8 octobre 2013
Des prescriptions n’ont pas été respectées concernant les protections d’ampèremètre qui pourraient être à l’origine d’un départ d’incendie. Ce problème pourrait compromettre le système de mise en arrêt sûr des deux réacteurs du site.
Type : BWR - P. : n°1 = 3 612 MWth - n°2 = 3 458 MWth - Première divergence : n°1 : 4 1990 - n°2 : 3 1993
Available in english only.
Event Number : 49419 Facility : COMANCHE PEAK - State : TX - Unit : [1] [2] - RX Type : [1] W-4-LP,[2] W-4-LP
Event Date : 10/08/2013 - Event Time : 12:40 - 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 regarding the impact of unfused Direct Current (DC) ammeter circuits in the control room has determined the described condition to be applicable to Comanche Peak Nuclear Power Plant resulting in a potentially unanalyzed condition with respect to 10CFR50 Appendix R analysis requirements. The original plant wiring design and associated analysis for the Class 1 E batteries 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 could 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 reportable in accordance with 10CFR50.72(b)(3)(ii)(B) as an unanalyzed condition. Compensatory measures (fire watches) have been implemented for affected areas of the plant."
The licensee has notified the NRC Resident Inspector.
See related Event #49411.
Source : https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2013/20131009en.html