05000352/LER-2025-002, Loss of Power to the 1A Reactor Protection System Resulted in Multiple Invalid Primary Containment Isolations
| ML25224A176 | |
| Person / Time | |
|---|---|
| Site: | Limerick  (NPF-039) |
| Issue date: | 08/12/2025 |
| From: | Gillin M Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LG-25-118 LER 2025-002-00 | |
| Download: ML25224A176 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3522025002R00 - NRC Website | |
text
Constellation.
10 CFR 50.73 LG-25-118 August 12, 2025 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 2025-002-00 Loss of Power to the 1A Reactor Protection System Resulted in Multiple Invalid Primary Containment Isolations 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
On June 13, 2025, at 10:23, Limerick Generating Station (LGS) Unit 1 experienced a loss of power to the "A" Reactor Protection System (RPS) 120 VAC Distribution Panel that resulted in a Unit 1 "A" RPS half scram, Main Steam Isolation Valve (MSIV) half isolation signal, and primary containment isolations in multiple systems. The most probable cause of the power loss was due to an under-frequency relay spurious trip condition. The under-frequency relay was replaced and post maintenance testing was completed satisfactorily. Power was restored to the panel and all systems were returned to service.
This event caused invalid primary containment isolation signals in multiple systems which is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A).
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- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050 Corrective Actions Completed The under-frequency relay was replaced.
Corrective Actions Planned The station will evaluate implementing a replacement strategy for the under-frequency relay.
Previous Similar Occurrences Unit 1 LER 2024-002-00 Invalid Actuation Due to a Trip of 1B RPS Circuit Breaker - This trip was caused by a defective circuit breaker occurring after the completion of testing.
Component Data System - JC (Plant Protection System)
Component - RLY Manufacturer - A500 (Asea Inc) 3 3
Limerick Generating Station, Unit 1 352 2025 002 00
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