The incident was described as “serious” and preparedness protocols had been put in place at the facility.
A nuclear reactor in Finland went into an automatic shutdown after a radiation spike was detected within the plant’s systems on Thursday, but no radiation escaped the facility.
“This is an important and exceptional incident and we consider it important to disseminate correct information about it,” Finnish Minister of Social Affairs and Health Aino-Kaisa Pekonen told reporters.
The elevated readings came from a room that regularly showed higher values during normal operations, and no employee of the power company had been exposed to radiation or been injured.
Jarmo Tanhua, CEO of the TVO nuclear power plant operator, said the incident was an unprecedented event in the facility’s history. TVO is a consortium of electrical and industrial companies.
“There is no danger to people or the environment” from the incident at the Olkiluoto 2 power station in western Finland, said Tomi Routamo, deputy director of nuclear safety authority STUK.
Although radiation levels around the plant are normal and there were no external leaks, STUK described the incident in a tweet as “serious” and said preparedness protocols had been launched together with the plant’s operator, TVO.
STUK later announced: “The situation is stable and the plant is safe”, and radiation levels had returned to normal.
“No event of this kind has happened before in Finland,” Routamo added.
The automated systems detected elevated levels of radioactivity in the steam pipes of the reactor’s cooling system, although the cause of the spike was not yet known and investigations are ongoing, according to Routamo.
An earlier failure in a water pipe occurred at another Finnish nuclear plant some 30 years ago, but the Olkiluoto incident involves so-called primary circuit pipes that are closer to the reactor and therefore face higher concentrations of radiation.
The International Atomic Energy Agency (IAEA) said in a statement that it had been informed of the incident and was in contact with the Finnish authorities.
The TVO plant operator said an automatic reactor shutdown, or “scram,” was activated at 12:22 pm local time (10:22 GMT).
“It was automatically closed for some unknown reason, and nothing really happened,” said TVO spokesperson Pasi Tuohimaa. “There is no harm anywhere.”
The Olkiluoto 2 reactor, which began operating in 1980, will be “brought to a safer state” so that investigations can be carried out, Routamo said.
“They have to check that everything is fine and then they have to have our permission from STUK to start the reactor again,” Routamo added.
Finland receives around a third of its energy from nuclear sources and two new nuclear reactor construction projects are currently underway in the Nordic country.
The most advanced of these, a third reactor at the Olkiluoto site, is running more than 10 years behind schedule due to delays with the plant’s supplier, the French-led Areva-Siemens consortium.