At
1314 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />4.99977e-4 months <br /> [EDT] on May 25, 2010, with the unit defueled during Refueling Outage 26, an inadvertent Safety Injection (
SI) Signal occurred. The signal was received when Safeguards Train 'A' breaker DP-A-20 was closed during the performance of procedure PIC-020, 'Time Delay Relay Calibration Safeguards Train 'A'.' The
SI Signal resulted in a containment phase 'A' isolation, containment ventilation isolation, control room ventilation transfer to emergency pressurization mode, and Radiation Monitors R-11 and R-12 (Containment Vessel Airborne Particulate and Gas Monitors) isolation. Emergency Bus 1 and
Emergency Diesel Generator 'A' were under clearance, including the Train 'A' sequencer. Therefore, automatic loading of the 'A' Train Sequencer did not occur and no actual injection into the reactor vessel occurred. The affected systems actuated as expected.
The cause of the inadvertent SI Signal resulted from SI Initiation Latching Relay SIA1 when power was restored to Safeguards Rack 51. Subsequent investigation determined the SIA1 relay was in an unexpected position (i.e., latched). The SIA1 relay likely became inadvertently latched while performing cable pulls in Safeguards Rack 51 for work associated with Water Cooled Condensing Unit 1A.
Corrective actions include a revision to a procedure to address additional steps to require reset of SI Initiation Latching Relays SIA1 and SIA2 after cleaning and lubrication and development of a planning tool to better assess the risk associated with work being performed [on] plant equipment. In addition, a procedure will be developed for Operations to manually reset safeguards SI Initiation Latching Relays SIA1 and SIA2 prior to restoring system power. These actions are expected to be completed before or on December 16, 2010.
The licensee has notified the NRC Resident Inspector.
