Finland’s Teollisuuden Voima Oyj (TVO) said unit 3 of the Olkiluoto said the plant’s power had been automatically decreased from 1,600 MWe to approximately 1,220 MWe after one of the EPR’s control rods unexpectedly dropped into the reactor.
“The drop was caused by a failure in the control rod drive mechanism. Normally, the drive mechanism keeps the control rods outside the reactor, and in a disturbance, the safety automation system drops the control rods into the reactor,” TVO noted. “To investigate the cause of the disturbance and to repair the fault, the unit is being operated at a low power level.”
TVO said the event had no impact on nuclear safety and the issue was resolved after a few hours.
OL3 began regular electricity production in April 2023 following the completion of trial operation. 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 what was initially estimated.
OL3 attained first criticality in December 2021 and was connected to the grid on in March 2022. The EPR was operated at full capacity for the first time in late September 2022. However, cracks were identified in the impellers of the feedwater pumps located in 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 more time than planned and additional fuel inspections were required.
