ML25335A042
| ML25335A042 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 12/09/2025 |
| From: | V Sreenivas Plant Licensing Branch 1 |
| To: | Blair B Vistra Operations Company |
| Sreenivas, V | |
| References | |
| EPID L-2025-LRO-0026, EPID L-2025-LRO-0010 | |
| Download: ML25335A042 (0) | |
Text
December 9, 2025 Mr. Barry N. Blair Vistra Operations Company LLC Beaver Valley Power Station Mail Stop P-BV-SSB P.O. Box 4, Route 168 Shippingport, PA 15077-0004
SUBJECT:
BEAVER VALLEY POWER STATION, UNIT 2 - REVIEW OF THE FALL 2024 STEAM GENERATOR TUBE INSPECTION REPORTS (EPIDS: L--2025--LRO--0010 AND L-2025-LRO-0026)
Dear Mr. Blair:
By letters dated February 6, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25037A134) and May 1, 2025 (ML25121A190), Vistra Operations Company LLC (the licensee) submitted information summarizing the results of the fall 2024 steam generator (SG) inspections performed at Beaver Valley Power Station, Unit 2 (Beaver Valley, Unit 2). These inspections were performed during refueling outage 24 (2R24). The letters were submitted to satisfy 90-day and 180-day reporting requirements in Section 5.6.6.2 of the Beaver Valley, Unit 2, Technical Specifications. The licensee provided additional information about the inspections in a letter dated October 7, 2025 (ML25280A037).
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the submittal and concludes that the licensee provided the information as required. No additional follow-up is required at this time. The results of the NRC staffs review are enclosed.
If you have any questions, please contact me at 301-415-2597 or via email at v.sreenivas@nrc.gov.
Sincerely,
/RA/
V. Sreenivas, Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-412
Enclosure:
Review of the Steam Generator Tube Inspection Report cc: Listserv
BEAVER VALLEY POWER STATION, UNIT 2 REVIEW OF THE FALL 2024 STEAM GENERATOR TUBE INSPECTION REPORTS DOCKET NO. 50-412 By letters dated February 6, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25037A134) and May 1, 2025 (ML25121A190), Vistra Operations Company LLC (the licensee) submitted information summarizing the results of the fall 2024 steam generator (SG) inspections performed at Beaver Valley Power Station, Unit 2 (Beaver Valley, Unit 2). These inspections were performed during refueling outage 24 (2R24). The licensee provided additional information about the inspections in a letter dated October 7, 2025 (ML25280A037).
Section 5.6.6.2 in the Beaver Valley, Unit 2, Technical Specifications (TS) requires that a report be submitted withing 90 days after the initial entry into MODE 4 if the Generic Letter (GL) 95-05 Voltage-Based Alternate Repair Criteria (ARC) or F-Star methodology were applied to the inspection. Section 5.6.6.2 of the TS also 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. The licensees February 6, 2025, and May 1, 2025, letters were submitted to satisfy these 90-day and 180-day reporting requirements, respectively.
Beaver Valley, Unit 2, is a 3-loop plant with Westinghouse Model 51M SGs. Each SG contains 3,376 mill-annealed Alloy 600 tubes with a nominal outside diameter of 0.875 inches and a nominal wall thickness of 0.050 inches. The tubes are supported by drilled-hole carbon steel tube support plates and Alloy 600 anti-vibration bars. The tubes were roll-expanded at both ends for the full depth of the tubesheet. The primary side portion of tubes from about three inches above the top of the tubesheet to about one inch above the tube ends was shot-peened on both the hot-leg and cold-leg side of the SG, prior to operation. In addition, the U-bend region of the small radius tubes received in-situ thermal stress relief prior to operation.
The SGs were in service for 32.0 effective full power years entering 2R24.
The licensee provided the scope, extent, methods, and results of the SG tube inspections in the letters 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 U.S. Nuclear Regulatory Commission (NRC) staff has the following observations:
The 2R24 outage was the eighth application of the GL 95-05 voltage-based ARC to the Beaver Valley, Unit 2, Model 51M SGs. For Cycle 25, SG-B is the limiting SG for probability of burst and for leakage.
The licensee continued returning tubes to service (tube recovery) with tube inspection and installation of sleeves at the top of the tubesheet (TTS). A total of 31 distorted support indications (DSIs) were returned to service with TTS sleeves (3 DSIs in 3 tubes in SG-A, and 28 DSIs in 19 tubes in SG-B). No tubes were returned to service in SG-C.
The original identification of axial indications in four tubes deplugged and returned to service in SG-B was confirmed with a rotating probe (+Point'). The corresponding eddy current analysis code is Historical Axial Indication (HAI). This code was first used in refueling outage 22, along with Historical Circumferential Indication (HCI), as part of the implementation of the tube recovery program.
One new axial signal was found on the inside surface of a parent tube behind the nickel band in the lower joint of a tubesheet sleeve installed in refueling outage 23 (2R23) (SG-A, Row 31, Column 58). The tube was removed from service by plugging because the 2R23 baseline data was insufficient to determine if the signal had changed during the subsequent operating cycle. The licensee stated that the baseline data for that location were characteristic of a rough entry of the probe into the tube, and that the axial signal was considered similar to signals confirmed as benign. The licensee is planning to provide additional training to analysts to ensure that the quality of the baseline data for installed sleeves is sufficient over the full inspection length. The staff notes that it is unlikely that a service-induced flaw would initiate and propagate to a detectable depth in one operating cycle.
An in-situ pressure test was performed to evaluate a mixed-mode (circumferential/axial)
ODSCC indication pair at the hot leg expansion transition (SG-B, Row 18, Column 26).
In-situ pressure testing was not required based on the screening criteria in industry guidelines. However, the testing was performed to demonstrate structural and leakage integrity due to the difficulty of verifying condition monitoring by calculating burst and leakage for a mixed-mode flaw. The in-situ pressure proof and leak testing results were acceptable with no burst and no leakage.
In the description of the tubes plugged or repaired during 2R24, the notes describing tube plugging and repair for SG21B (page 16 of 29 of May 1, 2025, letter) state that two tubes were de--plugged and returned to service without sleeving based on no degradation detected. The licensee explained in their letter dated October 7, 2025, that the tubes were plugged in 2000 and 2005 based on volumetric signals characteristic of one-time mechanical damage. Because the signals have not changed, the licensee concluded there is no active degradation.
Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by their TS. In addition, the staff concludes that there are no technical issues that warrant additional 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.
- via eConcurrence NRR-106 OFFICE NRR/DORL/LPL1/PM*
NRR/DORL/LPL1/LA*
NRR/DNRL/NCSG/BC NAME VSreenivas KEntz SBloom DATE 11/28/2025 12/8/2025 11/18/2025 OFFICE NRR/DORL/LPL1/BC (A)*
NRR/DORL/LPL1/PM*
NAME UShoop VSreenivas DATE 12/9/2025 12/9/2025