Unit 3 at Finland’s Olkiluoto NPP has resumed service after being taken offline since 19 November because of a technical problem, according to owner/operator Teollisuuden Voima Oy (TVO). The reactor "was in normal production when a fault in the turbine plant automatically stopped the facility's electricity production”, TVO said. "The cause of the fault was revealed to be a malfunctioning temperature measurement in the generator's cooling system." TVO added that "the incident had no impact on nuclear safety.
The next-generation European pressurised water reactor (EPR), built by the French-led Areva-Siemens consortium, produces more than 10% of Finland's electricity when it is operating.
After years of delays, the reactor was finally put into regular service in April 2023. In May, TVO reported that several cases of signal failures in safety-classified temperature measurements had been detected at the EPR reactor in 2022-2023. As a result, a decision was made to carry out more extensive inspections on the temperature measurements. In February, it was found that some connectors of temperature measurements were missing either one or both of the required seals, TVO said.
Construction of OL3 began in 2005 and various setbacks and delays mean the plant is some 14 years behind the original schedule and significantly over budget. OL3’s final price tag is put at some $11bn ($12bn), some three times the initial estimate. OL3 attained first criticality in December 2021 and was connected to the grid on in March 2022. The 1600 MWe EPR was operated at full capacity for the first time in late September 2022. However, cracks were then identified in the impellers of the feedwater pumps located in the turbine island, causing further delays.
Image: Olkiluoto 3 (courtesy of TVO)