Event Notification Report for June 08, 1999

REACTOR SCRAM DUE TO MAIN TRANSFORMER LOCKOUT

The following text is a portion of a facsimile received from the licensee.

"On June 8, 1999, Susquehanna Unit 2 was operating at 100% power. The unit experienced a unit primary lockout associated with [the] 'A' main transformer resulting in a main turbine trip and a reactor scram on turbine control valve fast closure. [All rods fully inserted.] Reactor water level dropped to approximately 0.4 inches on wide range instrumentation, [and] level was restored to 35 inches using feedwater. Reactor pressure peaked at approximately 1,114 psig which is higher than the reactor scram setpoint of 1,087 psig. Two [safety relief valves] cycled once during the initial event, and [the] turbine bypass valves are now open controlling at [the] pressure setpoint. There were no [emergency core cooling system] initiations or diesel generator starts. There were no challenges to containment."

"This event is an unplanned actuation of an engineered safety feature and, therefore, requires a 4-hour ENS notification under 10 CFR 50.72(b)(2)(ii)."

The licensee stated that the lockout was caused by a sudden pressure relay and that oil was initially spraying from the transformer. The fire brigade responded and has since been secured. A fire watch is currently in place. The licensee plans to place the unit in Cold Shutdown.

The licensee notified the NRC resident inspector and plans to issue a press release.

******************** UPDATE AT 1850 ON 06/08/99 FROM MIKE PEAL TO LEIGH TROCINE ********************

The licensee notified the Pennsylvania Department of Environmental Protection of the oil spill from the 'A' main transformer. The licensee stated that the state notification was not required and was made as a courtesy. The transformer leaked for more than 1 hour, and the licensee drained the transformer from the bottom to stop the leak. This oil was placed into the pit so that it was contained. The quantity of oil that sprayed from the transformer and landed on the ground outside the transformer's berm was not known, but it covered only a small area. None of the oil entered the storm drains, and there was no run off.

The licensee notified the NRC resident inspector of this update. The NRC operations officer notified the R1DO (Caruso).

UNEXPECTED LOW PRESSURE COOLANT INJECTION SYSTEM LOOP SELECT LOGIC ACTUATION DURING LOGIC SYSTEM TESTING

At 1740 EDT on 06/08/99, with the unit in the Refueling mode, moderator temperature of 105°F, reactor water level of 40 inches in the normal band, and the 'A' loop of shutdown cooling in service; the low pressure coolant injection (LPCI) loop select logic caused the 'A' loop injection valve to travel from the throttled position to fully open. At the time, the 'B' loop was removed from service for maintenance, and the 'B' loop injection valve went fully closed. The effect on the plant was that shutdown cooling flow increased from 9,600 gpm to 11,200 gpm. After 5 minutes, control was restored to the 'A' loop injection valve, and flow was reduced to 9,600 gpm. There was no noticeable change on level because LPCI takes a suction from the vessel and returns water to the vessel.

The initiation occurred during a Recirculation Motor-Generator Set Lockout Relay and 4,160-V Drive Motor Trip Control Test. Investigation into the cause of the event is ongoing. Logic system testing has been suspended until the cause has been determined and until a verification that all initiations occurred as designed has been completed.

The licensee notified the NRC resident inspector and plans to notify the Massachusetts Civil Defense tomorrow morning.