Video: Second sun

Handle with care (Image: EIT/Goddard Space Flight Centre/NASA)

Editorial: Fusion is a gamble worth taking

THE balmy south of France has always been a magnet for sun worshippers. So it is perhaps fitting that here, not far from the Côte d’Azur, an international team of researchers is building a machine to recreate the sun. It will take tens of thousands of tonnes of steel and concrete, plus a whole host of more unusual materials: beryllium, niobium, titanium and tungsten; frigid liquid nitrogen and helium. Oh, and a supply of burnt coconuts.

This eclectic mix of ingredients will be turned into ITER, the International Thermonuclear Experimental Reactor – the next big thing in nuclear fusion research. When completed in 2018, the reactor will fuse together two heavy isotopes of hydrogen to release vast quantities of energy. In theory, the result will be clean electricity galore with no carbon emissions and far less radioactive waste than today’s nuclear fission reactors leave behind.

So why we are not already flooding our electricity grids with fusion energy? While the concept of nuclear fusion is simple, the practicalities are anything but. That’s because the nuclei themselves are reluctant participants: each carries a positive electrical charge and these repel one another, so forcing two nuclei together is almost impossible. Only at stupendously high temperatures do the nuclei acquire enough energy to overcome their mutual aversion, smash into one another, and fuse.

It is much the same picture in the sun. There, heat is generated from the fusion of hydrogen nuclei. But the fuel barely smoulders even at 15 million kelvin, the temperature of …