|EMERGENCY DIESEL GENERATOR AUTOMATIC START |
"At 1644 [11/01/04], with River Bend Station in Mode 5 (Refueling), voltage on offsite power line Reserve Station Service (RSS) No. 2 was lost. This offsite power line is the 230 KV power supply to the Division 2, 4160 volt safety related electrical bus. The Division 2 emergency diesel generator (EDG) automatically started and loaded on a loss of voltage to the 4160 volt safety bus.
"At the time of the event, Division 2 Residual Heat Removal (RHR) was in the fuel pool cooling assist mode and the pump secured due to the loss of power. It was subsequently restarted and continues to provide the shutdown cooling function.
"The following systems were isolated as a result of this event: Reactor Water Clean-up, Alternate Decay Heat Removal, and Floor Drains.
"Investigation of the cause of the event is ongoing."
There was no impact on spent fuel pool level or temperature. At the event reporting time, power to the bus was still being provided by the Division 2 EDG with plans to restore normal power shortly. The licensee informed the NRC Resident Inspector. See also similar event EN # 41164 of 10/31/04.