25 septembre 2014
Les relais incriminés avaient dépassé le nombre d’heures acceptables pour des relais alimentés électriquement en permanence. Deux vannes d’isolement primaire pour divers chemins de circulation sont concernées par le problème. La déclaration est faite suite à la défaillance d’éléments nécessaires à contrôler le relâchement de radioactivité dans l’environnement et à atténuer les conséquences d’un accident.
Type : Fukushima I (BWR MARK I) - Puissance : 1 775 MWth - Première divergence : 12/1970
Available in english only.
De plus les actions requises nécessitent la fermeture manuelle de six chemins de flux. Cette fermeture a pour effet de rendre inopérant les analyseurs d’hydrogène / oxygène pour deux voies et constitue une perte de protections civile suite à l’urgence ainsi qu’une perte de capacité dévaluation sur un accident. La position des vannes a été remise en position fermée. Les relais montés il y a 19 ans, auraient fonctionné 11 ans pour une durée de vie maximum de 10 ans.
Event Number : 50496
Facility : MONTICELLO - State : MN
Unit : [1] - RX Type : [1] GE-3
Event Date : 09/25/2014 - Event Time : 22:00
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(v)(C) - POT UNCNTRL RAD REL 50.72(b)(3)(v)(D) - ACCIDENT MITIGATION 50.72(b)(3)(xiii) - LOSS COMM/ASMT/RESPONSE
Initial PWR : 69 % - Current PWR : 69 % -
Event Text
CONTAINMENT ISOLATION DECLARED INOPERABLE DUE TO RELAY AGE
"At 2200 CDT on September 25, 2014, the Duty Shift Manager was notified that Agastat relays associated with Primary Containment Isolation valves on the Hydrogen-Oxygen Analyzing System are beyond the analyzed shelf life for relays that are in the normally energized state and are considered INOPERABLE. This affected both primary containment isolation valves for a containment penetration on multiple flow paths. This issue was determined to be reportable under [10 CFR] 50.72 (b)(3)(v)(C) & (D) for an event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material and mitigate the consequences of an accident.
"Additionally, the required actions involved isolating six flow paths via manual isolation valves. This action rendered the Hydrogen-Oxygen Analyzers non-functional for both trains and constitutes a loss of Emergency Preparedness and Accident Assessment Capability. This is reportable under [10 CFR] 50. 72(b)(3)(xiii).
"The Primary Containment Isolation Valves have been, and remain, in their closed position to satisfy their Primary Containment Function and protect the health and safety of the public.
"The NRC Senior Resident Inspector has been notified."
The licensee will notify the state on Minnesota.
The relays of concern were manufactured 19 years ago and have been in operation for 11 years, versus a manufacturer assumption of a 10 year operational lifespan.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140926en.html#en50496
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