This notification of a system actuation is provided in accordance with
10 CFR 50.73(a)(2)(iv)(A). The Licensee is providing a telephone notification to the NRC Operations Center in accordance with
10 CFR 50.73(a)(1) instead of submitting a written Licensee Event Report, as the system actuation was invalid and was not the result of an actuation of the
reactor protection system when the reactor was critical. The event involved the invalid actuation of 'Emergency
AC electrical power systems, including:
emergency diesel generators' as discussed in
10 CFR 50.73(a)(2)(iv)(B).
At 1827 on November 16, 2008, with Calvert Cliffs Unit 2 operating at approximately 100% power, the Train A (2A) Emergency Diesel Generator (EDG) automatically started from the standby condition. The automatic start was caused by a degraded switch in the start circuit for the EDG. The 2A EDG successfully started and functioned properly, but did not automatically connect to the associated bus ('21' 4KV Bus) because no bus undervoltage signal was present. The 2A EDG start is considered to be invalid, as the start signal was not generated in response to actual plant conditions or parameters satisfying the requirements for initiation of the EDG start. The start was also not the result of an intentional manual action.
The 2A EDG was removed from service and the Station Blackout diesel generator was aligned to '21' 4KV Bus.
Following replacement of the degraded switch, the 2A EDG was tested and returned to Service at 2030 on November 17, 2008.
The 2B EDG remained operable during this event.
The licensee notified the NRC Resident Inspector.
The degraded switch was in the
EDG room and had degraded resulting in high resistance i.e. simulated an open circuit, which started the diesel.
