ML24141A243

Response to Request for Additional Information Regarding Alloy 600 Aging Management Program Submittal Related to License Renewal Commitment No. 15

ML24141A243
Person / Time
Site:	Millstone
Issue date:	05/20/2024
From:	James Holloway Dominion Energy Co, Dominion Energy Nuclear Connecticut
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
23-291A
Download: ML24141A243 (1)

Text

Serial No. 23-291A Docket No. 50-423

Attachment

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING ALLOY 600 AGING MANAGEMENT PROGRAM SUBMITTAL RELATED TO LICENSE RENEWAL COMMITMENT NO. 15.

Dominion Energy Nuclear Connecticut, Inc.

Millstone Power Station Unit 3 Serial No. 23-291A Docket No. 50-423 Attachment, Page 1 of 4

By letter dated November 20, 2023 Agencywide Documents Access and Management System (ADAMS) Accession No. ML23324A430, Dominion Energy Nuclear Connecticut, Inc. (DENC) submitted a description of its revised aging management program (AMP) for management of nickel-based alloy (also referred to as Alloy 600). This document was submitted in accordance with Commitment Item No. 15 of NUREG-1838, the safety evaluation report for the renewed operating license for Millstone Power Station, Unit No.

3 (MPS3).

In an email dated April 22, 2024, the NRC issued a draft request for additional information (RAI) related to Alloy 600 AMP submittal. On April 22, 2024, the NRC staff conducted a conference call with DENC staff to discuss clarifications on the draft RAI. In an email dated April 22, 2024, the NRC transmitted the final version of the RAI. DENC agreed to respond to the RAI within 30 days of issuance, or no later than May 22, 2024.

This attachment provides DENCs response to the RAI.

RAI Background

On page 2 of 10 of the Attachment to the November 20, 2023, letter, the licensee noted that the MPS3 Alloy 600 Inspection program had evolved to implement the requirements of applicable NRC publications and industry guidance, including References 6.14, 6.15 and 6.16. Further, the licensee noted that the Dominion Nuclear Fleet Alloy 600 Management Plan is described in Program Description ER-AA-MAT-11 and is applicable to all Alloy 600/82/182 components in primary systems at Dominion nuclear plants. As part of these activities, the NRC staff requests that the licensee confirm that the following actions have been addressed within these aging management programs for MPS3 for the period of license renewal.

RAI-1

The licensee identified several of the MPS3 ASME Code Class 1 dissimilar metal (DM) butt welds were mitigated by the full structural weld overlay (FSWOL). These FSWOL welds are required to be inspected in accordance with ASME Code N-770-5, Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated With UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities,Section XI, as mandated by 10 CFR 50.55a(g)(6)(ii)(F), Augmented ISI requirements: Examination requirements for Class 1 piping and nozzle dissimilar metal butt welds. Note 10 of ASME Code N-770-5 states, in part, Those welds not included in the 25 percent sample shall be examined prior to the end of the mitigation evaluation period if the plant is to be operated beyond that time. Confirm that the licensee has reviewed the design basis for each of these FSWOL welds for the period of extended operation to verify that the Serial No. 23-291A Docket No. 50-423 Attachment, Page 2 of 4

reinspection frequency in accordance with Note 10 of ASME Code Case N-770-5 are incorporated into the aging management program.

DENC Response to RAI-1

A listing of the Alloy 82/182 butt welds for MPS3 is included in the Dominion Energy Nuclear Fleet Alloy 600 Management Plan (ER-AA-MAT-11). These butt welds include the Pressurizer Surge, Spray, Safety, and Relief Nozzle dissimilar metal welds (DMWs),

which were mitigated with FSWOLs during refueling outages in the fall of 2005 (Spray Line) and the spring of 2007 (Safety, Relief, and Surge Lines). These welds are the only FSWOLs at MPS3.

The design life of these FSWOLs was considered to ensure that Note 10 of Code Case N-770-5 is properly implemented. The Pressurizer Surge Line Nozzle DMW, which has a design life of 22 years, was last examined in the spring of 2016, and is scheduled to be examined again in the fall of 2026. The Pressurizer Safety, Relief, and Spray Nozzle DMWs have a design life of 60 years, which exceeds the period of extended operation.

RAI-2

Due to industry operating experience (OE), Electric Power Research Institute (EPRI)

Technical Report 3002012244, Revision 3, Nondestructive Evaluation: Guideline for Conducting Ultrasonic Examinations of Dissimilar Metal Welds, dated February 2018, provides enhanced guidance and Nuclear Energy Institute (NEI) 03-08, Guideline for the Management of Materials Issues, (ML19079A256) requirements and recommendations for the examinations of DM welds.

Confirm that the licensee has reviewed EPRI Technical Report 3002012244, Revision 3, and incorporated the enhanced guidance requirements and recommendations in accordance with NEI 03-08 in the aging management program.

DENC Response to RAI-2

DENC has confirmed that EPRI Technical Report 3002012244, Revision 3 was incorporated into the applicable Dominion Nuclear Fleet Nondestructive Examination (NDE) Procedure (ER-AA-NDE-122, Dominion Energy Written Program for the Implementation of ASME Section XI, Appendix VIII Requirements).

Serial No. 23-291A Docket No. 50-423 Attachment, Page 3 of 4

RAI-3

NRC Regulator Issuance [sic] Summary (RIS) 2015-10, Applicability of ASME Code Case N-770-1 as Conditioned in 10 CFR 50.55a, Codes and Standards, to Branch Connection Butt Welds,(ML15068A131) issued on July 16, 2015, informs nuclear utilities about reactor coolant system (RCS) Alloy 82/182 branch connection DM nozzle welds that may be of a butt weld configuration, and therefore require inspection under 10 CFR 50.55a(g)(6)(ii)(F), Augmented ISI requirements: Examination requirements for Class 1 piping and nozzle dissimilar-metal butt welds.

Confirm that the licensee has reviewed RIS 2015-10 for applicability to MPS3 and taken any corrective actions necessary to ensure compliance with 10 CFR 50.55a(g)(6)(ii)(F).

DENC Response to RAI-3

A listing of the Alloy 82/182 butt welds for MPS3 is included in the Dominion Nuclear Fleet Alloy 600 Management Plan (ER-AA-MAT-11). MPS3 has no Alloy 82/182 branch connection DMWs. The MPS3 DMWs are inspected per the requirements of 10 CFR 50.55a.

RAI-4

Due to lessons learned and industry OE, EPRI Report 3002017288, Materials Reliability Program: Guideline for Nondestructive Examination of Reactor Vessel Upper Head Penetrations, Revision 1 (MRP-384), dated 2019, as required under NEI 03-08 implementation criteria, provides guidance for planning and executing reactor vessel upper head penetration examinations.

Confirm that the licensee has reviewed MRP-384 and incorporated the enhanced guidance requirements and recommendations in accordance with NEI 03-08 in the AMP.

DENC Response to RAI-4

DENC has confirmed that MRP-384, Revision 1 was incorporated into the applicable Dominion Nuclear Fleet NDE Procedure (ER-AA-NDE-147, Procedure for the Implementation of Materials Reliability Program (MRP), Guideline for NDE of Reactor Vessel Upper Head Penetrations (MRP-384)).

Serial No. 23-291A Docket No. 50-423 Attachment, Page 4 of 4

RAI-5

NRC RIS 2018-06, Clarification of the Requirements for Reactor Pressure Vessel Upper Head Bare Metal Visual Examinations, issued on December 10, 2018 (ML18178A137),

informs nuclear utilities about acceptable methodologies to evaluate relevant conditions that require further evaluation when performing bare metal visual examinations of the RPV upper head.

Confirm that the licensee has reviewed RIS 2018-06 for applicability to inspection programs and procedures at MPS3 and has taken any corrective actions necessary to ensure compliance with 10 CFR 50.55a(g)(6)(ii)(D).

DENC Response to RAI-5

DENC has confirmed that NRC RIS 2018-06 was added as a reference to the applicable Dominion Energy Nuclear Fleet NDE Procedure (ER-AA-NDE-VT-604, Visual Examination (VE) for Leakage of PWR Reactor Head Penetrations).