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Old 07-13-2006, 09:02 PM
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Issue 124 , July 2006
The return of nuclear fusion?
by Fred Pearce
The world's biggest ever nuclear fusion reactor is about to begin construction in the hills of Provence. But with persistent doubts over fusion's capacity to generate energy efficiently and a raft of engineering conundrums, is this really money well spent?
The author's book "The Last Generation: How nature will take her revenge for climate change" is published in June by Eden Project Books
They call themselves "fusion gypsies"—scientists who have travelled the world, moving from one nuclear reactor to the next, living the dream that some day, somewhere, they can re-create the reactions that take place in the heart of the stars to generate huge amounts of cheap, clean electricity for the world.

Their goal is nuclear power, but not as we know it. This is fusion and not fission. Fission involves mining, processing and irradiating vast amounts of uranium, and leaving behind an even larger legacy of radioactive waste with half-lives stretching into the next ice age. Whereas, say the fusion gypsies, a small vanload of fuel supplied to a fusion power station could supply the electricity needs of a city of 1m people for a year, and leave behind only paltry amounts of radioactive waste that will decay to nothing within a century.

Fission reactors split atoms to make power; fusion reactors force the elemental particles of the universe together till they fuse, releasing energy in the process. Fusion powers the sun, the gypsies say, and one day it could power the world's electricity grids too.

Fusion research got going in the 1950s. The first fusion gypsies are approaching retirement. But scientific progress has been slow and funding sporadic. They have yet to see a watt of power delivered to any grid anywhere. But earlier this year, after more than a decade in the doldrums, the gypsies had their biggest boost, when governments representing most of the world's population decided to invest $10bn in trying to make the dream come true.

This summer, the fusion gypsies are reassembling in the wooded hills of Provence in southern France, where a new machine is to be built. Britons, Australians, Russians, Americans, Germans, Chinese, Japanese Czechs and many others are united now in a last stand to prove to the world they were right all along. John How, a bearded, sandalled Brit was the pioneer. He bought himself a farmhouse a couple of years ago in Provence in anticipation of just this moment. Now he can settle down at last, he told me, after a career stretching from Australia to Germany, France and Britain. "It's now or never for fusion power," he said.

The moment seems right. As oil prices soar, as concern grows about global warming, and as politicians balance the potential of conventional nuclear power and renewables, there is a growing need for a new source of electricity that combines the capacity of a nuclear power plant with the cleanness and safety of a wind farm. Fusion could, eventually, be the answer. Even fusion's most ardent supporters admit it will be several decades before the technology becomes commercial. But if the physics comes to fruition, it could be very big—just as the oil runs out and climate change accelerates.

In May, the governments of the EU, the US, China, India, Japan, Russia and Korea initialled a treaty to build the International Thermonuclear Experimental Reactor (ITER), the world's largest fusion machine, in a forest at Cadarache in Provence. They will sign formally in November. Half of the money will come from the EU. ITER will take a decade to build and will then run for two further decades, performing tens of thousands of fusion experiments. At the end of that time, say its backers, the world will know once and for all if nuclear fusion has a viable future. Technically viable, that is. The economics will come later.

"This is the most significant science treaty ever signed, the world's biggest scientific collaboration," said Janez Potoc?nik, EU commissioner for science and research, at the initialling ceremony in Brussels. Britain's top fusion administrator, Chris Llewellyn Smith, smiled in the background. A tall, white-haired physicist and knight of the realm, he is director of the world's largest existing reactor, in the village of Culham in Oxfordshire. He says simply: "This project is of huge significance. It could lift billions out of poverty," by providing them with cheap electricity for the first time.

Not everyone is so sure. Greens dismiss the project as a "dangerous toy" and a waste of money that could be paying for thousands of wind farms. Even among physicists not everyone thinks that fusion has a future. Embarrassingly, shortly before the Brussels ceremony, America's leading research journal Science published the posthumous testament of one of fusion's pioneers, William Parkins, who concluded that "the history of this dream is as expensive as it is discouraging." The US alone, Parkins said, had spent $20bn on the fusion quest over 50 years, without result. It was time to write off the venture. The journal's editor publicly backed the conclusion. As of May, the world is engaged in a game of double or quits to prove them wrong.


How does fusion work?

To see fusion in action, go to Culham in Oxfordshire. As well as being the largest, the fusion reactor known as JET (Joint European Torus) is, by common consent, the world's most successful. It is the prototype for the ITER machine, standing 20 metres high and surrounded by an acre of equipment on the site of the British Atomic Energy Authority.

It cost €1bn to build and so far, over its 23-year life, has cost another €1bn to run. It has at times soaked up half of Britain's entire government budget for energy research.

The reactor is constantly doing experiments into the more abstruse physics of how to make fusion happen, how to control it and how to do it better. Its greatest moment came in 1997 when, for a fraction of a second, the reactor produced 16.1 megawatts of electricity, which is still a world record. Headlines went round the world, though few mentioned that it took 25 megawatts to heat the reactor, and even more to run the other bits needed to keep it going, just for that fraction of a second.

The fact is that the Culham reactor, far from producing power, is by some way Britain's biggest single electricity user. During a typical experiment, of a kind undertaken several times a night and some 66,000 times in its history, the plant briefly consumes up to 2 per cent of all the electricity capacity available in the country. Its proximity to Didcot power station is probably no coincidence.

So what happens inside this extraordinary machine? Superficially it is a gas-burning boiler. But it is a boiler that requires only a tiny amount of nuclear fuel—about a gram at any one time—to generate vast amounts of energy. The fuel is made up of two isotopes of hydrogen, known as deuterium and tritium. The former is extracted from ordinary water. The latter, which is mildly radioactive, can be collected from the waste streams of some nuclear fission reactors, manufactured from lithium, a relatively common metal, or generated inside the fusion reactor itself. The purpose of the reactor is to burn these two isotopes at super-high temperatures, generated by the world's hottest microwave oven. Heated enough, they form a plasma—a superheated gas—and fuse together. When that happens, they create another element, helium, plus large amounts of energy.

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