ML23061A090

Review of the Fall 2021 Steam Generator Tube Inspection Report

ML23061A090
Person / Time
Site:	Mcguire
Issue date:	03/06/2023
From:	Klos L Plant Licensing Branch II
To:	Pigott E Duke Energy Carolinas
Klos L
References
EPID L-2022-LRO-0151
Download: ML23061A090 (1)

Text

March 6, 2023 Mr. Edward Pigott Site Vice President Duke Energy Carolinas, LLC McGuire Nuclear Station 12700 Hagers Ferry Road Huntersville, NC 28078-8985

SUBJECT:

MCGUIRE NUCLEAR STATION, UNIT 2 - REVIEW OF THE FALL 2021 STEAM GENERATOR TUBE INSPECTION REPORT (EPID: L-2022-LRO-0151)

Dear Mr. Pigott:

By letter dated March 24, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22088A236), Duke Energy Carolinas, LLC (the licensee), submitted information summarizing the results of the fall 2021 steam generator inspections performed at McGuire Nuclear Station, Unit 2 during the end-of-cycle 27 refueling outage.

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 enclosure documents the NRC staffs review of the submittal.

If you have any questions, please contact me at 301-415-5136 or via e-mail at John.Klos@nrc.gov.

Sincerely,

/RA/

L. John Klos, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-370

Enclosure:

Review of Steam Generator Tube Inspection Report cc: Listserv

REVIEW OF THE FALL 2021 STEAM GENERATOR TUBE INSPECTION REPORT DOCKET NO. 50-370 In its letter dated March 24, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22088A236), Duke Energy Carolinas, LLC (the licensee), submitted information summarizing the results of the fall 2021 steam generator (SG) tube inspections performed at McGuire Nuclear Station (McGuire), Unit 2, during the end-of-cycle refueling outage 27 (M2R27). During the outage on September 27, 2021, the U.S. Nuclear Regulatory Commission (NRC) staff held a conference call with the licensee to discuss preliminary inspection results and documented a summary of the call (ML21291A150).

McGuire, Unit 2 has four model CFR80 SGs manufactured by Babcock and Wilcox Canada that were installed in 1997. Each SG has 6,633 thermally treated Alloy 690 tubes, which have a nominal outside diameter of 0.688 inches and a nominal wall thickness of 0.040 inches. The tubes have a triangular pitch of 0.930 inches and were hydraulically expanded at each end for the full depth of the 26.63-inch (without cladding) tubesheet. The tubes are supported by stainless steel lattice grid support plates and fan bars. The SGs have two-stage moisture separators with curved-arm primary separators.

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

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

Visual exams of components in the 2A SG steam drum are being used to assess the material condition of the various components within this region. The condition of the steam drum in the 2A SG is used as a lead indicator for the other three SGs.

In addition to the steam drum inspections previously performed, the SG manufacturer recommended additional steam drum inspections in M2R27, including:

o a sample of the secondary separator bottom plates, and all separator skimmer walls where erosion had previously been identified, and o additional visual inspections of other areas based on recent operating experience, including inspections of 30 primary separators with particular interest in the top plate, a sample inspection of the inside surface of the curved arms, stiffener plates via a sample of the curved arms, and the inside diameter surface of the outer cylinder.

These examinations confirmed that flow accelerated corrosion of the secondary separator skimmer walls and bottom plates is continuing and that portions of these components are flaking off and migrating to the top of the tubesheet.

Enclosure

Based on the 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.

Principal Contributor: A. Johnson, NRR

ML23061A090 *by email OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DNRL/NCSG/BC*

NAME JKlos KGoldstein SBloom DATE 03/01/2023 03/02/2023 02/28/2023 OFFICE NRR/DORL/LPL2-1/BC* NRR/DORL/LPL2-1/PM NAME MMarkley JKlos DATE 03/03/2023 03/06/2023