Monticello Nuclear Generating Plant - Automatic Reactor Scram While Performing Turbine - Generator Testing

November 19, 2011, at approximately 2312 CST, during performance of regularly scheduled Turbine-Generator Quarterly Surveillance, an unplanned reactor scram occurred. Following the reactor scram, reactor water level lowered below the Group II isolation initiation setpoint (+9 in) and an actuation of Primary Containment Isolation System occurred.

The direct cause of the scram was the actuation of the Main Turbine acceleration relay (load rejection) pressure switches. The root cause is under investigation by the site. A supplement to this Licensee Event Report will be submitted following completion of the investigation and will outline corrective actions to address the root cause.