23 juin 2014
Ce défaut a enclenché le diesel de secours d’urgence D1. Le bus a retrouvé sa tension suite à la fermeture automatique du disjoncteur par l’alimentation depuis le diesel. Une défaillance d’un transformateur est à l’origine de la perte de courant issue de l’alimentation extérieure au site. La voie d’alimentation extérieure normale a été rétablie et le diesel éteint.
Type : PWR - Puissance : 1 677 MWth - Première divergence : 12/1973
Available in english only.
Event Number : 50221
Facility : PRAIRIE ISLAND - State : MN
Unit : [1] - RX Type : [1] W-2-
Event Date : 06/23/2014 - Event Time : 11:07
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Initial PWR : 100 % Current PWR : 100 %
Event Text
EMERGENCY DIESEL GENERATOR AUTO START DUE TO DEGRADED BUS VOLTAGE SIGNAL
"At 1107 [CDT] on 6/23/14, Safeguards Bus 15 received a degraded voltage signal that resulted in the bus load shed and the automatic start of the D1 Emergency Diesel Generator (EDG). Bus 15 re-energized to normal voltage after the source breaker from D1 [EDG] automatically closed. This event is reportable under 10 CFR 50.72(b)(3)(iv)(A) for valid actuation of the D1 EDG.
"The initiating condition appears to be a failure of the automatic voltage tap changer on the 10-Bank transformer which affected voltage to the normal offsite power supply to the 1R transformer and Safeguards Bus 15.
"Currently Bus 15 is powered from offsite via the CT-11 transformer and D1 [EDG] has been shutdown.
"When Bus 15 power supply was transferred from D1 [EDG] to CT-11 transformer, a lockout was received on D1 [EDG] due to reverse power. Unit 1 is in TS [Technical Specification] 3.8.1 Condition D for one path inoperable and one EDG inoperable.
"At no time during the event were the health and safety of the public challenged. The redundant AC power supply train (Bus 16 and D2 EDG) remained operable and Bus 16 remained powered from offsite power.
"The Senior Resident Inspector has been notified."
TS 3.8.1 Condition D requires that the one inoperable offsite power path or the D1 EDG be returned to operable status by 2334 CDT or be in Mode 3 in 6 hours. Unit 2 is not affected by this issue.