18 août 2014
Lors d’une intervention de maintenance programmée sur une voie de dissipation ultime de chaleur, l’autre voie est tombée en panne. Les spécifications techniques prévoient la mise à l’arrêt à chaud dans les 6 heures et en arrêt froid dans les 30. La seconde voie ayant été rétablie après 83 minutes d’indisponibilité, le réacteur a été maintenu à 100 % de sa puissance.
Type : PWR - Puissance : 3 716 MWth - Première divergence : 03/1985
Available in english only.
Event Number : 50378
Facility : WATERFORD
State : LA - Unit : [3] - RX Type : [3] CE -
Event Date : 08/18/2014 - Event Time : 08:53 -
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(v)(B) - POT RHR INOP 50.72(b)(3)(v)(D) - ACCIDENT MITIGATION
Initial PWR : 100 % - Current PWR : 100 % -
Event Text
ULTIMATE HEAT SINK SYSTEM INOPERABLE
"Conditions were met that require immediate NRC notification per 10 CFR 50.72(b)(3)(v)(B) and 10 CFR 50.72(b)(3)(v)(D) due to both trains of the Ultimate Heat Sink (UHS) system being inoperable for approximately 83 minutes. This condition resulted from a planned system outage of train B Component Cooling Water (CCW), as a subsystem of the Train B UHS, and an unexpected trip of a Train A Auxiliary Component Cooling Water (ACCW) Wet Cooling Tower (WCT) fan, which is also a subsystem of the Train A UHS.
"CCW Train B was declared inoperable at 0820 CDT and removed from service for a planned relay replacement, resulting in entry of 72 hour shutdown Technical Specification (TS) LCO 3.7.3, and associated cascading TS on Train B, including TS LCO 3.7.4 Action a. Subsequently, at approximately 0853 [CDT], the 6A ACCW WCT fan tripped, rendering the redundant Train A UHS inoperable, causing entry into 1 hour TS LCO 3.7.4 Action b, which states, ’With both UHS trains inoperable, restore at least one UHS train to OPERABLE status within 1 hour or be in at least HOT STANDBY within the next 6 hours and COLD SHUTDOWN within the following 30 hours.’
"At approximately 0948 CDT the WCT Fan 6A electric motor thermal overload relays were reset, the fan restarted, and operated properly. At 1016 CDT, CCW train B had been restored from the planned maintenance and was declared operable, exiting TS LCO 3.7.3 and associated cascading TSs on Train B. Although a plant shutdown was not commenced following expiration of the one hour specified in TS LCO 3.7.4 ACTION b, Operations was preparing for a power reduction and TS required plant shutdown.
"During this reported condition, an outside air intake valve of the Control Room Emergency Filtration system was inoperable for planned maintenance, for which TS 3.7.6.1 mitigating actions were in place. This valve was restored to Operable at 1210 CDT. Other safety systems remained available. The plant remained stable at 100% during this time."
The NRC Resident Inspector was notified.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140819en.html#en50378
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