05000260/LER-2020-001, For Browns Ferry Nuclear Plant, Unit 2, Core Spray System Inoperable for Longer than Permitted by Technical Specifications
| ML20244A273 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/31/2020 |
| From: | Bono S Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 2020-001-00 | |
| Download: ML20244A273 (9) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2602020001R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 August 31, 2020 10 CFR 50.73 10 CFR 50.4(a)
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 50-260/2020-001 Core Spray System Inoperable for Longer than Permitted by Technical Specifications The enclosed Licensee Event Report provides details of the inoperability of the Core Spray system for longer than allowed by plant Technical Specifications. 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. The TVA is also submitting this report in accordance with 10 CFR 50.73(a)(2)(v)(D), as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.
There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact J. L. Paul, Site Licensing Manager, at (256) 729-2636.
Respectfully, S. M. Bono Site Vice President Enclosure: Licensee Event Report 50-260/2020-001 Core Spray System Inoperable for Longer than Permitted by Technical Specifications
Abstract
On July 1, 2020, the motor thermal overloads associated with the 2A Core Spray Room Cooler Fan were found tripped during a surveillance test. The breaker was not tripped, and was found still in the "on" position.
Operators reset the thermal overloads, which restarted the room cooler fans without resetting the breaker.
The thermal overloads were replaced on July 2, 2020.
After a recurrent trip on July 6, 2020, troubleshooting determined that mechanical binding within the motor sporadically increased the running current, which tripped the thermal overloads. An engineering evaluation later determined that the non-functional Core Spray Room Cooler Fan rendered the Loop I Core Spray subsystem inoperable from May 29, 2020 until July 12, 2020, which is longer than allowed by Technical Specification (TS) 3.5.1, Emergency Core Cooling Systems (ECCS) -- Operating. On June 13, 2020 a planned surveillance rendered the Loop II Core Spray System inoperable. This resulted in a period of time with both Loops I and II of the Core Spray System concurrently inoperable resulting in a Safety System Functional Failure (SSFF) of systems that are needed to mitigate the consequences of an accident.
As a corrective action, the motor, thermal overloads, temperature switch, and starter coil were replaced.
As a corrective action to prevent recurrence, BFN is creating a new Preventative Maintenance (PM) to measure the motor current readings to the thermal overloads every two years, during the summer months when the fan is in high use. This will detect possible changes in continuous running current prior to overcurrent trips or motor damage.
Page 8 of 8 B. Corrective Actions to Prevent Recurrence or to reduce the probability of similar events occurring in the future BFN is creating a new Preventative Maintenance to measure the motor current readings to the thermal overloads every two years, during the summer months when the fan is in high use.
This will prevent reoccurrence for motor and thermal overload trips by detecting possible changes in continuous running current prior to overcurrent trips or motor damage.
VII. Previous Similar Events at the Same Site
A search of BFN Units 1, 2, and 3 LERs for the last five years identified no LERs associated with Core Spray Room Cooler Fan failures. A review of CRs and WOs did not identify any issues with operability in the past 3 years. All previous predictive maintenance monitoring over the last 3 years indicated that the motors performance was satisfactory.
VIII. Additional Information
There is no additional information.
IX.
Commitments
There is no additional information.