ML25178A250
| ML25178A250 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  (NFP-091, NPF-092) |
| Issue date: | 07/01/2025 |
| From: | John Lamb NRC/NRR/DORL/LPL2-1 |
| To: | Coleman J Southern Nuclear Operating Co |
| References | |
| EPID L-2025-LRO-0029 | |
| Download: ML25178A250 (1) | |
Text
July 1, 2025 Jamie M. Coleman Regulatory Affairs Director Southern Nuclear Operating Co., Inc.
3535 Colonnade Parkway Birmingham, AL 35243
SUBJECT:
VOGTLE ELECTRIC GENERATING PLANT, UNIT 3 - REVIEW OF THE REFUELING OUTAGE 3R01 STEAM GENERATOR TUBE INSPECTION REPORT (EPID L-2025-LRO-0029)
Dear Ms. Coleman:
By letter dated May 19, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25139A554), Southern Nuclear Operating Company (SNC, the licensee) submitted information summarizing the results of the steam generator (SG) inspections performed at Vogtle Electric Generating Plant (Vogtle), Unit 3, during refueling outage 01. The SG tube inspection report was submitted in accordance with Technical Specification 5.6.6, Steam Generator Tube Inspection Report.
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the information provided by SNC and concludes that the licensee provided the information required by Vogtle, Unit 3, technical specifications and no follow-up is required at this time. The NRC staffs review of the report is enclosed.
If you have any questions, please contact me at (301) 415-3100 or via email at John.Lamb@nrc.gov.
Sincerely,
/RA/
John G. Lamb, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No.52-025
Enclosure:
Review of the SG Tube Inspection Report cc: Listserv
Enclosure REVIEW OF THE FALL 2024 STEAM GENERATOR TUBE INSPECTION REPORT SOUTHERN NUCLEAR OPERATING COMPANY, INC VOGTLE ELECTRIC GENERATING PLANT, UNIT 3 DOCKET NO.52-025 By letter dated May 19, 2025 (Agencywide Documents Access and Management System Accession No. ML25139A554), Southern Nuclear Operating Company (the licensee) submitted information summarizing the results of the fall 2024 steam generator (SG) inspections performed at Vogtle Electric Generating Plant, Unit 3 (Vogtle, Unit 3). These inspections were performed during the first refueling outage (3R01). The U.S. Nuclear Regulatory Commission (NRC) staff held a conference call with the licensee on October 28, 2024, and a summary of the conference call is available in ADAMS under Accession No. ML24305A166. Section 5.6.6 in Vogtle, Unit 3, Technical Specifications (TSs) requires that a report be submitted within 180 days after the initial entry into hot shutdown (MODE 4) following completion of an inspection of the SGs.
Vogtle, Unit 3, is a two-loop plant with Westinghouse Model D-125 SGs. Each SG contains 10,025 thermally treated Alloy 690 tubes with a nominal outside diameter of 0.6875 inches and a nominal wall thickness of 0.041 inches (Rows 1 and 2) and 0.040 inches (Rows 3 through 146). The tubes are supported by 10 stainless steel tube support plates (TSPs) with trifoil broached holes. The U-bend sections are supported by six sets of stainless-steel anti-vibration bars (AVBs). The first 17 rows of tubes received stress relief heat treatment. The tubes were hydraulically expanded into the tubesheet through the full thickness of the tubesheet.
The licensee provided the scope, extent, methods, and results of the SG tube inspections in the letter referenced above. In addition, the licensee described corrective actions (e.g., tube plugging) taken in response to the inspection findings.
Based on the review of the information provided, the NRC staff has the following observations:
The following wear indications were reported:
3 anomalous indications due to manufacturing (also reported in the preservice inspection).
82 AVB wear indications (25 in SG-1 and 57 in SG-2).
170 TSP wear indications (104 in SG-1 and 66 in SG-2).
A total of 17 tubes (13 in SG-1 and 4 in SG-2) were preventatively plugged due to TSP wear.
For the operational assessment, the licensee used the maximum growth rate from the preservice inspection to 3R01 for AVB wear, and the bounding growth rate calculated in the limiting SG considering all wear locations for TSP wear (95th percentile of 18.8 percent through wall (TW) per effective full power years (EFPY). SNC did consider whether a subpopulation growth rate should be used for TSP wear in low row tubes (Rows 1 and 2 contained most of the wear indications), however, the licensee stated that the growth rate for this subpopulation (95th percentile of 19.0 percent TW/EFPY) did not change the operational assessment conclusion.
A total of 17 foreign objects were found during foreign object search and retrieval and all were determined to be acceptable to leave in place. No foreign object wear indications were reported.
The licensee stated that the next planned SG inspection will be in spring 2026.
Based on a review of the information provided, the NRC staff concludes that SNC provided the information required by their TS. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action at this time since the inspections appear to be consistent with the objective of detecting potential tube degradation and the inspection results appear to be consistent with industry operating experience at similarly designed and operated units.
Contributor: L. Terry, NRR.
Date: July 1, 2025.
- via eConcurrence NRR-106 OFFICE DORL/LPL2-1/PM DORL/LPL2-1/LA DNRL/NCSG/BC DORL/LPL2-1/BC DORL/LPL2-1/PM NAME JLamb KZeleznock SBloom MMarkley JLamb DATE 6/26/2025 6/30/2025 6/26/2025 7/1/2025 7/1/2025