14 mai 2010
L’opérateur a lancé l’arrêt d’urgence quand le niveau d’eau est arrivé trop haut. L’équipe a rétabli le niveau d’eau dans sa plage normale via le circuit d’isolation et de refroidissement du cœur. Au moment du problème, l’opérateur contrôlait le système numérique d’alimentation en eau installé récemment. Il semble que l’affichage de niveau de ce système ne répondait pas assez vite. Le réacteur a été conduit en arrêt normal.
Type : BWR Mark 2 - Puissance : 3 592 MWth - Première divergence : 09/1982
Available in english only.
Event Number : 45930 Facility : SUSQUEHANNA Region : 1 State : PA Unit : [1] - RX Type : [1] GE-4
Event Date : 05/14/2010 - Event Time : 23:01
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 : 94 % Current PWR : 0 %
MANUAL REACTOR SCRAM DUE TO INCREASING REACTOR WATER LEVEL
"At approximately 2301 hours EDT on May 14, 2010, Susquehanna Steam Electric Station Unit One reactor scrammed while performing a condensate pump trip test. The reactor operator placed the mode switch in shutdown when reactor water level reached +51 inches and rising. The main turbine tripped due to high reactor water level. All control rods inserted and both reactor recirculation pumps tripped. Reactor water level lowered to -30 inches causing Level 3 (+13 inches) isolations. The Operations crew restored reactor water level to the normal operating band using RCIC [Reactor Core Isolation Cooling] and subsequently the feedwater system. All isolations 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 reactor is currently stable in Mode 3. An investigation into the cause of the shutdown is underway. Unit Two continued power operation.
"The NRC Resident Inspectors were notified. A press release will occur."
The licensee was performing testing on the digital feedwater control system which was installed during their recent refueling outage when the loss of level control occurred. It appears that the control system did not respond fast enough to control water level. This resulted in the reactor operator inserting a manual scram at +51 inches prior to reaching the reactor automatic scram setpoint of +54 inches for water level.
Currently, the plant is removing decay heat via main steam line drains to the condenser. The plant is in its normal shutdown electrical lineup with all safety equipment available. The licensee has notified the Pennsylvania Emergency Management Agency.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2010/20100517en.html
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