Fusion reactor

Fusion power is energy generated by nuclear fusion, or more broadly, the use of that power as an energy source. Fusion has a number of advantages over fission as a source of power, including reduced radioactivity, ample fuel supplies, and increased safety. However, controlled fusion has proven to be extremely difficult to produce in a practical manner. Research into fusion reactors began in the 1940s, but as of 2017^[update] no design has produced positive net energy.

Fusion reactions fuse two lighter atomic nuclei to form a heavier nucleus. It is the process used in stars to produce energy and heavier elements. The reaction normally takes place in a plasma of deuterium and tritium heated to millions of degrees. At such temperatures the only way to confine the plasma while the reactions take place is to use electric or magnetic fields. Designing a system that can confine the plasma long enough at high enough temperature and density is the major challenge in the development of fusion power.

Many confinement concepts have been investigated. In the early days the three main systems were the z-pinch, stellarator and magnetic mirror. Today, the current leading designs are the tokamak and inertial confinement (ICF) by laser. Both of these designs are being built at very large scales, most notably the ITER tokamak in France, and the National Ignition Facility laser in the USA. Many other designs are also being studied as they may offer lower-cost approaches, among these the magnetized target fusion and new inertial electrostatic confinement designs are seeing increased interest. As of 2017^[update], these technologies cannot produce more energy than are required to initiate and sustain a fusion reaction.

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