3 avril 2015
Un niveau trop bas d’eau dans les générateurs de vapeur a été réglé par la mise en route des pompes auxiliaires. L’arrêt s’est effectué correctement selon l’organisme de contrôle (NRC), avec l’insertion correcte des barres de contrôle. L’évacuation de la chaleur s’est effectuée par le condenseur. C’est le microrupteur de détection de dépression de la pompe principale qui est à l’origine du problème.
Type : PWR - Puissance : 1 677 MWTh - Première divergence : 12/1974
Available in english only.
Event Number : 50950
Facility : PRAIRIE ISLAND - State : MN
Unit : [2]
RX Type : [2] W-2-LP
Event Date : 04/03/2015 - Event Time : 06:52 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 : 0 % Current PWR : 100 %
Event Text
MANUAL REACTOR SCRAM DUE TO LOSS OF MAIN FEEDWATER PUMP
"On April 3, 2015 at 0652 CDT, the Unit 2 reactor was manually tripped while operating at 100 percent power due to a lockout trip of 21 Main Feedwater Pump as required by the annunciator response procedure for the lockout alarm. This also resulted in a turbine trip. The crew entered the reactor trip emergency operating procedures and stabilized the unit in Mode 3 at normal operating pressure and temperature. All control rods fully inserted into the core following the trip. The manual trip is reportable per 10 CFR 50.72(b)(2)(iv)(B). The Auxiliary Feedwater System actuated to start the auxiliary feedwater pumps as designed on low narrow range steam generator level and provided makeup flow to the steam generators. The auxiliary feedwater actuation is reportable per 10 CFR 50.72(b)(3)(iv)(A). Steam generator levels have been returned to normal. The auxiliary feedwater pumps have subsequently been secured and returned to automatic. Steam generators are being supplied by 22 Main Feedwater Pump and decay heat is being removed by the condenser steam dump system.
"The cause of 21 Main Feedwater Pump trip has been determined to be a failed suction pressure switch.
"There was no effect on Unit 1 as a result of this trip. The health and safety of the public and site personnel were not at risk at any time during this event.
"The NRC Senior Resident Inspector has been notified."
The licensee plans to issue a press release.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2015/20150406en.html#en50950