1er juin 2015
Le transitoire est intervenu suite à la perte d’une pompe d’alimentation en eau suivie d’un l’arrêt automatique d’urgence suivi lui-même de la perte d’une seconde pompe d’alimentation en eau. Le niveau d’eau a été rétabli correctement suite au démarrage d’une troisième pompe. Un problème sur le contrôle de niveau d’eau principal a été découvert suite au mauvais positionnement d’un interrupteur par un opérateur. Durant le transitoire, le signal d’une vanne de contrôle du circuit de vapeur n’a pas été reçu correctement. La pression du réacteur a été rétablie dans sa plage normale de fonctionnement avec contournement de la vapeur des turbines vers les soupapes. L’origine du transitoire est en cours de recherche.
Type : BWR Mark 3 - Puissance : 3 091 MWth - Première divergence : 10/1985
Available in english only.
Event Number : 51112
Facility : RIVER BEND - State : LA
Unit : [1] - RX Type : [1] GE-6
Event Date : 06/01/2015 - Event Time : 21:11
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 : 90 % Current PWR : 0 %
Event Text
REACTOR SCRAM DUE TO LOW REACTOR WATER LEVEL
"At 2111 [CDT] River Bend Nuclear Station sustained an Automatic Reactor Scram due to low Reactor Water Level (Level 3). The plant is currently stable, with level being maintained in a normal band of 10 - 51 inches with Condensate and Feedwater. Reactor Pressure is in the prescribed band of 500-1090 psig. The plant is in Mode 3, Hot Shutdown, and will remain in Mode 3 until investigation of the scram is complete. The transient began with a trip of Reactor Feed Pump ’A’, followed by a Reactor Scram and a trip of Reactor Feed Pump ’C’. Reactor water level was recovered with Reactor Feed Pump ’B’ to a normal post scram level band. There was a problem noted with the Reactor Feedwater Master Level Controller ; this was mitigated by the Operator placing the controller to manual. There was no subsequent Level transient. Reactor Pressure was stabilized in normal pressure band with Turbine bypass valves. During the transient, a Reactor Recirculating Flow Control Valve Runback was not received as expected. Reactor Recirculating Pump ’A’ responded as expected to transient [switching to low pump speed], Reactor Recirculating Pump ’B’ tripped during transient. A Level 3 isolation signal was received, all expected isolations occurred.
"The cause of the transient is currently under investigation."
The reactor is stable in Mode 3 with decay heat being removed via turbine bypass valves, and a normal electrical line up.
The NRC Resident Inspector has been notified.
* * * UPDATE FROM JACK MCCOY TO HOWIE CROUCH AT 0712 EDT ON 6/2/15 * * *
"At 2231 on 6/1/15, Reactor Water Cleanup System isolated on High Reactor Water Cleanup System Heat Exchanger room temperature due to loss of Turbine Building chill water during the initial transient. All Reactor Water Cleanup System Valves isolated as expected. Reactor Water Cleanup was the only system affected by this isolation signal."
The licensee has notified the NRC Resident Inspector.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2015/20150603en.html#en51112
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