05000352/LER-2024-002, Invalid Actuation Due to a Trip of 1B Reactor Protection System Circuit Breaker
| ML24162A325 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 06/10/2024 |
| From: | Gillin M Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LG-24-066 LER 2024-002-00 | |
| Download: ML24162A325 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3522024002R00 - NRC Website | |
text
Constellation 10 CFR 50.73 LG-24-066 June 10, 2024 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Unit 1 Renewed Facility Operating License No. NPF-39 NRC Docket No. 50-352 Subject: LER 2024-002-00 Invalid Actuation Due to a Trip of 1 B Reactor Protection System Circuit Breaker In accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), Limerick Generating Station hereby submits the enclosed Licensee Event Report.
There are no commitments contained in this letter.
If you have any questions, please contact Jordan Rajan at (610) 718-3400.
Respectfully, Michael F. Gillin Vice President - Limerick Generating Station Constellation Energy Generation, LLC cc: Administrator Region I, USNRC USNRC Senior Resident Inspector, Limerick Generating Station
Abstract
Limerick Generating Station Unit 1
352 3
Invalid Actuation Due to a Trip of 1B Reactor Protection System Circuit Breaker 04 11 2024 2024 002 00 06 10 2024 5
0
Jordan Rajan 610-718-3400 B
JC 52 W121 Yes
On April 11, 2024, Limerick Generating Station (LGS) Unit 1 was in Operational Condition (OPCON) 5, refueling, performing a surveillance test on the 1B Reactor Protection System (RPS) Power Monitoring System.
Following the completion of the testing, when returning the system to the normal plant alignment, an invalid isolation occurred due to a trip of the 1B-Y160 RPS panel.
Troubleshooting on circuit breaker 52-DY24801 found the circuit breaker contacts were not closed even though the handle was in the closed position. The circuit breaker was replaced. This resulted in containment isolation signals that actuated containment isolation valves in more than one system; therefore, the loss of the RPS bus is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A).
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Cause of the Event
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Failure analysis on circuit breaker 52-DY24801 identified a mechanical problem with the circuit breaker closing handle.
The handle failed to reposition to the tripped position during testing of the circuit breaker. Failure of the circuit breaker to close could not be reproduced in the post-event testing.
Corrective Actions Completed Circuit breaker 52-DY24801 was replaced.
Corrective Actions Planned Evaluate options to determine if the series circuit breakers are closed prior to opening the maintenance switch during testing.
Previous Similar Occurrences There have been no previous similar occurrences for an actuation due to a circuit breaker that appeared to be closed, but was open, within the past five years.
Component Data System: JC (Plant Protection System)
Component: 52 (Circuit Breaker, AC)
Manufacturer: W121 (Westinghouse) 3 3
Limerick Generating Station Unit 1 352 2024 002 00
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