ML25147A126
| ML25147A126 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 05/23/2025 |
| From: | Mahesh Chawla Plant Licensing Branch IV |
| To: | Elwood T Union Electric Co |
| Chawla M | |
| References | |
| EPID L-2025-LLR-0054 | |
| Download: ML25147A126 (1) | |
Text
From:
Mahesh Chawla To:
Elwood, Thomas B Cc:
Tony Nakanishi; Matthew Mitchell; Angie Buford; Ami Agrawal; Michael Bloodgood; Jay Collins; John Tsao; Scott Schwind; Nathan Brown; Vicki Rand; James Drake; Greg Warnick; Smith, Erin S; Hannah McLatchie; William Orders
Subject:
Callaway Plant, Unit 1 - Verbal Authorization of Request for Alternative I5R 48-Hour Non-Destructive Examination Hold - EPID: L-2025-LLR-0054 Date:
Friday, May 23, 2025 4:35:00 PM Attachments:
Callaway script Rev 4 - 052325.docx
Dear Mr. Elwood,
By telephone conversation on May 23, 2025, the U.S. Nuclear Regulatory Commission (NRC) staff provided a verbal authorization to Union Electric Company (dba Ameren Missouri)(the licensee) for the Request for Alternative I5R-01, for a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold on Non-Destructive Examination. By letter dated May 22, 2025, (Agencywide Documents Access and Management System Accession Nos.ML25142A386 and ML25142A387), Ameren Missouri Corporation (the licensee) submitted a proposed alternative from the 48-hour non-destructive examination (NDE) hold time requirement of Subparagraph 4(a)(2) of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)
Case N-638-11, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW [Gas Tungsten Arc Welding] Temper Bead Technique,Section XI, Division 1, for Callaway Plant, Unit 1 (Callaway). The licensee submitted alternative I5R-01 pursuant to 10 CFR 50.55a(z)(1) on the basis that the proposed repair, without the 48hour hold time to perform NDE, will provide for an acceptable level of quality and safety. The duration of the request is through the end of plant life for Callaway Plant, Unit 1.
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)
Ami Agrawal - Branch Chief - Region IV, Projects Branch B 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)
UNION ELECTRIC COMPANY (dba AMEREN MISSOURI)
Thomas B. Elwood - Manager, Regulatory Affairs Stephanie H. Thomure - Senior Performance Improvement Coordinator Lee E. Eitel - Supervising Engineer - Nuclear Engineering Design Rigel Davis - Consulting Engineer, Regulatory Initiatives Erin Smith - Consulting Engineer, Licensing and Regulatory Affairs J. C. Sellers - Manager, Nuclear Project Management
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 5/23/2025 5/23/2025 5/23/2025
VERBAL AUTHORIZATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR ALTERNATIVE I5R-01 REQUEST FOR AN ALTERNATE FOR 48 HOUR NON-DESTRUCTIVE EXAM HOLD 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 May 22, 2025, (Agencywide Documents Access and Management System Accession Nos. ML25142A386 and ML25142A387), Ameren Missouri Corporation (the licensee) submitted a proposed alternative from the 48-hour non-destructive examination (NDE) hold time requirement of Subparagraph 4(a)(2) of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) Case N-638-11, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW [Gas Tungsten Arc Welding] Temper Bead Technique,Section XI, Division 1, for Callaway Plant, Unit 1 (Callaway). The licensee submitted alternative I5R-01 pursuant to 10 CFR 50.55a(z)(1) on the basis that the proposed repair, without the 48-hour hold time to perform NDE, will provide for an acceptable level of quality and safety. The duration of the request is through the end of plant life for Callaway Plant, Unit 1.
During the current refueling outage in Spring 2025, the licensee detected boric acid deposits indicative of reactor coolant leakage from 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 three penetration nozzles which require repair, numbers 30, 35 and 48. In the performance of the half-nozzle repair, the licensee will utilize U. S. Nuclear Regulatory Commission (NRC)-approved ASME Code Case N-638-11 to use the ambient temperature temper bead welding technique to install a weld pad, thereby precluding post weld heat treatment of the affected area of the RVBH. Subparagraph 4(a)(2) of ASME Code Case N-638-11 requires a 48-hour hold time after welding the temper bead layers to perform NDE. The purpose of this hold time is to allow sufficient time for any potential hydrogen induced cracking (HIC) to develop prior to NDE. The licensee provided a technical basis for the elimination of the 48-hour hold time requirement in Attachment 1 of the submittal. The NRC staff reviewed the licensees basis and considered the operating experience of using this technique for the past 20 years at over 50 nuclear plants with no indications of HIC. NRC staff found the licensees basis for the proposed alternative acceptable and consistent with previous NRC approvals for the elimination of the 48-hour hold time, as listed in Section 7 of the licensees submittal.
Therefore, the NRC staff finds that the licensees proposed alternative to eliminate the 48-hour hold requirement of Subparagraph 4(a)(2) of ASME Code Case N-638-11 for the installation of weld pads for RVBH BMI nozzles 30, 35 and 48, provides an acceptable level of quality and safety through the end of plant life for Callaway Plant, Unit 1.
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-01, 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 May 23, 2025, the NRC authorizes the use of alternative I5R-01 through the end of plant life for Callaway Plant, Unit 1 for the half-nozzle repairs to reactor vessel bottom head bottom mounted instrumentation penetration nozzles 30, 35 and 48.
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.