The German-designed Atucha II plant is expected to be fully operational in six to eight months after engineers run a series of tests.

Construction on the plant began in the early 1980s, but worked soon stopped and did not resume until 2006, when then-president Nestor Kirchner (2003-2007), the current leader's late husband, ordered the plant to be completed.

"We are diversifying our energy grid," Kirchner told a crowd of hundreds of workers as she opened the plant.

Argentina currently relies heavily on natural gas and oil for its energy, much of which is imported.

Once fully operational, Antucha II will supply some 700 megawatts of energy to the power grid, enough for the needs of some four million people. Argentina has just over 40 million people.

Argentina's other nuclear plants are Atucha I (335 megawatts) and the Embalse plant (600 megawatts). Once the new plant is online 10 percent of Argentina's electrical needs will be provided by nuclear power.

Plans are on the drawing board for an Atucha III nuclear plant as well as an overhaul of the Embalse plant to add 30 years to its operational life, said Planning Minister Julio de Vido.

Atucha II is located on the banks of the Parana river in the town of Zarate, in Buenos Aires province, some 100 kilometers (62 miles) north of the capital. It was built at a cost of more than 2.4 billion dollars.