On May 22, 2013, at approximately 1134
CDT, while Unit 1 was operating at 100% power, the 1A
Reactor Protection System (
RPS) Motor Generator (M/G) set tripped causing a loss of the A
RPS bus. This caused the actuation of the Division 1 (outboard)
primary containment isolation logic. This was an event that resulted in the actuation of a general containment isolation signal affecting more than one system. However, as this event meets the definition of an invalid actuation (i.e. not a response to an actual plant parameter exceeding a trip setpoint), this notification is being made in accordance with
10 CFR 50.73(a)(1) in lieu of a Licensee Event Report.
In response to the trip of the 1A RPS M/G, operators swapped the A RPS bus to the alternate power supply using the applicable response procedure. The containment isolation signal was reset and the systems were restored to their normal lineup. Reactor power was not affected by this event. All safety related equipment controlled by the affected primary containment isolation circuits operated as designed.
The 1A RPS M/G trip was due to a motor fault requiring motor replacement. Replacement of the motor was completed on 5/26/13 and the A RPS bus was restored to its normal power supply on 5/27/13.
The licensee has notified the NRC Resident Inspector.
