At 1525 the plant experienced a load reject generator trip due to a catastrophic failure in the 345 Kv
switchyard. A reactor
scram occurred as a result. The degraded
AC power system prevented a fast transfer from occurring. Degraded bus voltage caused the
emergency diesel generators (
EDGs) to start. A residual bus transfer restored power to the 4 Kv busses. The [main steam isolation valves] (
MSIVs) closed on a low-low reactor water level of 82.5 inches. [Reactor Core Isolation Cooling] and [High Pressure Coolant Injection] (
HPCI) also started on the low-low
reactor vessel water level.
The [Safety Relief Valves] were cycled twice for pressure control. OT 3100 Reactor Scram procedure was executed. EOP-3 was entered due to elevated torus water temperature and both loops of [Residual Heat Removal] (RHR) are in torus cooling. Water level has restored and is being maintained by feedwater. The MSIVs have been reopened and the scram reset. EDGs were secured.
The plant is currently shutdown and stable with all control rods fully inserted. Decay heat removal is being accomplished with HPCI in pressure control mode. The licensee is transitioning to feeding with normal feedwater and steam exhausting through drains. Both trains of RHR are providing torus cooling. Electric power is being provided by offsite power. The licensee is currently investigating the event in the switchyard.
The licensee notified the NRC Resident Inspector and will issue a press release.
- * * UPDATED ON 07/29/05 BY MACKINNON * * *
Corrected incorrect entry for
Scram Code from N (N/A) to A/R (Automatic/with Rod Motion). R1DO (Glenn Meyer) notified.