ENS 57689
ENS Event | |
|---|---|
17:30 May 4, 2025 | |
| Title | Both Trains of Emergency Core Cooling System Inoperable |
| Event Description | The following information was provided by the licensee via phone and email:
On May 4, 2025, with the plant in mode 4 during restart from a refueling outage, operators were flushing the chemical volume and control system [CVCS] `B' train mixed bed demineralizers, with makeup [water] from the refueling water storage tank (RWST). During the evolution at 1230 CDT, it was discovered that the borated water level in the RWST had been inadvertently lowered to less than the technical specification (TS) limit of 394,000 gallons. Under TS 3.5.4, `Refueling Water Storage Tank (RWST),' surveillance requirement (SR) 3.5.4.2 requires verifying that the RWST borated water volume is [greater than or equal to] 394,000 gallons (93.7 percent level). The minimum level (volume) reached in the tank during the flushing operation was 93 percent. Upon discovery of the lowered level in the RWST, the flushing activity was terminated, and water level in the RWST was restored to above the TS limit by 1427. The RWST supplies borated water to the CVCS during abnormal operating conditions, and to the emergency core cooling system (ECCS) and the containment spray system during accident conditions. The RWST supplies both trains of the ECCS and the containment spray system through a common suction supply header during the injection phase of a loss of coolant accident recovery. During mode 4, in accordance with TS 3.5.3, `ECCS - Shutdown,' only one ECCS train is required to be operable. With the RWST declared inoperable, the one required ECCS train in mode 4 was not supported. Therefore, the identified condition is being reported pursuant to 10 CFR 50.72(b)(3)(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. The NRC Resident Inspector was notified. |
| Where | |
|---|---|
Callaway  Missouri (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| LER: | 05000483/LER-2025-001 Refueling Water Storage Tank Lowered Below TS 3.5.4 Limit |
| Time - Person (Reporting Time:+4 h0.167 days <br />0.0238 weeks <br />0.00548 months <br />) | |
| Opened: | Zach Milligan 21:30 May 4, 2025 |
| NRC Officer: | Ian Howard |
| Last Updated: | May 4, 2025 |
| 57689 - NRC Website
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