05000260/LER-2023-001-01, Pressure Boundary Leak on Recirculation Pump Discharge Isolation Valve Drain Line Due to Fatigue Failure
| ML23261C399 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/18/2023 |
| From: | Sivaraman M Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LER 2023-001-01 | |
| Download: ML23261C399 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded |
| 2602023001R01 - NRC Website | |
text
Post Office Box 2000, Decatur, Alabama 35609-2000 September 18, 2023 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 2 Renewed Facility Operating License No. DPR-52 NRC Docket No. 50-260
Subject:
Licensee Event Report 50-260/2023-001-01
References:
- 1. Non-Emergency Event Notification 56371 - Degraded Condition
- 2. Letter from TVA to NRC, Licensee Event Report 50-260/2023-001-00, dated April 19, 2023 (ML23109A362)
The enclosed Licensee Event Report provides details of a pressure boundary leak on Browns Ferry Nuclear Plant, Unit 2. The Tennessee Valley Authority is submitting this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plants Technical Specifications; and 10 CFR 50.73(a)(2)(ii)(A), as any event or condition that resulted in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded.
There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact David J. Renn, Nuclear Site Licensing Manager, at (256) 729-2636.
Respectfully, Manu Sivaraman Site Vice President Enclosure: Licensee Event Report 50-260/2023-001 Pressure Boundary Leak on Recirculation Pump Discharge Isolation Valve Drain Line Due to Fatigue Failure cc (w/ Enclosure):
M Si
U.S. Nuclear Regulatory Commission Page 2 September 18, 2023 NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant NRC Project Manager - Browns Ferry Nuclear Plant
ENCLOSURE Browns Ferry Nuclear Plant Unit 2 Licensee Event Report 50-260/2023-001-01 Pressure Boundary Leak on Recirculation Pump Discharge Isolation Valve Drain Line Due to Fatigue Failure See Enclosed
Abstract
On February 17, 2023, during a drywell entry for leak identification, Browns Ferry Nuclear Plant (BFN) personnel discovered a cracked weld on the 2A Recirculation Pump discharge isolation valve drain line. On February 18, 2023, at 0439 Central Standard Time (CST), it was determined that this drain line was classified as American Society of Mechanical Engineers Code Class I piping and constitutes part of the BFN, Unit 2 Reactor Coolant System (RCS) pressure boundary. On February 18, 2023, at 1025 CST, eight-hour Event Notification 56371 was made to the NRC. On March 19, 2023, work was completed to remove and replace the drain line.
The root cause of this event was that small bore piping was not analyzed for vulnerability of fatigue failure due to operational or resonance vibration. Corrective actions are to implement changes that will result in bounded life cycles for all levels of vibrational stress that the piping will experience; and to implement additional actions, for Unit 2 systems where failure of small bore branch piping would cause a unit shutdown or loss of RCS boundary, to modify the operating ranges of the system and/or the piping assembly. TVA has concluded that sufficient systems were available to provide the required safety functions needed to protect the health and safety of the public.
- 2. On December 2, 2022, at 2330 CST, during a drywell entry for leak identification, BFN Engineering personnel discovered a through-wall piping leak on a test line between the two RHR Shutdown Cooling test line isolation valves. On December 3, 2022, at 1000 CST, it was determined that this test line was classified as ASME Code Class 1 piping and constitutes part of the BFN, Unit 3 RCS pressure boundary. Operations personnel maintained BFN, Unit 3 in Mode 4 or 5 until the leak was repaired. On December 3, 2022, at 1205 CST, eight-hour Event Notification56257 was made to the NRC. The test line was cut and capped pending permanent repairs.
This event was reported to the NRC under LER 50-296/2022-003 Pressure Boundary Leak on Residual Heat Removal System Low Pressure Coolant Injection Test Line The root cause of both of these events was small bore piping which was not specifically analyzed for fatigue failure vulnerability due to operational or resonance vibration. The corrective action for both of these events is to implement ECPs for small bore piping with vulnerability to fatigue failure due to exceeding the endurance limit due to operational vibration.
VIII. Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments.