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Etats-Unis : Dresden : fuite excessive sur les vannes d’isolement du circuit primaire du réacteur n°2




1er novembre 2017


Ces clapets antiretours servent au confinement, et, en tant que tel, ils sont nécessaires pour assurer le confinement correct du circuit primaire. Suite aux résultats obtenus en essai de fuite locale (Local Leak Rate Testing ou LLRT) les spécifications techniques n’auraient pas été remplies dans le dernier cycle de fonctionnement.

 Type : Fukushima 1 (BWR Mark 1) - Puissance : 2 957 MWth- Première divergence : 1 / 1970 -

Available in english only


Event Number : 53048

Facility : DRESDEN - State : IL

Unit : [2] - RX Type : [2] GE-3

Event Date : 11/01/2017 - Event Time : 12:25 [CDT]

Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(ii)(A) - DEGRADED CONDITION

Initial PWR  : 0 % Current PWR  : 0 %

Event Text

UNIT 2 FAILED LLRT SURVEILLANCE TEST DUE TO EXCESSIVE LEAKAGE

"On November 1, 2017 at 1225 CDT, both the 2-220-58A Feed Water Inboard Check Valve and the 2-220-62A Feed Water Outboard Check Valve failed Local Leak Rate Testing (LLRT) acceptance criteria due to excessive leakage. These valves are considered primary containment isolation valves, and as such, are required to ensure that an adequate primary containment boundary is maintained.

"Technical Specification (TS) 5.5.12, ’Primary Containment Leakage Rate Testing Program,’ establishes limits for Primary Containment leakage. Based upon the results of the LLRT, Dresden, Unit 2, may not have met the limits for primary containment leakage during the last operating cycle as specified in TS 5.5.12.C.

"Dresden Unit 2 is currently in Mode 5 for a refueling outage and per Dresden TS 3.6.1.1, ’Primary Containment,’ Primary Containment is not required in the current mode of operation (i.e., Mode 5). However, in accordance with 10 CFR 50.72(b)(3)(ii)(A), this event is reportable as a condition that resulted in a principal safety barrier being seriously degraded.

"The NRC Resident Inspector has been notified."

https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2017/20171102en.html