The Finnish Radiation and Nuclear Safety Authority (Stuk) is investigating what it has called "a serious operational disruption" involving high levels of radiation at the Olkiluoto nuclear power plant.
The facility, located on the west coast between the cities of Rauma and Pori, was forced to undergo an emergency shutdown (scram) on Thursday shortly after noon.
According to Stuk, the problems in the plant started "when radiation measurement systems detected higher levels within the plant." However, the nuclear watchdog said "no radiation has been released into the surroundings from the facility" and the radiation situation in the vicinity of the plant is "normal."
Previously, the operator of the plant (TVO) reported "a plant emergency situation" occurred at 12:22 in which "an isolation of main steam lines has launched an isolation which has isolated also the containment." (sic).
However, in a subsequent communication, the operating company TVO changed the phrase "emergency situation" to "disturbance" to describe what happened.
The second statement read: "There has been a disturbance at Olkiluoto 2 (OL2) nuclear power plant at 12.22, where the main steam line’s isolation has been triggered and the containment has been isolated."
According to TVO, the plant reacted according to the procedures during the automatic emergency shutdown and "the incident has not caused danger to people or the environment."
Both the Finnish nuclear agency (Stuk) and TVO said they are investigating the situation.
The International Atomic Energy Agency (IAEA) published a statement after being informed about "an event at Unit 2 of the Olkiluoto Nuclear Power Plant."
"Elevated radiation levels were measured inside the plant and the reactor was shut down."
The AIEA, headquartered in Vienna, is in contact with the Finnish authorities and will provide further public information as it becomes available.
Not the first incident
This is not the first incident to occur at the Olkiluoto nuclear plant this year.
Finland has four nuclear rectors, two of them at Olkiluoto, which provide about a third of the country's electricity. A fifth reactor is being built at Olkiluoto, but the project has been suffering serious delays.
In may, Olkiluoto's third reactor, which is being built by France's Areva and Germany's Siemens, suffered another incident which affected its long-delayed construction.