France has won the competition to host the International Thermonuclear Experimental Reactor (ITER), the world's first nuclear-fusion reactor. Japan fought hard to win the project, but in the end the projected cost and the promise of playing a significant role in subsequent research gave Tokyo ample reason to withdraw its bid. That may not have been a bad thing: It is still unclear if one of the most costly projects in history will be worth the price tag. Nevertheless, Japan must now work exceptionally hard to ensure that the program is a success.

Thermonuclear fusion utilizes the same process that powers the sun -- nuclear-fusion reactions -- to produce energy. Scientists at the ITER plant will create nuclear-fusion reactions in a tokamak -- a doughnut-shaped chamber -- by filling it with a plasma of deuterium and lithium and heating it to temperatures of more than 100 million degrees to force the nuclei to fuse.

Fusion offers numerous advantages over other sources of nuclear energy. It is efficient: It is estimated that just 100 grams of deuterium and 3 tons of lithium can produce 1 gigawatt of electricity. It is clean: The radioactive waste that is produced has a short life and there are no carbon-dioxide emissions, so the process does not contribute to global warming. Finally, deuterium, the principal fuel, is found in water, so supplies are abundant.