ML19282A144

Review of the Fall 2018 Refueling Outage 21 Steam Generator Tube Inspection Report

ML19282A144
Person / Time
Site:	Vogtle
Issue date:	11/05/2019
From:	John Lamb Plant Licensing Branch II
To:	Gayheart C Southern Nuclear Operating Co
Lamb J, 415-3100
References
EPID L-2019-LRO-0079
Download: ML19282A144 (4)

Text

November 5, 2019 Ms. Cheryl A. Gayheart Regulatory Affairs Director Southern Nuclear Operating Company, Inc.

P. O. Box 1295, Bin 038 Birmingham, AL 35201-1295

SUBJECT:

VOGTLE ELECTRIC GENERATING PLANT, UNIT 1 - REVIEW OF THE FALL 2018 REFUELING OUTAGE 21 STEAM GENERATOR TUBE INSPECTION REPORT (EPID L-2019-LRO-0079)

Dear Ms. Gayheart:

By letter dated March 21, 2019 (Agencywide Document Access and Management System Accession No. ML19080A329) Southern Nuclear Operating Company, Inc. (SNC, the licensee) submitted information summarizing the results of the fall 2018 steam generator (SG) inspections at Vogtle Electric Generating Plant (VEGP), Unit 1. These inspections were performed during the refueling outage (RFO) 21. The SG tube inspection report was submitted in accordance with Technical Specification 5.6.10, 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 their 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 Nos. 50-424

Enclosure:

Steam Generator Tube Inspection Report cc: Listserv

REVIEW OF THE REFUELING OUTAGE 21 STEAM GENERATOR TUBE INSPECTION REPORT SOUTHERN NUCLEAR OPERATING COMPANY VOGTLE ELECTRIC GENERATING PLANT, UNIT 1 DOCKET NO. 50-424 By letter dated March 21, 2019, (Agencywide Documents Access and Management Systems Accession No. ML19080A329), Southern Nuclear Operating Company (SNC or the licensee) submitted information summarizing the results of the fall 2018 steam generator (SG) tube inspections that were performed at Vogtle Electric Generating Plant (VEGP), Unit 1, during the refueling outage (RFO) 21.

VEGP, Unit 1, has four Westinghouse Model F SGs, each of which contains 5,626 U-bend thermally treated Alloy 600 tubes. Each tube has a nominal outside diameter of 0.688 inches and a nominal wall thickness of 0.040 inches. During SG fabrication, the tubes were hydraulically expanded, at both ends, over the full depth of the tubesheet. Type 405 stainless steel support plates, which have broached quatrefoil holes, support the vertical section of the tubes, and anti-vibration bars support the U-bend section of the tubes.

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 U.S. Nuclear Regulatory Commission (NRC) staff has the following comments/observations:

Three axial outside diameter stress corrosion cracking indications were reported in two tubes by +Point probe inspections. The indications were located at the top of the tubesheet hot leg expansion transition locations in the tubes located at row 5, column 90 (two indications) and row 16, column 65 (one indication). The maximum depths for these indications were 62.3, 67.7, and 71.0 percent through-wall (TW). No tubes exhibited degradation in excess of the condition monitoring limits and, therefore, no in situ pressure tests were required.

An axial primary water stress corrosion cracking (PWSCC) indication was detected in the U-bend of the tube located at row 1, column 58 in SG 2. This indication had a maximum depth of 55 percent TW and a length of 0.40 inches. The tube was plugged without stabilization since the degradation is axial and will, therefore, not result in tube severance.

Due to the discovery of the PWSCC indication in SG 2, the licensee expanded the scope of the +Point probe inspections from 50 to 100 percent of row 1 and 2 U-bends in all SGs. No other PWSCC indication was reported in the low row U-bend section of the tubes.

Enclosure

Based on a review of the information provided, the NRC staff concludes that the SNC provided the information required by their technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant 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.

Contributor: Alan Huynh

ML19282A144 *via email OFFICE DORL/LPL2-1/PM DORL/LPL2-1/LA DMLR/MCCB/BC DORL/LPL2-1/BC DORL/LPL2-1/PM NAME JLamb KGoldstein SBloom* MMarkley JLamb DATE 10/8/19 10/11/19 11/4/19 11/4/19 11/5/19