Fusion could one day generate limitless cheap energy from little more than water, while emitting no greenhouse gases. We look at its promise as the ultimate power panacea for a warming world.
It is a clear winter day in Cadarache, in southern France. The dry mistral wind from Africa has blown away the morning’s lingering clouds and the afternoon sun has brought a glow to the gold and red leaves of the valley’s trees. In the nearby pine forest, wild boar, mouflon sheep and deer are grazing. When it comes to rustic tranquillity, this is hard to beat.
But dramatic changes are heading for this tranquil corner of Provence. Fleets of cranes, dump trucks, earth-moving equipment and concrete mixers are about to turn it into a massive construction site. This rural backwater is to become home to one of the world’s most important scientific projects: ITER, the International Thermonuclear Experimental Reactor – a machine designed to recreate the energy that powers the stars.
A total of €10 billion (about A$16.7 billion) has been earmarked for the construction and initial operation of ITER, a giant fusion reactor. It will generate a cloud of super-hot plasma in which isotopes of hydrogen will fuse to form helium, releasing vast amounts of energy.
If successful, the project will realise a dream that has preoccupied physicists for many decades: the harnessing of the power that drives the Sun. The potential is, to say the least, immense.
Fusion plants could one day generate billions of watts of power, entirely replacing 19th century coal and 20th century gas, oil and nuclear fission, and all without producing any carbon dioxide or long-lived radioactive waste. Advocates of fusion imagine a future where power is cheaper, cleaner and more plentiful than ever before. It’s the ultimate power panacea for a warming world.
And it is at Cadarache that fusion power’s supporters will learn whether the idea is a pipe dream or a real contender for the future. If successful, it could lead to the development, by around 2035, of huge electric generators powered by fusion. If it fails, humanity may be faced with the reality that there are few quick fixes to the problems of energy generation in an overheating world.
In preparation for the forthcoming construction work, a 300-strong team has taken up residence in a cluster of pre-fabricated huts at the site, 35 km from Aix-en-Provence. These scientists, engineers and administrators have been recruited from the project’s backers: the European Union, China, India, Japan, Russia, South Korea, and the USA. Half the population of the world is represented by the staff of ITER, and although its official language is English, it is spoken here in all sorts of accents and inflections. There is a real United Nations feel to the place.
The director general, Kaname Ikeda, is Japanese, while his deputy, and head of construction, Norbert Holtkamp, is a German who worked for several years at America’s Oak Ridge particle physics laboratory. ‘‘Working with a truly international staff does present problems: you have to be very sure that we are all singing from the same song sheet and that nothing is taken for granted,” admits Holtkamp. “On the other hand, it does mean we will be sharing knowledge in an unprecedented way.”
Sometime early in 2008 the ITER team is expected to begin their construction work in earnest. The first trees and earth will be levelled at the 70-hectare site in readiness for the construction of the vast concrete platforms on which the great device will rest. Slowly, over the coming decade, ITER will take shape here – the final outcome of a half century-old dream that has seen fusion reactors being built across the world with increasing size and ambition.
No device on this scale has ever been planned before, however. ITER will have a huge central chamber, capable of holding about seven times more plasma than any fusion reactor built before it. Coated with beryllium and tungsten, it will glow eerily during its 24-hour-a-day operation as hydrogen is fused into helium in a ghostly mimicry of the forces that sustain and light the Sun. Putting together a machine like that is not a business for the faint-hearted. Nevertheless, Holtkamp is unperturbed about dabbling with such potent forces.
“There will be tricky moments, particularly when the main plasma chamber and the superconducting magnets that will contain the super-hot hydrogen atoms are put together,” he says. “However, we will take it all very slowly and very carefully.”
Intriguingly, the construction of these two key components has been shared out evenly among the members of ITER. The chamber will be the handiwork of Russia, Korea and Europe, for example, while the building of the magnets will be shared between all seven participants in the collaboration. No one nation will be allowed to dominate any single area of expertise in construction. As an effort in scientific cooperation alone, ITER is certainly ambitious.
Finally, when the last pieces are joined, the machine will be covered in a giant, white, hangar-like structure that will be clearly visible from the main Marseilles road that sweeps through Cadarache. There will be no globular containment vessel like those that give nuclear power plants their distinctive look, nor cooling towers that typify fossil fuel plants. ITER may be a fantastic concept but it is going to look distinctly boring.
It is a strange combination – high-tech science with low-rent architecture. But then fusion itself is a rather odd concept. The standard fission reactors in operation at nuclear plants today use fuel made up of large atoms, like uranium. When encouraged to break apart, these atoms release energy. But fusion works in reverse. Light atoms are coalesced to make heavier ones, and in the process energy is released. The basic fuel for this task is the hydrogen atom, while the product is the helium atom – and bountiful energy.
Christopher Llewellyn-Smith, head of Europe’s Joint European Torus reactor (JET), based at the Culham laboratory in Oxfordshire (currently the biggest fusion reactor in the world – see image bottom left for a glimpse of it in action), outlines the basic physics: “The nucleus at the heart of the helium atom is the most tightly bound of all nuclei in nature. It takes enormous energy to rip it apart. The logical corollary of that observation is that when you put a helium nucleus together from smaller components, you will liberate huge amounts of energy.”
This process only occurs when the nuclei of the atoms are in very energetic states, however. Heated to 100 million degrees Celsius, they barge into each other at such colossal energies that the electrical repulsion, which normally prevents them from interacting, is overcome. Nuclei are pressed together, up close and personal, and fuse – producing neutrons and a great quantity of pent-up energy. A total of 17.6 million electronvolts is released during an individual fusion reaction. This compares with the one electronvolt produced by a typical chemical reaction – for example, by the oxidisation of a carbon atom, the basic process that underpins the burning of fossil fuel.
Recreating the fusion process clearly offers great rewards, but it is not an easy task – to say the least. In particular, the business of containing a cloud of plasma that has been heated to around 100 million degrees Celsius has taxed the imaginations of a great many scientists. You can’t hold super-hot matter in an old bathtub, after all. In the end, it took the ingenuity of Russian scientists Igor Tamm and Andrei Sakharov, working at Moscow’s Kurchatov Institute in the late 1950s, to come up with the answer: the tokamak.
The key feature of a tokamak is its central chamber which is shaped like a giant, hollow doughnut or torus, and which gives the device its name. Abbreviating the Russian ‘TOroidalnaya KAmera v MAgnitnykh Katushkakh’ results in ‘tokamak’, or its similar English equivalent, TOroidal CHAmber in MAgnetic Coils (tochamac). Powerful electric currents are passed through coils that wind round the doughnut-shaped chamber and through the plasma inside it, creating a twisting magnetic field that holds the super-hot plasma in a tight, invisible grip.
However, massive amounts of electricity are needed to create this unseen container, and to date, far more energy has been spent powering-up tokamaks than has been released through the resulting fusion of atoms. For example, JET soaks up 25 megawatts of electrical power to generate only 16 megawatts of fusion power. However, ITER – which will be the biggest tokamak reactor ever built when completed – is scheduled to have an output of 500 megawatts for an input of only 50 megawatts of electricity.
Once a tokamak’s magnetic field is switched on, and air is pumped out of its central chamber, small amounts of the hydrogen isotopes tritium and deuterium are inserted. Then an electric current is driven through the gases, heating them up to about 30 million degrees Celsius. At this temperature, electrons are stripped from their orbits around the atomic nuclei, producing a soup of basic particles. Finally this plasma is heated even further, to about 100 million degrees Celsius, either by bombarding it with highly energetic particles or by injecting microwaves. At this temperature, deuterium and tritium nuclei in the reactor begin to fuse to create helium and neutrons.
Importantly, of the 17.6 million electronvolts of energy created with each reaction, most of it – about 14 million electronvolts – is transferred to the neutron. It has no charge and cannot be contained by the tokamak’s magnetic field. So it whizzes out of the reactor and smashes into the atoms of the reactor wall, transferring its considerable kinetic energy to them. The end product is heat, which can then be used to drive turbines.
THE SOMEWHAT GRANDIOSE idea of building fusion power plants is not without its critics of course. As one French scientist remarked: “They say that they will put the Sun in a box. The idea is pretty. The problem is, we don’t know how to build the box.”
ITER’s engineers and scientists would beg to disagree. They are very confident that they know precisely how to build that box and are going to do so right here in Cadarache. Not everyone is convinced, however. Some query the costs involved and the practicality of the project. Others have complained that ITER is risky. Jan Vande Putte of Greenpeace dismisses the reactor as “a dangerous toy, which will never deliver any useful energy”. Instead, the world should invest in other renewable forms of energy generation, he argues.
And there are other criticisms. Journalists who have been following the fusion saga for decades (myself included) have noted that, when pressed about the prospects of building commercially viable reactors, supporters of the idea have made the constant, unchanging claim that “fusion power is only 30 years away”. They were making that promise 30 years ago and they are still making it today, a point I raised with Llewellyn-Smith, who – as the newly appointed chairman of ITER’s ruling council – has an unrivalled knowledge of fusion research.
Lean, with a distinctive mop of a white hair, and crisply dressed in a white shirt and dark blue tie, Llewellyn-Smith comes across as an effortlessly effective spokesman for the cause of fusion power. So why, I asked him, have scientists been promising for so long to deliver fusion power, yet it still remains locked in an experimental phase? Money – not surprisingly – has been the main stumbling block, he replies.
“The fundamental problem with fusion is that you cannot demonstrate it on a small scale. If I wanted to convince you of the worth of steam power I could boil a kettle full of water, and we could have a little steam-power plant to experiment with. But I cannot do that with fusion power. The only way to show its potential is to build a full-size plant – because it is only when you reach a certain size that a fusion reactor starts to produce more power than it consumes.”
In other words, you have to start at a fairly ambitious level, which costs billions. Llewellyn-Smith’s own machine, JET, required backing from the whole European Union. Its far larger successor, ITER, is funded by most of the developed world and was only given the go-ahead because the problem of climate change – and the need to secure carbon-free energy sources – was becoming so urgent.
Even then, there was fierce disagreement about the device, particularly over the site of its construction. The United States, Japan and South Korea wanted it to be built at Rokkasho, where Japan has a major nuclear fission facility, while Russia, China and the European Union (EU) championed the case for Provence, which has several nuclear research facilities. When a final vote was taken by ITER’s council in December 2003, the outcome was a three-to-three deadlock that required a further 18 months of negotiation, and construction delay, before the issue was resolved in favour of France.
Superficially it looked like a straightforward victory for European diplomats. However, the EU has had to pay a steep price for the privilege of having ITER in its backyard. No less than 45 per cent of its €10 billion bill will be picked up the European Union. By comparison, the other six members of the ITER club will each have to pay only nine per cent. On the other hand, industry in the EU is going to be well-placed should fusion prove to be a winner.
In any case, the decision to go ahead with ITER was an important and historic one. Two decades after Mikhail Gorbachev, then leader of the Soviet Union, and U.S. president Ronald Reagan first tentatively agreed to discuss plans to build an international fusion reactor in the mid-1980s, approval for this grand vision was granted and preliminary work has now begun. “We have set up ITER as an organisation, so we can hire employees, and order equipment, and we have begun preparing the site,” says Holtkamp. “We are ready to go.”
However, I should note at this point that ITER itself will not be an electricity-producing device. It will merely demonstrate that fusion energy is a practicality. It will be up to individual nations, or groups of nations, to use the technology perfected at Cadarache to build plants fitted with turbines that can then make electricity. To do that, a primary cooling circuit – most likely one that uses water or liquid sodium – will transfer heat from the reactor wall to a secondary circuit that will pass it on to the turbines that will make electricity. It is standard technology and no one foresees problems with this part of the program.
Perfecting the fusion system will be a different matter, however. And it won’t be a speedy one. “ITER is an experimental demonstration device and will take about ten years to construct,” says Llewellyn-Smith. “Then we will have to run it for about ten years to get confidence in it, and to learn lessons from it, before we take the next step: the building of a real power station. That will take another ten years. So you end up at around 30 years from now as the earliest time you can expect to build a full-scale reactor that is producing electricity. And that is still not what you want – which is to see 50 of them out there contributing to the world’s energy. It will take even longer to get to that point. So, yes, it is going to be a very slow business.”
Nor should it be assumed that there will be no major problems encountered in scaling up from a reactor like JET to one that is the size of ITER – for there is a major qualitative difference between the two devices. With JET, which has been running since 1983, and its predecessors, plasma was heated by external sources, by engineers pumping in electrical power. On only a few occasions has fusion lasted long enough to generate significant amounts of power on its own. Things will be very different with ITER, however. More than 90 per cent of its heat will come from its own fusion reactions and it is conceivable that something new, unexpected and possibly unpleasant could happen. Some form of plasma instability could be triggered, for example.
It is a danger acknowledged by Holtkamp. “We simply don’t know how plasma will behave in these conditions. It could become unstable and the magnetic fields will not be able to contain it. Plasma could leak out and melt bits of the reactor,” he admits. Such an event would not threaten lives but it could cause serious, long-term damage that might set the cause of fusion power back many years. “For that reason we will be proceeding very cautiously when we get to the stage of burning plasma in the reactor,” adds Holtkamp.
In short, it is going to be a long, careful program. But, scientists like Llewellyn-Smith remain cautiously confident. “Yes, it is going to be very difficult, very challenging. I have no doubt about that. Nevertheless, I am confident we can make a fusion power station. The much harder question is this, however: can we make one of them reliable and economically competitive? At present our calculations suggest that fusion power will be competitive with current methods of power generation. However, it is very hard to be sure because we don’t know what we will be competing with as sources of power in the middle of the 21st century. However, I wouldn’t be here doing this job now if I didn’t believe fusion power was not going to play some role in energy generation in the future.”
Robin McKie has been reporting on fusion research for many years. He is the science editor of Britain’s The Observer, and a contributing editor of Cosmos.
