ML24122A150

Audit Plan to Support Review of Steam Generator License Renewal Response to Commitment Nos 34 and 35

ML24122A150
Person / Time
Site:	Callaway
Issue date:	05/07/2024
From:	Mahesh Chawla Plant Licensing Branch IV
To:	Diya F Ameren Missouri
Chawla M
References
EPID L 2024 LRO 0009
Download: ML24122A150 (1)

Text

May 7, 2024

Fadi Diya Senior Vice President and Chief Nuclear Officer Ameren Missouri Callaway Energy Center 8315 County Road 459 Steedman, MO 65077

SUBJECT:

CALLAWAY PLANT, UNIT NO. 1 - AUDIT PLAN TO SUPPORT REVIEW OF STEAM GENERATOR LICENSE RENEWAL RESPONSE TO COMMITMENT NOS. 34 AND 35 (EPID L-2024-LRO-0009)

Dear Fadi Diya:

By letter dated December 20, 2023 (Agencywide Documents Access and Management System (ADAMS) Package Accession No. ML23354A244), Union Electric Company, doing business as Ameren Missouri (the licensee), submitted to the U.S. Nuclear Regulatory Commission (NRC) a response to license renewal Commitment Nos. 34 and 35 for the Callaway Plant, Unit No. 1 (Callaway). In March 2015, the NRC published NUREG-2172, Safety Evaluation Report Related to the License Renewal of Callaway Plant, Unit 1, which documents the technical review of the Callaway license renewal application (ML15068A342).

The NRC staff reviewed the Callaway submittal regarding the license renewal resolution for Commitment Nos. 34 and 35 and determined that a regulatory audit would be necessary to support its review of the submittal. A regulatory audit is a planned activity that includes the examination and evaluation of primarily non-docketed information. The audit will be conducted to increase the staffs understanding of the submittal and identify information that will need to be docketed to support staffs regulatory findings.

The NRC staff plans to conduct the audit from May 20, 2024, through August 30, 2024, in accordance with the enclosed audit plan.

F. Diya

If you have any questions, please contact me at 301-415-8371 or via email at Mahesh.Chawla@nrc.gov.

Sincerely,

/RA/

Mahesh L. Chawla, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Docket No. 50-483

Enclosure:

Audit Plan

cc: Listserv

AUDIT PLAN

TO SUPPORT REVIEW OF LICENSE RENEWAL RESPONSE

TO COMMITMENT NOS. 34 AND 35

UNION ELECTRIC COMPANY

CALLAWAY PLANT, UNIT 1

DOCKET NO. 50-483

1.0 BACKGROUND

By letter dated December 20, 2023 (Agencywide Documents Access and Management System (ADAMS) Package Accession No. ML23354A244), Union Electric Company doing business as Ameren Missouri (the licensee), submitted to the U.S. Nuclear Regulatory Commission (NRC) a response to license renewal Commitment Nos. 34 and 35 for the Callaway Plant, Unit No. 1 (Callaway). In March 2015, the NRC published NUREG-2172 Safety Evaluation Report Related to the License Renewal of Callaway Plant, Unit 1, Volume 1, which documents the technical review of the Callaway license renewal application (ML15068A342).

In accordance with the requirements of Title 10 of the Code of Federal Regulations (10 CFR)

Part 54, Requirements for Renewal of Operating Licenses for Nuclear Power Plants, and NUREG-2172, appendix A, License Renewal Commitments, the NRC staff will perform an audit to gain a better understanding of: (1) how the Callaway steam generator reactor coolant system (RCS) pressure boundary is adequately maintained in the presence of divider plate weld cracking, and (2) how the susceptibility of the Callaway steam generator tube-to-tubesheet welds to primary water stress corrosion cracking (PWSCC).

2.0 REGULATORY AUDIT BASES

License renewal requirements are specified in 10 CFR Part 54. In March 2015, the NRC published NUREG-2172, a final safety evaluation report to the license renewal of Callaway.

In NUREG-2172, appendix A, Callaway Plant Unit 1 License Renewal Commitments, Callaway Commitment No. 34 provided the licensee three options to fulfill this commitment. The licensee has chosen Option 2: Analysis, which requires Callaway to:

Perform an analytical evaluation of the steam generator divider plate welds in order to establish a technical basis which concludes that the steam generator RCS pressure boundary is adequately maintained with the presence of steam generator divider plate weld cracking. The analytical evaluation will be submitted to the NRC for review and approval.

Callaway Commitment No. 35 provided the licensee three options to fulfill this commitment. The licensee has chosen Option 2: Analysis, which requires Callaway to:

Perform an analytical evaluation of the steam generator tube-to-tubesheet welds either determining that the welds are not susceptible to PWSCC or redefining the

Enclosure

reactor coolant pressure boundary of the tubes, where the steam generator tube-to-tubesheet welds are not required to perform a reactor coolant pressure boundary function. The redefinition of the reactor coolant pressure boundary will be submitted as part of a license amendment request requiring approval from the NRC. The evaluation for determination that the welds are not susceptible to PWSCC and do not require inspection will be submitted to the NRC for review.

3.0 REGULATORY AUDIT SCOPE AND METHODOLOGY

The licensee performed an analytical evaluation specific to the Callaway steam generators because it could not be determined if the steam generators were bounded by the industry analyses, Electric Power Research Institut e (EPRI) Steam Generator Management Program Report 3002002850, Investigation of Crack Initiation and Propagation in the Steam Generator Channel Head Assembly, that the staff accepted for the divider plate PWSCC evaluation in License Renewal (LR) Interim Staff Guidance (ISG) LR-ISG-2016-01, Changes to Aging Management Guidance for Various Steam Generator Components (ML16237A383).

The NRC staff is unable to determine from the information submitted whether the licensees analysis establishes an adequate technical basis for (1) concluding that the steam generator reactor coolant boundary would be maintained in the presence of divider plate cracking, and (2) evaluating the susceptibility of the steam generator tube-to-tubesheet welds to PWSCC. The audit team will view documentation and calculat ions the licensee referenced as technical support, focusing on the key assumptions, methodology, and inputs.

4.0 AUDIT ACTIVITIES

For the audit, the NRC staff will review the licensees submittal dated December 20, 2023, and documentation on the licensees electronic portal (ePortal). The staff will have the opportunity to have technical discussions with the licensee to gain context, clarity, and information on the documentation to support the staffs review. The audit is coordinated to support the development of the reviewers reasonable assurance for the safety findings to be documented in the safety evaluation.

The Division of Operating Reactor Licensing (DORL) Plant Licensing Branch 4 (LPL 4) project manager will coordinate all communications with the licensee. NRC technical staff requests for communication with the licensee will require approval of their respective technical branch chief and the DORL branch chief. Following completion of the audit, an audit report will be iss ued.

5.0 INFORMATION AND OTHER MATERIAL NECESSARY FOR THE REGULATORY AUDIT

Throughout the audit, the NRC staff will review the supporting documents as appropriate and requested, on the ePortal. The staff may request additional documents to be added to the ePortal over the course of the audit. The staff requests for ePortal additions shall be made, as needed, to the DORL project manager, who will provide the requests to the licensee.

6.0 AUDIT TEAM

Team Member Branch/Division David Rudland Division of New and Renewed Licenses (DNRL)

Andrew Johnson Corrosion and Steam Generators Branch (NCSG)/DNRL Gregory Makar NCSG/DNRL Paul Klein NCSG/DNRL Mahesh Chawla DORL/LPL4

7.0 LOGISTICS

The attachment to this audit plan provides a list of documents needed for this audit. The audit will be conducted using telecommunications from May 20 2024, through August 30, 2024.

Entrance and exit briefings will be held at the beginning and end of the audit.

8.0 DELIVERABLES

An audit summary will be prepared within 90 days of the completion of the audit. If the NRC staff identifies information during the audit that is needed to support its regulatory decision, the staff will issue a request for additional information to the licensee after completion of the audit.

Attachment:

List of Documents List of Documents

References From Enclosure 1 of the Submittal Dated December 20, 2023 (Agencywide Document Access and Management System (ADAMS) Package Accession No. ML23354A244) for Callaway Plant, Unit No. 1

Framatome Document 51-9268036-000, EPRI [Electric Power Research Institute]

SGMP [Steam Generator Management Program] for Channel Head Aging of the Framatome RSG [Replacement Steam Generator] Designs (Reference 2).

Framatome Document 32-9360111-000, Framatome RSG Channel Head and Tubesheet Stress Analysis for Flaw Evaluation (Reference 3).

Framatome Document 32-9364633-000, Framatome RSG Channel Head and Tubesheet Flaw Tolerance Evaluation (Reference 4).

Framatome Document 32-9055891-007, Fatigue and PWSCC [Primary Water Stress Corrosion Cracking] Crack Growth Evaluation Tool AREVACGC (Reference 7).

EPRI-Framatome Project Agreement 10012545, Divider Plate Cracking Assessment for Framatome Replacement Steam Generator s, EPRI Task ID 1-072913-04-01, May 29, 2020 (Reference 13).

License Renewal Other Documentation

Documentation of inputs for the calculation of the tube-to-tubesheet chromium content described in section 2.0 of enclosure 2 of the submittal dated December 20, 2023 (e.g.,

a summary of the manufacturing completion reports that provide the detailed chromium contents).

Attachment

ML24122A150 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA NRR/DNRL/NCSG/BC NAME MChawla PBlechman SBloom DATE 4/30/2024 5/1/2024 5/6/2024 OFFICE NRR/DNRL/NLRP/BC NRR/DORL/LPL/BC NRR/DORL/LPL4/PM NAME LGibson JRankin MChawla DATE 5/7/2024 5/7/2024 5/7/2024