22 octobre 2013
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 : n° 1 : BWR Mark 1, n° 2 : BWR Mark 2 - Puissance : n° 1 : 1 850 MWTh, n° 2 : 3 467 MWTh - Première divergence : n° 1 09/1969, n° 2 : 05/1987
Available in english only.
Facility : NINE MILE POINT - State : NY - Unit : [1] [2] - RX Type : [1] GE-2,[2] GE-5
Event Date : 10/22/2013 - Event Time : 14:00 [EDT]
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 Nine Mile Point, Units 1 and 2 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 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 short to the ground plane. Simultaneously, it is postulated that the fire causes another DC wire from the opposite polarity on the same battery to also short to the ground plane. This could cause a ground loop through the unprotected ammeter wiring. This event could result in excessive current flow (i.e., 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 10 CFR 50 Appendix R. This condition has been entered into the Nine Mile Point corrective action program as Condition Reports CR-2013-008747 (NMP1) and CR-2013-008749 (NMP2).
"This condition is being reported in accordance with 10 CFR 50.72(b)(3(ii)(B). Interim compensatory measures (i.e., fire watches) have been implemented for affected areas of the plants.
"The licensee has notified the NRC Resident Inspector."
Event Number : 49464
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2013/20131023en.html
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