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Nuclear watchdog approves power-up of Olkiluoto 3 reactor

Stuk said that the new Olkiluoto nuclear reactor can boost its output beyond five percent of its full capacity. The long-delayed unit was switched on just before Christmas.

The third unit of the Olkiluoto power plant in Eurajoki was started up on 21 December. Image: Heikki Saukkomaa / Lehtikuva

The Radiation and Nuclear Safety Authority (Stuk) has given permission to energy company Teollisuuden Voima (TVO) to increase the capacity of its new Olkiluoto 3 (OL3) nuclear power unit.

The capacity may be increased to more than five percent of the unit's full thermal capacity of 4,300 megawatts, STUK said in a press release on Tuesday.

OL3 was started up in Eurajoki, southwest Finland, on 21 December.

"After the start-up, the low power tests carried out by TVO together with the plant provider showed that the plant is operating as planned," Stuk said on Tuesday.

TVO will next need a permit from Stuk before it increases the reactor's capacity to more than 30 percent of full capacity.

Electricity generation is scheduled to start at 30 percent later this month, with full regular electricity generation slated to begin in June.

Olkiluoto to provide nearly 1/3 of nation's electricity

After this, the entire Olkiluoto power plant is expected to generate almost a third of Finland's electricity.

Its first two units began commercial operations in 1979 and 1982. Construction of OL3 began in 2005 with a scheduled start date of 2009. It was beset by a series of delays and cost overruns.

These spurred an extended legal battle between TVO and main contractor Areva, which was resolved in 2018. The total cost of the project was estimated to have risen to some 11 billion euros.

In 2015, TVO shelved plans for a fourth reactor.