Réseau Sortir du nucléaire
BoutiqueAgendaFaire un donEN

Des accidents nucléaires partout

Image / illustration
Etats-Unis : Fermi : Perte des soupapes de sécurité de secours de décharge




2 octobre 2015


Les techniciens de maintenance ont découvert que 75 % des boulons n’étaient pas serrés correctement sur cette soupape de sécurité qui sert à l’arrêt du réacteur à distance. Les qualifications sismiques étaient impactées par ce problème.

Type : Fukushima I (BWR Mark 1) - Puissance : 3 430 MWth - Première divergence : 06/1985

Available in english only.


Event Number : 51440

Facility : FERMI

State : MI

Unit : [2] - RX Type : [2] GE-4

Event Date : 10/02/2015 - Event Time : 08:25

Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(ii)(B) - UNANALYZED CONDITION 50.72(b)(3)(v)(A) - POT UNABLE TO SAFE SD

Initial PWR : 0 % Current PWR : 0 %

Event Text

LOOSE SAFETY RELIEF VALVE DISCHARGE FLANGE BOLTS

"On October 2nd, at approximately 0825 EDT, maintenance technicians were performing as-found torque checks on the discharge flange of the ’B’ Safety Relief Valve (SRV). 12 of the 16 bolts were not adequately torqued. The ’B’ Safety Relief Valve is credited for Remote Shutdown. The as-found condition of inadequate torque potentially impacts the seismic qualification of the ’B’ SRV.

"An investigation and extent of condition review is ongoing. The NRC Resident Inspector has been notified."

Before the outage, there were no abnormal indications of leakage as indicated by a rise in drywell temperature or pressure. The SRVs had been cycled under pressure with no abnormal indications.

The four bolts that were tight were in a diagonal pattern. The looses bolts were described as "finger tight." The licensee is determining the actions to take regarding the remaining 14 SRVs.

http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2015/20151005en.html#en51440