ML25098A257
| ML25098A257 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 04/14/2025 |
| From: | Ilka Berrios Plant Licensing Branch III |
| To: | Rhoades D Constellation Energy Generation |
| Wall, S | |
| References | |
| EPID L-2024-LLR-0062 | |
| Download: ML25098A257 (1) | |
Text
April 14, 2025 BYRON STATION, UNITS 1 & 2 - AUTHORIZATION AND SAFETY EVALUATION FOR ALTERNATIVE REQUEST NO. I5R-02 ASSOCIATED WITH THE REPAIR OF REACTOR VESSEL HEAD PENETRATIONS (EPID L-2024-LLR-0062)
LICENSEE INFORMATION Recipients Name and Address:
David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Rd Warrenville, IL 60555 Licensee:
Constellation Energy Generation, LLC Plant Name(s) and Unit(s):
Byron Staton, Units 1 & 2 Docket No(s).:
STN 50-454 and STN 50-455 APPLICATION INFORMATION Submittal Date: September 13, 2024 Submittal Agencywide Documents Access and Management System (ADAMS) Accession No.: ML24257A063 Applicable Inservice Inspection (ISI) Program Interval and Interval Start/End Dates:
Fifth ISI program interval is currently scheduled to begin July 16, 2025, and end on July 15, 2037.
Alternative Provision: The applicant requested an alternative under Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(z)(1)
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Applicable Code Edition and Addenda===
ISI Program Code Record: 2019 Edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code),Section XI, Construction Code of Record for the Reactor Pressure Vessel (RPV): ASME Section III, 1971 Edition through Summer 1973 Addenda.
Augmented ISI requirements for examinations of the vessel head penetrations (VHPs) are performed in accordance with 10 CFR 50.55a(g)(6)(ii)(D), which mandates the use of ASME Code Case N-729-6, with associated conditions.
Applicable Code Requirements:
IWA-4000 of ASME Code,Section XI contains requirements for the removal of defects from and welded repairs performed on ASME components. The specific ASME Code requirements for which use of the proposed alternative is being requested under IWA-4000 can be found in the submittal.
Brief Description of the Proposed Alternative:
The licensee is requesting to use the embedded flaw process as referenced in Westinghouse Electric Company (Westinghouse) WCAP-15987-P, Revision 2-P-A, Technical Basis for the Embedded Flaw Process for Repair of Reactor Vessel Head Penetrations, December 2003, with certain modifications as detailed in Section 5.1 of the licensees submittal, for the repair of RPV VHPs at Byron Station, Units 1 & 2 (Byron), as an alternative to the defect removal requirements of ASME Section XI and Section III.
For additional details on the licensees request, please refer to the documents located at the ADAMS accession numbers identified above.
REGULATORY EVALUATION Regulatory Basis: 10 CFR 50.55a(z)(1)
Paragraph 10 CFR 50.55a(z) states, in part, that alternatives to the requirements of 10 CFR 50.55a(b)-(h) may be used, when authorized by the Director, Office of Nuclear Reactor Regulation, if (1) the proposed alternatives would provide an acceptable level of quality and safety or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The licensee has submitted this request on the basis that a proposed alternative would provide an acceptable level of quality and safety.
STAFF EVALUATION The NRC staff reviewed the licensees proposed alternative, to use the embedded flaw repair methodology, to determine if it provides an acceptable level of quality and safety under 10 CFR 50.55a(z)(1). The licensee made previous requests under this provision to utilize the embedded flaw repair in previous ISI intervals. The latest NRC authorization and safety evaluation, dated March 6, 2017, was for the Fourth ISI Interval (ML17062A428).
The purpose of the licensees proposed repair is to address primary water stress corrosion cracking (PWSCC), which typically initiates in susceptible materials, such as alloy 600 base and alloy 82/182 weld materials, in areas of tensile stress and under certain environmental conditions, such as higher temperatures and primary coolant environments. The reactor VHPs and their associated J-groove attachment welds at Byron are peened to provide compressive residual stress on the wetted surface. In the event cracking did occur, the proposed repair technique would further isolate the susceptible material from the primary coolant environment by using a seal weld of alloy 52M weld material, which is less susceptible to PWSCC.
The NRC staff reviewed Section 5.1 of the licensees current submittal to ensure the licensees proposed actions would meet the requirements of NRC approved WCAP-15987-2-P-A and any modifications would be acceptable under 10 CFR 50.55a(z)(1). The NRC staff found that the licensees modifications were consistent with the previous modifications for the Fourth ISI Interval proposed alternative (ML17044A294), with mostly minor editorial changes and updating to the ISI Code of Record for the Fifth ISI Interval at Byron. The NRC staff found that these editorial and ISI Code of Record changes did not have an impact on the previous NRC staff technical review for acceptance of the embedded flaw repair for use at Byron. One additional change of note was updating to use the latest inspection requirements of 10 CFR 50.55a(g)(6)(ii)(D), which changed from mandating the use of ASME Code Case N-729-1 to N-729-6 with associated conditions. Specifically, the condition 10 CFR 50.55a(g)(6)(ii)(D)(5) which establishes the examination requirements stated in MRP-335, Revision 3-A, Materials Reliability Program: Topical Report for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement (ML16319A282). The requirements of MRP-335, Revision 3-A, and NRC Condition 5.2 on its use, provides additional steps to ensure effective repairs of any new flaw identified in a peened Byron VHP. The NRC staff review finds this change does not challenge the previous technical review for the acceptable level of quality and safety of the peened VHPs at Byron.
Therefore, the NRC staff finds that the licensees use of the embedded flaw repair technique referenced in WCAP-15987-P, Revision 2-P-A, with modifications as detailed in Section 5.1 of the licensees submittal, continues to either meet or provide additional quality for the embedded flaw repair technique. As such, the licensees proposed alternative provides an acceptable level of quality and safety for the VHPs at Byron for the Fifth ISI Interval.
CONCLUSION The NRC staff has determined that the proposed alternative in the licensees request referenced above would provide an acceptable level of quality and safety.
The NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1).
The NRC staff authorizes the use of proposed alternative I5R-02 at Byron Station, Units 1 & 2, for the Fifth ISI Interval currently scheduled to begin July 16, 2025, and end on July 15, 2037.
All other ASME BPV Code,Section XI, requirements for which an alternative was not specifically requested and authorized remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: Jay Collins, NRR Date: April 14, 2025 Ilka Berrios, Acting Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation cc: Listserv ILKA BERRIOS Digitally signed by ILKA BERRIOS Date: 2025.04.14 09:52:58 -04'00' BYRON STATION, UNITS 1 & 2 - AUTHORIZATION AND SAFETY EVALUATION FOR ALTERNATIVE REQUEST NO. I5R-02 ASSOCIATED WITH THE REPAIR OF REACTOR VESSEL HEAD PENETRATIONS (EPID L-2024-LLR-0062) DATED APRIL 14, 2025 DISTRIBUTION:
PUBLIC RidsNrrDorlLpl3 Resource RidsRgn3MailCenter Resource RidsNrrLASLent Resource RidsNrrLASRohrer Resource RidsAcrs_MailCTR Resource RidsNrrPMByron Resource RidsNrrDnrlNphp Resource JCollins, NRR Accession No.: ML25098A257
- via memo NRR-028 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DNRL/NPHP/BC*
NAME SWall SRohrer (SLent for)
MMitchell DATE 04/08/2025 04/11/2025 04/03/2025 OFFICE NRR/DORL/LPL3/BC (A)
NRR/DORL/LPL3/PM NAME IBerrios SWall DATE 04/11/2025 04/14/2025 OFFICIAL RECORD COPY