Leakage spotted at OL3 nuke plant´s radioactive coolant

A leakage of some 100 cubic metres of reactor coolant occurred at Olkiluoto 3 (OL3) nuclear power plant in connection with the filling of the reactor pool, said the owner of the plant Teollisuuden Voima Oyj (TVO) in a press release on Monday.

The coolant flowed into containment rooms closed to the environment and into the floor drain system of the containment.

The incident, however, did not pose any risk to the personnel, the environment, or nuclear safety.

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 March 7, 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.

The leakage occurred as a result of a human error through a hatch of the reactor pool that had not been closed properly.

The significance of the event to radiation safety was low, in the end, owing to the safety actions taken.

TVO has initiated an event investigation about the incident and will implement necessary actions to prevent the recurrence of the event.

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.