Pulling power

The race to harness the power of nuclear fusion as a commercial energy source began to intensify this week, with development of a powerful superconducting magnet.

The 150-tonne magnet, designed by a team of engineers from MIT in the US and JAERI, the Japan Atomic Energy Research Institute, is the latest stage in an international project to build a prototype nuclear fusion power plant, called Iter.

The device is a testbed for the 925-tonne magnet that will eventually be used in the power plant, which is to be built by European, Japanese and Russian fusion teams at a cost of around 4bn Euros (£2.5bn).

Nuclear fusion, which replicates the atomic reaction in the sun, does not produce greenhouse gases, and has significantly fewer waste disposal problems than fission.

The Iter reactor is likely to be completed in 10 years’ time, and this latest development shows a significant portion of the technology is available, said Joseph Minervini, a senior research engineer at MIT’s Plasma Science and Fusion Centre.

‘This is a high-level demonstration that the magnetic technology is now quite advanced. Magnets of this size and complexity have not been produced before,’ he said.

The reactor is based on the Tokamak concept, in which an electrically charged gas, or plasma, is controlled within a magnetic field and fed with deuterium tritium fuel. Fusion takes place when the plasma is hot enough, dense enough and contained for long enough for the atomic nuclei within it to start fusing together, releasing large amounts of energy.

Researchers involved in a rival UK-Japanese project, based on the use of a high-powered laser, claimed recently they could build a prototype reactor in eight years for less than £1bn.

The concept is based on inertial confinement fusion, which generates energy when frozen pellets of deuterium tritium fuel are fired into a vacuum chamber and hit by two lasers. The team said it could make commercial fusion power possible within 25 years.

But Gary Voss, group leader of future concepts at Culham Science Centre, said people have been working on inertial confinement fusion for many years, and it is generally considered to be behind magnetic confinement fusion in its development. ‘Iter is the leading state-of-the-art project attempted, and it is getting closer.’

Fusion power using magnetic confinement technology could be available within 30 years given the political will and enough funding, he said.In tests at the Fusion Research Establishment near Tokyo the 150-tonne magnet produced a field of 13 tesla, about 260,000 times more powerful than the Earth’s magnetic field.

The research team also found it could operate the superconducting magnet in pulses, bringing it to 13 tesla and back down again in a few seconds, allowing it to initiate and heat the plasma.