HELSINKI -- Finland's long-delayed and costly new nuclear reactor went online Saturday amid expectations that it will boost the Nordic country’s electricity self-sufficiency and help to achieve its carbon neutrality targets.

       Finnish operator Teollisuuden Voima said the Olkiluoto 3 nuclear reactor in the country's west started supplying electricity to the national power grid.

       It will go through a trial period of about four months during which it will generate electricity only at a fraction of its 1,600 megawatt capacity.

       The reactor will reach peak capacity in July when it will cover an estimated 14% of Finland’s total electricity demand, reducing the country’s need to import electricity from Norway, Russia and Sweden, Teollisuuden Voima said.

       The last time a new nuclear reactor was commissioned in Finland was over 40 years ago. The Olkiluoto 3 is among western Europe's first new reactors in over a decade.

       The Olkiluoto 3 is a third generation European-type pressurized water reactor developed and built by a joint venture between France’s Areva and Germany’s Siemens. Construction began in 2005 and was to be completed four years later. However, the project was plagued by several technological problems that lead to lawsuits.

       Finnish public broadcaster YLE said late last year that the reactor's final price tag was put at around 11 billion euros ($12 billion) - almost three times more than what was initially estimated.

       Finland now has five nuclear reactors in two power plants located on the shores of the Baltic Sea. Combined, they cover more than 40% of Finland’s electricity demand.