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On October 11, 2012, at 1208 PDT, the Diab … On October 11, 2012, at 1208 PDT, the Diablo Canyon Power Plant Unit 2 500kV line differential relay actuated, resulting in a unit trip. The unit trip actuated the turbine trip. With the turbine tripped and Unit 2 operating above the P-9 50% power permissive, a reactor trip was initiated from the reactor protection system. All plant equipment responded as designed.</br>Unit 2 is stable at normal operating temperature and pressure. All power transferred to the plant startup source without incident. Condenser vacuum was maintained. The cause of the differential relay actuation is under investigation. Based on personnel observation it appears to have been initiated due to a flashover to ground across the phase 'A' main bank transformer capacitive coupled voltage transformer.</br>PG&E will issue a press release regarding the Unit 2 trip. </br>NRC Resident Inspectors have been informed of this event.</br>* * * UPDATE FROM DAN STERMER TO DONG PARK AT 2259 EDT ON 10/11/12 * * * </br>This update to clarify the status of the auxiliary feedwater system during the above noted transient. Both motor driven pumps and the steam driven pump automatically started as expected.</br>In addition, on October 11, 2012, at 12:26 PDT, the Diablo Canyon Power Plant Unit 2 turbine driven auxiliary feedwater pump was secured by plant operators manually closing the steam supply valve to the pump turbine. This action was performed in accordance with plant operating procedures after the operators had verified that the indicated steam generator levels were greater than the procedural requirement of 16%. However, because the steam generator low level bistables associated with the auxiliary feedwater actuation circuits had not yet cleared, the emergency safeguards actuation signal drove the steam supply valve back open, restarting the turbine driven auxiliary feedwater pump.</br>Operators increased steam generator levels to clear the bistables and successfully reclosed the steam supply valve.</br>The NRC Resident Inspector has been informed of this event.</br>Notified R4DO (Hagar).informed of this event.
Notified R4DO (Hagar).
19:08:00, 11 October 2012 +
18:44:00, 11 October 2012 +
19:08:00, 11 October 2012 +
On October 11, 2012, at 1208 PDT, the Diab … On October 11, 2012, at 1208 PDT, the Diablo Canyon Power Plant Unit 2 500kV line differential relay actuated, resulting in a unit trip. The unit trip actuated the turbine trip. With the turbine tripped and Unit 2 operating above the P-9 50% power permissive, a reactor trip was initiated from the reactor protection system. All plant equipment responded as designed.</br>Unit 2 is stable at normal operating temperature and pressure. All power transferred to the plant startup source without incident. Condenser vacuum was maintained. The cause of the differential relay actuation is under investigation. Based on personnel observation it appears to have been initiated due to a flashover to ground across the phase 'A' main bank transformer capacitive coupled voltage transformer.</br>PG&E will issue a press release regarding the Unit 2 trip. </br>NRC Resident Inspectors have been informed of this event.</br>* * * UPDATE FROM DAN STERMER TO DONG PARK AT 2259 EDT ON 10/11/12 * * * </br>This update to clarify the status of the auxiliary feedwater system during the above noted transient. Both motor driven pumps and the steam driven pump automatically started as expected.</br>In addition, on October 11, 2012, at 12:26 PDT, the Diablo Canyon Power Plant Unit 2 turbine driven auxiliary feedwater pump was secured by plant operators manually closing the steam supply valve to the pump turbine. This action was performed in accordance with plant operating procedures after the operators had verified that the indicated steam generator levels were greater than the procedural requirement of 16%. However, because the steam generator low level bistables associated with the auxiliary feedwater actuation circuits had not yet cleared, the emergency safeguards actuation signal drove the steam supply valve back open, restarting the turbine driven auxiliary feedwater pump.</br>Operators increased steam generator levels to clear the bistables and successfully reclosed the steam supply valve.</br>The NRC Resident Inspector has been informed of this event.</br>Notified R4DO (Hagar).informed of this event.
Notified R4DO (Hagar).
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