Fusion energy

Fusion powers the Sun and stars, and is potentially an environmentally responsible and intrinsically safe source of essentially limitless energy on earth. Experiments at the Joint European Torus (JET) in the UK, which has produced 16MW of fusion power, and at other facilities, have shown that fusion can be mastered on earth. Fusion power is still being developed, and will not be available as soon as we would like. We are confident that it will be possible to build viable fusion power stations, and it looks as if the cost of fusion power will be reasonable. But time is needed to further develop the technology in order to ensure that it would be reliable and economical, and to test in power station conditions the materials that would be used in its construction. Assuming no major surprises, an orderly fusion development programme— properly organized and funded—could lead to a prototype fusion power station putting electricity into the grid within 30 years, with commercial fusion power following some ten or more years later. A fusion power station is effectively a tiny ‘artificial sun’. Reactions between light atomic nuclei in which a heavier nucleus is formed with the release of energy are called fusion reactions. The reaction of primary interest as a source of power on Earth involves two isotopes of hydrogen (Deuterium and Tritium) fusing to form helium and a neutron: . . . D + T → 4He + n + energy (17.6 million electric volts [Me V]) (7.1) . . . Energy is liberated because Helium-4 is very tightly bound: it takes the form of kinetic energy, shared 14.1 MeV/3.5MeV between the neutron and the Helium-4 nucleus (a chemical reaction typically releases ∼1 eV [electron volt], which is the energy imparted to an electron when accelerated through 1 volt). To initiate the fusion reaction (1), a gas of deuterium and tritium must be heated to over 100 million◦C (henceforth: M◦C)—ten times hotter than the core of the Sun. At a few thousand degrees, inter-atomic collisions knock the electrons out of the atoms to form a mixture of separated nuclei and electrons known as a plasma.