's range of experience in the assigned areas.

iii. The overall review team experience includes two qualified reviewers for each F&O. An exception to this is allowed for the closure of an F&O related to a single SR, in which case, a single independent reviewer is acceptable, in alignment with the peer review guidance in the main body of this document and in accordance with the A SMElANS PRA Standard.

DENC Response Two qualified reviewers were assigned to the closure of each F&O.

iv. Each member of the independent assessment team should be knowledgeable about the F&O independent assessment process used to assess the adequacy of the F&O resolution.

DENC Response Each member of the independent assessment team met this requirement and was knowledgeable of the F&O independent assessment process.

v. The total number of reviewers is a function of the scope and number of finding F&Os to be reviewed for closure.

DENC Response The number of reviewers was selected based on the scope and number of finding-level F&Os to be reviewed for closure. Since the scope included review of 108 F&Os, ten members were selected for the team.

Describe how the selection of members for the March 2018 independent assessment met this criteria.

DENC Response Each criterion from Section X.1.3 of Appendix X was met by every member of the peer review team, as described in the responses to items i-v above.

Serial No.18-230 Docket No. 50-336 Attachment 1, Page 5 of 6 d) Explain how closure of the F&Os was assessed to ensure that the capabilities of the PRA elements, or portions of the PRA within the elements, associated with the closed F&Os now meet the appropriate capability category (CC) I for all the .

applicable supporting requirements (SRs) of ASMEIANS RA-Sa-2009 as endorsed by RG 1.200 Revision 2. If the 2000 /EPRA was peer reviewed against the GEOG checklist, include a discussion of the validity of the F&O closure results given that the F&Os review by the closure team were tied to applicable SRs using the NE/ 00-02 to ASMEIANS mapping. .

DENC Response As part of the F&O closure process, the independent assessment team reviewed the SRs associated with each F&O. For SRs associated with F&Os that were not previously assessed to meet capability category II, th.e team provided an assessment of the SRs to determine if capability category II was now met. This ensured that the capabilities of the PRA elements are met for the application since the assessment to capability category II goes beyond the capability category I requirements. The SRs that were previously assessed as meeting capability category II were not affected by this assessment.

The F&Os from the 2000 peer review performed against the Combustion Engineering Owner's Group (CEOG) checklist were associated with one or more CEOG checklist elements. The CEOG checklist elements associated with each F&O were mapped to ASME/ANS SRs to support the F&O closure. At the time the independent assessment team was on site, it was determined that the mapping between the CEOG elements and ASME/ANS SRs did not properly account for the translation provided in WCAP-15930. Dominion Energy subsequently used WCAP-15930 to properly map between CEOG. checklist elements and ASME/ANS SRs using the following process:

1. The CEOG checklist elements were mapped to the NEI 00-02 checklist elements using WCAP-i 5930.

2. The NEI 00-02 checklist elements were mapped to the 2005 ASME PRA Standard SRs using Table B-4 in RG 1.200, Rev. 2.

3. The 2005 ASME PRA Standard SRs were mapped to the 2009 ASME/ANS PRA Standard SRs using Appendix F in NEI 05-04, Rev. 3.

The revised mapping between the 2000 peer review F&Os and the 2009 ASME/ANS SRs was provided to the independent assessment team. The team used the revised mapping for the F&O closure process and documented their conclusions in the F&O closure report. In addition, the SRs mapped to each F&O were reviewed by the independent assessment team to ensure that each F&O was closed against applicable SRs. The incorporation of corrected SR mappings for each F&O, and the independent verification of the applicability of identified SRs to each F&O, ensure the validity of the F&O closure results.

Serial No.18-230 Docket No. 50-336 Attachment 1, Page 6 of 6 e) Discuss whether the F&O closure review scope included all finding-level F&Os, including those finding-level F&Os that are associated with "Met" supporting requirements (SRs). If not, identify and provide detailed descriptions for any F&Os that were excluded from the F&O closure review scope, and their disposition for the application.

DENC Response Two finding-level F&Os (LE-F1-01 and LE-F2-01) were not submitted to the independent assessment team for closure. All other finding-level F&Os, including those associated with "Met" SRs, were included in the F&O closure review scope. A detailed description of the F&Os that remain open following the F&O closure and their disposition for the application is provided in the MPS2-R05g PRA model quality summary. See Table 3 of Attachment 2.

f) For the F&Os and self-assessment items that remained open after the F&O Closure, provide the complete text of the original peer review F&O, self-assessment finding, and Appendix X F&O closure review assessment comments and recommendations. If necessary, provide revised dispositions for each open F&O and self-assessment item that addresses how resolution to each element of the F&O/self-assessment item impacts the application.

DENC Response The F&Os and self-assessment items that remain open after the F&O closure are listed with the complete text of the original peer review F&O, self-assessment finding, and Appendix X F&O closure review assessment comments and recommendations in the MPS2-R05g PRA model quality summary. See Table 3 of Attachment 2. The dispositions were updated to include a description of the issue with respect to the MPS2-R05g model and to address the 2018 peer review comments, as applicable.

Serial No.18-230 Docket No. 50-336 ATTACHMENT 2 MPS2-R05g PRA MODEL QUALITY

SUMMARY

DOMINION ENERGY NUCLEAR CONINECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 1 of 26 MPS2-R0591 PRA Quality Summary RG 1.200 Rev. 2 requires that any risk-informed application that uses a licensee PRA model must demonstrate PRA technical adequacy. RG 1.200, Rev. 2 endorsed the ASME/ANS RA-Sa-2009 consensus PRA Standard and the NEI 00-02 Self-Assessment process as a method for complying with the peer review requirements of the ASME/ANS standard, if the PRA model had been previously peer reviewed against a different standard. ASME/ANS RA-Sa-2009 states that a PRA model will undergo an industry peer review against the requirements of the standard before being used in an application. The following discussion summarizes the history and results of industry peer reviews performed on the MPS2 PRA model, including a summary of the overall status of the MPS2 PRA model with respect to RG 1.200, Rev. 2 and the requirements of ASME/ANS RA-Sa-2009.

Historical PRA Model Reviews, Assessments and Comparison to ASME/ANS RA-Sa-2009 I RG 1.200 Revision 2 Requirements The MPS2 PRA model was originally peer reviewed in 2000 using the Combustion Engineering Owner's Group (CEOG) peer review process. The GEOG process was adapted from a similar Boiling Water Reactor Owner's Group (BWROG) process and features a structured review of the PRA and a set of checklists covering eleven technical areas using a four-tiered grading process. WCAP-15930 performs a detailed comparison of the GEOG peer review process to the requirements of the NEI 00-02 and concluded that the GEOG peer review process is fully equivalent to the NEI 00-02 process and that the checklists used by the GEOG are equivalent to NEI 00-02 Appendix B, and in some cases go beyond the requirements of the NEI 00-02 checklists. This peer review resulted in the preparation of 81 A or B significance level Fact and Observations on various PRA elements, all of which were addressed and resolved in subsequent updates to the MPS2 PRA model.

The NRC issued RG 1.200, Revision 1 in January 2007 which endorsed the ASME RA-Sb-2005 standard and the NEI 00-02 Appendix D self-assessment process, with certain clarifications and qualifications, as a method to demonstrate the acceptability of an industry PRA model for use in risk-informed applications. A self-assessment of the MPS2 PRA model was performed in 2007 to compare the MPS2 PRA model against the requirements of ASME RA-Sb-2005/RG 1.200 Rev 1. The supporting requirement (SR) assessment was led by Maracor, a vendor that provided a team of experts with experience in performing NEI PRA certifications and ASME PRA standard reviews, with Dominion Energy providing a review of the assessment. This self-assessment process exceeded the requirements of NEI 00-02, Attachment D. For example, instead of taking credit for the existing grade assigned to the NEI 00-02 technical elements from the 2000 GEOG review and completing only the industry self-assessment actions to achieve CC-II, the self-assessment evaluated the MPS2 PRA model directly against the ASME standard CC-II requirements for each ASME RA-Sb-2005 SR, including any RG 1.200 Rev. 1 clarifications/comments. This self-assessment was used to determine the

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 2 of 26 technical adequacy of the MPS2 PRA with respect to ASME RA-Sb-2005/RG 1.200 Rev 1 requirements.

This assessment determined that 175 SRs of ASME RA-Sb-2005/RG 1.200 Rev 1 were not considered met to CC-II. These SRs were entered into Dominion Energy's configuration control process to determine the scope of subsequent PRA model updates.

• In March 2009, the NRC issued RG 1200 Rev. 2 endorsing ASME/ANS RA-Sa-2009 as a method to demonstrate the acceptability of an industry PRA model for use in risk-informed applications. Instead of performing a gap assessment to ASME/ANS RA-Sa-2009 requirements as described in NEI 05-04 Section 3.3, Dominion Energy performed a self-assessment of the MPS2 PRA model against the 316 SRs in ASME/ANS Ra-Sa-2009/ RG 1.200 Rev 2, which exceeded NEI 05-04 requirements. This assessment determined that 39 SRs of ASME/ANS RA-Sa-2009/RG 1.200 Rev 2 did not meet CC II.

These SRs were entered into Dominion Energy's configuration control process to determine the scope of subsequent PRA model updates. This self-assessment was used to determine the technical adequacy of the MPS2 PRA model with respect to ASME RA-Sa-2009/RG 1.200 Rev 2 requirements.

MPS2 PRA Model Peer Reviews Against ASME/ANS Ra-Sa-2009 / RG 1.200 Rev 2 Requirements Both the ASME standard and RG 1.200 require that any upgrade to a PRA model involving a new methodology or significant changes in scope or capability that impact the significant accident sequences or the significant accident progression sequences, undergo a peer review specific to those portions of the PRA model affected by the change. In 2012, Dominion Energy contracted with Westinghouse to perform a focused scope PRA peer review of the MPS2 PRA model to determine compliance with ASME/ANS RA-Sa-2009 (RG 1.200 Rev. 2), focusing on upgrades to the PRA model.

The following SRs were in scope of the 2012 peer review:

• Serial No.18-230 Docket No. 50-336 Attachment 2, Page 3 of 26 Table 1 Scope of 2012 Focused Scope Peer Review Element Description SRs In Scope Review topics IE Initiating Events IE-C10, IE-C11 Initiating Event Fault Trees Identify systems, functions AS Accident Sequence Analysis AS-A2,AS-A3, AS-A6 and arrangement SY-All (containment sump), SY-SY Systems Analysis B2 (AFW CCF), SY-B7 (Ventilation)

HR Human Reliability Analysis HLRs: HR-C, HR-D, HR-G DA Data Analysis DA-DS CCF Parameter Approach IF Internal Flooding All All QU Quantification QU-AS Include Recovery Actions LE Level 2 Analysis All All During the course of this review, 28 finding-level F&Os were identified and 28 SRs were considered to not meet CC II requirements. These items were entered into Dominion Energy's configuration control process to determine the scope of subsequent PRA model updates.

Closeout of MPS2 F&Os Using the NEI 05-04/07-12/12-13 Appendix X Process An accepted process for performing an F&O closure review is described in Appendix X to NEI 05-04/07-12/12-13. The process allows several options to achieve permanent closure of F&Os. In 2018, Dominion Energy contracted with EPM to perform a "Closeout of F&Os by Independent Assessment" for the MPS2 PRA model. This process is similar to a peer review in accordance with NEI 05-04 but with a scope limited to evaluating the closure of F&Os. In addition, the NRG provided specific expectations when using this process, documented in NRG Memorandum, "U.S.

Nuclear Regulatory Commission Staff Expectations for an Industry Facts and Observations Independent Assessment Process", May 1, 2017, which were used in the conduct of this assessment.

During the independent assessment, EPM assessed open F&Os for closure by reviewing the Dominion Energy dispositions and related documentation for applicability and correctness. The PRA Standard SRs associated with the F&Os were also assessed for the completeness of the dispositions. Dominion Energy mapped the GEOG peer review F&Os to ASME/ANS PRA Standard RA-Sa-2009 SRs to ensure that the SRs were properly accounted for during the F8t0 closure process. Lastly, an

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 4 of 26 assessment was made regarding whether the model changes applied to resolve F&Os were considered upgrades to the PRA model or were considered to be PRA model maintenance per the definitions in the PRA ~tandard. One hundred and six F&Os were presented to the independent assessment team for closure. Of these, 103 were closed, two were partially closed, and one remains open. Two additional F&Os were not presented for closure and remain open. The model changes associated with resolving 24 of the F&Os were determined to be upgrades that require a focused scope peer review for closure. The SRs associated with the 24 F&Os were also reviewed during a concurrent focused scope peer review and determined to be met such that these F&Os could be closed. The impact on this application of each open F&O is described in Table 3.

A focused scope peer review was conducted concurrently with the F&O closure independent assessment. The primary purpose of the focused scope peer review was to review upgrades made to the MPS2 PRA model in the process of resolving F&Os.

These upgrades were reviewed against PRA standard elements and SRs to confirm the upgraded model meets the requirements of the PRA standard. One hundred and seventy-eight SRs were reviewed and determined to meet the CC II requirements. The following elements and SRs were included in the scope of the 2018 focused scope peer review:

Table 2 Scope of 2018 Focused Scope Peer Review Element Description SRs In Scope AS Accident Sequence Analysis All HR Human Reliability Analysis All SY Systems Analysis All IFSN Internal Flood Scenarios All IFEV Internal Flood Induced Events All 11=Qu Internal Flood Accident Sequences All and Quantification QU Quantification All During the course of this peer review, two new finding-level F&Os were generated.

The newly identified F&Os will be entered into Dominion Energy's configuration control process to determine the scope of subsequent PRA model updates. The impact on this application of the two additional F&Os is described in Table 3.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 5 of 26 The status of how the MPS2-R05g PRA model has been assessed against ASME/ANS RA-Sa-2009 SRs is provided in Table 4.

Review of Pending PRA Model Changes The Dominion Energy PRA configuration control process ensures that the PRA model used in this application continues to reflect the MPS2 as-built and as-operated plant.

The process delineates the responsibilities and guidelines for updating the PRA models.

The process includes provisions for monitoring potential areas affecting the PRA models (e.g., due to changes in the plant, errors or limitations identified in the model, and industn; operational experience) for assessing the risk impact of unincorporated changes, and for controlling the model and associated computer files.

This process satisfies configuration control requirements specified in Sections 1-5 of the ASME/ANS PRA standard and Section 1.4 of RG 1.200 Rev. 2. In accordance with this process, the MPS2 PRA model was reviewed to ensure that the MPS2-R05g model does not contain any upgrades which have not received a peer review. The impact of the pending changes to the PRA model, including changes to reflect the as-built, as-operated plant, were considered in the PRA model evaluation that supports this application.

Open Finding-Level Facts and Observations (F&Os) against the MPS2 PRA Model Table 3, which corresponds to Table 7-2 in Attachment 4 of the LAR, contains a summary of open findings and issues generated from the peer review and self-assessment. This table includes the impact of these open issues on this application.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 6 of 26 Table 3 Impact of Open Peer Review Findings and Self-Assessment Items on the Application CC-II Finding Supporting Currently Description Disposition Number Requliement(s)

Met?

Self- AS-C2 Met Self-Assessment Comment: Unresolved.

Assessment A one-to-one correlation between each initiating event and the associated event tree is not clearly provided. The system success criteria There is no impact on the application.

AS-C2 and associated basis is not clearly provided. A discussion of the accident No model changes are pending. This sequences will need to revised pending resolution of issues associated was identified in the self-assessment with other AS SRs. For example, the phenomenological conditions as a documentation enhancement.

created by the accident. Operator actions needed are not clearly delineated along with any associated dependencies on system success or other operator actions Self-Assessment Recommendation:

Revise the documentation as necessary to address resolution of the recommendations cited for the AS-A and AS-8 elements in a manner that satisfies this SR. For example, provide a one-to-one correlation between each event in the IE analysis and the event tree models.

Provide a table that clearly states the success criteria for each system credited with mitigating each initiating event, the associated success criteria, and the associated reference.

Self- SY-A4 Met Self-Assessment Comment: Unresolved.

Assessment While the /PE documentation and conversations with the PRA engineers indicate that these tasks were performed, no documentation exists There is no impact on the application.

SY-A4 (walkdown sheets, system engineer interviews) to support this No model changes are pending. This supposition. was identified in the self-assessment as a documentation enhancement.

Self-Assessment Recommendation:

Need to perform updates of all system notebooks to the enhanced format implemented for SPS, which includes all of the documentation required for this SR. This updated format includes placeholders for the walkdown and system engineer interviews. The walkdown sheets and interviews should be completed and added to the system notebooks.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 7 of 26 CC-II Finding Supporting Currently Description Disposition Number Requirement(s)

Met?

Self- SY-C2 Met Self-Assessment Comment: Unresolved.

Assessment ii/a walkdown information, documentation of operating history, or room heatup calculations exists. There is no impact on the application.

SY-C2 This is a documentation enhancement, Self-Assessment Recommendation: and no model changes are pending.

Upgrade system notebooks to new approved format, which contains the The PRA documentation has been appropriate level of documentation. updated to contain the appropriate level of information for operating history and room heatup calculations.

Documentation of the walkdown information is still pending.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 8 of 26 CC-II Finding Supporting Currently Description Disposition Number Requirement(s)

Met?

LE-C3-01 LE-C3 Met 2012 Peer Review Comment: Unresolved.

(2012) MPS2 did not review significant accident progression sequences resulting in a large early release to determine if repair of equipment can The peer review identified that the be credited. To move up to CCII, perform and document a review of process developed to review significant accident progression sequences resulting in a large early significant accident progression release to determine if repair of equipment can be credited. If any such sequences to determine if repair can actions are identified, provide the basis for their feasibility. be credited to reduce LERF is sufficient to meet Category II, and the process Dominion dise_osition ot2012 Comment: was applied to the model of record.

MPS2 LE.1 RS Significant accident progression sequences have now However, the interim model update been reviewed to determine if repair can help reduce LERF. However, no did not complete this process.

credit for repair is taken. {MPS2 LE.1 - section 5.1 and "Repair of Although this review did not take Significant Equipment" sheet of Attachment 5). place on the interim model, it is not expected that new insights would be 2018 Peer Review Comment: identified concerning credit for repair The section has been provided and assessment performed to address that would reduce LERF. Given that the F&O. However, the current documentation does not address the repair is not currently credited, any current model results and is not completely closed. The process additional modeling that would be developed is sufficient to meet Category JI for SR LE-C3. performed as a result of this review would result in a reduction in LERF, Proe.osed Resolution: which would not adversely impact the To close this F&O, the documentation of each interim update {MC.1 conclusions of the application.

report) should include an evaluation that concludes that the current Model of Record results (i.e., latest QU.2) documentation reasonably represents the results documentation expected for the current interim model. The evaluation should also conclude that there are no new insights or conclusions to be obtained based on the changes that would otherwise require fully documenting the results to meet the necessary SRs.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 9 of 26 CC-II Finding Supporting Currently Description Disposition Number Requirement(s)

Met?

LE-C12-01 LE-C12 Met 2012 Peer Review Comment: Unresolved.

(2012} There is no evidence that MPS2 performed a review of accident progression accident sequences to determine if it was possible for The peer review identified that the continued operation of equipment or personnel that would reduce LERF. process developed to determine if continued equipment operation or Dominion dise.osition 0[2012 Comment: operator actions after containment MPS2 QU.2 RS (section 2.3.5.5 and Attachment 4) MPS2 LE.1 RS (section failure can help reduce LERF is 5.1 and Attachment 5) Significant accident progression sequences have sufficient to meet Category II, and the now been reviewed to determine if continued equipment operation or process was applied to the model of operator actions after containment failure can help reduce LERF. The record. However, the interim model review is documented (see above referenced PRA notebooks). However, update did not complete this process.

no credit is taken for additional equipment or operator actions because Although this review did not take the significant LERF contributors are bypass scenarios, not a failure of place on the interim model, it is not containment isolation. expected that new insights would be identified concerning credit for 2018 Peer Review Comment: continued equipment operation or Documentation is provided and addresses the F&O by adding the operator actions after containment appropriate Section and at that time there was a discussion addressing failure that would reduce LERF. Given the top 97% of contributions to LERF. This process is still pending for the that no credit is currently taken, any most current interim release, but the process exists and therefore the additional modeling that would be F&O as generated is considered partially closed. The associated SR LE- performed as a result of this review C12 requires an approach to be developed and is considered now met. would result in a reduction in LERF, which would not adversely impact the Proe.osed Resolution: conclusions of the application.

To close this F&O, the documentation of each interim update (MC.1 report) should include an evaluation that concludes that the current Model of Record results (i.e., latest QU.2} documentation reasonably represents the results documentation expected for the current interim model. The evaluation should also conclude that there are no new insights or conclusions to be obtained based on the changes that would otherwise require fully documenting the results to meet the necessary SRs.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 10 of 26 CC-II Finding Supporting Currently Description Disposition Number Requirement(s)

Met?

LE-Fl-01 LE-Fl Met 2012 Peer Review Comment: Partially Resolved.

(2012) QU.2 Section 2.3.2 provided LERF by initiating event, Section 2.3.6 presented the dominant LERF cutsets, Section 2.3.9 presents the LERF There is no impact on the application.

importance analysis, and Table 15 presents the system contribution to The SR meets CC-I or greater. Plant LERF. Attachment 4 to QU.2 also presents the containment failure mode damage state (PDS) logic was contribution to LERF. However, there is no identification of the developed in the LERF model, but PDS contributors to LERF by plant damage states. contributions to LERF have not been clearly documented. However, LERF 2018 Peer Review Comment: results are presented by initiating N/A event, dominant cutsets, importance analysis, system contribution, and Proposed Resolution: containment failure mode MPS2 needs to calculate and present the dominant LERF contributors to contribution. No impact on LERF is LERF by plant damage state. expected by also presenting the LERF results by plant damage state.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 11 of 26 CC-II Finding Supporting Currently Description Disposition Number Requirement(s)

Met?

LE-F2-01 LE-F2 Not Met 2012 Peer Review Comment: Partially Resolved.

(2012) There is no evidence that MP52 reviewed the LERF contributors for reasonableness. While MP52 did group and present the LERF results by The LERF contributors were reviewed initiating event, system contribution and containment failure mode, for reasonableness for the base model there is no evidence that MPS2 reviewed the results for reasonableness. of record, and the review was documented in the PRA quantification 2018 Peer Review Comment: documentation. PRA documentation N/A includes review and explanation of significant accident progression Proposed Resolution: sequences and the top LERF cutsets.

MPS2 needs to perform and document a review of the LERF results to The interim model update did not show that they are explainable based on what would be expected for perform the same level of review.

the plant. However, the LERF quantification did include a review of the top LERF cutsets, a comparison of the top cutsets with the previous model, and justification for any difference in the top cutsets. It also involved a thorough evaluation of the LERF-related importance measures for basic events and the impact of changes on applications such as MSPI and Maintenance Rule Risk Ranking.

Performing additional reviews for reasonableness using the interim model is not expected to reveal any insights that would impact the conclusions of the analysis supporting this application.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 12 of 26 CC-II Finding Supporting Currently Description Disposition Number Requirement(s)

Met?

LE-GS-01 LE-GS Not Met 2012 Peer Review Comment: Unresolved.

(2012) f\tiPS2 has not reviewed their Level 2 analysis to identify any limitations that may have the potential to impact applications. MPS2 needs to This issue is associated with identifying review their Level 2 analysis to identify any limitations that may have the limitations associated with the the potential to impact applications. MPS2 should document the process LERF analysis for applications.

used for the review and the results of the review. If no limitations are Limitations have been identified for identified, this needs to be clearly stated. the LERF analysis, including applicable modes, the scope of hazards, and Dominion dis12.osition 0[2012 Comment: limitations with use of MAAP for Level MPS2 LE.1 RS, section 7.0 PRA Notebook MPS2 LE.1 has been updated 2. The Level 2 analysis contains to include documentation of LERF limitations in Section 7.0 of the sufficient scope and detail for this notebook. application, including consideration of various containment failure modes 2018 Peer Review Comment: and plant damage state modeling, The current section provides only general discussion and does not which allows the core damage provide any support for limitations when applying the LERF model. sequences to be binned to the EPRI Limitations in MAAP should be included as well as any plant-specific acGident classes. A more thorough modeling considerations. The SR LE-GS remains not met. documentation of LERF analysis limitations that accounts for the items Pro12.osed Resolution: identified in the proposed resolution The current section on limitations should be updated to reflect any new would not impact the conclusions of or additional limitations identified for the current model of record and this application.

the quantification results. The documentation should capture the insights gained from the uncertainty and sensitivity section and highlight possible limitations with respect to the use of the PRAfor applications.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 13 of 26 CC-II Finding Supporting Currently Description Disposition Number Requirement(s)

Met?

IFQU-A7-1 IFQU-A7 Met 2018 Peer Review Comment: Unresolved.

(2018) IFQU-81 Met Detailed quantification notebook is not available for the MC documentation. To meet this requirement, a detailed QU notebook will The focus of the finding is HLR-QU-F, be required. which is associated with documentation of the model Assessment Basis: quantification. Although this The quantification process met the requirements of QU SR groups A-E. documentation update did not take Because these results were not contained in the model update place with the interim model update, documentation, a finding was given to create a detailed QU that it is not expected that new insights addresses HLR F SRs. would be identified through this process that would impact the internal Proposed Resolution: flooding quantification results. As a Generate a detailed QU notebook either for the integrated PRA model result, this finding is assessed to have or for the flooding specific model that meets the requirements of IFQU no impact on the application.

and QU of the standard.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 14 of 26 CC-II Finding Supporting Currently Description Disposition Number Requirement(s)

Met?

QU-F2-01 QU-F2 Met 2018 Peer Review Comment: Partially Resolved.

(2018) QU-F3 Met Dominions' PRA update process periodically creates a new "model of record" that addresses the requirements of QU-F2 & QU-F3. However The documentation for the analysis of interim updates are performed to maintain the PRA consistent with the quantification results was completed as-built/asoperated plant that do not address all of requirements of for the base model of record, which is QU-F2 & QU-F3 to document sensitivities, uncertainty assessments and confirmed by the 2018 Peer Review significant contributors. Comment. The interim model update did not perform the same level of Proposed Resolution: analysis of quantification results and The full quantification analysis, which addresses the SRs for QU-F2 and documentation. However, the QU-F3, should be updated to for use with quantification did include a review of risk informed submittals or peer reviews, or justification should be the top CDF and LERF cutsets, a included in the documentation for the interim comparison of the top cutsets with the quantification results detailing why elements of the previous previous model, and justification for quantification analysis still apply to the interim model results. any difference in the top cutsets. It also involved a thorough evaluation of the importance measures for basic events and the impact of changes on applications such as MSPI and Maintenance Rule Risk Ranking.

Performing additional analysis of quantification results using the interim model is not expected to reveal any insights that would impact the conclusions of the analysis supporting this application.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 15 of 26 Status of MPS2 PRA with respect to ASME/ANS RA-Sa-2009 Supporting Requirements Table 4 (below) corresponds to Table 7-1 in Attachment 4 of the LAR. This table identifies the most recent technical review performed for each individual ASME/ANS RA-Sa-2009 supporting requirement. For those SRs that have not been peer reviewed against the RA-Sa-2009 PRA standard, the basis is provided for how the MPS2-R05g PRA model has been assessed to the requirements of ASME/ANS RA-Sa-2009 for determining the capability category supported by the model. This table reflects the current status of the MPS2-R05g PRA model.

Table 4 Millstone 2 PRA Standard Supporting Requirements Capability Category CC II RG 1.200 RA-Sa-2009 /

RA-Sa-2009 Currently Most Recent Technical Review Version RG 1.200 Gap SR Met? Reviewed Assessment AS-Al Met 2018 Focused Scope Peer Review 2 None Required AS-AlO Met 2018 Focused Scope Peer Review 2 None Required AS-All Met 2018 Focused Scope Peer Review 2 None Required AS-A2 Met 2018 Focused Scope Peer Review 2 None Required AS-A3 Met 2018 Focused Scope Peer Review 2 None Required AS-A4 Met 2018 Focused Scope Peer Review 2 None Required AS-AS Met 2018 Focused Scope Peer Review 2 None Required AS-A6 Met 2018 Focused Scope Peer Review 2 None Required AS-A7 Met 2018 Focused Scope Peer Review 2 None Required AS-A8 Met 2018 Focused Scope Peer Review 2 None Required AS-A9 Met 2018 Focused Scope Peer Review 2 None Required AS-Bl Met 2018 Focused Scope Peer Review 2 None Required AS-B2 Met 2018 Focused Scope Peer Review 2 None Required AS-B3 Met 2018 Focused Scope Peer Review 2 None Required AS-B4 N/A 2018 Focused Scope Peer Review 2 None Required AS-BS Met 2018 Focused Scope Peer Review 2 None Required AS-B6 Met 2018 Focused Scope Peer Review 2 None Required AS-B7 Met 2018 Focused Scope Peer Review 2 None Required AS-Cl Met 2018 Focused Scope Peer Review 2 None Required AS-C2 Met 2018 Focused Scope Peer Review 2 None Required AS-C3 Met 2018 Focused Scope Peer Review 2 None Required DA-Al Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-A2 Met NEI 00-02 Self-Assessment None *Note 1 DA-A3 Met NEI 00-02 Self-Assessment None *Note 1 DA-A4 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-Bl Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-B2 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-Cl Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-ClO Met NEI 00-02 Self-Assessment None *Note 1 DA-Cll Met NEI 00-02 Self-Assessment None *Note 1 DA-C12 Met NEI 00-02 Self-Assessment None *Note 1

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 16 of 26 CC II RG 1.200 RA-Sa-2009 /

RA-Sa-2009 Currently Most Recent Technical Review Version RG 1.200 Gap SR Met? Reviewed Assessment DA-C13 Met NEI 00-02 Self-Assessment None *Note 1 DA-C14 Met NEI 00-02 Self-Assessment None *Note 1 DA-C15 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-C16 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-C2 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-C3 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-C4 Met NEI 00-02 Self-Assessment None *Note 1 DA-CS Met NEI 00-02 Self-Assessment None *Note 1 DA-C6 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-C7 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-CS Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-C9 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-Dl Met NEI 00-02 Self-Assessment None *Note 1 DA-D2 Met NEI 00-02 Self-Assessment None *Note 1 DA-D3 ' Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-D4 Met NEI 00-02 Self-Assessment None *Note 1 DA-DS Met 2012 Focused Scope Peer Review 2 None Required DA-D6 Met 2018 Focused Scope Peer Review 2 None Required DA-D7 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-D8 Met NEI 00-02 / NEI 05-04 Gap Assessments None *Note 2 This SR was added in RG 1.200 Rev. 2 and has not been peer DA-D9 Met NEI 05-04 Gap Assessment N/A reviewed.

DA-El Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-E2 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 DA-E3 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 HR-Al Met 2018 Focused Scope Peer Review 2 None Required HR-A2 Met 2018 Focused Scope Peer Review 2 None Required HR-A3 Met 2018 Focused Scope Peer Review 2 None Required HR-Bl Met 2018 Focused Scope Peer Review 2 None Required HR-B2 Met 2018 Focused Scope Peer Review 2 None Required HR-Cl Met 2018 Focused Scope Peer Review 2 None Required HR-C2 Met 2018 Focused Scope Peer Review 2 None Required HR-C3 Met 2018 Focused Scope Peer Review 2 None Required HR-Dl Met 2018 Focused Scope Peer Review 2 None Required HR-D2 Met 2018 Focused Scope Peer Review 2 None Required HR-D3 Met 2018 Focused Scope Peer Review 2 None Required HR-D4 Met 2018 Focused Scope Peer Review 2 None Required HR-DS Met 2018 Focused Scope Peer Review 2 None Required HR-D6 Met 2018 Focused Scope Peer Review 2 None Required

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 17 of 26 CC II RG 1.200 RA-Sa-2009 /

RA-Sa-2009 Currently Most Recent Technical Review Version RG 1.200 Gap SR Met? Reviewed Assessment HR-D7 Met 2018 Focused Scope Peer Review 2 None Required HR-El Met 2018 Focused Scope Peer Review 2 None Required HR-E2 Met 2018 Focused Scope Peer Review 2 None Required HR-E3 Met 2018 Focused Scope Peer Review 2 None Required HR-E4 Met 2018 Focused Scope Peer Review 2 None Required HR-Fl Met 2018 Focused Scope Peer Review 2 None Required HR-F2 Met 2018 Focused Scope Peer Review 2 None Required HR-Gl Met 2018 Focused Scope Peer Review 2 None Required HR-G2 Met 2018 Focused Scope Peer Review 2 None Required HR-G3 Met 2018 Focused Scope Peer Review 2 None Required HR-G4 Met 2018 Focused Scope Peer Review 2 None Required HR-GS Met 2018 Focused Scope Peer Review 2 None Required HR-G6 Met 2018 Focused Scope Peer Review 2 None Required HR-G7 Met 2018 Focused Scope Peer Review 2 None Required HR-G8 Met 2018 Focused Scope Peer Review 2 None Required HR-Hl Met 2018 Focused Scope Peer Review 2 None Required HR-H2 Met 2018 Focused Scope Peer Review 2 None Required HR-H3 Met 2018 Focused Scope Peer Review 2 None Required HR-11 Met 2018 Focused Scope Peer Review 2 None Required HR-12 Met 2018 Focused Scope Peer Review 2 None Required HR-13 Met 2018 Focused Scope Peer Review 2 None Required IE-Al Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-AlO Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-A2 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-A3 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-A4 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-AS Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-A6 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-A7 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-A8 Met NEI 00-02 Self-Assessment None *Note 1 IE-A9 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-81 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-82 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-83 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-84 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-BS Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-Cl Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-ClO Met 2012 Focused Scope Peer Review 2 None Required IE-Cll Met 2012 Focused Scope Peer Review 2 None Required IE-C12 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-C13 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-C14 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IE-ClS Met NEI 00-02 Self-Assessment None *Note 1

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 18 of 26 CC II RG 1.200 RA-Sa-2009 /

RA-Sa-2009 ICurrently Most Recent Technical Review Version RG 1.200 Gap SR Met? .Reviewed Assessment 1E-C2 Met 2000 Peer Review+ NEl 00-02 Self-Assessment None *Note 1 1E-C3 Met 2000 Peer Review+ NEl 00-02 Self-Assessment None *Note 1 1E-C4 Met 2000 Peer Review+ NEl 00-02 Self-Assessment None *Note 1 IE-CS Met NEl 00-02 Self-Assessment None *Note 1 IE-C6 Met NEI 00-02 Self-Assessment None *Note 1 1E-C7 Met NEI 00-02 Self-Assessment None *Note 1 IE-C8 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 1E-C9 Met NEl 00-02 Self-Assessment None *Note 1 lE-01 Met 2000 Peer Review+ NEl 00-02 Self-Assessment None *Note 1 lE-02 Met 2000 Peer Review+ NEl 00-02 Self-Assessment None *Note 1 IE-03 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 IF EV-Al Met 2018 Focused Scope Peer Review 2 None Required IFEV-A2 Met 2018 Focused Scope Peer Review 2 None Required IFEV-A3 Met 2018 Focused Scope Peer Review 2 None Required 1FEV-A4 Met 2018 Focused Scope Peer Review 2 None Required lFEV-AS Met 2018 Focused Scope Peer Review 2 None Required IFEV-A6 Met 2018 Focused Scope Peer Review 2 None Required IFEV-A7 Met 2018 Focused Scope Peer Review 2 None Required IFEV-A8 Met 2018 Focused Scope Peer Review 2 None Required IFEV-81 Met 2018 Focused Scope Peer Review 2 None Required lFEV-82 Met 2018 Focused Scope Peer Review 2 None Required IFEV-83 Met 2018 Focused Scope Peer Review 2 None Required lFPP-Al Met 2012 Focused Scope Peer Review 2 None Required 1FPP-A2 Met 2012 Focused Scope Peer Review 2 None Required IFPP-A3 N/A 2012 Focused Scope Peer Review 2 None Required 1FPP-A4 Met 2012 Focused Scope Peer Review 2 None Required IFPP-AS Met 2012 Focused Scope Peer Review 2 None Required IFPP-81 Met 2012 Focused Scope Peer Review 2 None Required IFPP-82 Met 2012 Focused Scope Peer Review 2 None Required IFPP-83 Met 2012 Focused Scope Peer Review 2 None Required IFQU-Al Met 2018 Focused Scope Peer Review 2 None Required IFQU-A10 Met 2018 Focused Scope Peer Review 2 None Required IFQU-A11 Met 2018 Focused Scope Peer Review 2 None Required 1FQU-A2 Met 2018 Focused Scope Peer Review 2 None Required 1FQU-A3 Met 2018 Focused Scope Peer Review 2 None Required IFQU-A4 Met 2018 Focused Scope Peer Review 2 None Required lFQU-AS Met 2018 Focused Scope Peer Review 2 None Required IFQU-A6 Met 2018 Focused Scope Peer Review 2 None Required 1FQU-A7 Met 2018 Focused Scope Peer Review 2 None Required 1FQU-A8 Met 2018 Focused Scope Peer Review 2 None Required 1FQU-A9 Met 2018 Focused Scope Peer Review 2 None Required lFQU-81 Met 2018 Focused Scope Peer Review 2 None Required lFQU-82 Met 2018 Focused Scope Peer Review 2 None Required

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 19 of 26 CC II RG 1.200 RA-Sa-2009 /

RA-Sa-2009 Currently Most Recent Technical Review Version RG 1.200 Gap SR Met? Reviewed Assessment IFQU-B3 Met 2018 Focused Scope Peer Review 2 None Required IFSN-Al Met 2018 Focused Scope Peer Review 2 None Required IFSN-AlO Met 2018 Focused Scope Peer Review 2 None Required IFSN-All Met 2018 Focused Scope Peer Review 2 None Required IFSN-A12 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A13 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A14 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A15 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A16 N/A 2018 Focused Scope Peer Review 2 None Required IFSN-A17 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A2 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A3 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A4 Met 2018 Focused Scope Peer Review 2 None Required IFSN-AS Met 2018 Focused Scope Peer Review 2 None Required IFSN-A6 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A7 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A8 Met 2018 Focused Scope Peer Review 2 None Required IFSN-A9 Met 2018 Focused Scope Peer Review 2 None Required IFSN-B1 Met 2018 Focused Scope Peer Review 2 None Required IFSN-B2 Met 2018 Focused Scope Peer Review 2 None Required IFSN-B3 Met 2018 Focused Scope Peer Review 2 None Required IFSO-Al Met 2012 Focused Scope Peer Review 2 None Required IFSO-A2 Met 2012 Focused Scope Peer Review 2 None Required IFSO-A3 Met 2012 Focused Scope Peer Review 2 None Required IFSO-A4 Met 2012 Focused Scope Peer Review 2 None Required IFSO-AS Met 2012 Focused Scope Peer Review 2 None Required IFS0-A6 Met 2018 F&O Closure 2 None Required IFSO-B1 Met 2012 Focused Scope Peer Review 2 None Required IFSO-B2 Met 2012 Focused Scope Peer Review 2 None Required IFSO-B3 Met 2018 F&O Closure 2 None Required LE-Al Met 2012 Focused Scope Peer Review 2 None Required LE-A2 Met 2012 Focused Scope Peer Review 2 None Required LE-A3 Met 2012 Focused Scope Peer Review 2 None Required LE-A4 Met 2012 Focused Scope Peer Review 2 None Required LE-AS Met 2012 Focused Scope Peer Review 2 None Required LE-Bl Met 2012 Focused Scope Peer Review 2 None Required LE-B2 Met 2012 Focused Scope Peer Review 2 None Required LE-B3 Met 2012 Focused Scope Peer Review 2 None Required LE-Cl Met 2012 Focused Scope Peer Review 2 None Required LE-ClO Met 2012 Focused Scope Peer Review 2 None Required LE-C11 Met 2012 Focused Scope Peer Review 2 None Required LE-C12 Met 2018 F&O Closure 2 None Required LE-C13 Met 2012 Focused Scope Peer Review 2 None Required

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 20 of 26 CC II RG 1.200 RA-Sa-2009 /

RA-Sa-2009 Currently Most Recent Technical Review Version RG 1.200 Gap SR Met? Reviewed Assessment LE-C2 Met 2018 F&O Closure 2 None Required LE-C3 Met 2018 F&O Closure 2 None Required LE-C4 Met 2012 Focused Scope Peer Review 2 None Required LE-CS Met 2012 Focused Scope Peer Review 2 None Required LE-C6 Met 2012 Focused Scope Peer Review 2 None Required LE-C7 Met 2018 F&O Closure 2 None Required LE-C8 Met 2012 Focused Scope Peer Review 2 None Required LE-C9 Met 2012 Focused Scope Peer Review 2 None Required LE-D1 Met 2012 Focused Scope Peer Review 2 None Required LE-D2 N/A 2012 Focused Scope Peer Review 2 None Required LE-D3 N/A 2012 Focused Scope Peer Review 2 None Required LE-D4 Met 2012 Focused Scope Peer Review 2 None Required LE-DS Met 2012 Focused Scope Peer Review 2 None Required LE-D6 Met 2012 Focused Scope Peer Review 2 None Required LE-D7 Met 2012 Focused Scope Peer Review 2 None Required LE-El Met 2012 Focused Scope Peer Review 2 None Required LE-E2 Met 2012 Focused Scope Peer Review 2 None Required LE-E3 Met 2012 Focused Scope Peer Review 2 None Required LE-E4 Met 2012 Focused Scope Peer Review 2 None Required LE-Fl Met 2012 Focused Scope Peer Review 2 None Required LE-F2 Not Met 2012 Focused Scope Peer Review 2 None Required LE-F3 Met 2012 Focused Scope Peer Review 2 None Required LE-Gl Met 2018 F&O Closure 2 None Required LE-G2 Met 2012 Focused Scope Peer Review 2 None Required LE-G3 Met 2012 Focused Scope Peer Review 2 None Required LE-G4 Met 2012 Focused Scope Peer Review 2 None Required LE-GS Not Met 2012 Focused Scope Peer Review 2 None Required LE-G6 Met 2012 Focused Scope Peer Review 2 None Required QU-Al Met 2018 Focused Scope Peer Review 2 None Required QU-A2 Met 2018 Focused Scope Peer Review 2 None Required QU-A3 Met 2018 Focused Scope Peer Review 2 None Required QU-A4 Met 2018 Focused Scope Peer Review 2 None Required QU-AS Met 2018 Focused Scope Peer Review 2 None Required QU-B1 Met 2018 Focused Scope Peer Review 2 None Required QU-B10 N/A 2018 Focused Scope Peer Review 2 None Required QU-B2 Met 2018 Focused Scope Peer Review 2 None Required QU-B3 Met 2018 Focused Scope Peer Review 2 None Required QU-B4 Met 2018 Focused Scope Peer Review 2 None Required QU-BS Met 2018 Focused Scope Peer Review 2 None Required QU-B6 Met 2018 Focused Scope Peer Review 2 None Required QU-B7 Met 2018 Focused Scope Peer Review 2 None Required QU-B8 Met 2018 Focused Scope Peer Review 2 None Required QU-B9 . N/A 2018 Focused Scope Peer Review 2 None Required

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 21 of 26 CC II RG 1.200 RA-Sa-2009 /

RA-Sa-2009 Currently Most Recent Technical Review Version RG 1.200 Gap SR Met? Reviewed Assessment QU-Cl Met 2018 Focused Scope Peer Review 2 None Required QU-C2 Met 2018 Focused Scope Peer Review 2 None Required QU-C3 N/A 2018 Focused Scope Peer Review 2 None Required QU-Dl Met 2018 Focused Scope Peer Review 2 None Required QU-D2 Met 2018 Focused Scope Peer Review 2 None Required QU-D3 Met 2018 Focused Scope Peer Review 2 None Required QU-D4 Met 2018 Focused Scope Peer Review 2 None Required QU-DS Met 2018 Focused Scope Peer Review 2 None Required QU-D6 Met 2018 Focused Scope Peer Review 2 None Required QU-D7 Met 2018 Focused Scope Peer Review 2 None Required QU-El Met 2018 Focused Scope Peer Review 2 None Required QU-E2 Met 2018 Focused Scope Peer Review 2 None Required QU-E3 Met 2018 Focused Scope Peer Review 2 None Required QU-E4 Met 2018 Focused Scope Peer Review 2 None Required QU-Fl Met 2018 Focused Scope Peer Review 2 None Required QU-F2 Met 2018 Focused Scope Peer Review 2 None Required QU-F3 Met 2018 Focused Scope Peer Review 2 None Required QU-F4 Met 2018 Focused Scope Peer Review 2 None Required QU-FS Met 2018 Focused Scope Peer Review 2 None Required QU-F6 Met 2018 Focused Scope Peer Review 2 None Required SC-Al Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-A2 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-A3 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-A4 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-AS Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-A6 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-Bl Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-B2 Met NEI 00-02 Self-Assessment None *Note 1 SC-B3 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-B4 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-BS Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-Cl Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-C2 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SC-C3 Met 2000 Peer Review+ NEI 00-02 Self-Assessment None *Note 1 SY-Al Met 2018 Focused Scope Peer Review 2 None Required SY-AlO Met 2018 Focused Scope Peer Review 2 None Required SY-All Met 2018 Focused Scope Peer Review 2 None Required SY-A12 Met 2018 Focused Scope Peer Review 2 None Required

• SY-A13 Met 2018 Focused Scope Peer Review 2 None Required SY-A14 Met 2018 Focused Scope Peer Review 2 None Required SY-AlS Met 2018 Focused Scope Peer Review 2 None Required SY-A16 Met 2018 Focused Scope Peer Review 2 None Required SY-A17 Met 2018 Focused Scope Peer Review 2 None Required

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 22 of 26 CC II RG 1.200 RA-Sa-2009 /

RA-Sa-2009 Currently Most Recent Technical Review Version RG 1.200 Gap SR Met? Reviewed Assessment SY-A18 Met 2018 Focused Scope Peer Review 2 None Required SY-A19 Met 2018 Focused Scope Peer Review 2 None Required SY-A2 Met 2018 Focused Scope Peer Review 2 None Required SY-A20 Met 2018 Focused Scope Peer Review 2 None Required SY-A21 Met 2018 Focused Scope Peer Review 2 None Required SY-A22 Met 2018 Focused Scope Peer Review 2 None Required SY-A23 Met 2018 Focused Scope Peer Review 2 None Required SY-A24 Met 2018 Focused Scope Peer Review 2 None Required SY-A3 Met 2018 Focused Scope Peer Review 2 None Required SY-A4 Met 2018 Focused Scope Peer Review 2 None Required SY-AS Met 2018 Focused Scope Peer Review 2 None Required SY-A6 Met 2018 Focused Scope Peer Review 2 None Required SY-A7 Met 2018 Focused Scope Peer Review 2 None Required SY-A8 Met 2018 Focused Scope Peer Review 2 None Required SY-A9 Met 2018 Focused Scope Peer Review 2 None Required SY-B1 Met 2018 Focused Scope Peer Review 2 None Required SY-B10 Met 2018 Focused Scope Peer Review 2 None Required SY-B11 Met 2018 Focused Scope Peer Review 2 None Required SY-B12 Met 2018 Focused Scope Peer Review 2 None Required SY-B13 Met 2018 Focused Scope Peer Review 2 None Required SY-B14 Met 2018 Focused Scope Peer Review 2 None Required SY-B15 Met 2018 Focused Scope Peer Review 2 None Required SY-B2 Met 2018 Focused Scope Peer Review 2 None Required SY-B3 Met 2018 Focused Scope Peer Review 2 None Required SY-B4 Met 2018 Focused Scope Peer Review 2 None Required SY-BS Met 2018 Focused Scope Peer Review 2 None Required SY-B6 Met 2018 Focused Scope Peer Review 2 None Required SY-B7 Met 2018 Focused Scope Peer Review 2 None Required SY-B8 Met 2018 Focused Scope Peer Review 2 None Required SY-B9 Met 2018 Focused Scope Peer Review 2 None Required SY-C1 Met 2018 Focused Scope Peer Review 2 None Required SY-C2 Met 2018 Focused Scope Peer Review 2 None Required SY-C3 Met 2018 Focused Scope Peer Review 2 None Required

• Note 1- The 2007 Self-Assessment was performed to assess potential gaps to RA-Sb-2005 / RG 1.200 Rev. 1 requirements. Per NEI 05-04 Rev. 3, no re-evaluation is required for RA-Sa-2009 / RG 1.200 Rev. 2.

• Note 2 - The 2007 Self-Assessment was performed to assess potential gaps to RA-Sb-2005 / RG 1.200 Rev. 1 requirements. Per NEI 05-04 Rev. 3 requirements, re-evaluation using a gap assessment to RA-Sa-2009 / RG 1.200 Rev. 2 has been performed. No open gaps have been identified.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 23 of 26 MPS2-R05g Risk Metrics for ILRT Extension The risk impact assessment for extending the ILRT interval to once every 15 years was performed using the MPS2-R05g PRA model to demonstrate that the risk metrics associated with extending the ILRT interval remain within the acceptance criteria. The methodology used for this assessment is consistent with Attachment 3 of the LAR.

The updated MPS2 core damage frequency (GDF), large early release frequency (LERF), and release category frequencies are shown in Table 4.2-1 below, which corresponds to Table 4.2-1 in Attachment 3 of the LAR. The population dose and mapping to the relevant EPRI Class remain unchanged for each release category.

Table 4.2-1 MPS2-R05g Release Category Definitions, Frequency, and Population Dose MPS2 Release Frequency Person-Rem EPRI Description Category per year (50 miles) Class 1 1.18E-08 2.27E+01 1 No CF 2 O.OOE+OO 9.34E+OO 7 Late CF, Cont Spray 3 O.OOE+OO 7.62E+04 7 Late CF, Early Spray 4 7.42E-06 7.62E+04 7 Late CF, No Spray SA 6.32E-06 1.S6E+01 7 Meltthru, Spray SB 3.90E-06 1.02E+06 7 Meltthru, No Spray 6 6.08E-09 1.32E+OS 2 Large Cl Fail 7 2.98E-07 2.27E+01 1 No CF 8 O.OOE+OO 1.32E+OS 2 Large Cl Fail 9 4.90E-08 3.90E+06 8 Event V 10 1.S4E-06 1.06E+06 8 SGTR 11 O.OOE+OO 1.06E+OS 8 SGTR (non-LERF)

CDF 1.9SE-OS LERF 1.27E-06 Based on the updated Table 4.2-1 information, the frequency and dose of each EPRI Class is shown in Table 4.2-2 below, which corresponds to Table 4.2-2 in Attachment 3 of the LAR.

Table 4.2-2 MPS2-R05g Release Frequency and Population Dose Organized by EPRI Release Category EPRI Class Frequency (/yr) Dose (person-rem) 1 3.lOE-07 2.27E+01 2 6.08E-09 1.32E+OS 7 1.76E-OS 2.S7E+OS 8 1.S9E-06 1.1SE+06 The assessment results based on the MPS2-R05g PRA model are summarized on the following page in Table 5.6-1 which corresponds to Table 5.6-1 of Attachment 3 in the LAR.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 24 of 26 Table 5.6-1 Summary of MPS2-R05g Results for ILRT Frequency Extensions Base Case (3 per 10 years) 1 per 10 years 1 per 15 years Without Corrosion With Corrosion Without Corrosion With Corrosion Without Corrosion With Corrosion Delta Delta Delta Person- Person- Person- Person- Person- Person-EPRI Frequency Frequency person- Frequency Frequency person- Frequency Frequency person-Rem per Rem per Rem per Rem per Rem per Rem per Class (per year) (per year) rem per (per year) (per year) rem per (per year) (per yr) rem per year year year year year year year year year 1 8.48E-08 1.93E-06 8.46E-08 1.92E-06 -3.89E-09 0.00E+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO O.OOE+OO 2 6.08E-09 8.03E-04 6.08E-09 8.03E-04 O.OOE+OO 6.08E-09 8.03E-04 6.08E-09 8.03E-04 O.OOE+OO 6.08E-09 8.03E-04 6.08E-09 8.03E-04 O.OOE+OO 3a 1.80E-07 4.09E-05 1.80E-07 4.09E-05 O.OOE+OO 6.00E-07 1.36E-04 6.00E-07 1.36E-04 O.OOE+OO 9.00E-07 2.04E-04 9.00E-07 2.04E-04 O.OOE+OO 3b 4.48E-08 1.02E-04 4.50E-08 1.02E-04 3.89E-07 1.49E-07 3.39E-04 1.SOE-07 3.41E-04 2.30E-06 2.24E-07 5.09E-04 2.26E-07 5.14E-04 5.46E-06 7 1.76E-05 4.54E+OO 1.76E-05 4.54E+OO O.OOE+OO 1.76E-05 4.54E+OO 1.76E-05 4.54E+OO O.OOE+OO 1.76E-05 4.54E+OO 1.76E-05 4.54E+OO O.OOE+OO 8 1.59E-06 1.83E+OO 1.59E-06 1.83E+OO O.OOE+OO 1.59E-06 1.83E+OO 1.59E-06 1.83E+OO O.OOE+OO 1.59E-06 1.83E+OO 1.59E-06 1.83E+OO O.OOE+OO Total 1.95E-05 6.366199 1.95E-05 6.366200 3.85E-07 2.00E-05 6.366530 2.00E-05 6.366532 2.30E-06 2.04E-05 6.366768 2.04E-05 6.366773 5.46E-06 Delta 3.30E-04 3.33E-04 5.68E-04 5.74E-04 1 N/A N/A Dose 0.0052% 0.0052% 0.0089% 0.0090%

CCFP 98.418% 98.419% 98.427% 98.432% 98.433% 98.445%

Delta 2 N/A N/A 0.008% 0.014% 0.015% 0.027%

CCFP Class 4.50E-08 1.50E-07 2.26E-07 3b 4.48E-08 1.49E-07 2.24E-07 3 {1.71E-10} {1.0lE-09} {2.41E-09}

LERF 3 1.05E-07 1.82E-07 Delta LERF From Base Case {3 per 10 years) 1.04E-07 1.79E-07

{1.0lE-09} {2.41E-09}

3 7.72E-08 Delta LERF From 1 per 10 years N/A 7.48E-08

{2.41E-09}

1. The delta dose is expressed as both change in dose rate (person-rem/year) from base dose rate and as% of base total dose rate.

2. The delta CCFP is calculated with respect to the base case CCFP.

3. The delta between the results with and without corrosion for each interval is shown in parentheses below the results with corrosion.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 25 of 26 The external events assessment used the ratio between the internal events LERF and GDF to calculate the external events LERF. Since this ratio changed between the R05e and R05g models, the external events LERF changed. The risk impact of extending the ILRT interval including both the MPS2-R05g PRA model and external events is summarized in Table 5.7-2 below, which corresponds to Table 5.7-2 in Attachment 3 of the LAR.

Table 5.7-2 Total LERF Increase for 15-year ILRT Interval Including Internal and External Events Initiating Class 3b Frequency (/yr} LERF LERF Class 3b Event CDF (/yr} 3 per 10 1 per 10 1 per 15 Increase

(/yr} Probability Grnup year ILRT year ILRT year ILRT (/yr}

Internal 1.9SE-OS 1.27E-06 0.0023 4.48E-08 1.49E-07 2.24E-07 l.79E-07 Events External 4.lOE-05 2.66E-06 0.0023 9.40E-08 3.13E-07 4.70E-07 3.76E-07 Events Total 6.0SE-05 3.93E-06 - 1.39E-07 4.63E-07 6.94E-07 5.55E-07 Using the MPS2-R05g PRA model, the following are conclusions regarding plant risk associated Vl(ith extending the Type A ILRT test frequency to fifteen years.

• The increase in internal events LERF, with corrosion, resulting from a change in the Type A ILRT test frequency from 3-per-10 years to 1-per-15 years, is conservatively estimated as 1.82E-07/yr (see Table 5.6-1 ). As such, the estimated change in internal events LERF is determined to be "small" using the acceptance guidelines of RG 1.174. The increase in LERF including both internal and external events is estimated as 5.55E-07/yr (see Table 5.7-2), which is considered a "small" change in LERF using the acceptance guidelines of RG 1.174.

• Although the total increase in LERF for internal and external events is greater than 1.OE-07 per reactor year, the total LERF can be demonstrated to be well below 1.0E-05 per reactor year. The total base LERF for internal and external events is 3.93E-06/yr (see Table 5.7-2). Since the increase in LERF for the fifteen-year ILRT interval is 5.55E-07/yr for internal and external events (see Table 5.7-2),

the total LERF for the fifteen-year interval can be estimated as 4.49E-06/yr. This is well below the RG 1.174 acceptance criteria for total LERF of 1.0E-05/yr.

• The change in dose risk for changing the Type A test frequency from 3-per-10 years to 1-per-15 years, measured as an increase to the total integrated dose risk for all accident sequences, is 5.74E-04 person-rem/yr or 0.0090% of the total population dose. EPRI TR-1018243 states that a very small population dose is defined as an increase of ~ 1.0 person-rem per year or < 1 . % of the total population dose, whichever is less restrictive for the risk impact assessment of the

• extended ILRT interval.

Serial No.18-230 Docket No. 50-336 Attachment 2, Page 26 of 26

• The increase in the conditional containment failure frequency from the 3-per-10 year frequency to 1-per-15 year frequency is 0.027% using the base case corrosion case in Table 5.6-1. EPRI TR-1018243 [18] states that increases in conditional containment failure probability (CCFP) of ::;; 1.5 percentage points are very small. Therefore, this increase is judged to be very small.

Increasing the ILRT interval to fifteen years is considered insignificant since it represents a small change to the MPS2 risk profile using either the R05e PRA model, as documented in Attachment 3 of the LAR, or the updated R05g PRA model.