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| Entered date | Event description | |
|---|---|---|
| ENS 40406 | 22 December 2003 11:39:00 | At 0827 on 12/22/2003, Comanche Peak Unit Two (2) tripped due to a turbine trip > 50%. The turbine trip was caused by ingestion of a small metallic cover plate into the main generator exciter housing, as witnessed by maintenance personnel. A small fire ensued, which self-extinguished in five (5) minutes. An Aux Feedwater auto start (ESF actuation) occurred due to normal post-trip steam generator shrink. The turbine-driven and both motor-driven aux feedwater pumps started as designed. All control rods inserted into the core upon trip. The local electrical grid is stable. The number one (1) steam generator atmospheric relief valve cycled as designed upon the secondary pressure transient. The number three (3) Reactor Coolant Pump tripped during the transfer of power sources post-trip. Unit 1 was not affected by the trip. Unit 2 is stable in Mode 3. Damage assessment is in progress which will determine future (near-term) plant mode of operation. RCPs are in operation transferring decay heat to the steam generators. Decay heat removal is through the MSIVs to the main condenser using the turbine steam dump valves. Both motor-driven AFW pumps are running to maintain Steam Generator levels. The trip of the number (3) Reactor Coolant Pump is being investigated. The licensee notified the NRC Resident Inspector. |