ML25268A178
| ML25268A178 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 09/30/2025 |
| From: | Markley M NRC/NRR/DORL/LPL2-1 |
| To: | Coleman J Southern Nuclear Operating Co |
| Kalathiveettil D, NRR/DORL/LPL2-1 | |
| References | |
| EPID L-2025-LLR-0015 | |
| Download: ML25268A178 (1) | |
Text
September 30, 2025 Jamie M. Coleman Regulatory Affairs Director Southern Nuclear Operating Co., Inc.
3535 Colonnade Parkway Birmingham, AL 35243
SUBJECT:
EDWIN I. HATCH NUCLEAR PLANT, UNIT NOS. 1 AND 2 - AUTHORIZATION OF ALTERNATIVE REQUEST RR-V SIXTH INSERVICE TESTING INTERVAL (EPID L-2025-LLR-0015)
Dear Jamie Coleman:
By letter dated January 30, 2025, Southern Nuclear Operating Company (SNC, the licensee) submitted Alternative Request RR-V-2 for the Sixth Inservice Testing (IST) interval at the Edwin I. Hatch Nuclear Plant (Hatch), Units 1 and 2, which is scheduled to begin on January 1, 2026.
The licensee requested Alternative Request RR-V-2 for Hatch, Units 1 and 2, on the basis that the proposed alternative provides an acceptable level of quality and safety for the IST activities for the American Society of Mechanical Engineers (ASME) valves affected. The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review and concludes that SNC has adequately addressed the regulatory requirements set forth in Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a, Codes and standards, paragraph (z)(1) for this alternative. Therefore, pursuant to 10 CFR 50.55a(z)(1), the NRC staff authorizes the use of this alternative to the 2022 Edition of the ASME Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (OM Code), as incorporated by reference in 10 CFR 50.55a, for the Code of Record interval, as defined in 10 CFR 50.55a(y), Definitions, that implements the 2022 Edition of the ASME OM Code, for Hatch, Units 1 and 2. Use of this alternative with other Codes of Record is not authorized.
All other ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for which relief or an alternative was not specifically requested, and granted or authorized (as appropriate), in the subject request remain applicable.
If you have any questions, please contact the Project Manager, Dawnmathews Kalathiveettil at Dawnmathews.Kalathiveettil@nrc.gov or 301-415-5905.
Sincerely, Michael Markley, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-366
Enclosure:
Safety Evaluation cc: Listserv MICHAEL MARKLEY Digitally signed by MICHAEL MARKLEY Date: 2025.09.30 11:27:18 -04'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION AUTHORIZATION OF VALVE ALTERNATIVE REQUEST RR-V-2 SIXTH INSERVICE TESTING INTERVAL SOUTHERN NUCLEAR OPERATING COMPANY EDWIN I. HATCH NUCLEAR PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-321 AND 50-366
1.0 INTRODUCTION
By letter dated January 30, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25030A363), and supplemented by letter dated May 15, 2025 (ML25135A409), Southern Nuclear Operating Company (SNC, the licensee) submitted RR-V-2 to the U.S. Nuclear Regulatory Commission (NRC) requesting authorization for a proposed alternative for specific affected valves in lieu of certain inservice testing (IST) requirements of the 2022 Edition of the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (OM Code), as incorporated by reference in Title 10 of the Code of Federal Regulations (10 CFR),
Section 50.55a, Codes and standards, for the Sixth Inservice Testing (IST) interval at the Edwin I. Hatch Nuclear Plant (Hatch), Units 1 and 2.
The licensee submitted Alternative Request RR-V-2 pursuant to 10 CFR 50.55a(z)(1),
Acceptable level of quality and safety, on the basis that the proposed alternative will provide an acceptable level of quality and safety for IST activities applied to the specific affected valves within the scope of this request.
2.0 REGULATORY EVALUATION
The NRC regulations in 10 CFR 50.55a(f)(4), Inservice testing standards requirement for operating plants, state, in part, that:
Throughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the inservice test requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in paragraphs (f)(2) and (3) of this section
[10 CFR 50.55a] and that are incorporated by reference in paragraph (a)(1)(iv) of this section [10 CFR 50.55a], to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The regulations in 10 CFR 50.55a(z), Alternative to codes and standards requirements, state, in part, that alternatives to the requirements of paragraphs (b) through (h) of 10 CFR 50.55a or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation.
The applicant or licensee must demonstrate that:
(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; or (2) Hardship without a compensating increase in quality and safety. Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
3.0 TECHNICAL EVALUATION
The applicable Code of Record for the Hatch, Units 1 and 2, Sixth IST interval is the 2022 Edition of the ASME OM Code. The Hatch, Units 1 and 2, Sixth IST interval is scheduled to begin on January 1, 2026.
3.1 Licensees Alternative Request RR-V-2 3.1.1 Applicable ASME OM Code Requirements The requirements in the ASME OM Code, Mandatory Appendix I, Inservice Testing of Pressure Relief Devices in Water-Cooled Reactor Nuclear Power Plants, as incorporated by reference in 10 CFR 50.55a, related to Alternative Request RR-V-2 are as follows:
Mandatory Appendix I, Paragraph I-1360, Test Frequency, Classes 2 and 3 Nonreclosing Pressure Relief Devices, states, in part, that:
Classes 2 and 3 non-reclosing pressure relief devices shall be replaced every 5 yr, [years]
unless historical data indicates a requirement for more frequent replacement.
3.1.2 Components for Which Alternative is Requested The alternative was proposed for the following components:
Component ID Component Description ASME Code Class ASME OM Code Category 1E41-D003 Unit 1 HPCI Turbine Exhaust Rupture Disc 2
D 1E41-D004 Unit 1 HPCI Turbine Exhaust Rupture Disc 2
D 2E41-D003 Unit 2 HPCI Turbine Exhaust Rupture Disc 2
D Component ID Component Description ASME Code Class ASME OM Code Category 2E41-D004 Unit 2 HPCI Turbine Exhaust Rupture Disc 2
D HPCI = High Pressure Coolant Injection 3.1.3 Licensees Proposed Alternative and Basis In its submittal dated January 30, 2025, the licensee states, in part, that:
The subject rupture discs will be replaced at least once every 3rd refueling outage, corresponding to once every 6 years.
As proven by the vendor testing, the subject rupture discs have adequate margin for operation well beyond the requested 6-year replacement frequency.
Therefore, the proposed alternative provides an acceptable level of quality and safety and should be authorized pursuant to 10 CFR 50.55a(z)(1).
By letter dated December 30, 2015 (ML15310A406), a similar alternative request was authorized for Hatch, Units 1 and 2.
3.1.4 Licensees Reason for its Request In its January 30, 2025, submittal, the licensee states, in part:
Pursuant to 10 CFR 50.55a(z)(1), relief is requested from the requirements of the ASME OM Code, 2022 Edition, Appendix I, Subsection I-1360 which requires that Class 2 and 3 Rupture Discs (Nonreclosing pressure relief devices) be replaced every 5 years.
This alternative request is a re-submittal of NRC approved 4th and 5th Interval(s)
Relief Request RR-V-5, previously submitted and approved for replacement of these rupture discs on a 72-month frequency based on vendor testing. There have been no substantive changes to this alternative or to the basis for use, which would alter the previous NRC Safety Evaluation conclusions for previous IST Intervals for Plant Hatch. (See Precedents for [safety evaluation reports]
SERs).
The subject rupture discs are supplied by Continental Disc Corporation. Southern Nuclear Operating Company requested the supplier to perform cyclic testing, to destruction, of a disc that had previously been installed in the HPCI system at Plant Hatch. The test disc was installed in an appropriate disc holder and flange assembly which simulated the installed configuration. The rupture disc assembly was cycled for full vacuum at 70% of the ambient burst pressure (219 psig). The cycle testing was conducted at ambient room temperature. Since the rupture disc is a differential pressure relief device, cycling conditions were achieved by placing a constant 15 psig pressure on the downstream side of the rupture disc and cycling the upstream pressure from zero to 70% of the ambient burst pressure plus 15 psig. The psig was added to the upstream cycling pressure which compensates for the constant 15 psig pressure on the downstream side.
An electronic counter recorded each cycle. The test disc completed 2,788 cycles before failure occurred. The rupture disc burst in the normal fashion as with disc of this design.
The HPCI system is typically tested every 3 months, but for conservatism a test frequency of each month will be assumed. Monthly testing would result in approximately 72 tests during 3 operating cycles (i.e., 72 months). To meet the Code 5-year replacement frequency, the disc must be replaced every 2nd refueling outage (48 months) or after approximately 48 HPCI system tests.
Therefore, a change from replacement every 48 months to every 78 months is insignificant when compared to the expected life of the disc as proven by the number of cycles required for disc rupture by vendor testing.
Plant Hatch operates on a 24-month fuel cycle. Replacement every 6 years results in replacement every 3rd refueling outage, whereas a 5-year replacement results in replacement every 2nd refueling outage. Extension of the replacement frequency by 1-year will coincide with the fuel cycle for Plant Hatch.
3.2
NRC Staff Evaluation
In RR-V-2, the licensee has proposed an alternative approach to the requirements of ASME OM Code, Mandatory Appendix I, paragraph I-1360, Test Frequency, Classes 2 and 3 Nonreclosing Pressure Relief Devices, which requires that ASME Code Class 2 and 3 rupture discs be replaced every 5 years, unless historical data indicate a requirement for more frequent replacement. This corresponds to the licensee replacing the discs every second refueling outage. The licensee proposes an alternative in which the rupture discs would be replaced every 6 years, resulting in their replacement every third refueling outage.
Cyclic testing of a previously installed rupture disc was performed for the licensee by Continental Disc Corporation. During testing, the rupture disc was cycled from full vacuum to 70 percent of the ambient burst pressure. Failure occurred after the disc was cycled 2,788 times. The cyclic testing performed was a conservative simulation of the pressure differential experienced by the rupture discs during quarterly testing of the HPCI system.
The licensee proposes a 6-year replacement frequency for the rupture discs within the scope of Alternative Request RR-V-2. At this frequency, the discs would be exposed to approximately 72 HPCI system tests or cycles. This is significantly less than the 2,788 cycles experienced before failure during the testing program conducted for the licensee. As proven by the vendor testing, the subject rupture discs have adequate margin for operation well beyond the requested 6-year replacement frequency. The licensees proposed alternative provides reasonable assurance of the operational readiness of the HPCI rupture discs.
As supplemented in a letter dated May 15, 2025 (ML25135A409), the licensee confirmed that the table providing the list of components within the scope of Alternative Request RR-V-2 contained a typographical error. The NRC staff confirmed the appropriate scope of components for the request as part of its review.
Based on the above, the NRC staff has determined that Alternative Request RR-V-2 may be authorized pursuant to 10 CFR 50.55a(z)(1) on the basis that the proposed alternative provides an acceptable level of quality and safety in lieu of the applicable valve IST requirements in the ASME OM Code.
The NRC staff notes that the applicable code of record for the Hatch, Units 1 and 2, Sixth IST interval, is the 2022 Edition of the ASME OM Code, as incorporated by reference in 10 CFR 50.55a. The Hatch, Units 1 and 2, Sixth IST interval, is scheduled to begin on January 1, 2026.
The ASME OM Code (2022 Edition), Subsection ISTA, General Requirements, paragraph ISTA-3120, Inservice Examination and Test Interval, as incorporated by reference in 10 CFR 50.55a, requires that licensees implement 10-year intervals for their IST programs. Although not requested, the NRC regulations in 10 CFR 50.55a allow licensees to implement the same ASME OM Code as their Code of Record for two consecutive IST program intervals.
4.0 CONCLUSION
As set forth above, the NRC staff determined that proposed alternative numbered RR-V-2 for Hatch, Units 1 and 2, provides an acceptable level of quality and safety for IST activities for the specific affected valves within the scope of the request. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(1) for this proposed alternative. Therefore, pursuant to 10 CFR 50.55a(z)(1), the NRC staff authorizes RR-V-2 for the Sixth IST Interval for the specified valves within the scope of the request in lieu of the applicable IST requirements in the 2022 Edition of the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, for Hatch, Units 1 and 2, for the Code of Record interval, as defined in 10 CFR 50.55a(y), Definitions, that implements the 2022 Edition of the ASME OM Code. Use of this alternative with other codes of record is not authorized.
All other ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for which relief or an alternative was not specifically requested, and granted or authorized (as appropriate), in the subject request remain applicable.
Principal Contributors: N. Hansing, NRR T. Scarbrough, NRR G. Bedi, NRR Date: September 30, 2025
- via eConcurrence NRR-028 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA*
NRR/DEX/EMIB/BC*
NAME DKalathiveettil KZeleznock SBailey DATE 09/24/2025 09/26/2025 07/16/2025 OFFICE NRR/DORL/LPL2-1/BC*
NRR/DORL/LPL2-1/PM*
NAME MMarkley DKalathiveettil DATE 09/30/2025 09/30/2025