16 décembre 2013
Une analyse des manuels de procédure a montré que, suite à un incendie sur un câble, ce dernier n’était pas isolé par le local pour la mise à l’arrêt sûr du réacteur : cet incendie enclencherait alors les pompes de retrait de chaleur résiduelle (RHR) qui surchargeraient le générateur diesel de secours lors de la tombée du 4 kV. Des actions compensatoires à mettre en œuvre par les opérateurs (OWA : Operator Work Around) visent à empêcher le démarrage de ces pompes durant la phase de mise en arrêt sûr.
Type : BWR Mark 1 : - Puissance 3458 MWTh : - Première divergence : n° 1 08/1973 ; n° 2 07/ 1974 ; n° 3 08/1976
Available in english only.
Event Number : 49639 : Facility : BROWNS FERRY - State : AL - Unit : [1] [2] [3] - RX Type : [1] GE-4,[2] GE-4,[3] GE-4 Event Date : 12/16/2013 - Event Time : 17:00
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(ii)(B) - UNANALYZED CONDITION 50.72(b)(3)(v)(A) - POT UNABLE TO SAFE SD 50.72(b)(3)(v)(B) - POT RHR INOP 50.72(b)(3)(v)(C) - POT UNCNTRL RAD REL
Initial PWR : 1, 2, 3 = 100 % Current PWR : 1, 2, 3 = 100 %
Event Text
POTENTIAL FOR SPURIOUS START OF VARIOUS PUMPS DURING POSTULATED FIRE EVENTS
"A circuit analysis review for Appendix R Operator Manual Action deficiency extent of condition identified that fire damage to cable ES194-I is not isolated by the local control power transfer switch utilized in the Safe Shut-down Instruction. Fire damage to the non-isolated cable ES194-I in Fire Areas 01-03, 02-01, and 02-03 could cause the RHR Pump 2C to spuriously start (or restart after the Operator local trip action) when 4kV Shutdown Board B is credited for these Fire Areas. An undesired spurious start of RHR Pump 2C could overload the credited Diesel Generator or take away the necessary load capacity to allow operation of other Appendix R fire safe shutdown credited loads.
"The fire damage postulated would require a short to ES194-I from a separate cable conductor energized with the positive potential of the battery supplying 4kV Shutdown Board B (i.e., normally Shutdown Battery B). It is postulated for a fire-event that the necessary short to ES194-I could come from a cable-to-cable short or from a short to ground as the fire event may cause a separate conductor energized with the positive potential of the associated battery to short to ground.
"Similar conditions also exist for : RHR Pumps 1A, 1B, 1D, 2A, 2B, 3A, and 3C due to fire damage to cables in one or more Fire Areas.
"Compensatory actions in the form of an Operator Work Around [OWA] to remove the affected RHR Pump breaker close circuit control power fuses during the affected Safe Shut-down Instructions, a caution order on the appropriate transfer switches referencing the OWA, and fire watches in the affected Fire Areas to mitigate this condition are in place in accordance with the BFNP [Browns Ferry Nuclear Plant] Fire Protection Report.
"This condition is being reported pursuant to 10CFR50.72(b)(3)(ii)(B) and 10CFR50.72(b)(3)(v).
"The NRC Resident Inspector has been notified."
The licensee is also reporting under 10CFR50.72(b)(3)(v)(D) Accident Mitigation.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2013/20131217en.html
La boutique
Informez vous