2 mai 2015
Alors que le réacteur était avec le cœur ouvert et sous eau pour rechargement de combustible, une erreur humaine a fait perdre le 4 kV et le centre de contrôle. Cette perte a entrainé la perte de commande d’une vanne du circuit de refroidissement à l’arrêt. La pompe de refroidissement s’est alors arrêtée suite au verrouillage de son aspiration. LE REACTEUR EST RESTE 3h 16 min SANS REFROIDISSEMENT mais selon la NRC : R.A.S. : en effet, selon elle, la température serait passée de 27 à 33 °C...
Type : Fukushima I (BWR Mark I) - Puissance : MWth - Première divergence : 12/1970
Availble in english only.
Event Number : 51034
Facility : MONTICELLO
State : MN : Unit : [1] - RX Type : [1] GE-3
Event Date : 05/02/2015 - Event Time : 12:47
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(v)(B) - POT RHR INOP
Initial PWR : 0 % - Current PWR : 0 % -
Event Text
LOSS OF SHUTDOWN COOLING DUE TO LOSS OF 4KV BUS
"On 5/2/2015 at 1247 CDT, while the plant was in MODE 5 for a refueling outage with the vessel cavity flooded, during logic testing of the non-credited essential 4kV bus, MNGP [Monticello Nuclear Generating Plant] experienced a human performance error that caused a loss of the 4kV bus and essential load center. Loss of the load center de-energized valve position indication on one shutdown cooling isolation valve. This tripped the shutdown cooling pump on a pump suction interlock, resulting in the loss of shutdown cooling. This is being reported under 10 CFR 50.72(b)(3)(v)(B) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat.
"Following the event, the safety related load centers were cross-tied to allow restoration of shutdown cooling. Shutdown cooling was restored at 1603. While shutdown cooling was out of service, vessel water temperature rose approximately 10�F to 91.1�F, which is within the allowed temperature band.
"This event did not result in the release of any radioactive material and did not challenge the health and safety of the public.
"The NRC Resident Inspector has been notified."
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2015/20150504en.html#en51034
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