9 novembre 2012
A 1h18, les opérateurs ont mis le réacteur n° 2 à l’arrêt d’urgence suite à la perte de du système intégré (Integrated Control system ou ICS) qui contrôle les retours de donnée du réacteur ainsi que les systèmes de recirculation. Malgré l’absence de ce système, le passage à l’arrêt se serait passé normalement.
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Le système d’injection haute pressions de liquide de refroidissement (High Pressure Coolant Injection ou HPCI) et le système d’isolation du refroidissement du réacteur (Reactor Core Isolation Cooling ou RCIC) se sont mis en service automatiquement.
Les soupapes de surpression de la vapeur ne seraient pas entrées en fonction.
Facility : SUSQUEHANNA - Region : 1 State : PA - Unit : [2] - Type : [2] GE-4
Event Date : 11/09/2012 - Event Time : 01:18 [EST]
Emergency Class : NON EMERGENCY
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION 50.72(b)(2)(iv)(A) - ECCS INJECTION
Initial PWR Current PWR 90 % 0% Hot Shutdown
Event Text
UNIT 2 MANUAL SCRAM DUE TO LOSS OF THE INTEGRATED CONTROL SYSTEM
"At approximately 0118 hours [EST] on November 9, 2012, Susquehanna Steam Electric Station Unit Two reactor was scrammed by plant operators due to a loss of ICS (Integrated Control System ; which controls the reactor feed and reactor recirculation systems). The reactor operator placed the mode switch in shutdown when reactor water level reached +25 inches and lowering. All control rods inserted and both reactor recirculation pumps tripped at -38 inches. Reactor water level lowered to -52 inches causing Level 3 (+13 inches) and level 2 (-38 inches) isolations. HPCI and RCIC both automatically initiated. HPCI was overridden prior to injection and RCIC was utilized to restore reactor water level to the normal band. All isolations and initiations at this level occurred as expected. No steam relief valves opened. Pressure was controlled via turbine bypass valve operation. All safety systems operated as expected.
"The [Unit 2] reactor is currently stable in Mode 3. An investigation into the cause of the loss of ICS is underway.
"Unit One continued power operation [at 78% power].
"The NRC Resident Inspectors were notified. A press release will occur."
The licensee will inform the State of Pennsylvania.
Decay heat removal is being maintained through the main condenser. On-site electrical power is in the normal configuration.