The Finnish Radiation and Nuclear Safety Authority (STUK) today informed the International Atomic Energy Agency (IAEA) that the cause of Thursday’s event at Unit 2 of the Olkiluoto Nuclear Power Plant was a malfunction in the purification system for the reactor cooling water. Due to the malfunction, some filter material was released into the cooling system causing a temporary rise of ?radiation levels in the steam lines.

STUK said that the event posed no danger to the safety of people or the environment, and that radiation levels at the plant and surroundings are at normal levels.

STUK rated yesterday’s event below scale/level 0 on the International Nuclear and Radiological Event Scale (INES), which is a tool to communicate the safety significance of nuclear and radiological events to the public. Events without a safety significance are rated below scale/level 0.

STUK said it will continue the oversight of corrective actions at Unit 2 of Olkiluoto. The plant operator, Teollisuuden Voima Oyj (TVO), has ended the emergency standby. Unit 2 remains in shutdown and TVO is now working according to standard procedures.

The IAEA remains in contact with its counterparts in Finland.

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