On July 23, 2012, at
2057 hours0.0238 days <br />0.571 hours <br />0.0034 weeks <br />7.826885e-4 months <br />, the Perry Nuclear Power Plant experienced a loss of the normal power supply to the
Reactor Protection System (
RPS) A electrical bus. The loss of
RPS bus A caused an actuation of several Division 1 containment outboard isolation valves. The actuation signal caused full closure of one or more valves in each of the following Division 1 subsystems:
Main Steam line drains, Containment Radiation Monitor, Drywell Radiation Monitor,
Reactor Water Cleanup,
Fuel Pool Cooling and Cleanup, Liquid Radwaste
Sumps, Containment Vessel Chilled Water, Containment Vacuum Relief, Condensate Transfer and Storage, Mixed Bed Demineralizer and Distribution, Containment Personnel Airlocks, Service Air, and Instrument Air. Division 2 components and valves were not affected.
This event is considered an invalid system actuation reportable under 10 CFR 50.73(a)(2)(iv)(A). The isolation was not initiated in response to actual plant conditions or parameters, and was not a manual initiation. Therefore, this notification is provided via a 60 day optional phone call in accordance with 10 CFR 50.73(a)(1) instead of submitting a written Licensee Event Report.
The event meets reporting criteria specified in 10 CFR 50.73(a)(2)(iv)(B)(2) as a general containment isolation valve signal affecting containment isolation valves in more than one system. All affected systems functioned as expected in response to an outboard isolation signal. The valves were reopened in accordance with plant procedures. The failure mechanism that caused the loss of RPS bus A was a degraded voltage regulator. The voltage regulator was replaced and retested with satisfactory results.
The NRC Resident Inspector has been notified.
