An automatic emergency shutdown of the Olkiluoto nuclear power plant in southwestern Finland on December 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.
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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.