Finland's Olkiluoto 3 (OL3) nuclear power reactor has postponed a restart of test production after maintenance to Feb. 10 from a previous plan to resume output on Feb. 6, operator TVO said on Sunday.

The startup of permanent production, originally scheduled to take place 14 years ago, is now meanwhile expected to take place on March 15, a delay of four days compared with a plan presented on Feb. 2, a regulatory filing by TVO showed.

Under construction since 2005, OL3 has faced several technical mishaps, which sparked costly delays and a lengthy legal battle.

During testing in September, OL3's output for the first time hit full capacity of 1,600 megawatts, making it the most powerful electricity production facility in Europe and the third-most powerful globally, according to TVO.

It is Finland's first new nuclear plant in more than four decades and Europe's first in some 15 years, with a capacity equal to about 14% of total Finnish electricity consumption, TVO has said. (Reporting by Terje Solsvik; Editing by Kim Coghill)