Finland's nuclear safety and radiation regulator, Stuk, has found no reason in principle why another nuclear power reactor could not be built at the Olkiluoto site. Two boiling water reactors already operate at the site and a pressurized water reactor is under construction, while owner Teollisuuden Voima Oyj has submitted an application to government for a decision in principle to allow construction of a fourth unit. Stuk's preliminary safety assessment said that a 1000-1800 MWe reactor could be built at Okiluoto, but the five alternative arrangements TVO has suggested would require varying amounts of extra structural work. Two other firms, Fennovoima and Fortum, have also asked the Finnish government for a decision in principle for new reactors. Stuk said it would complete its preliminary assessment of those plans by the end of October.