An experimental reactor that could harness nuclear fusion has yet to see the light of day, but preparations for the daring multi-billion-dollar project are well under way. The International Thermonuclear Experimental Reactor , backed by the European Union, the United States, China, India, Japan, South Korea and Russia, is expected to be fully operational in 2026. It is no less than an effort to reproduce the energy-yielded processes of the Sun and other stars -- which defenders say would be safe and cause little damage to its home on Earth.