ML25062A130
| ML25062A130 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/05/2025 |
| From: | Robert Kuntz NRC/NRR/DORL/LPL3 |
| To: | Tony Brown Vistra Operations Company |
| Kuntz R, NRR/DORL/LPL3 | |
| References | |
| EPID L-2024-LRO-0039 | |
| Download: ML25062A130 (1) | |
Text
March 5, 2025 Terry J. Brown Vistra Operations Company LLC c/o Davis-Besse Nuclear Power Station Mail Stop P-DB-3080 5501 N. State Route 2 Oak Harbor, OH 43449-9760
SUBJECT:
DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 - REVIEW OF THE SPRING 2024 STEAM GENERATOR TUBE INSPECTION REPORT (EPID NO. L-2024-LRO-0039)
Dear Terry Brown:
By letter dated September 11, 2024, as supplemented by letter dated February 12, 2025, Vistra Operations Company LLC, submitted information summarizing the results of the spring 2024 steam generator tube inspections performed at Davis-Besse Nuclear Power Station, Unit 1, during refueling outage 23.
The U. S. Nuclear Regulatory Commission (NRC) staff has completed its review of the report and concludes that the licensee provided the information required by their technical specifications and that no additional follow-up is required at this time. The NRC staffs review is enclosed.
If you have any questions, please contact me at 301-415-3733 or via email at robert.kuntz@nrc.gov.
Sincerely,
/RA/
Robert Kuntz, Senior Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-346
Enclosure:
Review of the 2024 Steam Generator Tube Inspection Report cc: Listserv
Enclosure REVIEW OF THE SPRING 2024 STEAM GENERATOR TUBE INSPECTION REPORT VISTRA OPERATIONS COMPANY LLC DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 DOCKET NO. 50-346 By letter dated September 11, 2024, (Documents Access and Management System (ADAMS) Accession No. ML24255A803), as supplemented by letter dated February 12, 2025 (ML25044A088), Vistra Operations Company LLC (the licensee), submitted information summarizing the results of the spring 2024 steam generator (SG) tube inspections performed at Davis-Besse Nuclear Power Station, Unit 1, (Davis-Besse) during refueling outage 23.
Davis-Besse has two once-through SGs designed by Babcock and Wilcox that were installed in 2014. Each SG contains 15,607 thermally treated Alloy 690 tubes. The tubes were hydraulically expanded for part of the length of the tubesheet and are supported by 16 carbon steel tube support plates (TSPs). There are 66 stainless-steel tie rods between each TSP. Tube support plate 15S is below the auxiliary feedwater nozzle and has drilled holes in the periphery through which the tubes pass. The remaining portion of TSP 15S and the other TSPs in the SGs have trefoil broached holes. The trefoil holes of the even numbered TSPs are offset from centerline to minimize tube wear at the TSP elevations.
The licensee provided the scope, extent, methods, and results of their SG tube inspections. In addition, the licensee described corrective actions, such as tube plugging, taken in response to the inspection findings.
After reviewing the information provided by the licensee, the staff has the following observations:
The licensee plugged 20 tubes in SG 2A due to wear at broached TSPs. An additional 5 tubes in SG 2A and 12 tubes in SG 1B were preventively plugged due to proximity indications. The licensee changed their reporting format in 2022 and 2024, compared to the format used in 2020. In 2022 and 2024, the tubes plugged due to proximity indications were not specifically called out in the inspection report. The table below provides a summary of tube plugging actions, for clarity.
Outage Number (Year)
SG 2A SG 1B Tubes plugged at start of outage Tubes reported as plugged during the outage Unreported tubes plugged due to proximity indications Tubes plugged at the end of outage Tubes plugged at start of outage Tubes reported as plugged during the outage Unreported tubes plugged due to proximity indications Tubes plugged at the end of outage 1R21 (2020) 27 78 0
105 3
66 0
69 1R22 (2022) 105 14 16 135 69 1
12 82 1R23 (2024) 135 25 5
165 82 0
12 94 Based on a review of the information provided, the staff concludes that the licensee provided the information required by their technical specifications. In addition, the staff concludes that there are no technical issues that warrant additional follow-up action currently, 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.
Principal Contributor: Andrew B. Johnson
ML25062A130 NRR-106 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DNRL/NCSG/BC NAME RKuntz SRohrer SBloom DATE 3/3/2025 3/4/2025 2/28/2025 OFFICE NRR/DORL/LPL3/BC (A)
NRR/DORL/LPL3/PM NAME IBerrios RKuntz DATE 3/4/2025 3/5/2025