Introduction to fusion


Nuclear fusion is one of the most promising options for generating large amounts of carbon-free energy in the future.

Illustration of the fusion reaction

Fusion is the process that heats the Sun and all other stars, where atomic nuclei collide together and release energy (in the form of neutrons, see diagram on the right). Fusion scientists and engineers are developing the technology to use this process in tomorrow’s power stations.

To get energy from fusion, gas from a combination of types of hydrogen – deuterium and tritium – is heated to very high temperatures (100 million degrees Celsius). One way to achieve these conditions is a method called ‘magnetic confinement’ – controlling the hot gas (known as a plasma) with strong magnets. The most promising device for this is the ‘tokamak’, a Russian word for a ring-shaped magnetic chamber.

Advantages of fusion power

The world needs new, cleaner ways to supply our increasing energy demand, as concerns grow over climate change and declining supplies of fossil fuels. Power stations using fusion would have a number of advantages:

  • No carbon emissions. The only by-products of fusion reactions are small amounts of helium, which is an inert gas that will not add to atmospheric pollution.
  • Abundant fuels. Deuterium can be extracted from water and tritium is produced from lithium, which is found in the earth’s crust. Fuel supplies will therefore last for millions of years.
  • Energy efficiency. One kilogram of fusion fuel can provide the same amount of energy as 10 million kilograms of fossil fuel.
  • No long-lived radioactive waste. Only plant components become radioactive and these will be safe to recycle or dispose of conventionally within 100 years.
  • Safety. The small amounts of fuel used in fusion devices (about the weight of a postage stamp at any one time) means that a large-scale nuclear accident is not possible.
  • Reliable power. Fusion power plants should provide a baseload supply of large amounts of electricity, at costs that are estimated to be broadly similar to other energy sources.

Progress in fusion research

JET plasma superimposed inside a photo of the JET vacuum vessel

Many of the scientific hurdles in fusion have now been overcome by researchers. The world’s largest tokamak, JET (Joint European Torus), has produced 16 megawatts of fusion power and proved the technical feasibility of fusion using deuterium and tritium, currently considered the most efficient fuels. The challenge now is to prove fusion can work on a power plant scale.

The next steps

International fusion research is following a roadmap to achieve power generation by 2050. It focuses on three main projects:

  • ITER – a multinational project that is being built in the south of France. ITER will be a 500 megawatt tokamak (equivalent to a small power plant) and aims to confirm that fusion power will be possible on a commercial scale;
  • IFMIF (International Fusion Materials Irradiation Facility) – a device that will test the materials needed in a fusion power station, planned to operate in parallel with ITER;
  • DEMO – a demonstration power plant supplying fusion electricity to the grid. This is being designed now and would be constructed during ITER and IFMIF operation. If successful, it will be followed by the first generation of commercial fusion power stations.

Fusion in the UK

The United Kingdom’s fusion research programme is based at Culham Centre for Fusion Energy (CCFE) in Oxfordshire. The work is funded by the Engineering and Physical Sciences Research Council and by the European Union under the Euratom treaty.

The UK contributes to fusion research in two main ways:

  • Its own fusion programme, centred on the MAST (Mega Amp Spherical Tokamak) device. The UK programme also makes important contributions to ITER preparations and to theory, materials and technology research;
  • Operating JET, Europe’s flagship experiment. JET is situated at CCFE next to the UK’s fusion laboratory. CCFE hosts the JET facility on behalf of fusion researchers around Europe via a contract between the European Commission and the United Kingdom Atomic Energy Authority.