ML19282A235

Review of the Spring 2019 Refueling Outage 20 Steam Generator Tube Inspection Report

ML19282A235
Person / Time
Site:	Vogtle
Issue date:	11/15/2019
From:	John Lamb Plant Licensing Branch II
To:	Gayheart C Southern Nuclear Operating Co
Lamb J
References
EPID L-2019-LRO-0071
Download: ML19282A235 (4)

Text

November 15, 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 2 - REVIEW OF THE SPRING 2019 REFUELING OUTAGE 20 STEAM GENERATOR TUBE INSPECTION REPORT (EPID L-2019-LRO-0071)

Dear Ms. Gayheart:

By letter dated September 10, 2019 (Agencywide Document Access and Management System Accession No. ML19255F170) Southern Nuclear Operating Company, Inc. (SNC, the licensee) submitted information summarizing the results of the spring 2019 steam generator (SG) inspections at Vogtle Electric Generating Plant (VEGP), Unit 2. These inspections were performed during the refueling outage (RFO) 20. 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. 50-425 cc: Listserv

REVIEW OF THE REFUELING OUTAGE 20 STEAM GENERATOR TUBE INSPECTION REPORT SOUTHERN NUCLEAR OPERATING COMPANY, INC.

VOGTLE ELECTRIC GENERATING PLANT, UNIT 2 DOCKET NO. 50-425 By letter dated September 10, 2019 (Agencywide Document Access and Management System Accession No. ML19255F170), Southern Nuclear Operating Company, Inc. (SNC, the licensee) submitted information summarizing the results of the spring 2019 steam generator (SG) inspections at Vogtle Electric Generating Plant (VEGP), Unit 2. These inspections were performed during the twentieth refueling outage (RFO 20).

The VEGP, Unit 2, 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. The vertical sections of the tubes are supported by Type 405 stainless steel support plates with quatrefoil-shaped holes and the U-bend sections of the tubes are supported by V-shaped, chrome-plated Alloy 600 anti-vibration bars (AVBs).

The licensee provided the scope, extent, methods, and results of their SG tube inspections in the document referenced above. In addition, the licensee described corrective actions, such as tube plugging, taken in response to the inspection findings.

After reviewing the information provided by SNC, the U.S. Nuclear Regulatory Commission (NRC) staff has the following comments/observations:

An indication in the tube located in row 57 column 68 (R57C68) in SG 4, which was previously characterized as a distorted support signal (DSS), was recharacterized as a 34-percent through-wall (TW) volumetric flaw, based on +PointTM probe examination in RFO 20. A review of historical +PointTM probe data showed the indication has been present and unchanged since at least 2002.

Based on inspection with a rotating pancake coil, a new 24-percent TW volumetric indication was identified in SG 2, in the tube located in R1C46, 10.78 inches above the tubesheet on the cold-leg side. The wear location and character were consistent with the other historical indications of mechanical wear and wall loss from secondary side cleaning. A review of historical bobbin data during RFO 20 showed this tube had been resolved as a differential freespan signal (DFS) in previous inspections, and the last time it was examined with a +PointTM probe was during the 2007 SG inspection.

Enclosure

A visual inspection of the SG channel head bowl, including the SG hot-leg and cold-leg divider plate and drain line areas, the entire divider plate-to-channel head weld, and all visible clad surfaces was performed in all SGs during RFO 20, in accordance with Westinghouse Nuclear Safety Advisory Letter NSAL-12-1, Steam Generator Channel Head Degradation, and industry operating experience. Satisfactory inspection results were observed in all SGs.

No cracking was detected during RFO 20.

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 NRC 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.

Contributor: Andrew Johnson

ML19282A235 *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 11/13/19 11/15/19 11/15/19