ML24095A107

– Review of the Spring 2023 Steam Generator Tube Inspection Report (C1R27)

ML24095A107
Person / Time
Site:	Catawba
Issue date:	04/08/2024
From:	Shawn Williams Plant Licensing Branch II
To:	Flippin N Duke Energy Carolinas
Stone Z
References
EPID L-2023-LRO-0089
Download: ML24095A107 (1)

Text

April 8, 2024

Nicole Flippin Site Vice President Catawba Nuclear Station Duke Energy Carolinas, LLC 4800 Concord Road York, SC 29745

SUBJECT:

CATAWBA NUCLEAR STATION, UNIT 1 - REVIEW OF THE SPRING 2023 STEAM GENERATOR TUBE INSPECTION REPORT (C1R27)

(EPID L-2023-LRO-0089)

Dear Nicole Flippin:

By letter dated November 16, 2023, Duke Energy (the licensee) submitted information summarizing the results of the spring 2023 steam generator inspections performed at Catawba Nuclear Station, Unit 1, during refueling outage 27 (C1R27).

The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the report and concludes that the licensee provided the information required by their technical specifications and that no additional follow-up is required at this time. The NRC staffs review is enclosed.

If you have any questions, please contact me at 301-415-1009 or via e-mail at Shawn.Williams@nrc.gov.

Sincerely,

/RA/

Shawn A. Williams, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Docket No. 50-413

Enclosure:

Review of Steam Generator Tube Inspection Report

cc: Listserv CATAWBA NUCLEAR STATION, UNIT 1

NRC STAFF REVIEW OF THE

SPRING 2023 STEAM GENERATOR TUBE INSPECTION REPORT (C1R27)

DOCKET NO. 50-413

By letter dated November 16, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23320A180), Duke Ener gy Carolinas, LLC (the licensee) submitted information summarizing the results of the spring 2023 steam generator (SG) inspections performed at Catawba Nuclear Station, Unit 1 (Catawba Unit 1) during Refueling Outage 27 (C1R27, hereafter referred to as RFO27).

Catawba Unit 1 has four Babcock and Wilcox Canada Model CFR80 recirculating SGs that were installed in 1996 as replacements for the original SG s. As of RFO27, the replacement SGs have been in service for 24.37 effective full power years (EFPY). Each SG has 6,633 thermally treated Alloy 690 tubes with an outside diameter of 0.688 inches and a nominal wall thickness of 0.040 inches. The tubes were hydraulically expanded for the full depth of the tubesheet at each end and are flush seal welded at the primary face of the tubesheet. The straight section of tubes are supported by nine stainless steel lattice grid supports. The U-bend portion of tubes are restrained by eight fanbars that are attached to connector bars. The tubes in rows 1 through 27 were stress relieved after bending.

The licensee provided the scope, extent, methods, and results of the SG tube inspections in the letters referenced above. In addition, the licensee described corrective actions (e.g., tube plugging), in response to the inspection findings.

After reviewing the information provided, the NRC staff noted the following:

During RFO27 the licensee performed a 100 percent full-length bobbin probe examination of all in service tubes. In addition, an array probe inspection was performed in both hot leg and cold leg periphery tubes (5 tubes in from periphery) from the top of the tubesheet to the first tube support. By letter dated March 4, 2022 (ADAMS Accession No. ML22010A281), the NRC issued amendments that revised the Catawba Unit 1 technical specifications based on Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections (ADAMS Package Accession No. ML21099A086). The 100 percent full-length inspection of all in service tubes starts the TSTF-577 inspection period.

Tube wear at support structures and tube wear due to a presumed foreign object was reported at the RFO27 inspection. The maximum depth wear at fanbars was 29 percent through-wall (TW). The largest 95 th percentile fanbar wear growth rate among all SGs was 0.72 percent TW/EFPY. The deepest lattice grid wear indication was 12 percent TW, with

Enclosure

a maximum growth rate (new or existing indication) of 1.20 percent TW/EFPY. One tube was plugged during RFO27 due to 41 percent TW wear from a foreign object.

Based on review of the information provided, t he NRC staff concludes that the licensee provided the information required by their technical specifications. In addition, the 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.

Principal Contributor: Paul A. Klein

ML24095A107 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NAME JMinzerBryant EMiller KGoldstein DATE 04/02/2024 04/03/2024 04/04/2024 OFFICE NRR/DNRL/NCSG/BC NRR/DORL/LPL2-1/BC NRR/DORL/LPL2-1/PM NAME SBloom MMarkley SWilliams DATE 03/28/2024 04/04/2024 04/08/2024