5 octobre 2015
Cet arrêt, effectué dans le cadre d’un rechargement de combustible, a connu ce problème à 15% de sa puissance. Les opérateurs ont tenté de démarrer manuellement une pompe à eau qui a déclenché par surintensité. Une autre pompe a été enclenchée manuellement pour maintenir le niveau en eau des générateurs de vapeur. A 1h05, ce niveau d’eau étant trop faible (à 36,5 % avec un coeur qui n’était plus critique), deux pompes auxiliaires d’alimentation en eau ont démarrées automatiquement. Parallèlement il y a eu activation du système de protection du réacteur. Les deux décharges de vapeur principales étaient en service avec le condenseur comme dissipateur de chaleur.
Type : PWR - Puissance : 3 587 MWth - Première divergence : 03/1988
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Event Number : 51450
Facility : BRAIDWOOD
State : IL - Unit : [2] - RX Type : [2] W-4-LP
Event Date : 10/05/2015 - Event Time : 01:05
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Initial PWR : 100 % Current PWR : 100 %
Event Text
SPECIFIED SYSTEM ACTUATIONS
"Braidwood Unit 2 was performing a planned plant shutdown for refueling outage A2R18. In accordance with plant shutdown procedures while in Mode 1 (Power Operations) at approximately 15% power, operators attempted to start the Start Up Feedwater (SFWP) pump and the pump immediately tripped on Phase A Overcurrent. The 2A Motor Driven Feedwater pump (MDFWP) was manually started to maintain Steam Generator Water Level during the shutdown and subsequent plant cooldown. While in Mode 3 (Hot Standby) at [550 Degree-F], the 2A MDFWP was manually secured due to pump inboard journal bearing temperature exceeding its [200 Degree-F] operating limit. At 0105 [CDT] an anticipated automatic Auxiliary Feedwater actuation signal was generated on low Steam Generator level (36.3%) and both the 2A and 2B Auxiliary Feedwater pumps (AFP) auto-started. Also at 0105 [CDT] a Reactor Protection System (RPS) Reactor trip signal was received due to low Steam Generator level (36.3%) with the reactor not critical. Both Auxiliary Feedwater trains operated as designed with the Main Steam Dumps in service and the Main Condenser providing the heat sink.
"All systems operated as designed with the exception of the SFWP and the MDFWP described above.
"The plant is currently stable in Mode 5 with both AFPs secured.
"This report is being made per 10 CFR 50.72(b)(3)(iv)(A) for automatic actuation of the (1) RPS Reactor Trip with the reactor not critical and (6) Auxiliary Feedwater System, 8 hour notification."
The licensee notified the NRC Resident Inspector.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2015/20151006en.html#en51450
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