The well-publicized failures of cold fusion may have tainted the field’s reputation, but physicists have been successfully joining nuclei with hot fusion since 1932. Today, research in hot fusion could lead to a clean energy source free from the drawbacks that dog fission power plants. Fusion power plants cannot melt down; they won’t produce long-lived, highly radioactive waste; and fusion fuel cannot be easily weaponized.
At the forefront of the effort to realize fusion-based power is ITER, an international collaboration to build the world’s largest fusion reactor. At the heart of the project is a tokamak, a doughnut-shaped vessel that contains the fusion reaction. In this vessel, magnetic fields confine a plasma composed of deuterium and tritium, two isotopes of hydrogen, while particle beams, radio waves and microwaves heat it to 270 million degrees Fahrenheit, the temperature needed to sustain the fusion reaction. During the reaction, the deuterium and tritium nuclei fuse, producing helium and a neutron. In a fusion power plant, those energetic neutrons would heat a structure, called a blanket, in the tokamak and that heat would be used to turn a turbine to produce electricity.
The ITER reactor will be the largest tokamak ever made, producing 500 megawatts of power, about the same output as a coal-fired power plant. But ITER won’t generate electricity; it’s just a gigantic physics experiment, albeit one with very high potential benefits. A mere 35 thousandths of an ounce of deuterium-tritium fuel could produce energy equivalent to 2,000 gallons of heating oil. And ITER’s process is “inherently safe,” says Richard Pitts, a senior scientific officer on the project. “It can never, ever be anything like what you see in the fission world--in Chernobyl or Fukushima--and this is why it is so attractive.”