3 novembre 2012
Le réacteur n° 1 s’est arrêté en urgence automatiquement suite à la détection de niveau bas de son eau de refroidissement. Les barres de contrôle ont été correctement insérées et le processus d’arrêt s’est déroulé normalement avec une injection haute pression de liquide de refroidissement primaire également déclarée comme normale par la NRC.
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Note : le réacteur n° 1 a déjà subi un arrêt d’urgence il y a 5 jours
Avant l’arrêt, pour une raison inconnue, une pression anormalement élevée a été détectée dans le réacteur. Le réacteur est en arrêt à chaud avec les conditions de pression et de température maintenues dans les plages normales.
Facility : NINE MILE POINT - Region : 1 State : NY Unit : [1] - RX Type : [1] GE-
Event Date : 11/03/2012 - Event Time : 08:23
Emergency Class : NON EMERGENCY
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
Initial PWR Current PWR 1 A/R Y 24 Power Operation 0 Hot Shutdown
Event Text
AUTOMATIC SCRAM ON LOW REACTOR WATER LEVEL
"On November 3, 2012 at 0823 EDT, Nine Mile Point Unit 1 experienced an automatic reactor scram on low reactor water level. All control rods fully inserted and all plant systems responded per design following the scram. Prior to the automatic scram, an unexpected high Reactor Pressure Vessel (RPV) water level was experienced, followed by a turbine trip and subsequent lowering of RPV water level to the RPV low level scram set point. The cause of the water level transient is unknown.
"Following the automatic scram, the High Pressure Coolant Injection (HPCI) System automatically initiated as expected. HPCI is a flow control mode of the normal feedwater systems, and is not an Emergency Core Cooling System. At 0824 EDT, RPV level was restored above the HPCI System low level actuation set point and the HPCI System initiation signal was reset. Pressure control was established on the Turbine Bypass Valves, the preferred system. No Electromatic Relief Valves actuated due to this scram.
"Nine Mile Point Unit 1 is currently in Hot Shutdown, with reactor water level and pressure maintained within normal bands. Since the scram, there have been no anomalies observed with feedwater system operation. Decay heat is being removed via steam to the main condenser using the bypass valves. The offsite grid is stable with no grid restrictions or warnings in effect. The unit is currently implementing post scram recovery procedures.
"The licensee has notified the NRC Resident Inspector."
Unit 2 was not affected during this event.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2012/20121105en.html
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