The situation at the Olkiluoto nuclear plant is now "stable" after the emergency situation that occurred on Thursday that forced a scram (emergency stop) due to a radiation increase inside the plant.
"The situation of unit 2 at the Olkiluoto nuclear power plant is stable and the plant will be shut down to cold state so that the cause of the fault can be determined. The inspectors of the Radiation and Nuclear Safety Authority (STUK) monitor the situation on site," said the Finnish nuclear authority in a statement on Thursday night.
The nuclear watchdog already said on Thursday that what they called a "severe abnormal disturbance" that led to reactor shutdown was "possibly caused" by a fault in the purification system for the reactor water.
"The rise of the radiation levels inside the containment caused a full scale emergency response at STUK and at the Olkiluoto power plants."
On Friday morning, a new statement confirmed that the cause for the alarm was "a fault in the purification system for the reactor cooling water. Contaminated filter material got into the cooling circuit and caused a temporary rise of the radiation levels in the circuit. The fuel was not damaged, consequently there was no risk of harmful radioactive release."
The situation at the Olkiluoto NPP unit 2 is stable and TVO is continuing investigations and corrective activities. STUK has continued the oversight of the situation during the night. The radiation situation at the plant and in the environment is normal. https://t.co/ZuACcd6qGh— STUK - Säteilyturvakeskus (@STUK_FI) December 11, 2020
The company that operates the plant Teollisuuden Voima (TVO) is continuing investigations and corrective activities concerning the event. The Radiation and Nuclear Safety Authority is continuing the enhanced oversight of TVO:s work.
STUK says it has continued the oversight of the situation during the night. On Friday morning, they said the radiation situation at the plant and in the environment was normal.
"No radioactivity was released that would have had any impact on people or environment. The plant personnel have neither been exposed to radiation," the nuclear safety agency said.
Teollisuuden Voima has ended the "emergency standby" and is working according to standard procedures.