ENS 57963
ENS Event | |
|---|---|
21:52 Oct 2, 2025 | |
| Title | Two Trains of ECCS Inoperable |
| Event Description | The following information was provided by the licensee via phone and email:
On October 2, 2025, at 1651 CDT, essential cooling water pump '1C' tripped. Essential chiller '1C' and cascading equipment, including emergency core cooling system (ECCS) train '1C,' was declared inoperable. Essential chiller '12A' and cascading equipment, including ECCS train '1A,' was concurrently inoperable for ongoing maintenance. This condition resulted in an inoperable condition on 2 out of 3 safety trains for the accident mitigating functions, including the train 'A' and train 'C' high head safety injection (SI), low head SI, containment spray, electrical auxiliary building heating ventilation and air conditioning (HVAC), and essential chilled water. All 'B' train safety related equipment remains operable. There was no impact on the health and safety of the public or plant personnel. The repair timeline is unknown. We have already entered the configuration risk management program to mitigate additional maintenance induced risk with a risk informed completion time of October 19, 2025, at 1140 CDT. We are limited by TS 3.7.7.C to restore 1 train of control room HVAC by October 5, 2025, at 1651 CDT. This condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The 'C' emergency diesel generator is unavailable due to the loss of cooling water. Maintenance on the ECCS train '1A' is partially complete and operators are working to restore the train to an operable status prior to the technical specification deadline. The essential cooling water pump trip was due to a hot spot causing the pump to overheat. The cause of the hot spot is still under investigation.
The following information was provided by the licensee via phone and email: The purpose of this notification is to retract EN 57963, which was made on October 2, 2025, at 2055 EDT. [The] notification was initially made due to two of three trains of emergency core cooling system (ECCS) being declared inoperable. After the notification was made, South Texas Project determined, using an engineering evaluation, that one of the two inoperable ECCS trains was operable because the elevated chilled water outlet temperature of the associated essential chiller (Train A) did not impact the technical specification specified function. Therefore, this event was not a condition that could have prevented fulfillment of a safety function. The NRC Resident Inspector has been notified. Notified R4DO (Vossmar) |
| Where | |
|---|---|
South Texas  Texas (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+-0.95 h-0.0396 days <br />-0.00565 weeks <br />-0.0013 months <br />) | |
| Opened: | Long Han 20:55 Oct 2, 2025 |
| NRC Officer: | Jordan Wingate |
| Last Updated: | Oct 20, 2025 |
| 57963 - NRC Website
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