Nuclear Fusion
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The lightest nuclei can fuse to form heavier nuclei, releasing energy in the process.
An example is the sequence of fusion processes that change hydrogen into helium in the Sun.
They are listed here with the energy released in each: |
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The net effect is to transform four protons into a helium nucleus plus two positrons, two neutrinos, and two gamma rays.
More massive stars can fuse heavier elements in their cores, all the way up to iron, the most stable nucleus.
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There are three fusion reactions, shown on the right that are being considered for power reactors.
These reactions use very common fuels – deuterium or tritium – and release much more energy per nucleon than fission does. A successful fusion reactor has not yet been achieved, but fusion, or thermonuclear, bombs have been built. Several geometries for the containment of the incredibly hot plasma that must exist in a fusion reactor have been developed – the tokamak, which is a torus; or inertial confinement, which is tiny pellets of deuterium ignited by powerful lasers.
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