05000414/LER-2022-002, Indications Identified During Reactor Vessel Head Penetration Embedded Flaw Repair Surface Examination
| ML22340A427 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 12/06/2022 |
| From: | Simril T Duke Energy Carolinas |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RA -22-0333 LER 2022-002-00 | |
| Download: ML22340A427 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded |
| 4142022002R00 - NRC Website | |
text
~ ~ DUKE
~ ENERGY RA-22-0333 December 6, 2022 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555
Subject:
Duke Energy Carolinas, LLC Catawba Nuclear Station, Unit 2 Docket No. 50-414 Licensee Event Report (LER) 414/2022-002-00 Tom Simril Vice President Catawba Nuclear Station Duke Energy CN01VP 14800 Concord Road York, SC 29745 o: 803.701.3340 f: 803. 701.3221 10 CFR 50.73 Pursuant to 10 CFR 50.73(a)(1) and (d), attached is LER 414/2022-002-00, entitled "Indications Identified During Reactor Vessel Head Penetration Embedded Flaw Repair Surface Examination." This report is being submitted in accordance with 10 CFR 50.73(a)(2)(ii)(A).
There are no regulatory commitments contained in this letter or its attachment.
This event is considered to be of no significance with respect to the health and safety of the public.
If questions arise regarding this LER, please contact Sherry E. Andrews of Regulatory Affairs at (803) 701-3424.
Sincerely, Tom Simril Vice President, Catawba Nuclear Station Attachment
United States Nuclear Regulatory Commission Page2 December 6, 2022 xc (with attachment):
L. Dudes Regional Administrator U.S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, GA 30303 S. Williams NRC Project Manager (CNS)
U.S. Nuclear Regulatory Commission 11555 Rockville Pike Mailstop O-8G9A Rockville, MD 20852 David Rivard NRC Senior Resident Inspector Catawba Nuclear Station
Abstract
On October 15, 2022, during the Catawba Nuclear Station Unit 2 refueling outage, it was determined that the results of a planned surface examination Liquid Penetrant test (PT) performed on a previous weld overlay repair on nozzle penetration 74 of the reactor vessel closure head (RVCH) did not meet applicable acceptance standards. The examination was being performed to meet the requirements of Relief Request RA-21-0144, 'Proposed Alternative to Use Reactor Vessel Head Penetration Embedded Flaw Repair for Life of Plant.' The penetration required repairs for the discovered indications. The repairs were completed in accordance with the ASME Code of Record prior to returning the RVCH to service.
Based on industry experience, the cause of this event is attributed to mechanical discontinuities/minor subsurface voids
!Which were exposed to the weld surface due to thermal and/or pressure stresses during plant operation.
rrhis report is being submitted in accordance with 10 CFR 50.72(a)(2)(ii)(A), "any event or condition that results in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded."
YEAR 2022 SEQUENTIAL NUMBER
- - 002 REV NO.
- - 00
!The following information is provided to assist readers in understanding the event described in this LER. Applicable Energy Industry Identification [EIIS] system and component codes are enclosed within brackets. Catawba Nuclear Station unique system and component identifiers are contained within parentheses.
BACKGROUND On October 15, 2022, Unit 2 of Catawba Nuclear Station was in a scheduled refueling outage (Mode 6, 0% power) for
~ycle 25 (C2R25). During the outage, a liquid penetrant (PT) surface examination was performed on the embedded flaw repair of nozzle [NZL] penetration 74 of the reactor vessel closure head (RVCH) [RPV] in accordance with the requirements of Catawba relief request RA-21-0144 (ML22020A283). The RVCH is a Westinghouse Design manufactured by Combustion Engineering.
No Structures, Systems, or Components (SSCs) were inoperable at the start of this event that contributed to the event.
No change in plant mode or in reactor power occurred as a result of this event.
EVENT DESCRIPTION
During the Catawba Unit 2 spring 2021 refueling outage (C2R24), an indication was discovered in the J-groove weld of RVCH nozzle penetration 74 which required repair. Catawba used the embedded flaw repair process, in accordance with
~he NRC approved WCAP-15987-P-A report, and Duke Energy relief request dated April 24, 2021 (RA-21-0145) to repair lthe weld. The embedded flaw repair process involves depositing weld material, which is Primary Water Stress Corrosion Cracking (PWSCC) resistant, over the entire surface of the J-groove weld on the penetration nozzle of interest, as well as pver the outside surface of the nozzle tube. On April 24, 2021 (ML21117A129), the NRC provided verbal authorization for the licensee's proposed alternative repair for one cycle of operation and by letter dated September 20, 2021 (ML21253A082), the NRC provided its follow-up safety evaluation for the verbal relief request. By letter dated January 20, 2022 (RA-21-0144), as supplemented by letter dated July 7, 2022, Catawba provided additional technical basis to support he continued use of the repair. Catawba made this request in accordance with 10 CFR 50.55a(z)(1) on the basis that the proposed alternative repair will provide an acceptable level of quality and safety. On August 31, 2022, Catawba was notified that the NRC staff had determined that the proposed alternative provided an acceptable level of quality and safety iand authorized the use of the proposed alternative in RA-21-0144 through the remainder of the current fourth 10-year inservice inspection interval.
During the Catawba Unit 2 fall 2022 refueling outage (C2R25), a PT surface examination was performed on the embedded
!flaw repair of nozzle penetration 7 4 of the RVCH in accordance with the requirements of Catawba relief request RA 0144. On October 15, 2022, the examination identified indications which did not meet the applicable acceptance standards from ASME Section 111, NB-5350 and were therefore deemed rejectable. The indications were removed by buffing/grinding, localized weld build-up applied to restore the embedded flaw repair thickness, and a final PT of the locations was performed to ensure acceptance standards were met in the as-left condition. The as-left condition has met he applicable acceptance standards and no additional field work is required.
This event is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(A), "Any event or condition that results in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded" because the discovered indications did not meet the acceptance standards from ASME Section Ill, NB-5350 and were therefore deemed rejectable, in accordance with the Catawba relief request RA-21-0144. Page 2 of 3 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023 (08-2020)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 3. LERNUMBER Catawba Nuclear Station, Unit 2 05000-414 CAUSAL FACTORS YEAR 2022 SEQUENTIAL NUMBER
- - 002 REV NO.
- - 00 Based on industry experience, the cause of this event is attributed to mechanical discontinuities/minor subsurface voids
~etting exposed to the weld surface due to thermal and/or pressure stresses during plant operation.
CORRECTIVE ACTIONS
To correct the condition, the indications were removed by buffing/grinding, and localized weld build-up was applied to restore the embedded flaw repair thickness. A final PT of the location was performed to ensure acceptance standards were met in the as-left condition. The as-left condition met the applicable acceptance standards, and no additional field work is required.
SAFETY ANALYSIS
rrhis condition had no effect on the health and safety of the public. The indications discovered on RVCH nozzle penetration
~4 were identified in a timely manner and repaired. The indications were identified as part of a required periodic inspection and did not penetrate through the embedded flaw repair weld. The frequency of the required inspections would ensure degradation was detected before it reached any level of significance. All of the RVCH head penetrations were volumetrically inspected during C2R25, and no other rejectable indications were identified. There were no actual safety consequences for the event. This event is not considered an event or condition that could have prevented fulfillment of a safety function.
ADDITIONAL INFORMATION
~ previous Licensee Event Report was submitted in June 2021 at Catawba Nuclear Station for Unit 2 for a discovered indication on RVCH nozzle penetration 74 caused by PWSCC. A previous Licensee Event Report was submitted in July 2020 for Unit 1 RVCH nozzle 18 for an indication that was attributed to a localized weld fabrication anomaly (not PWSCC). Page 3 of 3