Finland’s Teollisuuden Voima (TVO) said the EPR reactor at unit 3 of the Olkiluoto NPP (OL3) will now resume electricity production 25 February with regular electricity production expected to start on 29 March. This represents an additional delay of five days, following the detection of a valve fault during start-up of the reactor. TVO said the inspections by the plant supplier [Areva-Siemens] of the OL3 turbine island had been completed. “However, during the startup of the plant unit, a valve fault was observed, which must be repaired during a cold shutdown before continuing the test production phase.

In autumn 2022, cracks were identified in the impellers of the feedwater pumps located in OL3’s turbine island. Tests at full power were continued after extensive investigations with two cracked impellers and two spare impellers. The observations made during the feedwater pumps’ inspections were in accordance with the calculations and analyses performed earlier. To avoid the recurrence of similar damage, impellers with more robust measurements were designed for OL3. New impellers were installed in all four of OL3’s feedwater pumps during a scheduled outage and the plant supplier carried out inspections in preparation for resumed trial operation.

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. The Areva-Siemens consortium constructed the OL3 plant under a fixed-price turnkey contract. Construction began in 2005 and various setbacks and delays mean the plant is now more than 10 years behind the original schedule and significantly over budget. Once regular electricity production starts, OL3 will produce about 14% of Finland's total electricity consumption.

Image: Olkiluoto unit 3 (courtesy of TVO)