ML24289A015
| ML24289A015 | |
| Person / Time | |
|---|---|
| Site: | Millstone  (NPF-049) |
| Issue date: | 10/21/2024 |
| From: | Richard Guzman NRC/NRR/DORL/LPL1 |
| To: | Carr E Dominion Energy Nuclear Connecticut |
| References | |
| EPID L-2024-LRO-0023 | |
| Download: ML24289A015 (3) | |
Text
October 21, 2024 Eric S. Carr President - Nuclear Operations and Chief Nuclear Officer Dominion Energy Nuclear Connecticut, Inc.
Millstone Power Station Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711
SUBJECT:
MILLSTONE POWER STATION, UNIT NO. 3 - REVIEW OF THE FALL 2023 STEAM GENERATOR TUBE INSPECTION REPORT (EPID L-2024-LRO-0023)
Dear Eric S. Carr:
By letter dated May 20, 2024 (Agencywide Documents Access and Management Systems Accession No. ML24142A095), Dominion Energy Nuclear Connecticut, Inc. (the licensee) submitted information to the U.S. Nuclear Regulatory Commission (NRC) summarizing the results of the fall 2023 steam generator tube inspection that were performed at Millstone Power Station, Unit No. 3 (Millstone Unit 3). This inspection was performed during the Millstone 3 Refueling Outage 22.
The NRC staff has completed its review of this report and concludes that the licensee provided the information required by the Millstone Unit 3 Technical Specifications. No additional follow-up is required at this time. The NRC staffs review is enclosed.
If you have any questions concerning this matter, please contact me at (301) 415-1030 or by email to Richard.Guzman@nrc.gov.
Sincerely,
/RA/
Richard V. Guzman, Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-423
Enclosure:
Review of the Fall 2023 Steam Generator Tube Inspection Report cc: Listserv
Enclosure STAFF ASSESSMENT BY THE OFFICE OF NUCLEAR REACTOR REGULATION REVIEW OF THE FALL 2023 STEAM GENERATOR TUBE INSPECTION REPORT DOMINION ENERGY NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION, UNIT NO. 3 DOCKET NO. 50-423 By letter dated May 20, 2024 (Agencywide Documents Access and Management Systems Accession No. ML24142A095), Dominion Energy Nuclear Connecticut, Inc., (the licensee) submitted information summarizing the results of the fall 2023 steam generator (SG) tube inspections performed at Millstone Power Station, Unit No. 3 (Millstone Unit 3), during Refueling Outage 22 (3R22).
Millstone Unit 3 has four Westinghouse Model F recirculating SGs. Each SG has 5,626 thermally treated Alloy 600 tubes with a nominal outside diameter of 0.688 inches and a nominal wall thickness of 0.040 inches. The tubes are arranged in a square pitch pattern and are hydraulically expanded at each end for the full depth of the tubesheet. The tubes are supported by stainless steel tube support plates (TSPs) with quatrefoil-shaped holes and three sets of chrome plated Alloy 600 anti-vibration bars (AVBs) on the U-bend section of the tubing. There is a flow distribution baffle plate between the tubesheet and the first TSP. The U-bend region of the tubes installed in rows 1-10 was thermally treated after bending to reduce stress. The SGs had accrued 30.1 Effective Full Power Years of operation prior to the outage.
The licensee provided the scope, extent, methods, and results of the SG tube inspections in the document referenced above. In addition, the licensee described corrective actions (e.g., tube plugging), if any were 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:
One hundred percent of in-service tubes were inspected full length in all four SGs. The U-bend portion of Rows 1 and 2 were inspected with the +PointTM probe. All tubes with potential indications of improper heat treatment (-2 sigma tubes) were inspected full length with the array/bobbin combination probe. There is a total of 67, 30, 39, and 23 of the -2 sigma tubes in SGs A, B, C, and D, respectively.
AVB wear, TSP wear, and foreign object wear were the existing degradation mechanisms detected during 3R22. Five foreign objects were removed from the SGs. There were no stress corrosion cracking indications or new degradation mechanisms detected.
Ten strategically located tube locations in each SG were inspected with the array probe to assess deposit loading and potential clogging of the TSP broached openings.
Based on a review of the information provided, the NRC 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 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.
ML24289A015 NRR-106 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DNRL/NCSG/BC NAME RGuzman KZeleznock SBloom DATE 10/15/2024 10/17/2024 10/09/2024 OFFICE NRR/DORL/LPL1/BC NRR/DORL/LPL1/LA NAME HGonzález RGuzman DATE 10/21/2024 10/21/2024