Andrew Norris, of Ilam School, asks :-

Have scientists succeeded in producing power from nuclear fusion?

Rodger Sparks, a nuclear physicist formerly with the Institute of Geological and Nuclear Sciences, responded.

If by power we mean useful energy that can drive an electric motor or a computer, the answer is no.

It has proved very difficult to make fusion work in a way that is useful. In order for two nuclei to fuse together they must approach within touching distance of each other. But the electric charge that all nuclei have causes a force that pushes them apart, and gets stronger the closer they come together. The nuclei can collide and fuse together only if they are moving fast enough that they can overcome the strong repulsive force, and one way to do that is to make a gas, such as hydrogen, very hot.

This requires temperatures of several millions of degrees. The most common method used in experimental fusion reactors is to heat the gas by passing a huge electric current through it. Strong magnetic fields are used to confine the gas in a small volume, to squeeze it together and stop it approaching the container walls. This is called “magnetic confinement”.

There is another way that is being investigated as a nuclear fusion generator. Light from powerful lasers strikes a small plastic sphere containing hydrogen. The intense blast of light literally squeezes the sphere to a tiny dot in a few billionths of a second, and the gas atoms are slammed against each other so violently that some of the nuclei can fuse together. This process is called “inertial confinement”, and it is still a long way from being developed into a practical power generator.

At present, interest is focussing on a new magnetic confinement system called ITER (International Thermonuclear Experimental Reactor) that is being built at Cadarache in the south of France. If all goes well it should begin operating in 2016, but it will still take several more years before it can produce useful power.

It is now about 50 years since the first serious attempts to harness fusion power began, and the prospects are that will be at least another 20 to 30 years before all the problems are solved and a useful generator built.