Unusual Event Declared Due to a Loss of Offsite Power
At 2312 EDT, on August 4, 2020, Brunswick Unit 1 declared an Unusual Event due to a loss of offsite power. The unit was at approximately 20 percent power and was not synced to the grid when the unit automatically scrammed. All control rods fully inserted. Emergency Diesel Generators started and began powering the safety buses. Safety systems actuated as expected.
The Unit also experienced a loss of Fuel Pool Cooling and Cleanup System, but one pump was returned to service.
Unit 2 remains at 100 percent power and is unaffected.
The licensee notified State and local governments, as well as the NRC Resident Inspector.
Notified DHS SWO, FEMA Operations Center, CISA IOCC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).
* * UPDATE FROM MARK TURKAL TO DONALD NORWOOD AT 0120 EDT ON 8/4/2020 * * *
At approximately 2302 EDT, a loss of offsite power occurred on Unit 1. This resulted in a Reactor Protection System (RPS) actuation. Per design, emergency diesel generators 1 and 2 properly started and loaded to their respective emergency buses. The Reactor Core Isolation Cooling (RCIC) system was manually started and is being used to control reactor water level. The High Pressure Coolant Injection (HPCI) system was manually started and is being used for pressure control. As previously reported, an Unusual Event was declared at 2312 EDT due to the loss of offsite power. At the time of the event, Unit 1 was in the process of shutting down for maintenance associated with a ground on the main generator.
Due to the RPS actuation while critical, this event is being reported as a four-hour, nonemergency notification per 10 CFR 50.72(b)(2)(iv)(B).
As a result of the reactor trip, reactor water level reached low level 1 (LL1). The LL1 signal causes a Group 2 (i.e., floor and equipment drain isolation valves), Group 6 (i.e., monitoring and sample isolation valves) and Group 8 (i.e., shutdown cooling isolation valves) isolations. The LL1 isolations occurred as designed; the Group 8 valves were closed at the time of the event. Per design, the loss of offsite power also caused a Group 1 (i.e., main steam isolation valve) isolations.
Due to the Emergency Diesel Generator and Primary Containment Isolation System (PCIS) actuations, this event is also being reported as an eight-hour, nonemergency notification in accordance with 10 CFR 50.72(b)(3)(iv)(A).
Unit 2 was not affected. There was no impact to the health and safety of the public or plant personnel. The safety significance of the event is minimal. All safety related systems operated as designed.
Investigation of the cause of the loss of offsite power is in progress.
The licensee notified the NRC Resident Inspector. Notified R2DO (Inverso).