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Event Report Forms (ERFs) are filed to the IAEA. Sometimes there are multiple event reports, updating the rating, the event description. Here you only see the latest event report

ERF send date: Wed, 09-06-1999
ERF description: Prior to the event the plant was in steady state operation (mode 1) at 84% rated power. All systems were operable as required for this mode.
At 11:00 pm operators in the main control room observed slight level increase in the SG#1. Main feedwater flow control valve FCV 551 did not respond to demands while operated in automatic mode. Operators switched control of the FCV 551 for automatic to manual control trying to maintain SG#1 level at programmed value. Operators could not maintain progammed SG#1 level. SG#1 level increased to the value of 82% which is the setpoint for HI-HI SG#1 level signal. That caused trubine trip (HI-HI level on SG#1 + P7) and consequently reactor trip at 11:11 p.m. The reactor tip sequence went on according to the design.
The plant personnel are still investigating the reasons for abnormal valve operation.
The plant was stabilized at "no-load" parameters. All safety systems performed in accordance with the design.
Justification of Rating:
Real initiator - reactor trip, safety function operability - full, initiator frequency - expected. Table IV-3.2.1.3 (a)
ERF rating date: 09-06-1999
ERF contact person: Mr. M.F. Levstek
ERF address: Vojkova 59, 1113 LJUBLJANA, Slovenia
ERF affiliation: Slovenian Nuclear Safety Administration

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