A leakage of reactor coolant has occurred at the Olkiluoto Nuclear Power Plant on the west coast of Finland, according to the operator of the plant, Teollisuuden Voima Oyj (TVO) in a 10 March statement.
Around 100m3 of reactor coolant* was reported to have leaked from the reactor Olkiluoto 3 (OL3) in connection with the filling of the reactor pool. The coolant flowed into containment rooms closed to the environment and into the floor drain system of the containment. The incident did not pose any risk to the personnel, the environment, or nuclear safety, said the group.
The annual outage started at OL3 on 1 March 2025 and is planned to go on until early May. The maintenance activities carried out have progressed on schedule. However, on Friday 7 March, a significant operating event occurred during the maintenance work when radioactive coolant leaked at the reactor plant into part of the rooms of the containment. TVO said the leakage occurred as a result of human error, caused by a hatch of the reactor pool not having been closed properly.
“The significance of the event to radiation safety was low, in the end, owing to the safety actions taken,” said a statement on the group’s website.
“The reactor coolant that leaked into the containment flowed from the rooms into the drains of the floor drain system which are designed to collect and drain any reactor coolant leakages.”
As a press release explained, radioactive wastewater will be handled in accordance with appropriate procedures utilising various systems. Cleaning work was commenced quickly in the containment rooms and personnel instructed about necessary changes in accessible areas.
Notes
*The reactor coolant is heated in the reactor pressure vessel of the nuclear power plant and then flows in the reactor coolant piping to the steam generator where a heat transfer to the secondary circuit occurs. The coolant is then pumped from the steam generators back to the pressure vessel.