The Olkiluoto 2 reactor was disconnected from the national grid following a generator malfunction, said Teollisuuden Voima Oyj (TVO), a Finnish nuclear power company operating the plant.
The company launched an investigation into the incident. The unit, put into operation on February 18, 1980, will remain disconnected for at least 24 hours.
Olkiluoto 2 along with Olkiluoto 1 produces one sixth of all electricity consumed in the country, according to TVO. The Olkiluoto nuclear power plant is located in the Finnish region of Satakunta.