ML23132A254

Supplemental Information Needed for Acceptance of Requested Licensing Action LAR to Adopt 10 CFR 50.69,Risk-Informed Categorization & Treatment of Structures,Systems & Components for Nuclear Power Reactors EPID L-2023-LLA-0057

ML23132A254
Person / Time
Site:	Comanche Peak
Issue date:	05/23/2023
From:	Dennis Galvin Plant Licensing Branch IV
To:	Peters K Vistra Operations Company
Galvin D
References
EPID L-2023-LLA-0057
Download: ML23132A254 (1)

Text

May 23, 2023 Mr. Ken J. Peters Senior Vice President and Chief Nuclear Officer Attention: Regulatory Affairs Vistra Operations Company LLC Comanche Peak Nuclear Power Plant 6322 N FM 56 P.O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 -

SUPPLEMENTAL INFORMATION NEEDED FOR ACCEPTANCE OF REQUESTED LICENSING ACTION RE: LICENSE AMENDMENT REQUEST TO ADOPT 10 CFR 50.69, RISK-INFORMED CATEGORIZATION AND TREATMENT OF STRUCTURES, SYSTEMS AND COMPONENTS FOR NUCLEAR POWER REACTORS (EPID L-2023-LLA-0057)

Dear Mr. Peters:

By letter dated April 19, 2023, Vistra Operations Company LLC (Vistra OpCo, the licensee) submitted a license amendment request (LAR) (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23109A333) for Comanche Peak Nuclear Power Plant, Unit Nos. 1 and 2. The proposed LAR would allow, by the addition of license conditions, the implementation of the provisions of Title 10 of the Code of Federal Regulations (10 CFR) Section 50.69, Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors.

The purpose of this letter is to provide the results of the U.S. Nuclear Regulatory Commission (NRC) staffs acceptance review of this amendment request. The acceptance review was performed to determine if there is sufficient technical information in scope and depth to allow the NRC staff to complete its detailed technical review. The acceptance review is also intended to identify whether the application has any readily apparent information insufficiencies in its characterization of the regulatory requirements or the licensing basis of the plant.

Consistent with 10 CFR 50.90, an application for an amendment to a license (including the technical specifications) must fully describe the changes requested, and following as far as applicable, the form prescribed for original applications. Section 50.34 of 10 CFR addresses the content of technical information required. This section stipulates that the submittal address the design and operating characteristics, unusual or novel design features, and principal safety considerations.

The NRC staff has reviewed your application and concluded that the information delineated in the enclosure to this letter is necessary to enable the staff to make an independent assessment

K. Peters regarding the acceptability of the proposed amendment in terms of regulatory requirements for the protection of public health and safety and the environment.

In order to make the application complete, the NRC staff requests that Vistra OpCo supplement the application to address the information requested in the enclosure by June 12, 2023. This will enable the NRC staff to begin its detailed technical review. If the information responsive to the NRC staffs request is not received by the above date, the application will not be accepted for review pursuant to 10 CFR 2.101, and the NRC will cease its activities associated with the application. If the application is subsequently accepted for review, you will be advised of any further information needed to support the NRC staffs detailed technical review by separate correspondence.

The information requested and associated timeframe in this letter were discussed with Nic Boehmisch of your staff on May 23, 2023.

If you have any questions, please contact me at (301) 415-6256 or by e-mail to Dennis.Galvin@nrc.gov.

Sincerely,

/RA/

Dennis J. Galvin, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-445 and 50-446

Enclosure:

Supplemental Information Needed cc: Listserv

SUPPLEMENTAL INFORMATION NEEDED LICENSE AMENDMENT REQUEST TO ADOPT 10 CFR 50.69, RISK-INFORMED CATEGORIZATION AND TREATMENT OF STRUCTURES, SYSTEMS AND COMPONENTS FOR NUCLEAR POWER REACTORS VISTRA OPERATIONS COMPANY LLC COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-445 AND 50-446 By letter dated April 19, 2023, Vistra Operations Company LLC (Vistra OpCo, the licensee) submitted a license amendment request (LAR) (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23109A333) for Comanche Peak Nuclear Power Plant, Unit Nos. 1 and 2 (Comanche Peak or CPNPP). The proposed LAR would allow, by the addition of license conditions, the implementation of the provisions of Title 10 of the Code of Federal Regulations (10 CFR) Section 50.69, Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors. The U.S. Nuclear Regulatory Commission (NRC) staff has identified that the following information is needed to begin its technical review:

Acceptance Review Information Insufficiencies

1. The LAR references the approval of the Comanche Peak adoption of Technical Specifications Task Force (TSTF) Traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF [Risk-Informed TSTF] Initiative 4b, dated August 22, 2022 (ML22192A007), as the basis for the probabilistic risk assessment (PRA) technical acceptability. Section 3.2 of the enclosure to the 50.69 LAR indicates that the PRA models credited in this request are the same PRA models credited in the TSTF-505 LAR dated May 11, 2021 (ML21131A233), for internal events, internal floods, and internal fire. The safety evaluation for the Comanche Peak TSTF-505 LAR has a number of items dispositioned specifically for the adoption of TSTF-505 at Comanche Peak, such as certain supporting requirements that are met at Capability Category-I, and a number of fire PRA related topics. Those items dispositioned specifically for the TSTF-505 LAR do not apply to the 50.69 LAR given the different risk parameters used. For example, for the TSTF-505 LAR, the change in core damage frequency and large early release frequency parameters are used, while importance measures, such as Fussell-Vesely and risk achievement worth, are used for the 50.69 LAR.

The LAR also states that with regards to PRA assumptions and sources of uncertainty:

Key CPNPP PRA model specific assumptions and sources of uncertainty were identified and dispositioned for the RICT [risk-informed completion time] calculation as identified in Section 3.2.4.1.5 in Reference 1. The conclusion of this review was that no additional sensitivity analyses are Enclosure

required to address CPNPP PRA model specific assumptions or sources of uncertainty.

However, the NRC staff noted that disposition of impact of PRA uncertainty to in the TSTF-505 LAR does not apply to the 50.69 LAR given the different risk metrics used.

Therefore, provide the following information to allow the NRC staff to review the PRA technical acceptability for the 50.69 LAR:

a) Discuss any updates for the PRA models since the submittal of the TSTF-505 LAR.

b) Discuss how the assessment of the PRA assumptions and sources of uncertainty for the 50.69 LAR was performed and provide the results of the assessment.

c) Provide an assessment of the impact of the two supporting requirements that were assessed as Capability Category-I in the TSTF-505 LAR on the 50.69 LAR.

d) Provide an assessment of the impact of any fire PRA related items that were dispositioned in the TSTF-505 LAR on the 50.69 LAR.

2. LIC-109, Revision 3, Acceptance Review Procedures (ML20036C829), states that (1) lacking an analysis necessary for the NRC staffs review should be considered unacceptable, (2) simply referencing unapproved guidance may not be acceptable, and (3) deviations from guidance should not be considered acceptable unless fully justified.

The LAR states To address seismic hazard in the Structures, Systems and Components (SSC) categorization process, an alternative method to NEI [Nuclear Energy Institute] 00-04 [10 CFR 50.69 SSC Categorization Guideline (ML052900163)],

has been implemented consistent with the Electric Power Research Institute (EPRI)

Alternative Seismic Approach described in EPRI Report 3002022453 [Alternate Approaches for Addressing Seismic Risk in 10 CFR 50.69 Risk-Informed Categorization]. Further, section 3.1.1 of the enclosure to the LAR states evaluation of impact of the seismic hazard, which will use the EPRI Alternative Tier 1 Seismic Approach described in EPRI Report 3002022453. The NRC staff has not reviewed EPRI Report 3002022453. The report has not been submitted by the licensee as part of the LAR and it is currently unavailable in ADAMS. Further, EPRI Report 3002022453 includes changes beyond technical updates compared to prior EPRI reports reviewed by the NRC staff. Review of these changes can increase the NRC staffs resources and schedule for this LAR. The NRC staff has communicated issues resulting from the use of EPRI Report 3002022453 to licensees and EPRI.

EPRI Report 3002017583, Alternative Approaches for Addressing Seismic Risk in 10 CFR 50.69 Risk-Informed Categorization, is available in ADAMS (ML21082A170) and has been used by several licensees to support their approved Tier 1 alternative seismic approach. EPRI Report 3002017583 includes the updates to the Tier 1 approach resulting from the NRC staff's review of the Calvert Cliffs Nuclear Power Plant, Units 1 and 2, 10 CFR 50.69 amendment (ML19330D909).

Provide EPRI Report 3002022453 for the NRC staff's review as a supplement to the LAR. Alternately, the licensee can choose to support its proposed alternative seismic

approach by using and citing an approach previously accepted by the NRC, such as EPRI Report 3002017583.

3. LIC-109, Revision 3, states that the staff should determine if there are significant, obvious problems with the information and analyses provided. Section 3.2.4 of the enclosure to the LAR references the screening performed in the licensee's TSTF-505 LAR. However, information specific to the 50.69 LAR on categorization of SSCs considering other external hazards is not included in the LAR. Specifically, there is no discussion on whether any SSCs are credited in the screening of other external hazards and if yes, how those SSCs will be categorized, including justification for any deviations from the guidance in NEI 00-04 for the categorization of these SSCs.

Describe how SSCs that are credited for screening of other external hazards will be categorized consistent with the guidance in NEI 00-04. Identify and justify any deviations from relevant guidance in NEI 00-04 for the categorization of such SSCs.

4. Section 2.3 of the enclosure to the LAR proposes a condition on the licensee's operating license, which states, in part, Vistra OpCo is approved to implement 10 CFR 50.69 using the EPRI alternative Tier 1 seismic approach for active categorization of RISC

[Risk-Informed Safety Class]-1, RISC-2, RISC-3, and RISC-4 SSCs, and as specified in License Amendment No. [XXX] dated [DATE]. The NRC staff has not reviewed and approved the EPRI report(s) documenting the so-called Tier 1 process as generic topical reports. Therefore, the proposed license condition needs to reflect the fact that the alternative seismic approach is proposed by the licensee. Several precedents are available where the NRC staff has approved proposed license conditions stating simply the proposed alternative seismic approach Justify the use of the EPRI alternative Tier 1 seismic approach in the proposed license condition when the licensee is requesting the methodology on a plant-specific basis and the NRC staff has not approved the approach or the EPRI report(s) as a generic methodology. Alternately, the licensee can choose to propose a condition which identifies the alternative seismic approach as the licensee's proposed approach.

ML23132A254 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA NRR/DRA/APLA/BC NAME DGalvin PBlechman RPascarelli DATE 5/12/2023 5/16/2023 5/11/2023 OFFICE NRR/DRA/APLC/BC NRR/DORL/LPL4/BC NRR/DORL/LPL4/PM NAME SVasavada JDixon-Herrity DGalvin DATE 5/9/2023 5/12/2023 5/23/2023