6 mars 2013
Perte de refroidissement à l’arrêt sur le réacteur n° 1 pendant une minute et 30 secondes. Il n’y a pas d’explication au fait que la vanne d’injection se soit fermée. Durant le problème, le refroidissement a continué via la piscine de combustible.
Première divergence : décembre 1970 - Puissance nette : 572 MW - BWR Mark I -
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Event Number : 48809
Facility : MONTICELLO - State : MN
Unit : [1] - RX Type : [1] GE-3
Event Date : 03/06/2013 - Event Time : 04:01
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(v)(B) - POT RHR INOP
Initial PWR 0% Current PWR 0%
Event Text
MOMENTARY LOSS OF SHUTDOWN COOLING
"At 0401 CST on 3/6/2013, while in RHR-High [Residual Heat Removal-High] water level the plant experienced a momentary Loss of Shutdown Cooling which resulted in a loss of safety function for Residual Heat Capability. Division 2 RHR shutdown cooling was restored within approximately 90 seconds without issue. No changes were experienced in refuel volume temperature or level during the loss of RHR shutdown cooling. This occurred shortly after a flow adjustment on the system was made utilizing the outboard valve. The inboard valve was reopened and an investigation is in progress. At the time of the valve closure, decay heat removal continued from Reactor Water Cleanup in heat reject mode and fuel pool cooling (with the fuel pool gates removed) is in service. Division 1 RHR (Shutdown Cooling) was available (not Operable) at the time of the loss. It is not currently understood why the injection valve closed. All systems functioned as required except for the spurious closing of MO-2015 (the Div 2 RHR inboard injection valve). The following make-up sources are available : Divisions 1 and 2 RHR, Divisions 1 and 2 Core Spray, CRD [Control Rod Drive], CST [Condensate Storage Tank] via a Core Spray with pressurizing station bypassed."
The licensee notified the NRC Resident Inspector.
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