ML24197A170

Request for Additional Information Two Proposed Alternatives (RA-23-0242) for the Inspection of Reactor Vessel Closure Head Penetrations

ML24197A170
Person / Time
Site:	McGuire, Catawba, Mcguire
Issue date:	07/15/2024
From:	Bryant J Plant Licensing Branch II
To:	Treadway R Duke Energy Carolinas
Minzer Bryant J
References
EPID L-2024-LLR-0003
Download: ML24197A170 (4)

Text

From: Jack Minzer Bryant To: Treadway, Ryan I Cc: Edwards, Nicole D; Shawn Williams; Ed Miller

Subject:

Catawba, Units 1 and 2, McGuire, Units 1 and 2 - Request for Additional Information RE: Two Proposed Alternatives (RA-23-0242) for the Inspection of Reactor Vessel Closure Head Penetrations (EPID L-2024-LLR-0003)

Date: Monday, July 15, 2024 2:12:00 PM Attachments: Catawba-McGuire RR RAI Enclosure.docx

Dear Ryan Treadway,

By letter dated January 10, 2024, Duke Energy Carolinas, LLC, submitted two alternative requests for Catawba Nuclear Station, Units 1 and 2, and McGuire Nuclear Station, Units 1 and 2. Specifically, Duke Energy is requesting relief from the requirements of 10 CFR 50.55a(g)(6)(ii)(D) for the timing of the follow-up examination of the reactor vessel closure head penetration nozzles subsequent to the performance of peening and an alternative to the depth of compression requirement in the peening performance demonstration criteria of 10 CFR 50.55a(g)(6)(ii)(F)

(2)(ii).

The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed as discussed in the enclosure. A clarification call to ensure mutual understanding was conducted on July 10, 2024.

As agreed during the clarification call, please respond within 45 days of the date of this e-mail.

Please note that the NRC staffs review is continuing and further requests for information may be developed. If you have any questions, please contact me.

Very Respectfully,

Jack Minzer Bryant, Project Manager Nuclear Regulatory Commission Division of Operating Reactor Licensing NRR/DORL/LPL2-1 (301) 415-0610

Docket Nos.

50-413, 50-414 50-369, 50-370

Enclosure:

Request for Additional Information

cc: Listserv REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CATAWBA/MCGUIRE - A LT ( R A-23-0242) TO PEENING DEPTH COMPRESSION DUKE ENERGY CAROLINAS, LLC CATAWBA, UNITS 1, 2; MCGUIRE, UNITS 1, 2 DOCKET NO. 05000369, 05000370, 05000413, 05000414 ISSUE DATE: 07/15/2024

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Background===

By Letter dated January 10, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24010A033), Duke Energy Carolinas, LLC, (the licensee) submitted a proposed alternative, RR 0242, for Catawba Nuclear Station, Units 1 and 2 (CNS) and McGuire Nuclear Station, Units 1 and 2 (MNS). The licensee is requesting relief from the requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(6)(ii)(D) for the timing of the follow-up examination of the Reactor Vessel Closure Head (RVCH) Penetration Nozzles subsequent to the performance of peening for CNS and MNS. The licensee is also requesting an alternative to the surface stress and depth of compression requirement in the peening performance demonstration criteria of 10 CFR 50.55a(g)(6)(ii)(F)(2)(ii), for the Auxiliary Head Adapter (AHA) butt welds at each plant. The licensee is making this request pursuant to 10 CFR 50.55a(z)(2).

The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed to complete its review, as described below.

Regulatory Basis

The inservice inspection (ISI) of the American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME) Code,Section XI, Class 1, 2 and 3 components shall be performed in accordance with the requirements of Section XI, Rules for In-service Inspection of Nuclear Power Plant Components, of the ASME Code and applicable editions and addenda as required by 10 CFR Part 50 Paragraph 50.55a(g), except where specific written relief has been granted or proposed alternative authorized by the Commission.

The Materials Reliability Program: Topical Report for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement (MRP-335, Revision 3-A) (ML16319A282) is incorporated by reference in 10 CFR 50.55a(g)(6)(ii)(D) and 10 CFR 50.55a(g)(6)(ii)(F) to address the regulatory requirements for peening mitigation of RVCH penetration nozzles and associated partial penetration welds and dissimilar metal butt welds. This NRC approved topical report provides the performance criteria, inspection requirements and the associated technical basis for the subject components of this proposed alternative with certain NRC conditions.

In order to complete its review of the licensee's proposed alternative, the NRC staff requests the following information:

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Question 1 Request for Additional Information

The licensees proposed alternative for the use of the ID penetration nozzle performance criteria of MRP-335, Revision 3-A, in lieu of the butt weld performance criteria, requires a similar technical basis as MRP-335, Revision 3-A. The NRC staff requests the following additional information.

1. Please describe the actual method of peening application for the AHA butt welds. Include drawings or sketches of the applicator, penetration nozzle and associated weld dimensions, as necessary, to clearly describe application and limitations. Discussion should include any changes in the essential variables which were necessary and maintained during application to meet the distance required from peening nozzle to butt weld surface from the Special Process Qualification Record for the qualification of the cavitation peening process for the AHA butt welds.

Question 2 Please provide the testing and analysis performed to determine the Section 4.2.8.1.1, "Magnitude of Surface Stress," and Section 4.2.8.1.2, "Nominal Depth of Compressive Residual Stress," of MRP-335, Revision 3-A. These results should include discussion of mockup testing on similar weld material surfaces with similar weld configurations to verify effectiveness on typical weld residual stresses created by the AHA weld geometry location. Please justify any conservative assessments that are used to support the request. Essential variables for testing should include or bound application variables used to peen the AHA butt welds for CNS and MNS.

a) Please clarify if testing and analysis shows Sections 4.2.8.1.1 and 4.2.8.1.2 performance criteria of MRP-335, Revision 3-A, are met, and any needed alternative from the current regulatory requirements. Confirm that the AHA butt welds for CNS and MNS will be inspected at the N+3 refueling outage, to support the technical basis for hardship for extension of the volumetric examination of the remaining RVH penetration nozzles at each plant from the N+2 to N+3 refueling outages.

b) Please clarify if testing and analysis shows Sections 4.2.8.1.1 and 4.2.8.1.2 performance criteria of MRP-335, Revision 3-A, are not met, and supporting analysis in accordance with Section 5 for a bounding (most limiting) stress analysis of the peened AHA butt welds at CNS and MNS. Include deterministic and probabilistic analysis, as deemed necessary by the licensee, to address the bounding stress state achieved for the AHA butt welds including possible use of any probabilistic assessment methods considered in Draft Regulatory Guide -

1422, Preparing Probabilistic Fracture Mechanics Submittals. Include representative weld residual and operating stress(es), loadings, and cycles, as well as initial flaw sizes used in the calculations for technical justification of Section 4.2.3, "Follow-Up Inspection," and Section 4.2.4, "Subsequent ISI Program," examination frequencies. Also, please provide a qualitative

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and/or quantitative assessment to indicate that the remaining performance criteria of Section 4.2.1 will be met for the design life of the mitigation.