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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, 28-08-1996
ERF description: At 09:18 reactor of the NPP Krsko tripped on the steam generator no. 2 low-low level signal. Investigation showed that the low-low level signal was caused by closure of the train "B" feedwater isolation valve. Prior to the event, calibration of the temperature sensor on the train "B" feedwater line was initiated. When the sensor was put into the test mode the corresponding relay was deenergized thus one of the two inputs to the "OR" logic device controlling opening of the feedwater isolation valve was lost. The second input to the "OR" logic device (feedwater flow) which was supposed to be present was lost due to blown fuses at the corresponding relay. Therefore there was no output from the "OR" logic device which was the prerequisite for the feedwater isolation valve being in open position and the valve closed leading to the feedwater isolation steam generator low-low level and the reactor trip. The plant was stabilized at "NO LOAD" parameters. All safety systems performed in accordance with the design.
Cause of the blown fuses is under investigation.
Initiator - expected, reactor trip.
Safety Function Availability: full
ERF rating date: 28-08-1996
ERF contact person: Mr. M.F. Levstek
ERF address: Vojkova 59, 1113 LJUBLJANA, Slovenia
ERF affiliation: Slovenian Nuclear Safety Administration

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