17 octobre 2014
Ce problème a conduit à soupçonner un mauvais fonctionnement du système de contrôle électro-hydraulique, alors que le cœur était critique. La pompe de recirculation d’une voie a été déclenchée et le relais a été pris par l’autre voie. Tous les systèmes d’arrêt auraient répondu correctement mais une perte d’eau, suite à un problème de pompe sur le circuit de déminéralisation, est survenue. Le niveau d’eau et sa circulation sont rentrés dans l’ordre. La cause du problème est en cours de recherche.
Type : BWR Mark III - Puissance : 3 091 MWth - Première divergence : 10/1985
Available in english only.
Event Number : 50546
Facility : RIVER BEND - State : LA -
Unit : [1] - RX Type : [1] GE-6
Event Date : 10/17/2014 - Event Time : 03:03
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Initial PWR : 100 % Curent PWR : 0%
Event Text
AUTOMATIC REACTOR SCRAM ON HIGH AVERAGE POWER RANGE MONITOR FLUX
"At 0303 [CDT], River Bend Nuclear Station sustained a reactor scram due to high Average Power Range Monitor [APRM] flux, suspected due to a malfunction of the Electrohydraulic Control System. Reactor recirculation pump ’B’ tripped, reactor recirculation pump ’A’ responded appropriately. All other systems responded appropriately except for loss of feed water due to low suction pressure trip from isolating the condensate demineralizers. Reactor water level did not get out of level band. Condensate demineralizers and feedwater were restored to service. Level 3 [isolation] was initiated due to scram. [One] system, Suppression Pool Cooling isolated accordingly due to level 3 signal. Currently the plant is in mode 3, hot shutdown. Plant will remain in mode 3 until investigation of scram is complete."
During the scram, all rods inserted into the core. No relief valves lifted as a result of the transient. All safety equipment is available although reactor core isolation cooling is functional but inoperable due to an earlier issue discovered during a surveillance test. The reactor is at normal pressure and temperature for Mode 3. The cause of the high APRM flux and the identified anomalies are under investigation.
The licensee has notified the NRC Resident Inspector.
* * * UPDATE FROM DANIEL PIPKIN TO DANIEL MILLS AT 1043 EDT ON 10/17/2014 * * *
The licensee is updating the notification to include an 8 hour notification for a specified system actuation due to the Level 3 isolation signal. Licensee is proceeding to cold shutdown to troubleshoot the EHC system.
The licensee will notify the NRC Resident Inspector.
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