5 novembre 2010
Réacteur à pleine puissance, la pression du circuit de commande de barres de contrôle était en dessous de 110 bars. Malgré cela les barres se seraient insérées correctement dans le coeur et l’arrêt d’urgence se serait passé normalement.
Type : BWR Mark 3 - Puissance : 3758 MWth - Première divergence : 06 1986 -
Event Number : 45918
Facility : PERRY - 3 State : OH
Unit : [1] - RX Type : [1] GE-6
Event Date : 05/11/2010 - Event Time : 23:18
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(2)(i) - PLANT S/D REQD BY TS 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
Initial PWR : 100 % Power Operation : 0 %
Event Text MANUAL REACTOR SCRAM DUE TO LOSS OF CONTROL ROD DRIVE CHARGING WATER HEADER PUMPS
"On May 11, 2010, at approximately 2318 hours, a manual Reactor Protection System (RPS) actuation was initiated as required by Technical Specification (TS) Limiting Condition for Operation (LCO) 3.1.5 ’Control Rod Scram Accumulators.’ Control Rod Drive (CRD) charging water header pressure was less than 1520 psig (i.e., no CRD pumps operating) and there were multiple accumulator faults on withdrawn control rods. At the time of the event, the plant was in Mode 1 at 100% power. All control rods are inserted into the core and the plant is currently stable, in Mode 3 (Hot Shutdown) with reactor pressure at approximately 930 psig. No Emergency Core Cooling Systems were required or utilized to respond to the event and there were no other 10 CFR 50.72 reportable actuations. Reactor coolant level is being maintained in its normal band by the feedwater system and decay heat is being removed by the condenser. The plant is in a normal electrical line-up with all three Emergency Diesel Generators operable and available if needed.
"The cause of the event initiator, an invalid Division 2 Loss of Coolant Accident (LOCA), i.e., High Drywell Pressure/Low Reactor Vessel Water Level, signal, is currently under investigation. Prior to the manual RPS Actuation, the invalid LOCA signal resulted in invalid actuations of Division 2 equipment and systems including, the Division 2 Emergency Diesel Generator (EDG), (which started but did not load onto the bus), Low Pressure Coolant Injection B and C subsystems (which started the pumps but did not inject into the vessel), discharge of the Suppression Pool Makeup subsystem B into the suppression pool, startup of the Control Room Emergency Recirculation subsystem B, and isolation of Group 2B Containment isolation valves which included the Nuclear Closed Cooling System Containment Return Isolation valve that was not already closed. The affected equipment is being restored in accordance with plant procedure. The NRC Resident Inspector has been notified."
The licensee experienced an instrumentation rack loss of power which appears to have resulted in the inadvertent Division 2 initiation. The initiator of this event also and led to a loss of power to both control rod drive charging water header pumps resulting in charging water header pressure less than required and related accumulator faults which placed the licensee in a technical specification required shutdown condition. The action statement allows only 20 minutes to restore the condition which was insufficient time for the licensee to correct the condition so a manual scram was initiated from 100% power. The scram was characterized as an uncomplicated scram and all system responses (not related to the initial instrument fault) functioned as required.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2010/20100513en.html
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