ML20153A744

Review of the Fall 2018 Steam Generator Tube Inspection Report

ML20153A744
Person / Time
Site:	Comanche Peak
Issue date:	06/04/2020
From:	Dennis Galvin Plant Licensing Branch IV
To:	Peters K Vistra Operations Company
Galvin D
References
EPID L-2019-LRO-0104
Download: ML20153A744 (5)

Text

June 4, 2020 Mr. Ken J. Peters Senior Vice President and Chief Nuclear Officer Attention: Regulatory Affairs Vistra Operations Company LLC Comanche Peak Nuclear Power Plant 6322 N FM 56 P.O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NO. 2 - REVIEW OF THE FALL 2018 STEAM GENERATOR TUBE INSPECTION REPORT (EPID L-2019-LRO-0104)

Dear Mr. Peters:

By letter dated June 10, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19171A190), Vistra Operations Company LLC (Vistra OpCo, the licensee) submitted information summarizing the results of the fall 2018 steam generator inspections performed at Comanche Peak Nuclear Power Plant (Comanche Peak), Unit No. 2.

The inspections were performed during refueling outage 17. The information was submitted in accordance with Comanche Peak Technical Specification (TS) 5.6.9, Unit 1 Model D76 and Unit 2 Model D5 Steam Generator Tube Inspection Report.

The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the information provided by Vistra OpCo and concludes that the licensee provided the information required by Comanche Peak TS 5.6.9 and that no followup is required at this time. A summary of the NRC staffs review is enclosed.

K. Peters If you have any questions, please contact me at 301-415-6256 or via e-mail at Dennis.Galvin@nrc.gov.

Sincerely,

/RA/

Dennis J. Galvin, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-446

Enclosure:

Review of the Fall 2018 Steam Generator Tube Inspection Report cc: Listserv

REVIEW OF THE FALL 2018 STEAM GENERATOR TUBE INSPECTION REPORT COMANCHE PEAK POWER COMPANY LLC AND VISTRA OPERATIONS COMPANY LLC COMANCHE PEAK NUCLEAR POWER PLANT, UNIT 2 DOCKET NO. 50-446 By letter dated June 10, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19171A190), Vistra Operations Company LLC (Vistra OpCo, the licensee) submitted information summarizing the results of the fall 2018 steam generator (SG) inspections performed at Comanche Peak Nuclear Power Plant (Comanche Peak), Unit No. 2.

The inspections were performed during refueling outage 17 (2RF17). The information was submitted in accordance with Comanche Peak Technical Specification 5.6.9, Unit 1 Model D76 and Unit 2 Model D5 Steam Generator Tube Inspection Report.

Comanche Peak Unit 2 has four Westinghouse Model D5 SGs, which have been in service since the plant began commercial operation in 1993. Each SG contains 4,570 thermally-treated Alloy 600 tubes with a nominal outside diameter of 0.750 inches and a nominal wall thickness of 0.043 inches. The tubes are hydraulically expanded at both ends for the full depth of the tubesheet. On the hot-leg side, the U-tubes are supported by seven Type 405 stainless steel quatrefoil broached-hole tube support plates. Also, on the hot-leg side there is a Type 405 stainless steel round drilled-hole flow distribution baffle plate between the tubesheet and the first tube support plate. On the cold-leg side there are four Type 405 stainless steel quatrefoil broached-hole tube support plates, six round drilled-hole preheater baffle plates, and a round drilled-hole flow distribution baffle. The U-bend regions of the tubes are supported by two sets of chrome plated Inconel anti-vibration bars. To reduce residual stress, the U bend rows 1 through 9 (short radius) were stress-relieved after heat treatment. One-hundred and forty tubes in all four SGs were hydraulically expanded prior to unit startup at the B and D preheater baffle plates to reduce tube vibration.

The licensee provided the scope, extent, methods, and results of the SG tube inspections in the letter referenced above. Based on the review of the information provided, the U.S. Nuclear Regulatory Commission (NRC) staff has the following observations:

During 2RF16, four indications of circumferential primary water stress corrosion cracking in three tubes in SG 2-03 were detected. In accordance with the Comanche Peak Unit 2 Technical Specifications, which requires SG inspections at the next refueling outage following detection of crack indications, the licensee performed SG inspections during 2RF17. The focus of the SG inspections in 2RF17 was +Point' probe tubesheet examinations to examine for stress corrosion cracking. No additional stress corrosion cracking indications were detected, and no tubes were plugged during 2RF17.

Visual inspections of all accessible upper steam drum components in all four SGs were performed in 2RF17. The licensee observed small amounts of incipient erosion in various upper steam drum components and stated that it was consistent with the observations made during 2RF08.

Enclosure

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

On April 17, 2020, the NRC approved an amendment that allowed the licensee to defer the Comanche Peak Unit 2 SG inspections from the spring 2020 refueling outage to the fall 2021 refueling outage (ADAMS Accession No. ML20108E878). The licensee requested the amendment in response to social distancing recommendations provided by the United States Center for Disease Control, which have been issued as a defensive measure against the spread of the Coronavirus Disease 2019. As part of its review of the amendment request, the NRC staff considered the results from multiple inspections, including the 2RF17 SG inspections.

Principal Contributor: Leslie Terry Date: June 4, 2020

ML20153A744 *by email OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA* NRR/DNRL/NCSG/BC*

NAME DGalvin PBlechman SBloom DATE 6/4/2020 6/4/2020 5/27/2020 OFFICE NRR/DORL/LPL4/BC* NRR/DORL/LPL4/PM*

NAME JDixon-Herrity DGalvin DATE 6/4/2020 6/4/2020