Lyman Spitzer devised and began work on the first fusion device – a stellarator – at the Princeton Plasma Physics Laboratory in 1951. The energy density of fusion reactions in gas is very much less than for fission reactions in solid fuel, and as noted the heat yield per reaction is 70 times less. The European Union (EU) and France would contribute half of the then estimated €12.8 billion total cost, with the other partners – Japan, China, South Korea, USA and Russia – putting in 10% each. Because stellarators have no toroidal plasma current, plasma stability is increased compared with tokamaks. Fusion can also be combined with fission in what is referred to as hybrid nuclear fusion where the blanket surrounding the core is a subcritical fission reactor. "And so we need a carbon free source of energy that can complement renewables in the future. Nuclear fusion has the potential to be an unlimited clean, safe and carbon-free energy source and we want the first commercially viable machine to be …
Fusion power could easily satisfy the energy needs associated with continued economic growth, given the ready availability of fuels. Experiments were due to begin in 2018, when hydrogen will be used to avoid activating the magnets, but this is now expected in 2025. The tokamak with 1.8 metre major radius is the first to use Nb3Sn superconducting magnets, the same material to be used in the ITER project. The result is a magnetic field with force lines following spiral (helical) paths that confine and control the plasma.In magnetic confinement fusion (MCF), hundreds of cubic metres of D-T plasma at a density of less than a milligram per cubic metre are confined by a magnetic field at a few atmospheres pressure and heated to fusion temperature.Research is also being carried out on several types of stellarator. With a half-life of about 12.3 years, the presence of tritium remains a threat to health for about 125 years after it is created, as a gas or in water, if at high levels.
After deadlocked discussion, the six partners agreed in mid-2005 to site ITER at Cadarache, in southern France. The technical objectives of STEP are: to deliver predictable net electricity greater than 100 MW; to exploit fusion energy beyond electricity production; to ensure tritium self-sufficiency; to qualify materials and components under appropriate fusion conditions; and to develop a viable path to affordable life-cycle costs.In March 1989, spectacular claims were made for another approach, when two researchers, in the USA (Stanley Pons) and the UK (Martin Fleischmann), claimed to have achieved fusion in a simple tabletop apparatus working at room temperature. Designs for plasma containment must consider:In general terms, fusion reactors would create far less radioactive material than a fission reactor, the material it would create is less damaging biologically, and the radioactivity "burns off" within a time period that is well within existing engineering capabilities for safe long-term waste storage.To produce self-sustaining fusion, the energy released by the reaction (or at least a fraction of it) must be used to heat new reactant nuclei and keep them hot long enough that they also undergo fusion reactions.Confinement refers to all the conditions necessary to keep a plasma dense and hot long enough to undergo fusion. The funds will contribute to core development work on high temperature superconducting (HTS) magnets and plasma exhaust system (divertor) technologies.
It also comes without the danger of explosions.Despite the hopes, no one to date has managed to get more energy out of a fusion experiment than they have put in.The most widely known approach to making fusion happen involves a doughnut shaped vacuum chamber called a Tokomak.
Up to 16 MW of fusion power for one second and 5 MW sustained has been achieved in D-T plasmas using the device, from 24 MW of power injected into its heating system, and many experiments are conducted to study different heating schemes and other techniques. In September 2016 it achieved a plasma pressure of 2.05 atmospheres at a temperature of 35 million degrees Celsius. PETAL will be coupled with LIL to demonstrate the physics and laser technology of fast ignition. It has achieved an ion temperature of 13.5 keV (about 160 million degrees) and plasma stored energy of 1.44 million joules (MJ).A range of MTF systems are currently being experimented with, and commonly use a magnetic field to confine a plasma with compressional heating provided by laser, electromagnetic or mechanical liner implosion. Nova failed to do this and was closed in 1999, but provided essential data that led to the design of NIF.
There would be no danger of a runaway fusion reaction as this is intrinsically impossible and any malfunction would result in a rapid shutdown of the plant.In a fusion reactor, the concept is that neutrons generated from the D-T fusion reaction will be absorbed in a blanket containing lithium which surrounds the core.