9 octobre 2013
Comme pour les réacteurs de Wolf Creek et de Nine Mile Point, un examen 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 : 10/1984
Available in english only.
Event Number : 49422 - Facility : CALLAWAY - State : MO -
Unit : [1] - RX Type : [1] W-4-LP
Event Date : 10/09/2013 - Event Time : 15:00
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(ii)(B) - UNANALYZED CONDITION Person (Organization) : MICHAEL HAY (R4DO)
Initial PWR : 100 % Current PWR : 100 %
Event Text
POSTULATED FIRE EVENT COULD RESULT IN A HOT SHORT THAT COULD ADVERSELY IMPACT SAFE SHUTDOWN EQUIPMENT
"A review of industry operating experience regarding the impact of unfused Direct Current (DC) ammeter circuits in the control room has determined that the condition described below to be applicable to Callaway Nuclear Plant resulting in an unanalyzed condition with respect to 10 CFR 50 Appendix R analysis requirements. The original plant wiring design and associated analysis for the Class 1E Train B batteries and chargers (including the B Swing charger) control room ampere indications do not include overcurrent protection features to limit the fault current.
"In the postulated event, a fire in the control room could cause one of the ammeter wires to hot short to the ground plane ; simultaneously, the fire causes another DC wire from the opposite polarity on the same battery to also hot short to the ground plane. This would cause a ground loop through the unprotected ammeter wiring. 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 and potentially cause the loss of the ability to conduct a safe shutdown as required by 10CFR50 Appendix R.
"This condition is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition that significantly degrades plant safety. Compensatory measures (fire watches) have been implemented for affected areas of the plant.
"The NRC Resident Inspector has been notified."
Similar Events : EN #49411 and EN #49419
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2013/20131017en.html#en49312
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