Incident at Finland's OL3 reduces power

Finland’s Teollisuuden Voima Oyj (TVO) said Olkiluoto unit 3 said the plant’s power was automatically reduced from 1,600 MWe to approximately 1,220 MWe after one of the EPR control rods unexpectedly fell into the reactor.

“The crash was caused by a failure in the control rod actuation mechanism. Normally, the drive mechanism keeps the control rods outside the reactor, and in the event of a disturbance, the safety automation system drops the control rods into the reactor,” TVO noted. “To investigate the cause of the disturbance and repair the fault, the unit is being operated at a low power level.”

TVO said the event had no impact on nuclear safety and that the issue was resolved after a few hours.

OL3 started regular electricity production in April 2023, after completion of trial operation. Construction of OL3 began in 2005 and numerous setbacks and delays mean the factory is around 14 years behind the original schedule and significantly over budget. The final price of OL3 is estimated at around US$11 billion (US$12 billion), around three times what was initially estimated.

OL3 reached first criticality in December 2021 and was connected to the grid in March 2022. The EPR ran at full capacity for the first time in late September 2022. However, cracks were identified in the impellers of the feedwater pumps located on the turbine island, causing further delays.

During its first outage in April, technical problems resulted in delays in restarting the unit after fuel unloading took longer than planned and additional fuel inspections were required.