ENS 57831
ENS Event | |
|---|---|
04:29 Jul 29, 2025 | |
| Title | Both Trains of Control Room Air Conditioning Inoperable |
| Event Description | The following information was provided by the licensee via phone and fax:
At 2324 CDT, on July 28, 2025, control room air conditioning (CRAC) 'B' tripped at Grand Gulf Nuclear Station (GGNS) approximately 5 minutes after loading the compressor by adjusting the thermostat [down] per standby service water quarterly surveillance instructions. CRAC 'A' was manually started at 2326 CDT and at 2329 CDT it subsequently tripped. After investigating the compressors and breakers per the alarm response instructions with no abnormal indications, CRAC 'B' was restarted and tripped again. Cooling water was rotated from plant service water to standby service water and CRAC 'A' was successfully restarted at 2358 CDT and remains in service. While both control room air conditioning subsystems were inoperable GGNS entered technical specification limiting condition of operation (LCO) 3.7.4 condition 'B', actions requiring verification of control room temperatures less than 90 degrees F and restoring one subsystem to operable status in 7 days. Control room temperatures reached 79 degrees F, maximum, before CRAC 'A' was restarted. GGNS has exited condition 'B' in LCO 3.7.4 and entered condition 'A' to restore CRAC 'B' in 30 days. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(D) as an event or condition which could have prevented the fulfillment of a safety function. The NRC Senior Resident Inspector has been notified.
Investigation of the cause of the control room air conditioning (CRAC) `A' and `B' trips identified a plant service water / standby service water (SSW) crosstie valve which failed in its safety-related (closed) position as the cause. In an accident or transient, cooling water to CRAC `A' compressors would have been successfully provided by the safety-related SSW. As a result, CRAC `A' remained capable of fulfilling its safety function to maintain the control room environment less than 90 degrees F. The NRC Senior Resident Inspector has been notified of this retraction. Notified R4DO (Drake). |
| Where | |
|---|---|
Grand Gulf  Mississippi (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:+-0.75 h-0.0313 days <br />-0.00446 weeks <br />-0.00103 months <br />) | |
| Opened: | Christina Brogdan 03:44 Jul 29, 2025 |
| NRC Officer: | Robert A. Thompson |
| Last Updated: | Jul 30, 2025 |
| 57831 - NRC Website
Loading map... | |