Monday, August 2, 2010

Fusion Power

2010 is a big year for nuclear fusion but experts fear that a lack of fuel could push the dream of cheap, safe, clean and limitless energy far into the future.

As fossil fuels run dry and increasingly desperate attempts are made to control carbon emissions, the seductive promise of fusion energy has attracted billions of pounds of international funding.

A laser at the National Ignition Facility in California will fuse together pairs of hydrogen nuclei, releasing high energy neutrons that should, for the first time, produce more power than the laser itself has put in.

As Professor Mike Dunne, head of Europe's laser fusion project says, "The first credible attempt is now just a few months away after 50 years of trying. Incredibly exciting times."

Safety and Security
Rumbling voices of discontent may, however, be audible beneath the Californian back-slapping.

Dr. Marc Beurskens at the Culham Centre for Fusion Energy in Oxfordshire says that nuclear waste is not a serious problem as tritium decays relatively quickly.

There is, he says, "a proliferation issue with tritium because it is used in weapons and obviously decent security has to be set up, but it's much easier to control than stocks of uranium."

That still leaves the fundamental problem with fusion - the fuel supply.

Professor Steve Cowley, director of the fusion programme at the United Kingdom Atomic Energy Authority explains that the fuel is derived from two different forms of hydrogen.

"Deuterium is in sea water. The oceans of the world contain sixty billion year's worth of deuterium. Tritium comes from lithium, lithium salts are in sea water."

Things, sadly, aren't quite as simple as that sounds. There are only around 20 kilograms of tritium in the world.

Chain Reaction
Supplies come principally from nuclear reactors, specifically Canadian heavy water reactors. They can produce enough tritium to supply current experimental fusion plants but not enough for commercial production.

Jan Beranek of Greenpeace claims that, "to sustain a reaction for a year for just one reactor it would need to burn 50 kgs of tritium... at the moment we are able to get one kg for about $30 million (£20 million)".

And that price is expected to rise. So where could affordable fuel come from?

Professor Cowley admits: "That's part of the problem that we haven't done yet but we do know how to do it because it's been done with nuclear reactors."

Cowley and his colleagues expect fusion reactors to become self-sustaining, 'breeding' their own fuel supply.

"The principles are right, but there's a lot of difference between principles and practice and that's where we have to do our work," he says.

Dr. Michael Dittmar, a physicist at CERN working for the Swiss Federal Institute of Technology thinks this is a comforting folly, a process fraught with problems in physics, mathematics and engineering.

"You put 20 kgs of this tritium in and then you start to operate a kind of chain reaction. Even to come to the chain reaction there are so many fundamental problems that cannot be addressed at a single place in the world."

He says the vast expenditure on experimental reactors should be halted until that basic problem is resolved.

Some $3.5 billion (£2.1 billion) is being spent on America's National Ignition Facility and, at least 10 billion euros (£9 billion) on the ITER reactor under construction in France.

"If this doesn't work we can forget the entire rest of the project," he says.

Despite this the scientists behind the UK's fusion projects retain complete confidence in the technology.

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