Generating electricity by nuclear fusion has long looked like a chimera. A reactor being built in Germany may change that

Fusion power

Next ITERation?

Sep 3rd 2011 | from the print edition

AS THE old joke has it, fusion is the power of the future—and always will be. The sales pitch is irresistible: the principal fuel, a heavy isotope of hydrogen called deuterium, can be extracted from water. In effect, therefore, it is in limitless supply. Nor, unlike fusion’s cousin, nuclear fission, does the process produce much in the way of radioactive waste. It does not release carbon dioxide, either. Which all sounds too good to be true. And it is. For there is the little matter of building a reactor that can run for long enough to turn out a meaningful amount of electricity. Since the first attempt to do so, a machine called Zeta that was constructed in Britain in the 1950s, no one has even come close.
At the moment, the main bet being placed by fusion enthusiasts is on ITER, the International Thermonuclear Experimental Reactor, a research machine that can hold 840 cubic metres of hot, gaseous fuel. It is being bolted together at a projected cost of €15 billion ($22 billion) in the south of France. ITER is what is known as a tokamak, a doughnut-shaped device invented in Russia at about the same time Zeta was active. Deuterium (along with an even heavier hydrogen isotope called tritium, which is made by bombarding either deuterium or lithium with neutrons) is injected into the doughnut, heated to the point at which its electrons break free and it forms a plasma, and squeezed by magnetic fields.

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