Réseau Sortir du nucléaire
BoutiqueAgendaFaire un donEN

Des accidents nucléaires partout

Etats-Unis : Nine Mile Point : arrêt automatique d’urgence du réacteur n°1 suite à un niveau bas d’eau de refroidissement




6 September 2017


Cet arrêt a enclenché la fermeture de la vanne d’isolation de la vapeur principale et lancé le confinement. Suite à l’arrêt, la pression a été momentanément envoyée vers le système de condenseur d’urgence. Huit minutes après le début du problème, la pression est contrôlée par les lignes de vapeur principale vers le condenseur. Tous les systèmes d’arrêt d’urgence se sont correctement activés.
 Le système d’injection de liquide de refroidissement haute pression s’est enclenché et déclenché une minute plus tard suite à sa restauration du niveau d’eau au delà du minimum. Le système de refroidissement du coeur activé n’a pas alimenté le coeur et a été arrêté 18 minutes après le début du problème.

 Type : Fukushima 1 (BWR Mark 1) - Puissance : 1 850 MWth - Première divergence : 09 / 1969 -

Available in english only


Event Number: 52950

Facility: NINE MILE POINT

State: NY - Unit: [1] - RX Type: [1] GE-2

Event Date: 09/06/2017 - Event Time: 11:57 [EDT]

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 Person (Organization): GLENN DENTEL (R1DO)

Initial PWR : 100 % - Current PWR : 0 %

Event Text

AUTOMATIC REACTOR SCRAM ON LOW REACTOR VESSEL WATER LEVEL

"On September 6, 2017 at 1157 [EDT], Nine Mile Point Unit 1 experienced an automatic reactor scram with a Main Steam Isolation Valve (MSIV) and Containment isolation. The scram was due to reactor vessel low water level. The cause of the reactor vessel low water level is under investigation. All control rods fully inserted. Following the scram, pressure was momentarily controlled through the use of the Emergency Condenser (EC) system. At 1205, pressure control was established through the main steam lines to the condenser through the turbine bypass valves. All plant systems responded per design following the scram. The reactor scram is a 4-hour report per 10 CFR 50.72(b)(2)(iv)(B).

"The following systems automatically actuated after the scram as expected. These system actuations are an 8-hour report per 10 CFR 50.72(b)(3)(iv)(A):

1. The High Pressure Coolant Injection (HPCI) system. HPCI initiated at 1157 and was reset at 1158 when RPV level was restored above the HPCI system low level actuation set point. HPCI is a flow control mode of the normal feedwater systems, and is not an Emergency Core Cooling System. 2. The Core Spray system actuated, but did not discharge to the Reactor Coolant system. The Core Spray system was secured at 1216. 3. Containment and MSIV isolation on reactor vessel low-low water level signal.

"Nine Mile Point Unit 1 is currently in Hot Shutdown, with reactor vessel water level and pressure maintained within normal bands. Decay heat is being removed via steam to the main condenser using the turbine bypass valves. The offsite grid is stable with no grid restrictions or warnings in effect.

"The licensee has notified the NRC Resident Inspector."

No safety relief valves lifted during the transient. The main steam isolation valves were opened after the isolation signal cleared to facilitate decay heat removal. Offsite power is supplying all plant loads. There was no effect on Unit 2.

The licensee notified New York State Department of Environmental Protection and will be issuing a press release.

https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2017/20170907en.html