24 mars 2020
Le 24 mars, avec le réacteur n°1 à 0% et le n°2 à 100 %, le bus électrique du poste sud de la centrale a été mis hors tension. De fait le transformateur de secours n° 2 qui alimentait en 4 160 v les dispositifs de sécurité élaborés a été perdu. Les diesels de secours ont alors démarré automatiquement. C’est lors d’un test qu’une erreur dans les relais a été commise.
Type : PWR - Puissance : 3 853 MWTh - Première divergence : n° 1 : 03/1988 - n° 2 : 03/1989
Available in english only.
Event Number : 54605
Facility : SOUTH TEXAS - State : TX
Unit : [1] [2] - RX Type : [1] W-4-LP,[2] W-4-LP
Event Date : 03/24/2020 - Event Time : 10:46 [CDT]
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Initial PWR : n°1 0 % - n°2 100 % Current PWR : n°1 0 % - n°2 100 %
Event Text
SPECIFIED SYSTEM ACTUATION - AUTO START EMERGENCY DIESEL GENERATORS
"At 1046 CDT on 3/24/2020, with Unit 1 defueled and Unit 2 in Mode 1 at 100 percent power, the South Texas Project (STP) South switchyard electrical bus was deenergized. This resulted in a loss of power to Standby Transformer 2 which was supplying power to the Engineered Safety Features (ESF) 4160v busses for Unit 1 A- and C-Trains, and Unit 2 B-Train. Emergency Diesel Generators (EDGs) 11, 13, and 22 automatically started in response to the undervoltage condition.
"The cause for the loss of the South switchyard electrical bus was an error in relay testing in the switchyard.
"This event is reportable under 10 CFR 50.72(b)(3)(iv)(A) as an event that resulted in the valid actuation of emergency AC electrical power systems (50.72(b)(3)(iv)(B)(8)) as well as the Unit 1 A- and C-Train and Unit 2 B-Train Reactor Containment Fan Coolers (50.72(b)(3)(iv)(B)(7)) and Unit 2 B-Train Auxiliary Feedwater pump (50.72(b)(3)(iv)(B)(6)).
"There was no impact on the health and safety of the public or plant personnel.
"The NRC Resident Inspector has been notified."
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2020/20200325en.html