During the trial operation phase of the EPR reactor at unit 3 of Finland’s Olkiluoto nuclear power plant, an unplanned reactor trip occurred on 14 January, owner-operator power utility Teollisuuden Voima Oyj (TVO) announced.
During the pre-operational testing phase of a nuclear power plant, the plant unit and its safety systems are tested to verify that the plant operations comply with design. The pre-operational tests also comprise planned reactor trips.
"Occasionally unplanned reactor trips occur during pre-operational testing," TVO said. This was the case on 14 January in connection with the commissioning tests of steam generator level control. The reactor trip occurred when the level exceeded the reactor trip limit in one steam generator during the test.
Marjo Mustonen, Director of Electricity Production, noted: "The plant remained in a safe state the whole time. We look at events that occur during the pre-operational tests as if the plant unit was already in electricity production. We carefully investigate the causes of the events and implement the required corrective actions before moving on to the next pre-operational testing steps. This approach also secures the trouble-free operation of the plant unit in the future"
The reasons for the reactor shutdown have been clarified “and the necessary measures will be taken before the plant unit is restarted”, TVO said. After start-up, the power is increased stepwise and tests are performed according to the test programme.
“Preparations are ongoing at the plant unit for the start-up. Electricity production will start at 25%, or about 300-400MW, at the end of January 2022. OL3's regular electricity production will begin in June 2022.”
Olkiluoto 3 EPR is undergoing pre-operational testing (Photo: TVO)