Areva said it has successfully installed a reactor pressure vessel at the Olkiluoto 3 (OL3) nuclear reactor in Finland.
The power station, which is being built by a consortium of Areva and Siemens for Teollisuuden Voima Oyj, will have a power generation capacity of 1,600MW.
The 420t pressure vessel measuring 5.3m in diameter and 10.6m in height has been installed into the reactor pit with a polar crane.
The Olkiluoto 3 project is the first Generation III+ reactor to be built in the world.
The operation follows the fitting of the reactor dome in September 2009.
Nuclear operation of the OL3 plant including the fuel loading is expected to start at the end of 2012.