The world’s biggest nuclear fusion experiment may lead to endless clean energy

Thirty-five countries are working together to build the world’s first large-scale nuclear fusion reactor—and if successful, their efforts could help humans harness the “ultimate green energy.”

The reactor, currently estimated to cost $20 billion, is now under construction in southern France. Nuclear fusion—when atoms’ cores collide into each other, releasing tremendous amounts of energy—is much more powerful than reactions used in current nuclear plants and produces no radioactive waste or greenhouse gasses.

That’s primarily because it’s fueled by a type of hydrogen readily extractable from water, making it a limitless energy source. Sustained nuclear fusion has never been realized on a large scale before, and the project’s estimated budget has quadrupled over the decade-long planning period. While some skeptics say the project is too expensive and not scalable, the reactor’s engineers expect it to become fully operational in 20 years.

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