ML21201A326
| ML21201A326 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 08/02/2021 |
| From: | Vaughn Thomas Plant Licensing Branch II |
| To: | Lippard G Dominion Energy South Carolina |
| Williams S, NRR/DORL/LPLLPL | |
| References | |
| EPID L-2020-LRO-0084 | |
| Download: ML21201A326 (6) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 August 2, 2021 Mr. George A Lippard Site Vice President V.C. Summer Nuclear Station Dominion Energy South Carolina PO. Box 88 Jenkinsville, SC 29065
SUBJECT:
VIRGIL C. SUMMER NUCLEAR STATION, UNIT 1 REVIEW OF STEAM GENERATOR INSERVICE INSPECTION REPORT FOR UNIT 1 END OF CYCLE 25 REFUELING OUTAGE (EPID L-2020-LRO-0084)
Dear Mr. Lippard:
By letter dated October 20, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20296A692), as supplemented by letters dated June 3, 2021 (ADAMS Accession No. ML21154A180), and June 29, 2021 (ADAMS Accession No. ML21180A405), Dominion Energy South Carolina, Inc. (the licensee), submitted information summarizing the results of the spring 2020 steam generator inspections performed at Virgil C.
Summer Nuclear Station, Unit 1 (Summer 1), in accordance with Technical Specification (TS) 6.9.1.12, Steam Generator Tube Inspection Report. The report summarizes the steam generator tube inspections that the licensee performed in spring 2020 during the Cycle 25 refueling outage. The U.S. Nuclear Regulatory Commission (NRC) staff reviewed the submittal and concludes that the licensee provided the information required by TS 6.9.1.12 and that there are no technical issues that warrant additional follow-up action.
The enclosure documents the NRC staffs review of the submittal and completes the NRC staffs efforts for Enterprise Project Identifier (EPID) L-2020-LRO-0084. Any inquiries can be directed to Mr. Vaughn Thomas at 301-415-5897 or via e-mail at Vaughn.Thomas@nrc.gov.
Sincerely,
/RA/
Vaughn V. Thomas, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-395
Enclosure:
As stated cc w/encl: Listserv
REVIEW BY THE OFFICE OF NUCLEAR REACTOR REGULATION SPRING 2020 STEAM GENERATOR TUBE INSERVICE INSPECTION REPORT SOUTH CAROLINA ELECTRIC AND GAS COMPANY VIRGIL C. SUMMER NUCLEAR STATION, UNIT 1 DOCKET NO. 50-395 By letter dated October 20, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20296A692), as supplemented by letters dated June 3, 2021 (ADAMS Accession No. ML21154A180), and June 29, 2021 (ADAMS Accession No. ML21180A405), Dominion Energy South Carolina, Inc. (the licensee), submitted information summarizing the results of the spring 2020 steam generator (SG) inspections performed at Virgil C. Summer Nuclear Station, Unit 1 (Summer 1). A clarification call was held on June 22, 2021, to better understand the information submitted in the letter dated June 3, 2021, that resulted in the licensee submitting additional information. These inspections were performed during the end-of-cycle 25 spring refueling (RF25) outage.
The three replacement Delta-75 SGs at Summer, Unit 1, were installed in 1994. Westinghouse fabricated the SGs, and each SG contains 6,307 thermally treated Alloy 690 tubes, with a nominal outside diameter of 0.6875 inches and a nominal wall thickness of 0.040 inches. The tubes are supported by nine 1.125-inch-thick Type 405 stainless steel tube support plates (TSPs) with trefoil, broached holes. The U-bend sections are supported by four sets of Type 405 stainless steel anti-vibration bars. The first 17 rows of tubing were stress-relieved during fabrication. There is a flow distribution baffle plate between the tubesheet and the lowest support plate and a sludge collector above each primary separator.
The licensee provided the scope, extent, methods, and results of the SG tube inspections in the documents 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:
Its letter dated June 3, 2021, the licensee clarified that no signs of degradation, rust, deformation, or abnormal conditions were identified during the primary side visual inspections of the channel head bowl in all three SGs, which included the entire tubesheet, cladding, divider plate, and associated welds/components.
In its letter dated June 3, 2021, the licensee clarified that the secondary side inspections, which included the top of the tubesheet, flow distribution baffle, and the top TSP, were performed in all three SGs and that no abnormal conditions or conditions adverse to quality were identified.
In its letter dated June 3, 2021, the licensee stated that eight new dents (one in SG B at the 8th TSP and seven in SG C at the 9th TSP) were identified at the upper TSP intersections in the hot legs of SGs B and C during RF24 in the fall of 2018. During RF25 in the spring of 2020, inspections identified six new dents (one at the 8th TSP and five at the 9th TSP) at the upper TSP intersections in the hot leg of SG-C. The licensee stated that no wear has been Enclosure
identified at these tube dent locations. During the clarification call on June 22, 2021, the licensee stated that all these dented tubes were in the hot leg periphery.
In its letter dated June 29, 2021, the licensee indicated that the probable cause of the tube denting was elevated crossflow from flow restriction in the hot leg, due to deposit accumulation in the TSP flow broaches, which are the holes in the TSPs through which the tubes pass. In addition, the licensee stated that the tube dents ranged in size from 2.04 volts to 3.98 volts.
In its letter dated June 3, 2021, the licensee stated that 4,048 pounds (lbs) of sludge were removed from the SGs during RF25 through the Deposit Minimization Treatment process and subsequent sludge lancing. In its letter dated June 29, 2021, the licensee stated that prior to RF25, the deposit inventory estimates for the SGs ranged from 4,477 lbs to 7,217 lbs and that eddy current deposit mapping after the RF25 chemical cleaning, the deposit inventory estimate was 3,592 lbs.
During RF25, four total tubes were plugged; two tubes were preventively plugged in SG A due to TSP wear indications and two tubes (one in SG A and one in SG B) were plugged due to possible loose part (PLP) indications in locations not accessible for inspection or foreign object search and retrieval. In its letter dated June 3, 2021, the licensee stated that the tubes plugged due to PLP indications contained newly identified single PLP indications.
Based on the above, the NRC staff concludes that the licensee provided the information required by Technical Specifications 6.9.1.12, Steam Generator Tube Inspection Report. In addition, the NRC staff concludes that there are no technical issues that warrant additional follow-up action. 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: Leslie S. Terry Date: August 2, 2021
ML21201A326 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL2-1/LAiT NRR/DORL/LPL2-1/LA NAME VThomas KEntz KGoldstein DATE 07/20/2021 07/28/2021 07/28/2021 OFFICE NRR/DNLR/NCSG/BC NRR/DORL/LPL2-1/BC NRR/DORL/LPL2-1/PM NAME SBloom MMarkley VThomas DATE 07/14/2021 08/02/2021 08/02/2021