The promise of clean energy has moved closer to realisation with the launch of the latest stage in the development of nuclear fusion power.
This week, Europe’s nuclear scientists, meeting at the Culham Science Centre in Oxfordshire, explained how the £3.9bn ($5.72bn) International Thermonuclear Experimental Reactor for fusion power would be built and what new technologies would be involved.
The ITER project follows on from the European Union’s JET fusion research project, which began in 1983. The ITER reactor will be double the size of the JET reactor and is expected to cost £122m to run annually. The ITER partners are currently the European Union, Japan and Russia, though the US may yet join.
Commercial use 40 years off
ITER will be the first nuclear fusion device to generate electricity at commercial levels. It will also test the systems that will form the basis of future commercial fusion power stations. Scientists declined to give specific dates for the commercial use of fusion, but suggest 30 to 40 years.
In a fusion reaction, energy is produced when atoms are fused together to form heavier atoms. The gaseous fuel used is heated to temperatures in excess of 100mºC — several times hotter than the centre of the Sun – and becomes a plasma.
Powerful magnetic fields are used to stop the plasma coming into contact with the reactor walls. The most promising magnetic confinement configuration is toroidal, (doughnut-shaped), and the most advanced of these is known as the Tokamak. The JET reactor at Culham is the largest Tokamak in the world.
The fuels used for fusion are the hydrogen isotopes, deuterium and tritium and they are in plentiful supply. Deuterium occurs naturally and can be extracted from water and tritium can be manufactured by bombarding lithium – a common metal – with neutrons in a reactor. These fuels are cheap to find and produce. One kilogram has the equivalent energy of 1,000 tonnes of any fossil fuel.
The advantages of fusion reactors over existing fission nuclear power stations include the fact that they cannot reach critical meltdown. They also procuce only small amounts of short-lived radioactive material and the inert gas helium as waste.
France, Japan and Canada are bidding for ITER to be based within their borders. One source close to the project told The Engineer that Canada was favourite to win the contract as its bid is a ‘wholly commercial’ one, with no government involvement, and that it is an ‘excellent location’. The ITER reactor will be a huge building and transporting its components will be very difficult. The Canadian site has the advantage of being next to the Great Lakes that sit between Canada and the US, providing easy access for ship-borne transportation.
Belarus-born Dr Sergei Dudarev, a principal fusion scientist at the Culham Science Centre in Oxfordshire explained that lessons had been learned from the existing Joint European Torus fusion project that could be applied to ITER.
He said that carbon-based materials were not suitable because they reacted with the fusion fuel and formed volatile hydrocarbons, which prevent the tritium reacting.’Alternative materials are needed that will not be so reactive in terms of the absorption of carbon – and that are also high temperature-resistant.
‘From that point of view, tungsten, with its high melting temperature and beryllium, which is not reactive, are prime candidates for the plasma facing materials inside the reactor.’