Nuclear fusion power

Fusion power is a form of power generation in which energy is generated by using fusion reactions to produce heat for electricity generation. Fusion reactions fuse two lighter atomic nuclei to form a heavier nucleus, releasing energy. Devices designed to harness this energy are known as fusion reactors.

The fusion reaction normally takes place in a plasma of deuterium and tritium heated to millions of degrees. In stars, gravity contains these fuels. Outside of a star, the most researched way to confine the plasma at these temperatures is to use magnetic fields. The major challenge in realising fusion power is to engineer a system that can confine the plasma long enough at high enough temperature and density.

As a source of power, nuclear fusion has several theoretical advantages over fission. These advantages include reduced radioactivity in operation and as waste, ample fuel supplies, and increased safety. However, controlled fusion has proven to be extremely difficult to produce in a practical and economical manner. Research into fusion reactors began in the 1940s, but as of 2017^[update], no design has produced more fusion energy than the energy needed to initiate the reaction, meaning all existing designs have a negative energy balance.

Over the years, fusion researchers have investigated various confinement concepts. The early emphasis was on three main systems: z-pinch, stellarator and magnetic mirror. The current leading designs are the tokamak and inertial confinement (ICF) by laser. Both designs are being built at very large scales, most notably the ITER tokamak in France, and the National Ignition Facility laser in the USA. Researchers are also studying other designs that may offer cheaper approaches. Among these alternatives there is increasing interest in magnetized target fusion and inertial electrostatic confinement.

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