Event Notification Report for May 29, 2010

CONTAINMENT PURGE ISOLATION SIGNAL CAUSED CONTROL ROOM ISOLATION SYSTEM ACTUATION

"While operating in Mode 1, 100% rated thermal power (RTP), Wolf Creek received a Containment Purge Isolation Signal (CPIS) caused by Containment Purge Exhaust Radiation Monitor GT RE-33 exceeding the high radiation trip setpoint. There was no containment purge in progress at the time of the CPIS so no containment dampers actuated or were required to actuate. Control Room Ventilation Isolation Signal (CRVIS) was also received, as expected, from the actuation of the CPIS. All CRVIS components actuated as required. Review of GT RE-33 identified that the radiation monitor spiked high causing the CPIS then returned to normal values. All other containment radiation monitors are indicating normal values.

"The NRC Resident has been notified of this event by the Licensee."

GT RE-33 is currently removed from service.

* * * UPDATE AT 1630 EDT ON 06/21/10 FROM RICK HUBBARD TO S. SANDIN * * *

"The licensee is retracting this event based on the following:

"The Containment Purge Exhaust Radiation Monitor GT RE-33 failed due to a corrupted database initiated by a Radiation Monitor System (RMS) communication loop problem. The signal was not initiated by actual plant conditions or parameters, so this was an invalid actuation. This actuation did not involve a critical scram. So it is not reportable per 10 CFR 50.72."

The licensee will inform the NRC Resident Inspector. Notified R4DO (Pick).

INVALID ACTUATION OF PRIMARY CONTAINMENT ISOLATION VALVES DUE TO A FAULTY TRANSISTOR

"This report is being made under 10CFR50.73(a)(2)(iv)(A). On May 29,2010, at 0849 EDST Unit 2 received a trip of the 'B' RPS alternate supply. This trip was due to a faulty transistor on the internal circuit board for the voltage regulator. The transistor was replaced, the voltage regulator tested and replaced in the system. The trip of the 'B' RPS alternate supply resulted in isolation of Primary Containment Isolation Valves in more than one system. The systems that were isolated due to this event were Reactor Water Clean-up and Fission Products Monitoring. Except for critical scrams, invalid actuations are not reportable by telephone under º 50.72. NUREG 1022 defines by examples given that actuation of the reactor protection system constitutes actuation of RPS full scram signal when the reactor is critical. In the condition that occurred during day shift on Saturday, May 29, 2010 only one channel of RPS actuated on failure of the Unit 2 'B' RPS alternate supply. That being the case there was not sufficient logic made up to result in a reactor scram or RPS actuation. An RPS actuation would be considered a reportable event; however, the trip of only the 'B' alternate RPS supply would not be considered an RPS actuation. This condition did involve the initiation of some containment isolation signals resulting in containment isolation valves in more than one system since RWCU and fission product monitor isolation valves closing as a result of the loss of the 'B' RPS system. Valid signals are those signals that are initiated in response to actual plant conditions or parameters satisfying the requirements for initiation of the safety function of the system. In this case the isolation signal was caused by the loss of power to the affected instrumentation rather than response to required conditions or parameters which makes this an 'invalid' isolation signal. For this event, Plant Hatch has chosen to make this telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER.

"All actuations above were complete.

"No system actuations resulted from the trip of the 'B' RPS alternate supply."

The licensee has notified the NRC Resident Inspector.