10 mars 2014
Un réexamen étendu du site a montré l’absence de protection par fusible sur des câbles de contrôle de l’intensité de charge de batteries, ainsi que sur ceux de pompes à huile de lubrification. Cette absence de protection est susceptible de provoquer des court-circuits qui, en échauffant les câbles, provoqueraient des incendies secondaires. Ces départs de feux pourraient empêcher la mise à l’arrêt sûr des 2 réacteurs du site.
Type : PWR - Puissance : 2 737 MWTh - Première divergence : n° 1 : 10/74, n° 2 : 11/76
Available in english only.
Event Number : 49889
Facility : CALVERT CLIFFS - State : MD - Unit : [1] [2] - RX Type : [1] CE,[2] CE Event Date : 03/10/2014 - Event Time : 16:53
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
"An extent of condition review identified that there were unfused 250 VDC circuits for the battery charger ammeters and the control circuits for various DC lube oil pumps which left the turbine building and went through the respective cable spreading room and up into the Control Room. These circuits are protected by 200 amp fuses and in some cases 100 amp fuses. The concern is that under the fire safe shutdown rules, it is postulated that a fire in one fire area can damage these circuits and cause short circuits without protection that would overheat the cables and possibly result in secondary fires in other fire areas where the cables are routed. The secondary fires could adversely affect safe shutdown equipment and potentially cause the loss of the ability to conduct a safe shutdown as required by 10 CFR 50 Appendix R.
"This condition is reportable as an 8-hour ENS report in accordance with 10 CFR 50.72(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.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140311en.html