25 mai 2014
Les réacteurs 2 et 3 se sont arrêtés suite à la perte des alimentations électriques extérieures.
Type : PWR - Puissance n° 2 : 2700 MWth ; n° 3 : 3650 MWth - Première divergence n° 2 : 10/1975 ; n° 3 : 01/1986
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Les circuits électriques d’urgence ont été alimentés par les diesels de secours d’urgence.
Sur le réacteur 3, les manœuvres de mise à l’arrêt sûr ont été compliquées par la perte de l’air de commande des actionneurs. L’acheminement de l’eau de refroidissement n’a pu être assuré suite à la rupture du réservoir de secours du pressuriseur dû à la défaillance d’une soupape : la fuite d’eau de refroidissement s’est évacuée dans le bâtiment des auxiliaires et le débordement aurait été isolé. Les niveaux de radioactivité seraient normaux.
Event Number : 50141 - Facility : MILLSTONE - 1 State : CT - Unit : [3] - RX Type : W-4-LP
Event Date : 05/25/2014 - Event Time : 07:02 [EDT]
Emergency Class : UNUSUAL EVENT 10 CFR Section : 50.72(a) (1) (i) - EMERGENCY DECLARED 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Initial PWR : 100 % Current PWR : 0 %
Event Text
UNUSUAL EVENT DUE TO LOSS OF OFFSITE POWER
At 0702 EDT on 5/25/14, Millstone Units 2 and 3 experienced a loss of offsite power and subsequent trip of both units. An Unusual Event was declared by Millstone Units 2 and 3 at 0715 EDT.
Power is currently being supplied to all emergency busses by the emergency diesel generators. Offsite power is not available.
At this time, it appears that the loss of offsite power is due to a localized issue in the Millstone switchyard. The surrounding areas were not affected.
A decision was made to take the NRC to monitoring mode at 0749 EDT with Region 1 in the lead.
Notified DHS SWO, FEMA Ops Center, NICC Watch Officer, DOE Ops Center, USDA Ops Center, HHS Ops Center, and Nuclear SSA via email.
* * * UPDATE [...] AT 1330 EDT * * *
"The loss of offsite power was due to one main line coming into the plant shorting to ground. Emergency plan procedures have been implemented, natural circulation has been established, and the plant is stable. Offsite electrical power has been restored to both Unit 2 and Unit 3. Emergency diesel generators have been secured, and plant equipment has been restored to a normal line up.
"Extended loss of instrument air following the loss of offsite power complicated the recovery actions. The normal reactor coolant system letdown flow path was not able to be established. This resulted in the rupture of the pressurizer relief tank rupture disk inside containment. The relief valve on the volume control tank lifted when restoring normal letdown. This caused the primary drains transfer tank to overflow into the auxiliary building. This overflow path has been isolated. Supplementary leakage collection system radiation monitor HVR-RE19B, and auxiliary building normal ventilation radiation monitor HVR-RE10B, are indicating normal levels."
* * * UPDATE [...] AT 1548 EDT * * *
At 1414 EDT the licensee terminated the Unusual Event.
50142 Facility : MILLSTONE - 1 State : CT - Unit : [2] - RX Type : [2] CE -
Event Date : 05/25/2014 - Event Time : 07:02
Emergency Class : UNUSUAL EVENT 10 CFR Section : 50.72(a) (1) (i) - EMERGENCY DECLARED 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION 50.72(b)(3)(xiii) - LOSS COMM/ASMT/RESPONSE
Initial PWR : 100 % Current PWR : 0 %
Event Text
UNUSUAL EVENT DUE TO LOSS OF OFFSITE POWER
At 0702 EDT on 5/25/14, Millstone Units 2 and 3 experienced a loss of offsite power and subsequent trip of both units. An Unusual Event was declared by Millstone Units 2 and 3 at 0715 EDT.
Power is currently being supplied to all emergency busses by the emergency diesel generators. Offsite power is not available.
At this time, it appears that the loss of offsite power is due to a localized issue in the Millstone switchyard. The surrounding areas were not affected.
A decision was made to take the NRC to monitoring mode at 0749 EDT with Region 1 in the lead.
Notified DHS SWO, FEMA Ops Center, NICC Watch Officer, DOE Ops Center, USDA Ops Center, HHS Ops Center, and Nuclear SSA via email.
* * * UPDATE [...] AT 1330 EDT ON 5/25/14 * * *
All EDGs have been secured and offsite power has been restored.
The licensee is reporting the loss of two stack radiation monitors - 8168 and 8169. This is reportable under 10CFR50.72(b)(3)(xiii).
Notified R1DO (Gray), R1DRA (Lew), NRR EO (Kokajko), IRD MOC (Grant).
* * * UPDATE [...] AT 1548 EDT * * *
At 1414 EDT the licensee terminated the Unusual Event.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140527en.html#en50142
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