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Etats-Unis : Clinton : arrêt du réacteur suite à la perte d’alimentation de nombreux composants




9 décembre 2017


La tombée d’un disjoncteur est à l’origine de cette perte d’alimentation électrique. Parmi les composants qui ont perdu leurs fonctions, on trouve le matériel de confinement, les vannes d’isolement de l’air qui avaient été fermées suite à la perte de puissance. En raison de la perte du confinement, plusieurs barres de contrôle ont commencé à s’insérer dans le coeur. Six minutes après le début du problème, la phase d’arrêt du réacteur a été activée. Toutes les barres de commande ont été complètement insérées.

* * * MISE À JOUR À 1658 EST LE 12/10/2017 * * *

Lors d’examens, il a été constaté que la pression différentielle de confinement primaire / secondaire était en dehors des spécifications techniques. Le respect de ce paramètre vise à garantir que les pressions de confinement primaire restent dans les valeurs limites de conception lors d’un accident de perte de réfrigérant (APRP).

 Type : BWR Mark 3 - Puissance : 3 473 MWth - Première divergence : 01/02/1987 -

Available in english only


Event Number : 53110

Facility : CLINTON - Region : 3 State : IL

Unit : [1] - RX Type : [1] GE-6 -

Event Date : 12/09/2017 - Event Time : 13:48 [CST]

Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(v)(C) - POT UNCNTRL RAD REL 50.72(b)(3)(ii)(B) - UNANALYZED CONDITION

Initial PWR  : 98 % Current PWR  : 0 %

Event Text : MANUAL REACTOR SCRAM DUE TO LOSS OF DIVISION 1 AC POWER TO NUMEROUS COMPONENTS

"At approximately 1347 [CST] on 12/09/17, the Main Control Room received annunciators that indicated a trip of the 4160 V 1A1 breaker 1AP07EJ, 480V XFMR 1A and A1 breaker. Numerous Division 1 components lost power (powered from unit subs 1A and A1). The Division 1 containment Instrument Air isolation valves had failed closed by design due to the loss of power. Due to the loss of containment instrument air, several control rods began to drift into the core as expected and, by procedure, the reactor mode switch was placed in the shutdown position at 1353 [CST]. All control rods fully inserted.

"Also due to the loss of power, the Fuel Building ventilation dampers failed closed by design. With the normal ventilation system secured, secondary containment differential pressure rose to slightly greater than 0 inches water gauge which exceeded the Technical Specification requirement of greater than 0.25 inches vacuum water gauge at 1348 [CST]. The Control Room entered EOP-8, Secondary Containment Control. Secondary Containment differential pressure was restored within Technical Specification requirements at 1351 [CST] by starting the Division 2 Standby Gas Treatment system.

"This event is being reported as a manual actuation of the Reactor Protection System (RPS) and as a Condition that Could Have Prevented Fulfillment of a Safety Function.

"The cause is currently under investigation. The NRC Resident has been notified."

The licensee informed the NRC Resident Inspector.

* * * UPDATE FROM DALE SHELTON TO VINCE KLCO AT 1658 EST ON 12/10/2017 * * *

"During a review of plant logs it was identified that the primary to secondary containment differential pressure was identified to be outside of Technical Specification 3.6.1.4 limits of 0 plus or minus 0.25 psid at 2009 on 12/9/17 due to the primary containment ventilation system dampers closing as a result of the loss of power. This parameter is an initial safety analysis assumption to ensure that primary containment pressures remain within the design values during a Loss of Coolant Accident (LOCA). As a result, this condition is reportable as an unanalyzed condition that significantly degrades plant safety.

https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2017/20171211en.html