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Etats-Unis : Farley : système de filtration radioactive découvert défaillant en cas d’accident




7 mai 2018


Un calcul a été effectué sur un débit de fuite constaté à 0,77 litres par minute. En court-circuitant la vanne le débit est tombé à zéro l/mn. Ce débit de fuite à 0,77 l/mn engagerait un débit de dose supérieur à 50 mSv dans la salle de commande dans des conditions d’accident. Ce débit ne satisfait pas aux prescriptions techniques et le système de filtration ne remplirait donc pas sa fonction.

Type : PWR - Puissance : 2 775 MWTh - Première divergence : 08/1977

Available in english only


Event Number : 53392

Facility : FARLEY - State : AL

Unit : [1] - RX Type : [1] W-3-LP

Event Date : 05/07/2018 Event Time : 00:00 [CDT]

Last Update Date : 05/08/2018

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

Initial PWR  : 0 % Current PWR  : 0 %

Event Text

UNANALYZED CONDITION

"On May 7, 2018 at 1041 CDT, Unit 1 performed an RCS (reactor coolant system) leakrate procedure that calculated an unidentified RCS leakrate of 0.202 gpm. The leak source investigation concluded at 2150 that the packing for the charging flow control valve (FCV) was the source of the RCS leakage when it was bypassed, which isolated the leakage. A second RCS leakrate calculation was performed after the charging flow control valve was isolated which calculated an acceptable leakrate of 0.00 gpm.

"The packing leakage from the charging flow control valve represented leakage external to containment which would result in a greater that 5 Rem dose projection to control room personnel during accident conditions which does not satisfy the GDC19 criteria described in Technical Specification Bases 3.7.10. Therefore the control room emergency filtration system would not be able to fulfill its design function resulting in an unanalyzed condition.

"This condition is being reported pursuant to 10CFR50.72(b)(3)(ii) for a ’condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety’.

"The packing leak from the charging flow control valve will remain isolated until repaired under work order SNC944374."

The NRC Resident Inspector has been notified.

https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2018/20180508en.html