NL-24-0392, Response to Requests for Additional Information Related to Proposed Alternative GEN-ISI-AL T-2024-002
| ML24302A222 | |
| Person / Time | |
|---|---|
| Site: | Farley, Vogtle  |
| Issue date: | 10/28/2024 |
| From: | Coleman J Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-24-0392 | |
| Download: ML24302A222 (1) | |
Text
>. Southern Nuclear October 28, 2024 Docket Nos.: 50-348 50-424 50-364 50-425 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Regulatory Affairs Joseph M. Farley Nuclear Plant, Units 1 and 2 Vogtle Electric Generating Plant, Units 1 and 2 Response to Requests for Additional Information 3535 Colonnade Parkway Birmingham, AL 35243 205 992 5000 NL-24-0392 Related to Proposed Alternative GEN-ISi-AL T-2024-002 Ladies and Gentlemen:
By letter dated June 18, 2024 (Agencywide Document Access and Management System Accession Number ML24170B057), Southern Nuclear Operating Company submitted to the United States Nuclear Regulatory Commission (NRC) a proposed alternative, Alternative GEN-ISi-AL T-2024-002, to the inservice inspection (ISi) requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI regarding the steam generator (SG) welds at Joseph M. Farley Nuclear Plant, Units 1 and 2 and Vogtle Electric Generating Plant, Units 1 and 2. The proposed alternative requests to increase the inspection interval of ASME Section XI Table IWB-2500-1 Examination Category B-B and Table IWC-2500-1 Examination Category C-A for item numbers B2.40, C1.10, C1.20, and C1.30 from every ISi interval to every other interval.
By email dated September 26, 2024, the US NRC notified SNC that additional information is needed for the staff to perform their review.
The enclosure to this letter provides the SNC Responses to the NRC Request for Additional Information (RAI).
This letter contains no NRC commitments. If you have any questions, please contact Ryan Joyce at 205.992.6468.
U.S. Nuclear Regulatory Commission NL-24-0392 Page 2 Respectfully submitted, J~~
Regulatory Affairs Director JMC/dsp/cbg
Enclosure:
Response to Request for Additional Information cc:
Regional Administrator, Region II NRR Project Manager - Farley and Vogtle 1 & 2 Senior Resident Inspector - Farley and Vogtle 1 & 2 RType: CGA02.001
Joseph M. Farley Nuclear Plant, Units 1 and 2 Vogtle Electric Generating Plant, Units 1 and 2 Response to Requests for Additional Information Related to Proposed Alternative GEN-ISi-AL T-2024-002 Enclosure Response to Request for Additional Information
Enclosure to NL-24-0392 Response to Request for Additional Information REQUEST FOR ADDITIONAL INFORMATION (RAI)
By letter dated June 18, 2024 (Agencywide Document Access and Management System Accession Number ML24170B057), Southern Nuclear Operating Company (the licensee) submitted to the United States Nuclear Regulatory Commission (NRC) a proposed alternative, Alternative GEN-ISi-AL T-2024-002, to the inservice inspection (ISi) requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI regarding the steam generator (SG) welds at Joseph M. Farley Nuclear Plant, Units 1 and 2 and Vogtle Electric Generating Plant, Units 1 and 2.
Specifically, pursuant to Title 10 of the Code of Federal Regulations, Part 50, Section 55a, Paragraph (z)(1) (10 CFR 50.55a(z)(1 )), the licensee is proposing to perform the required volumetric examinations of the subject SG welds every other ISi interval, rather than the ASME Code Section XI requirement of every ISi interval. The licensee referred to the results of the probabilistic fracture mechanics (PFM) analyses in the following Electric Power Research Institute (EPRI) non-proprietary report as the primary basis for proposed alternative:
EPRI Technical Report 3002015906, "Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds," 2019 (hereinafter referred to as "EPRI report 15906," ADAMS Accession No.
ML20225A141 ).
The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is required for the staff to complete its review.
Regulatory Basis The NRC has established requirements in 10 CFR Part 50 to protect the structural integrity of structures and components in nuclear power plants. Among these requirements are the ISi requirements of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a to ensure that adequate structural integrity of SG vessels (including their welds) is maintained through the service life of the vessels. Therefore, the regulatory basis for the following request for additional information (RAI) is related to demonstrating that the proposed alternative ISi requirements would ensure adequate structural integrity of the licensee's SG welds, and thereby would provide an acceptable level of quality and safety per 10 CFR 50.55a(z)(1 ).
Issue SNC cited several precedents to support NRC approval of the proposed alternative, including references 9.15 through 9.18 of the licensee's submittal, dated June 18, 2024. However, the NRC staff noted some differences between the current submittal and the cited precedents. Some of the cited precedents were approved for one plant, while the current submittal applies to more than one plant site. Some of the cited precedents were related to ISi interval extensions, whereas the current submittal proposes to perform the examinations every other ISi interval. It appears that the safety evaluation (SE) dated September 25, 2023 (ML23256A088) may be a more appropriate precedent, as it more closely resembles these aspects of SNC's request. On page E-13 of SNC's submittal, dated June 18, 2024, SNC states that scope expansion will be performed in accordance with the ASME Section XI code of record. This approach to scope expansion appears to be not consistent with that approved by the NRC staff in the SE dated September 25, 2023. The
Enclosure to NL-24-0392 Response to Request for Additional Information supplemental letter dated July 20, 2023 (ML23201A140) from that licensee provides further information on an approach to scope expansion that the NRC staff found to be acceptable.
RAl-1 (a) If indications are detected that exceed the acceptance standards of ASME Code,Section XI, IWB-3500, confirm that it will be evaluated as required by ASME Code,Section XI (which includes requirements for successive inspections and additional examinations).
Describe other actions (if any) specified in the plant's corrective action program to ensure that the integrity of the component is adequately maintained.
SNC Response to RAl-1 (a):
If during the examinations outlined in the alternative Next Scheduled Examinations (ref.
ML24170B057 pg. E-15 and E-16), indications are detected that exceed the applicable ASME Code,Section XI acceptance standards of IWB-3500 or IWC-3500, then the indications will be addressed as required by ASME Code Section XI code of record at the time of the inspection, and the Southern Nuclear Corrective Action Program. The additional examination requirements of ASME Code,Section XI, also apply during the current outage. The number of additional exams scheduled as a result of the original exam that exceeded ASME Code acceptance criteria shall be in accordance with IWB-2430 and IWC-2430. If additional examinations reveal indications exceeding acceptance standards of IWB-3500 or IWC-3500, the examinations shall be further extended to include all remaining welds/components for that ASME inspection item number.
Successive examinations will be performed in accordance with the ASME Section XI code of record.
(b) If indications are detected that exceed the acceptance standards of ASME Code,Section XI, IWB-3500, then scope expansion may be appropriate to assess extent of condition.
Furthermore, if industry-wide operating experience indicates that a new or novel degradation mechanism is possible in SG welds, scope expansion may be appropriate to ensure that no such mechanism is occurring in the subject plants. Discuss the detailed scope expansion plans for these scenarios.
SNC Response to RAl-1 (b):
Any unacceptable indication(s) identified during examinations will result in additional and successive inspection requirements of ASME Code,Section XI IWB-2420, IWB-2430, IWC-2420, and/or IWC-2430. The expanded scope shall include the weld/component(s) as required by ASME Code,Section XI. Additional and successive inspection requirements of ASME Code,Section XI apply for all newly identified unacceptable indications.
If industry-wide operating experience indicates that a new or novel degradation mechanism is possible in SG welds, the operating experience will be evaluated for applicability in accordance with corrective action program and the operating experience program, and scope expansion will be performed as applicable, based on the evaluation results.