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Etats-Unis : Hatch : Arrêt d’urgence du réacteur n°2 suite à la dégradation du vide au condenseur




24 mars 2019


Cette dégradation est survenue alors que le réacteur était à 25 % de sa puissance nominale. Les opérateurs ont alors lancé la procédure d’arrêt. Lors de cet arrêt, le système de protection du cœur (RPS) s’est enclenché suite à la baisse du vide au condenseur. Le problème n’aurait eu aucun impact.

Type : Fukushima I (BWR Mark1) - Puissance : 2 804 MWth - Première divergence : n° 2 : 07/1978

Available in english only


Event Number : 53953

Facility : HATCH - State : GA

Unit : [2] - RX Type : [2] GE-4

Event Date : 03/24/2019 - Event Time : 01:59 [EDT]

Emergency Class : NON EMERGENCY
10 CFR Section :
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION

Initial PWR  : 25 %
Current PWR  : 0 %

Event Text

MANUAL REACTOR SCRAM DUE TO DEGRADING CONDENSER VACUUM

"At 0159 [EDT], with Unit 2 in Mode 1 at 25 percent power, the reactor was manually tripped due to degrading condenser vacuum. After the turbine was tripped, the station service electrical buses did not transfer to alternate supply resulting in loss of the condensate feedwater system and level being controlled by the RCIC system.

"Operators responded and stabilized the plant. Reactor water level is being maintained via the RCIC system.

"Pressure is being controlled and decay heat is being removed by the HPCI system in pressure control mode. Unit 1 is not affected.

"Additionally, an actuation of the primary containment isolation system occurred during the reactor scram. The reason for the actuation was a group II isolation signal was received on reactor water level and a group I isolation was received on decreasing vacuum.

"Due to the Reactor Protection System actuation while critical, this event is being reported as a four-hour, non- emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Additionally, this event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the primary containment isolation system.

"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/2019/20190325en.html