 INES 0 |
SAFETY INJECTION DUE TO PRESSURIZER SPRAY VALVE STACK |
Kori unit 2 was operated at rated power (650 MWe). During normal operation, pressurizer spray valve (PC655B) was stuck open due to the misoperation of pressure gauge (PT-455) and then resulted in pressure decrease of the PZR by the continuous spray.
Eventually excess temperature signal (OT Delta T) was actuated and then reactor trip by this signal at 21:48 on February 25, 1995. After about ten seconds from the trip safety injection was followed due to the PZR low pressure. Adequate recovery actions by operators were performed to keep the normal condition of the plant. Investigation was carried out and it revealed that the damage of the connection part of the valve caused this event. There were no rlease of radioactive materials outside the reactor building and no unplanned exposure to employees.
Justification: As full safety functions were available, the event is rated at level "0" as per user's manual Part III, Table II. A1.
Event date: Sat, 25-02-1995
