ML25178A223
| ML25178A223 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 06/26/2025 |
| From: | Mahesh Chawla Plant Licensing Branch IV |
| To: | Elwood T Ameren Missouri, Union Electric Co |
| Chawla M | |
| References | |
| EPID L-2025-LLR-0059 | |
| Download: ML25178A223 (1) | |
Text
From:
Mahesh Chawla To:
Elwood, Thomas B Cc:
Tony Nakanishi; Matthew Mitchell; Angie Buford; Jay Collins; John Tsao; Sean Hedger; Ami Agrawal; Scott Schwind; Nathan Brown; Smith, Erin S; Morton, Jeremy W
Subject:
Callaway Plant, Unit 1 - Verbal Authorization of Relief Request from Flaw Characterization and Removal Requirements - I5R EPID: L-2025-LLR-0059 Date:
Thursday, June 26, 2025 12:15:00 PM Attachments:
Callaway script Half Nozzle Repair_062525.docx Importance:
High
Dear Mr. Elwood,
By telephone conversation on June 25, 2025, the U.S. Nuclear Regulatory Commission (NRC) staff provided a verbal authorization to Union Electric Company (dba Ameren Missouri) (the licensee) for Relief Request from Flaw Characterization and Flaw Removal Requirements -
By letter dated June 24 2025, (Agencywide Documents Access and Management System Accession No. ML25175A342), Ameren Missouri Corporation (the licensee) submitted a proposed alternative to the flaw characterization requirements of IWA-3300 and IWB-3420 and to the flaw removal requirements of IWA-4412 of the 2019 Edition of Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for Callaway Plant, Unit 1 (Callaway). The licensee submitted alternative I5R-02 pursuant to 10 CFR 50.55a(z)(1) on the basis that the proposed half nozzle repair will provide for an acceptable level of quality and safety. The duration of the request is for the duration of Callaway Cycle 28, which is currently scheduled to conclude in the Fall of 2026.
The NRC staffs evaluation and verbal authorization is repeated in the attachment to this e-mail. The following NRC and licensee personnel participated in the conference call.
NRC Tony Nakanishi - Branch Chief - Plant Licensing Branch IV (LPL4)
Matthew Mitchell - Branch Chief - Piping and Head Penetrations Branch (NPHP)
Angie Buford - Branch Chief - Vessels, and Internals Branch (NVIB)
Jay Collins - Senior Materials Engineer - Piping and Head Penetrations Branch (NPHP)
John Tsao - Senior Materials Engineer - Vessels, and Internals Branch (NVIB)
Mahesh Chawla - Project Manager - Plant Licensing Branch IV (LPL4)
Sean Hedger - Senior Emergency Preparedness Inspector - Region IV
UNION ELECTRIC COMPANY (dba AMEREN MISSOURI)
Thomas B. Elwood - Manager, Regulatory Affairs Jeremy W. Morton - Supervising Engineer, Regulatory Affairs and Licensing Erin Smith - Consulting Engineer, Regulatory Affairs and Licensing Joseph S Raithel -Project Manager, Engineering Projects Rigel Davis - Consulting Engineer, Regulatory Initiatives Carissa Richardson - Supervising Engineer, Engineering Programs
FRAMATOME Brandon Caldwell - Project Engineer, Engineering Analysis
Please contact me if you have any questions.
Mahesh(Mac) Chawla, Project Manager Licensing Branch LPL4 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Phone: (301) 415-8371 Email: Mahesh.Chawla@nrc.gov
OFFICE NRR/DORL/LPL4/PM NRR/DNRL/NPHP/BC NRR/DORL/LPL4/BC NAME MChawla MMichell TNakanishi DATE 6/26/2025 6/26/2025 6/26/2025
VERBAL AUTHORIZATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR ALTERNATIVE I5R-02 REQUEST FOR AN ALTERNATE FOR FLAW CHARACTERIZATION AND FLAW REMOVAL AMEREN MISSOURI CORPORATION CALLAWAY PLANT, UNIT 1 DOCKET NO. 50-483 Technical Evaluation read by Matthew Mitchell, Chief of the Piping and Head Penetrations Branch, Office of Nuclear Reactor Regulation By letter dated June 24 2025, (Agencywide Documents Access and Management System Accession No. ML25175A342), Ameren Missouri Corporation (the licensee) submitted a proposed alternative to the flaw characterization requirements of IWA-3300 and IWB-3420 and to the flaw removal requirements of IWA-4412 of the 2019 Edition of Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for Callaway Plant, Unit 1 (Callaway). The licensee submitted alternative I5R-02 pursuant to 10 CFR 50.55a(z)(1) on the basis that the proposed half nozzle repair will provide for an acceptable level of quality and safety. The duration of the request is for the duration of Callaway Cycle 28, which is currently scheduled to conclude in the Fall of 2026.
During the current refueling outage in Spring 2025, the licensee detected boric acid leakage from the reactor vessel bottom head (RVBH) bottom mounted instrumentation (BMI) penetration nozzle No. 48. As part of the extent-of-condition investigation, the licensee performed ultrasonic testing and visual examinations on all 58 BMI nozzles and identified four penetration nozzles which require repair, numbers 30, 35, 48 and 57. The licensee repaired these penetration nozzles with a half nozzle repair modification as described in the submittal. The licensee provided technical basis to ensure the structural integrity of the half nozzle repairs and lower reactor pressure vessel head through an ASME Code Section III design analysis, a corrosion evaluation, a flaw evaluation, a loose parts assessment and a leakage detection program for one operating cycle. The NRC staff reviewed the licensees basis and found, for the proposed duration of one operating cycle, that: (1) the Section III design and stress requirements are met, (2) all reasonable corrosion mechanisms were assessed and will not challenge the structural integrity of the RVBH, (3) remaining flaws in the original penetration or J-groove weld will not challenge the structural integrity of the RVBH, (4) the stress assessment and past history of these repairs adequately support that generation of loose parts is unlikely, and (5) that the licensees leak detection actions will provide defense-in-depth and reasonable assurance that any potential repair issues will be identified prior to challenging structural integrity of the RVBH.
Therefore, the NRC staff finds that the licensees proposed alternative for the half nozzle repairs of RVBH BMI nozzles 30, 35, 48 and 57 provides an acceptable level of quality and safety for the duration of Callaway Cycle 28, which is currently scheduled to conclude in the Fall of 2026.
NRC Staff Conclusion read by Tony Nakanishi, Branch Chief, Plant Licensing Branch IV, Office of Nuclear Reactor Regulation As Chief of Plant Licensing Branch IV, I concur with the Piping and Head Penetration Branch's evaluation.
Based on information submitted, the NRC staff finds that the licensees alternative, I5R-02, provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR
50.55a(z)(1). Therefore, as of June 25, 2025, the NRC authorizes the use of alternative I5R-02 to install half nozzle repairs to reactor vessel bottom head bottom mounted instrumentation penetration nozzles 30, 35, 48 and 57 at Callaway Plant, Unit 1 for the duration of Cycle 28, which is currently scheduled to conclude in the Fall of 2026.
All other requirements of ASME Code, for which relief was not specifically requested and authorized by the NRC staff, remain applicable, including the third-party review by the Authorized Nuclear lnservice Inspector.
This verbal authorization does not preclude the NRC staff from asking additional clarification question(s) regarding the alternative while preparing the subsequent written safety evaluation.