10 juillet 2013
Lors de l’entretien des isolateurs - matériels qui supportent les conducteurs de la ligne 500 000 volts - un amorçage à la terre a fait disjoncter un relais qui a lui-même entrainé l’arrêt de la turbine. Cette turbine tournait à pleine puissance. Des disjoncteurs se sont également ouverts. Le cœur étant critique, les systèmes de protection du réacteur se sont enclenchés. Les opérations d’arrêt du réacteur se seraient correctement effectuées.
1ère divergence : août 1985 - type : PWR - P : 1 118 MWe
Available in english only.
Facility : DIABLO CANYON - State : CA - Unit : [2] - RX Type : [2] W-4-LP
Event Date : 07/10/2013 - Event Time : 09:50 -
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL50.72(b)(2)(xi) - OFFSITE NOTIFICATION 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Initial Power : 100% Current PWR : 0 %
Event Text
UNIT 2 AUTOMATIC REACTOR TRIP
"On July 10, 2013, at 0950 PDT, the Diablo Canyon Power Plant Unit 2 500kV line differential relay actuated. This action tripped the turbine and opened the generator output breakers to isolate the generator. 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. All three Unit 2 Auxiliary Feedwater pumps started, the Containment Fan Cooling units started and ran in slow speed, and the standby Auxiliary Saltwater train started, all as expected.
"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 preliminary cause of the differential relay actuation was a flashover of Phase A 500 kV to ground across the Phase A lightning arrestor during maintenance activities to wash the 500 kV insulators.
"NRC Resident Inspector has been informed of this event.
"A press release is planned for local media."
Decay heat is being removed by steam dumps to the condenser. No relief valves lifted during the transient. The steam generators are being supplied by the auxiliary feedwater pumps. There were no injuries to personnel. Unit 1 was not affected.
Event Number : 49184
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2013/20130711en.html#en49184
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