About 100 cubic metres of radioactive coolant spilled from Olkiluoto 3, the largest nuclear reactor in Europe, as reported by the operator, Teollisuuden Voima Oyj (TVO).

The leak occurred during the reactor's annual maintenance shutdown on a Friday, linked to the filling of the reactor pool.

TVO clarified that the coolant leaked into containment rooms that are isolated from the outside environment, as well as into the facility’s floor drainage system.

They stressed that there was no danger to staff, the surrounding environment, or overall nuclear safety as a consequence of the leak.

The company attributed the leak to human error, specifically noting that a hatch for the pool had not been properly secured.

TVO assessed the significance of the leak in terms of radiation safety to be low, owing to the safety measures that were in place.

In spite of the incident, TVO confirmed that it would not impact the planned duration of the reactor's annual outage, which is expected to continue until May.

Olkiluoto 3 is a next-generation European pressurised water reactor (EPR) created by a consortium led by Areva and Siemens.

It constitutes over 10 percent of Finland’s electricity output.

The reactor has encountered several challenges, including construction delays and considerable cost overruns, akin to other EPR projects.

While Olkiluoto 3 is recognized as the largest nuclear reactor in Europe, the Zaporizhzhia plant in Ukraine, with its six reactors, is noted as the largest nuclear power station on the continent.