Fusion power is the power generated by nuclear fusion processes. In fusion reactions two light atomic nuclei fuse together to form a heavier nucleus (in contrast with fission power). In doing so they release a comparatively large amount of energy arising from the binding energy due to the strong nuclear force which is manifested as an increase in temperature of the reactants. Fusion power is a primary area of research in plasma physics.
The term is commonly used to refer to potential commercial production of net usable power from a fusion source, similar to the usage of the term "steam power." The leading designs for controlled fusion research use magnetic (tokamak design) or inertial (laser) confinement of a plasma, with heat from the fusion reactions used to operate a steam turbine which in turn drives electrical generators, similar to the process used in fossil fuel and nuclear fission power stations.
As of July 2010, the largest experiment by means of magnetic confinement has been the Joint European Torus (JET). In 1997, JET produced a peak of 16.1 megawatts (21,600 hp) of fusion power (65% of input power), with fusion power of over 10 MW (13,000 hp) sustained for over 0.5 sec. Its successor, the International Thermonuclear Experimental Reactor (ITER), was officially announced as part of a seven-party consortium (six countries and the EU). ITER is designed to produce ten times more fusion power than the power put into the plasma. ITER is currently under construction in Cadarache, France.
Inertial (laser) confinement, which was for a time seen as more difficult or infeasible, has generally seen less development effort than magnetic approaches. However, this approach made a comeback following further innovations, and is being developed at both the United States National Ignition Facility, the French Laser Mégajoule as well as the planned European Union High Power laser Energy Research (HiPER) facility. NIF reached initial operational status in 2010 and has been in the process of increasing the power and energy of its "shots". Fusion ignition tests are to follow.
Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production was still believed to be unlikely before 2050.