9 octobre 2013
Un examen approfondi des documents a montré que, suite à l’hypothèse d’un incendie dans la salle de contrôle, l’absence de protection sur des câbles de mesure d’intensité engendrerait un second départ de feu. Cette situation compromettrait la mise à l’arrêt sûr des deux réacteurs du site.
Type : PWR - Puissance : 3 565 MWTh - Première divergence : 05/1985
Available in english only.
Facility : WOLF CREEK - KS : Unit : [1] RX Type : [1] W-4-LP
Event Date : 10/09/2013 - Event Time : 17:30
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(ii)(B) - UNANALYZED CONDITION
Initial PWR : 100 % Current PWR : 100 %
Event Text
POSTULATED HOT SHORT FIRE EVENT THAT COULD ADVERSELY IMPACT SAFE SHUTDOWN EQUIPMENT
"A review of industry operating experience with respect to fire induced damage to unfused Direct Current (DC) ammeter circuits in the control room has determined that the condition described below is applicable to Wolf Creek Nuclear Generating Station. This condition results in an unanalyzed condition with respect to 10CFR50 Appendix R analysis requirements. The original plant wiring design did not include overcurrent protection features to limit the fault current in these circuits. The wiring design for the ammeters contains a shunt in the current flow from each NK direct current (DC) battery or charger. Two leads run from the shunt to a current meter in the main control room (MCR). These leads are tied to the positive polarity of the NK battery system. The ammeter wiring attached to the shunt is not overcurrent protected. It is postulated that a fire could cause one of these ammeter wires to short to ground at the same time the fire causes another DC wire from the opposite polarity on the same battery to also short to ground. This would cause a ground loop through the unfused ammeter cable. This event could result in excessive current flow (heating) in the ammeter wiring to the point of causing a secondary fire in the raceway system. The secondary fire could adversely affect safe shutdown equipment. Reference Palo Verde plant event #49411. A Breech Authorization with compensatory Control Room hourly fire watch for this issue is in place and will remain in effect until this deficiency is resolved.
"This condition has been discussed with the Resident Inspector."
Similar Events #49422 and #49419
Event Number : 49423
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2013/20131017en.html#en49423
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