BBC Central Europe Reporter Nick Thorpe: "Critics have voiced doubts"

The reactor at Mochovce, about 180km east of Vienna, was built to an original Soviet design, but has since been equipped with Western technology.

It has been opposed by Austria on safety grounds. When the first reactor was switched on last month, the Austrian Chancellor, Viktor Klima, described the decision as an unfriendly and highly irresponsible act. He threatened to withdraw Austria's ambassador.

Prime Minister Vladimir Meciar: plans four reactors

International experts inspected it in May and expressed reservations about the safety of some new features as well as of the original design.

Such criticism has been rejected as politically motivated by the Slovak energy utility responsible for running Mochovce, which claims instead that the plant is a successful example of East-West co-operation in nuclear energy.

A second reactor is expected to go on line next year, after which it is planned that the plant will supply 14 % of the country's electricity.

Slovak Prime Minister Vladimir Meciar: "Water and coal will not do"

Mochovce's first reactor was connected to Slovakia's electricity grid in July. The Slovak Tasr news agency reported that the reactor begun operating at 20% of its 440 megawatt capacity.

Controversy from the start

Controversy has surrounded the power plant at Mochovce from the moment construction began in the early 1980s.

Work was halted in the early 1990s when the project ran into financial problems. A Franco-German plan to complete it collapsed when the European Bank for Reconstruction and Development withdrew in 1996.

The plant was finally finished mainly by Czech and Russian engineers, with limited French and German involvement.