ML22124A006

Review of the Spring 2021 Refueling Outage 24 Steam Generator Tube Inservice Inspection Report

ML22124A006
Person / Time
Site:	Wolf Creek
Issue date:	05/05/2022
From:	Samson Lee Plant Licensing Branch IV
To:	Reasoner C Wolf Creek
Lee S, 301-415-3168
References
EPID L 2021-LRO-0060
Download: ML22124A006 (5)

Text

May 5, 2022 Mr. Cleveland Reasoner Chief Executive Officer and Chief Nuclear Officer Wolf Creek Nuclear Operating Corporation Post Office Box 411 Burlington, KS 66839

SUBJECT:

WOLF CREEK GENERATING STATION, UNIT 1 - REVIEW OF THE SPRING 2021 REFUELING OUTAGE 24 STEAM GENERATOR TUBE INSERVICE INSPECTION REPORT (EPID L-2021-LRO-0060)

Dear Mr. Reasoner:

By letter dated November 1, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21305B855), as supplemented by letter dated March 15, 2022 (ML22074A281), Wolf Creek Nuclear Operating Corporation (the licensee) submitted a summary of the results of the spring 2021 steam generator (SG) inspections performed at Wolf Creek Generating Station, Unit 1. The inspections were performed during Refueling Outage 24.

The SG tube inspection report was submitted in accordance with Technical Specification (TS) 5.6.10, Steam Generator Tube Inspection Report.

Based on its review, the U.S. Nuclear Regulatory Commission (NRC) staff concludes that the licensee has provided the information required by TS 5.6.10, and that no follow-up is required at this time. A summary of the NRC staff's review is enclosed.

If you have any questions, please contact me at 301-415-3168 or via e-mail at Samson.Lee@nrc.gov.

Sincerely,

/RA/

Samson S. Lee, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-482

Enclosure:

Review of the Steam Generator Tube Inspection Report cc: Listserv

REVIEW OF THE SPRING 2021 REFUELING OUTAGE 24 STEAM GENERATOR TUBE INSERVICE INSPECTION REPORT WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION, UNIT 1 DOCKET NO. 50-482 By letter dated November 1, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21305B855), as supplemented by letter dated March 15, 2022 (ML22074A281), Wolf Creek Nuclear Operating Company (the licensee) submitted information summarizing the results of the spring 2021 steam generator (SG) inspections performed at Wolf Creek Generating Station, Unit 1 (Wolf Creek). These inspections were performed during Refueling Outage 24 (RF24). In addition, the U.S. Nuclear Regulatory Commission (NRC) staff held a conference call with the licensee on April 16, 2021, regarding the ongoing SG inspection activities at Wolf Creek. A summary of the conference call regarding the spring 2021 SG inspections is available in ADAMS under Accession No. ML21127A132. The licensee provided additional information concerning the inspections in its letter dated March 15, 2022 Wolf Creek has four Westinghouse Model F SGs. Each SG contains 5,626 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. The tubes are supported by stainless steel tube supports with quatrefoil-shaped holes and V-shaped chrome-plated Alloy 600 anti-vibration bars. The tubes are hydraulically expanded for the full depth of the tubesheet at each end.

The licensee provided the scope, extent, methods, and results of the SG tube inspections in its letter dated November 1, 2021, as supplemented. In addition, the licensee described corrective actions (e.g., tube plugging) that were taken in response to the inspection findings.

Based on the review of the information provided, the NRC staff has the following observations:

Wear was the only degradation mechanism found and 32 tubes were plugged due to wear during RF24. Thirty tubes with anti-vibration bars wear indications greater than 40 percent through-wall were plugged (5 in SG A, 12 in SG B, 3 in SG C, and 10 in SG D). Two tubes with new foreign object wear indications attributed to transient foreign objects were preventatively plugged (one each in SGs A and B).

No indications of primary water stress corrosion cracking or outside diameter stress corrosion cracking were found during RF24.

In the March 15, 2022, letter, the licensee clarified that full length Bobbin coil/Zephyr' probe inspections were performed in Rows 2 and higher. In addition, as stated in the licensees letter dated November 1, 2021, 50 percent of the Rows 1 and 2 U-bends received a mid-range +Point' probe inspection.

Enclosure

The area of channel head wastage due to cladding breach initially found in SG A during RF19 was visually and ultrasonically tested during RF24 and no changes were found.

No additional cladding degradation was found in any SG.

Based on the review of the information provided, the NRC staff concludes that the licensee provided the information required by Wolf Creek Technical Specification 5.6.10, Steam Generator Tube Inspection Report. In addition, the NRC staff concludes that there are no technical issues that warrant additional 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.

ML22124A006 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA NRR/DNRL/NCSG/BC NAME SLee PBlechman SBloom DATE 5/4/2022 5/4/2022 3/18/2022 OFFICE NRR/DORL/LPL4/BC NRR/DORL/LPL4/PM NAME JDixon-Herrity SLee DATE 05/05/2022 05/05/2022