Rostock, Germany - Cost over-runs may double the cost of a world project to build a new kind of nuclear reactor that leaves behind practically no nuclear waste, according to the deputy chief scientist Monday.

The 5.5-billion-euro (7.7-billion-dollar) ITER project, run by the European Union, the United States, Russia, China, Japan, India and South Korea, is building a fusion reactor to generate electricity in Cadarache in southern France.

Norbert Holtkamp, deputy director of the project, told a conference in Rostock, Germany that the final cost would exceed the budget by at least 10 per cent and perhaps 
100 per cent.

He told the fusion technology conference that reasons for the over-run included the higher costs of raw materials and energy as well as sophisticated new technologies that scientists want to include.

Octavi Quintana-Trias, an official from the European Commission, said the EU would pay 50 per cent of the cost of ITER, which would demonstrate that a fusion nuclear reactor was feasible.

In fusion reactors, atoms in a very hot gas fuse together, releasing energy. The heat from stars such as the sun is created in this type of nuclear reaction. Today's fission reactors split atoms, leaving radioactive waste.

ITER plans call for the Cadarache reactor, a type known as a tokamak, to produce power for the first time in 2018.

Quintana-Trias forecast that governments would pay up.

"At worst, the cost of this plant will be less than we spend on just a single day for energy generation in the European Union," he said. But if ITER failed, the world's fusion research would collapse.

The conference till Friday is being attended by more than 700 scientists from round the world. (dpa)