9 décembre 2013
Le 9 décembre 2013, le transformateur auxiliaire du réacteur n° 2 a pris feu et explosé. Les pompes principales de refroidissement et de circulation ne sont plus alimentées ! Le refroidissement du cœur s’effectue uniquement par convection naturelle. L’injection d’eau en situation d’urgence a été enclenchée suite à un niveau trop faible dans les générateurs de vapeur. Le cœur étant critique, les systèmes de protection du réacteur se seraient enclenchés et pourtant il n’y a aucune indication assurant que les barres de contrôles se seraient correctement insérées dans le cœur.
L’URGENCE A ETE DECLAREE
Type : PWR - Puissance : 3 026 MWTh - Première divergence : 12/1978
Available in english only.
Le réacteur est alimenté par un groupe électrogène et la vapeur est relâchée à l’atmosphère.
Le réacteur 1 pour sa part fonctionne à 98% de sa puissance avec la perte de l’alimentation électrique extérieure suite à la destruction du transformateur du réacteur n° 2.
L’incendie a été circonscrit en 1 h 29.
Des récupérateurs d’huile ont été mis en place suite à la découverte de contamination à la surface de l’eau.
L’urgence a été déclarée.
Le réacteur a été redémarré le 12 janvier et a atteint sa pleine puissance le 13 janvier 2014 (a) soit un mois après la survenue de l’accident.
Event Number : 49618
Facility : ARKANSAS NUCLEAR - State : AR - Unit : [2] RX Type : [1] B&W-L-LP,[2] CE -
Event Date : 12/09/2013 - Event Time : 08:00
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)(2)(xi) - OFFSITE NOTIFICATION 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Initial PWR ; 100 % - Current PWR 0 %
Event Text
UNUSUAL EVENT DECLARED DUE TO UNIT 2 AUXILIARY TRANSFORMER EXPLOSION
"At approximately 0748 [CST] on 12/9/2013, an electrical fault occurred resulting in a fire and explosion on the ANO [Arkansas Nuclear One] Unit 2 Unit Auxiliary Transformer. This caused a unit trip and a loss of power to Startup 3 Transformer, which is one of the two offsite power feeds to ANO Unit 2. ANO Unit 2 is currently in a stable shutdown condition. With Startup 3 and Unit Aux Transformer unavailable, power was lost to the Reactor Coolant Pumps and Circulating Water Pumps. RCS [Reactor Coolant System] natural circulation is in progress removing core decay heat. Emergency Feedwater actuated due to low steam generator levels and is supplying both steam generators. The unit is steaming to the atmosphere. 2A-1 and 2A-3 are powered from SU [Startup] 2 Transformer. 2A-4 is powered from 2K-4B Emergency Diesel Generator.
"ANO Unit 1 is currently operating at 98% power. The auto transformer tripped off line with the fault in ANO Unit 2 Unit Auxiliary Transformer. This has caused Startup Transformer 1 to be inoperable. This places ANO Unit 1 in a 72 hour Technical Specification action statement (T.S 3.6.1 for Loss of the SU-1 Transformer).
"No significant injuries were reported as a result of this condition and offsite agencies have been notified.
"At 0800 on 12/9/2013 Unit 2 declared a Notification of Unusual Event based on EAL HU4 Fire or Explosion inside Protected Area not extinguished in 15 minutes.
"At 0917 on 12/9/2013, the fire on Unit 2 Unit Auxiliary Transformer is OUT."
The Licensee notified the NRC Resident Inspector.
Notified DHS SWO, DOE Ops Center, FEMA Ops Center, HHS Ops Center, NICC Watch Officer, USDA Ops Center, EPA EOC, and Nuclear SSA vial email.
* * * UPDATE FROM DAN BREEDLOVE TO VINCE KLCO AT 1336 EST ON 12/9/2013 * * *
At 1215 CST, ANO terminated from the Unusual Event as per HU4 stable plant conditions.
ANO Unit 2 is stable and will be cooled down to Mode 5 via natural circulation and decay heat is being removed via emergency feedwater and downstream dump valves to atmosphere. There is no radiological release and no personnel injuries.
The licensee has notified the NRC Resident Inspector, Arkansas Department of Emergency Management, Arkansas Department of Health, and other local authorities.
Notified R4DO (Vasquez), NRR EO (King) and IRC MOC (Morris).
Notified DHS SWO, DOE Ops Center, FEMA Ops Center, HHS Ops Center, NICC Watch Officer, USDA Ops Center, EPA EOC, and Nuclear SSA vial email.
* * * UPDATE FROM ALBERT MARTIN TO VINCE KLCO AT 1812 EST ON 12/9/2013 * * *
"Outside agencies (National Response Center, Arkansas Department of Emergency Management, Corps of Engineers, and U.S. Coast Guard) were contacted due to a minor unknown amount of oil that entered the plant discharge to Lake Dardanelle. The oil was from the faulted Unit 2 Unit Auxiliary Transformer. The majority of oil was contained within the containment around the transformer or the oily water separator it drains to. Local inspection revealed only a small amount of what was released actually passed the containment booms that are continuously in place on the discharge canal. The oil boom was verified to be in good condition. The oil was verified to be mineral oil. The release was verified to be terminated. An additional oil boom was deployed. Reference [ANO] Condition Report CR-ANO-C-2013-03071."
The licensee notified the NRC Resident Inspector.
Notified the R4DO (Werner)
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2013/20131210en.html
POUR EN SAVOIR PLUS :
https://couriernews.com/view/full_story/24190351/article-Fire-reported-at-Arkansas-Nuclear-One
https://www.rivervalleyleader.com/gallery/collection_1dfae6aa-6165-11e3-838e-001a4bcf6878.html
(a) https://www.nrc.gov/reading-rm/doc-collections/event-status/reactor-status/2013/20131210ps.html
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