ML23144A019

– Review of the Spring 2022 Steam Generator Tube Inspection Report (O3R31)

ML23144A019
Person / Time
Site:	Oconee
Issue date:	05/25/2023
From:	Shawn Williams Plant Licensing Branch II
To:	Snider S Duke Energy Carolinas
Williams S
References
EPID L-2022-LRO-0152
Download: ML23144A019 (1)

Text

May 25, 2023

Mr. Steven M. Snider Site Vice President, Oconee Nuclear Station Duke Energy Carolinas, LLC 7800 Rochester Highway Seneca, SC 29672-0752

SUBJECT:

OCONEE NUCLEAR STATION, UNIT 3 - REVIEW OF THE SPRING 2022 STEAM GENERATOR TUBE INSPECTION REPORT (03R31) (EPID NO. L-2022-LRO-0152)

Dear Mr. Snider:

By letter dated November 21, 2022, as supplemented by letter dated April 26, 2023, Duke Energy (the licensee) submitted information summarizing the results of the spring 2022 steam generator inspections performed at Oconee Nuclear Station, Unit 3, during refueling outage 31 (O3R31).

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. 50-287

Enclosure:

Review of Steam Generator Tube Inspection Report

cc: Listserv OCONEE NUCLEAR STATION, UNIT 3

NRC STAFF REVIEW OF THE

SPRING 2022 STEAM GENERATOR TUBE INSPECTION REPORT (O3R31)

DOCKET NO. 50-287

By letter dated November 21, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22325A362), as supplemented by letter dated April 26, 2023 (ML23116A169), Duke Energy (the licensee) submi tted information summarizing the results of the spring 2022 steam generator (SG) inspections performed at Oconee Nuclear Station, Unit 3, during refueling outage 31 (O3R31).

Oconee, Unit 3, has two replacement once-through steam generators (OTSGs) designed and fabricated by Babcock and Wilcox International. Each OTSG has 15,631 thermally treated Alloy 690 tubes with a nominal outside diameter of 0.625 inches and a nominal wall thickness of 0.038 inches. The tubes were hydraulically expanded for 13 inches from the tube end into the 22-inch thick tubesheet. Tube support is provided by 15 stainless steel horizontal tube support plates (TSPs) with trefoil broached openings. Some of the openings in the 14 th TSP are drilled holes.

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) taken in response to the inspection findings.

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

Two degradation mechanisms were detected in the Oconee Unit 3 SGs in O3R31: tube wear at TSPs and tube-to-tube wear. There were 41 tubes in SG 3A and 43 tubes in SG 3B with TSP wear exceeding the plugging criterion of 40 percent through-wall. These 84 tubes were plugged. No tubes were plugged due to tube-to-tube wear.

The maximum reported tube-to-tube wear depth was 11 percent through-wall. Both SGs contain additional tube-to-tube wear indications designated Historical No Change (HNC) according to the licensees change criteria (i.e., indications sized three times with the array probe, and no change in the bobbin probe signal for the current outage compared to the previous outage). These indications were not sized during O3R31 and are listed in the April 26, 2023, letter.

Enclosure

Two tubes were plugged in SG 3A due to potential loose part (PLP) eddy current indications with no wear detected. Both tubes were plugged because they were located near tubes previously plugged for PLP indications, one of which also had a wear indication.

The Unit 3 SGs were not inspected during the previous refueling outage (O3R30). The licensee noted that this was the first skipped inspection for any of the Oconee units and that the O3R31 inspection results were bounded by the previous operational assessment with margin. (The SGs for all three units were replaced in 2004.)

Based on a review of the information provided, the 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 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.

Principal Contributor: Gregory Makar

Date: May 25, 2023

ML23144A019 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NAME ZTurner SWilliams KGoldstein DATE 05/24/2023 05/24/2023 05/24/2023 OFFICE NRR/DNRL/NCSG/BC NRR/DORL/LPL2-1/BC* NRR/DORL/LPL2-1/PM NAME SBloom MMarkley SWilliams DATE 05/23/2023 05/25/2023 05/25/2023