22 mai 2015
Cet arrêt d’urgence est intervenu alors que le réacteur était en cours de démarrage avec le coeur critique. La cause de la perte de vide au condenseur est en cours de recherche. Tous les systèmes d’arrêt ont fonctionné correctement. Les opérateurs ont anticipé l’arrêt d’urgence automatique avant déclenchement des alarmes suite à leur découverte de la baisse de presion au condenseur.
Type : Fukushima 1 (BWR Mark I ) - Puissance : 2 028 MWth - Première divergence : 06 / 1972 -
Available in english only
Event Number : 51087
Facility : PILGRIM
Region : 1 State : MA Unit : [1] - RX Type : [1] GE-3
Event Date : 05/22/2015 - Event Time : 10:02
Last Update Date : 05/24/2015 Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
Initial PWR : 3 % - Current PWR : 0 % -
Event Text
MANUAL REACTOR SCRAM DUE TO LOSS OF CONDENSER VACUUM
"On Friday, May 22, 2015 at 1002 EDT, with the Reactor Mode Select Switch in the Start-Up position and the reactor at approximately 3 percent core thermal power, while returning to power from Refueling Outage Number 20, a manual reactor scram was inserted due to degrading main condenser vacuum. The cause of the degraded vacuum is currently under investigation.
"Following the reactor scram, all rods were verified to be fully inserted and no Emergency Operating Procedure entry conditions existed.
"All plant systems responded as designed.
"Currently reactor pressure is being maintained at 400 psig with the Mechanical Hydraulic Control System (turbine by-pass valves). Reactor water level is being maintained in normal bands with the Condensate and Feedwater System. Off-site power is being supplied to the station by the Startup Transformer (normal power supply for shutdown operations).
"This event had no impact on the health and/or safety of the public. The NRC Resident Inspector is on-site and has been notified.
"The licensee has notified the Massachusetts Emergency Management Agency."
The licensee will be issuing a press release.
* * * UPDATE FROM EVERETT PERKINS TO DONALD NORWOOD AT 1110 EDT ON 5/24/2015 * * *
The following was provided by the licensee as clarifying information to the first paragraph of the original event notification :
"As a conservative measure, the operating crew had previously started reducing power from 20 percent core thermal power when it was first noticed that main condenser vacuum was degrading. This was well before any low condenser vacuum alarms were received.
"During the shutdown, after already securing the main turbine, the operating crew established benchmark values for degrading condenser vacuum for a normal plant shutdown and for a manual reactor scram should vacuum continue to decline to preclude an automatic scram."
The licensee notified the NRC Resident Inspector.
Notified R1DO (Dwyer).
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2015/20150526en.html#en51087
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