HELSINKI, Feb. 10 (Xinhua) -- An automatic emergency shutdown of the Olkiluoto nuclear power plant in southwestern Finland on Dec. 10 was caused by a human operation error, not any technological fault or equipment breakdown, the Finnish Radiation and Nuclear Safety Authority (STUK) reported on Wednesday.
This was the first emergency shutdown of a nuclear plant in Finland, since the start of using nuclear energy in the national power grid in the mid-1970s.
STUK explained that during maintenance a pump had been stopped, and when it was restarted improperly water had started going in the wrong direction, causing erroneous entry of hot water to the reactor cooling system.
STUK Deputy Director Tomi Routamo elaborated on Wednesday that this error had resulted in the development of highly radiating isotope 16 in the system. Then radiation levels in the circulation of steam increased three- or fourfold, triggering the emergency shutdown. Initially, a much more serious fuel leak was suspected.
Routamo said the International Atomic Energy Agency (IAEA) had also reacted upon a Finnish notification while the seriousness of the situation was still uncertain. Finland also notified neighboring countries. Olkiluoto is operated by the Finnish energy company Teollisuuden Voima.
After the incident, STUK had admitted in a statement that informing the public about the shutdown was too slow. The municipality of Eurajoki, in the immediate vicinity of the plant, was not informed until several hours after the incident, national broadcaster Yle said in an online article dated Dec. 17.
The relatively slow information about the incident was criticized at the time. In a survey by the Finnish National Rescue Association published on Wednesday, half of the respondents were dissatisfied with the communications about the incident.
