The Joint European Torus is Europe's experimental fusion reactor
By Alasdair Cross
Costing the Earth
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.
Later this year the payback on this investment should begin.
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.
At Greenpeace International, Jan Beranek worries about the safety and security of the radioactive tritium used in the reactor.
"There is always a risk that either the technology or the nuclear materials can fall into the wrong hands... Some of the materials can be used for hydrogen bombs."
WHAT IS NUCLEAR FUSION?
Nuclear fusion is the source of energy in stars such as the sun
The best fuels for fusion are two types, or isotopes, of hydrogen - deuterium and tritium
Energy is released as atomic nuclei are forced together at high temperatures and pressures to form larger nuclei
Reproducing these conditions on Earth is extremely challenging
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.
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.
The Joint European Torus (Jet) is a working nuclear fusion reactor in Culham, Oxfordshire
It can heat different forms of hydrogen (deuterium and tritium) to more than 100 million degrees
Jet initiates nuclear fusion at a rate far in excess of that in the centre of the Sun
Jet is too small to produce meaningful amounts of electricity, but it is a prototype for a much bigger design
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.
Professor Dunne expects to see a commercial fusion electricity plant being built in the 2020s whilst Professor Cowley says that the fusion future can be with us as quickly as we're willing to put our hands into our pockets.
"Having energy is what powers our civilisation. I can't imagine turning around to our children in 2050 and saying, 'we didn't want to pay that extra tax that was necessary'."
Costing the Earth can be heard on BBC Radio 4 at 9pm GMT on Monday 8 March and afterwards on