Coming Together with Nuclear Fusion

Soon after researchers discovered the fission process, they discovered another process, called fusion. Fusion is essentially the opposite of fission. In fission, a heavy nucleus is split into smaller nuclei. With fusion, lighter nuclei are fused into a heavier nucleus.

The fusion process is the reaction that powers the sun. In a series of nuclear reactions in the sun, four hydrogen-1 (H-1) isotopes are fused into a helium-4 (He-4) with the release of a tremendous amount of energy. Here on Earth, people use two other isotopes of hydrogen: H-2, called deuterium, and H-3, called tritium. (Deuterium is a minor isotope of hydrogen, but it’s still relatively abundant. Tritium doesn’t occur naturally, but people can easily produce it by bombarding deuterium with a neutron.) The following equation shows the fusion reaction: