Is the holy grail of energy finally within reach... and will it work?

In contrast to nuclear fission, a fusion reactor is expected to produce minimal radioactive waste. The fuel for a fusion reactor could be extracted from seawater. Access to materials such as uranium and plutonium has been one of the issues constraining the use of fission nuclear power. Fission nuclear power stations have a habit of overrunning during the construction phase and have a predicted budget that simply bears no resemblance to the final cost. Popular anxiety about fission nuclear power has also been a major issue holding back the expansion – or even the survival – of the fission industry. At the moment, smaller states that simply do not have the capacity to build their own fission nuclear reactors are buying them from third-party countries such as Russia or South Korea.

The single most popular design for a nuclear fusion reactor is a Tokamak. This concept was first proposed in 1950 by Soviet scientists Andrei Sakharov and Igor Tamm. Most but not all attempts to develop fusion involve the construction of a large doughnut-shaped reactor chamber that is filled with gas; most of that gas is hydrogen. The hydrogen is heated to fantastically high temperatures and constrained by huge electromagnets that are external to the reactor.

Other concepts are been tried too. For example, it is possible to shoot lasers at a pellet of hydrogen-like material and heat it up to such a high temperature that fusion then occurs. While research in this field goes on, the Iter project is based on the more traditional Tokamak.

In 1989, in one of the more bizarre subplots to the entire nuclear fusion story, two electrochemists in the United States claimed to have demonstrated nuclear fusion at room temperatures, the so-called cold fusion phenomenon. Somewhat idiotically, Stanley Pons and Martin Fleischmann then decided to hold a press conference before their work had been subject to peer review. A fantastic amount of public attention came their way but no other group was able to replicate their work and the concept was eventually abandoned.

Nuclear fusion is an attempt to replicate the processes of the sun on Earth (Getty/iStock)

The only way to achieve fusion seems to involve very high temperatures and exotic conditions. In order to understand the nature of nuclear fusion, we need to understand the fundamental physics of the universe.

Within that universe, one substance is more stable than all others: iron. The subatomic particles in the centre of an iron atom have the highest binding energy of any atom with the result that pretty much every other kind of atom in the universe has a deep-seated desire to become iron. If a smaller atom than iron wants to reach an idealised state it needs to increase its size by fusing with other smaller atoms. For atoms larger than iron, the reverse is true. A very large nucleus like uranium for example would have to fragment into smaller nuclei in order to scale itself down towards the glorious, ideal energetic state: iron.

Basically, glueing small atoms together to make bigger ones will release energy. A powerful example of this would be the hydrogen bomb. Not all the hydrogen atoms in this world want to spontaneously fuse together; the activation energies are out of this world and the only really reliable place to do it is in the centre of a star.

The Iter Tokamak reactor will rest on around 500 seismic pads that will protect it from earthquakes (AFP/Getty)

The centre of our own sun, for example, operates at temperatures of about 15 million degrees centigrade. Pressures vary between 3.4 x 108 and 2.25x 1011 times greater than the pressure of air you are breathing now. If you’re finding it difficult to imagine temperatures and pressures on this scale, don’t let it worry you. Nobody really can. Nuclear fusion is so difficult to achieve; it requires heating hydrogen gas up to temperatures of this kind in order for the nuclei to collide and glue together. To put this process in perspective, nuclear fusion only occurs in the centre of the sun; even the outer atmosphere of the sun isn’t hot enough.

The history of fusion research is simply littered with one false dawn after another. One group after another claimed to have achieved nuclear fusion only to have their achievement snatched away from them when new data came in that seemed to undermine their initial findings. To date, the largest Tokamak ever built is the Joint European Torus (JET) which was constructed on time and on budget in Culham in England in the early 1980s. As with the forthcoming Iter, there has never been any suggestion that JET would produce electricity, but it has proven to be a major step forward for fusion research. The project has also kept Britain as the forefront of a major scientific field.

This position will now pass to France.

Still half-finished, Iter’s ‘First Plasma’ – the first small star created inside the reactor – is scheduled for 2025 (AFP/Getty)

As with JET, it was quickly accepted that the next fusion research facility would be a joint effort between many nations and an argument soon broke out as to where the project would be sited. The United States, Russia, China, Japan, Australia, India, South Korea and the European Union have all contributed money and hardware to the project. Thanks to the miracle of the internet, many of their researchers will be able to monitor and participate in the experiments from their home countries.

Iter will see temperatures soar to 150 to 300 million degrees C, although internal pressures will be much less than those seen in the centre of a star (the pressure of the gas in the centre of the sun is 150 times greater than solid gold – impossible to simulate here on Earth). If we put some hydrogen in a box and slowly heat it up, we will soon run into a problem. Long before the temperature reaches the point at which fusion occurs, the box will melt. There is simply no material known on Earth that could remain solid at the temperatures required to achieve nuclear fusion.

However, scientists have thought of a way to overcome this problem. At very high temperatures, the atoms have been stripped of their orbiting electrons. As in the centre of a star, raw atomic nuclei bounce around in a sea of free electrons. This sort of gas is described as plasma and some scientists believe that it should be regarded as a fourth state of matter, completely distinct from solid liquid or gas. Since moving electrically charged particles bears a suspicious resemblance to electricity, any kind of convection current within the plasma will produce a magnetic field of its own. At the same time, an electrically charged gas can be manipulated from afar using magnets. Quite early on in the development of nuclear fusion, it became apparent that hot plasma could be contained within a box and effectively surrounded by a zone of pure vacuum. Since the unimaginably hot plasma never touches the wall, the wall cannot melt. Magnets on this scale need to be far more powerful than the sort of toy, bar magnets you probably played around with at school. They require massive coils of electrical wire to be wrapped around the doughnut-shaped reactor. For the Iter project, they will be augmented by yet another exotic technology: cryogenic superconductors.

Needless to say, this kind of research has become eye wateringly expensive. On top of that, everybody involved in the field is fully aware that it is likely to take 20 to 30 years before anything remotely useful comes out of it. None of the politicians involved in the decision-making process will still be in power when the first commercially credible reactor switches on. Quite a few of them will be dead and there are very few votes in nuclear fusion research. It does, however, offer the long-term prospects of immense electrical power that creates very little in the way of radioactive waste. The implications of being able to access power that might effectively become free are difficult to comprehend. Overnight, limitless fresh water may be available to anybody who needs it (there’s no shortage of seawater and it’s easy to desalinate seawater if you’ve got enough electricity). Vast areas of desert might suddenly bloom. Will those countries who funded the Iter project sell their technology to those who didn’t contribute to the project? Or will the  science of nuclear fusion ultimately become open source and available to everyone?

As you might expect, Iter has its detractors and its rivals. An Italian American group are in the process of planning a new mini-reactor called Sparc. Two British start-up companies are hoping to beat Iter to it with mini-reactors of their own. There have been so many false dawns in the history of fusion research that its hard to know just how credible any of these projects are.

But there are other issues at stake here including that of prestige. The host nation in this kind of project has to put forward a disproportionate amount of the capital and there was a protracted struggle between Japan and France as to who should win control of the Iter site. The eventual victory by France is a major boost to that country and seems to send a broader message to the entire world: France is a leading nation, a force to be reckoned with on the global stage. Still half-finished, Iter is an extraordinary construction project with its grandiose cathedral-like building having already captured the imagination of the next generation of scientists. Soon Iter will be up there with the International Space Station and the Hubble Space Telescope. This force that drives the stars. There is something truly seductive about the quest for nuclear fusion power, an excitement that ongoing research into wind turbine technology just doesn’t provide. It’s a feeling that only the people who work in nuclear science have really experienced and it isn’t going to go away fast.