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| Entered date | Event description | |
|---|---|---|
| ENS 57237 | 24 July 2024 09:31:00 | The following information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: A Notification of Unusual Event was declared by South Texas Project Unit 1 at 0718 CDT for emergency action level (EAL) SU.1, loss of all offsite power for greater than 15 minutes, following a fire in the switchyard. Unit 1 tripped following the loss of power and is stable in Mode 3. Unit 2 reduced power to 90 percent but was otherwise unaffected by this event. Offsite services responded to the switchyard fire. The fire was extinguished at 0925 CDT. There is no radioactive release and no threat to public safety. The licensee notified state and local authorities and the NRC senior resident inspector. Notified DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).
The following information was provided by the licensee via phone and email: At 0702 CDT on 7/24/2024, with Unit 1 in Mode 1 at 100 percent power, the Unit 1 reactor automatically tripped due to loss of offsite power. The trip was not complex, with all systems responding normally post-trip. No equipment was inoperable prior to the event that contributed to the event or adversely impacted plant response to the scram. Operations responded and stabilized the plant. Decay heat is being removed by steam generator power operated relief valves (PORV). Unit 2 was reduced in power to approximately 90 percent power due to conditions in the switchyard. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). There was no impact on the health and safety of the public or plant personnel. The NRC resident inspector has been notified. Notified R4DO (Azua)
The following is a summary of information provided by the licensee via phone: At 1146 CDT, South Texas Project Unit 1 terminated the previously declared Notification of Unusual Event due to restoration of an offsite source of electrical power. Notified R4DO (Azua), NRR EO (McKenna), IR MOC (Crouch), DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).
The following information was provided by the licensee via phone and email: For the 10 CFR 50.72(b)(3)(iv)(A) reporting requirements: At 0702 CDT on 7/24/2024, with both Unit 1 and 2 in Mode 1 at 100 percent power, the South Texas Project (STP) north and south switchyard electrical buses were de-energized. In Unit 1, all emergency diesel generators (EDGs) 11, 12, and 13 automatically started in response to loss of offsite power on train `A', `B', and `C' engineered safety feature (ESF) buses. Also in Unit 1, trains `A', `B', and `C' of the auxiliary feedwater (AFW) system automatically started. In Unit 2, EDG 22 automatically started in response to loss of offsite power on the train `B' ESF bus. Also in Unit 2, train `B' of the AFW system automatically started. This event is reportable under 10 CFR 50.72(b)(3)(iv)(A) as an event that resulted in the valid actuation of a pressurized water reactor auxiliary feedwater system (50.72(b)(3)(iv)(B)(6)) and emergency alternating current (AC) electrical power system (50.72(b)(3)(iv)(B)(8)). There was no impact on the health and safety of the public or plant personnel. The NRC resident inspector has been notified. For the 10 CFR 50.72(b)(2)(xi) reporting requirement: A news release was completed at 1140 CDT on 7/24/2024, by South Texas Project on the declaration of the Unusual Event. This media release is being reported in accordance with 10 CFR 50.72(b)(2)(xi): Any event or situation, related to the health and safety of the public or onsite personnel, or protection of the environment, for which a news release is planned or notification to other government agencies has been or will be made. Notified R4DO (Azua)
The following information was provided by the licensee via phone and email: After a review of station logs, it was determined that there was not a loss of all offsite AC power to Unit 1 related to the event that occurred on July 24, 2024. An offsite AC power source was available through the 138 kV transmission line. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: At this time the licensee is not retracting the declaration of emergency action level 'SU.1'. Notified R4DO (Werner) |