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| Entered date | Event description | |
|---|---|---|
| ENS 46863 | 19 May 2011 17:00:00 | At 1407 CDT CPNPP (Comanche Peak Nuclear Power Plant) Unit-2 was manually tripped due to indication of a main condenser tube failure. The trip was uncomplicated, all control and shutdown banks fully inserted, neither emergency diesel generator started, all safety systems functioned as designed. Both motor driven and the turbine driven AFW (auxiliary feedwater) pumps started as required to restore steam generator level as a result of the trip. The turbine driven AFW pumps has been returned to auto start status. Currently Unit-2 is in mode 3, no-load Tave 557 degrees F with temperature being maintained with AFW and steam dumps to the main condenser. Recovery actions are currently being planned. All electrical busses are powered from offsite power and grid conditions are stable. The reactor was manually tripped because of rising sodium concentration in the main condenser/feedwater. The licensee notified the NRC Resident Inspector, State of Texas, and local government. |
| ENS 45833 | 12 April 2010 10:00:00 | At 0721 (CDT) on 4/12/10 the Comanche Peak Nuclear Power Plant experienced a loss of 138 KV transformer XST1 due to a failed transmission line insulator. Unit 1 is currently defueled per 1RF14 refueling outage schedule. Unit 2 was subjected to actuation of both blackout sequencers causing an automatic start of both motor driven Aux Feedwater (AFW) pumps as well as the turbine driven AFW pump. No emergency diesel generator started as per design. Train B and the turbine driven AFW pumps have been returned to automatic. Train A AFW pump has been removed from service due to damaged pump packing. Unit 2 is currently operating in Technical Specification (TS) 3.8.1, Condition A, for one required source of offsite power inoperable and in TS 3.7.5, Condition B, for one train of AFW inoperable. With the exception of Train A AFW on Unit 2, all other safety systems functioned per design. The licensee has notified the NRC Resident Inspector. The loss of power to 138 KV transformer XST1 resulted in loss of power to both safeguards busses on Unit 2. The busses performed a load-shed and slow transfer to power supplied from 138 KV transformer XST2 as designed and were re-energized and loads sequenced back onto the busses. The emergency diesel generators are not required to start unless the busses are not re-energized by the alternate offsite transformer. All electrical power related actuations functioned as designed. During this event, the A train AFW pump on Unit 2 started as expected but had to be removed from service due to a pump packing leak. There was no impact on Unit 1 because of its defueled condition.
The faulted 138 KV (line) insulator has been repaired, and the Unit 2 safeguard busses have been transferred back to their normal power supplies. The 2-01 motor driven AFW pump has been successfully surveillance tested and is available. Unit 2 remains in TS 3.7.5 condition B pending the close out of an engineering evaluation. No further update notifications are planned. The licensee has informed the NRC Resident Inspector. Notified R4DO (Spitzberg). |
| ENS 44067 | 16 March 2008 14:12:00 | At 1137 CDT, Comanche Peak NPP, Unit 2 reactor tripped due to a broken sensing line feeding the vacuum inputs to the 2/3 low vacuum turbine trip. With the reactor power steady at 100%, the turbine trip signal generated a valid RPS reactor trip signal. All control rods fully inserted. Both motor driven AFW pumps and the turbine driven AFW pump started as a result of low steam generator level following the trip. Currently Unit 2 is in Mode 3, stable with RCS temperature at no-load program temperature of 557 degree F being maintained on the steam dumps. All 4 steam generators are at program level, being maintained by the motor driven AFW pumps. The turbine driven AFW pump has been returned to standby. The licensee notified the NRC Resident Inspector. |