THE NUCLEAR RENEGADES
A growing number of start-ups want to create and commercialise nuclear fusion, to generate clean energy for all. Can they succeed where the big guns have failed?
After a short journey, I’ve arrived at a bland industrial park just outside Abingdon in Oxfordshire. It’s populated by retailers of kitchen units and courier service companies, so it seems like an unlikely place for me to find an answer to the energy crisis. But within one of these anonymous warehouses, a company is seeking to recreate and harness the power of the Sun.
Tokamak Energy is building a device that looks like a steampunk submersible from a Jules Verne novel. Made from gleaming steel, it has glass-covered ports through which you can peer into the interior. Called ST40, it is still in the process of being assembled after its relocation from Tokamak’s previous premises. But once it is up and running, you wouldn’t want to be here. It will host a hydrogen plasma 10 times hotter than the centre of the Sun, with the aim of achieving nuclear fusion. When it was previously operating, says the company’s executive vice chairman Dr David Kingham, it was briefly the hottest place in the Solar System.
Tokamak Energy, with around 50 employees, is one of several small companies worldwide that believes the answer to the long-standing problem of how to harness nuclear fusion may come from fleet-footed private start-ups, rather than the gigantic international projects that have been trying to crack it for decades. As the global population soars, world energy consumption is expected to grow by around 30 per cent by 2040. Nuclear fusion has long been touted as a potential fix for this crisis, as it’s capable of releasing millions of times more energy than burning fossil fuels. What’s more, it doesn’t depend on the weather – unlike many sources of renewable energy.
A STAR IS BORN
Nuclear fusion energy generation is saddled with the reputation that it has been ‘only 20 years away’ for the best part of six or seven decades. But this time, advocates are convinced, it’s different.
All current nuclear power plants use the process of nuclear fission: the release of energy when heavy radioactive elements such as uranium decay into other elements. With nuclear fusion, on the other hand, the energy comes not from the splitting of heavy atoms, but by the merging (fusion) of light elements such as hydrogen to make heavier ones. Both processes convert a little of the atoms’ mass to energy, and Albert Einstein’s famous equation E=mc2 shows that even a tiny mass change can release awesome quantities of energy.
Both forms of nuclear energy generation are ‘greener’ than burning fossil fuels, in that they don’t
produce greenhouse gases such as carbon dioxide. Fission, however, has its problems. Both the spent fuel and the radioactive emissions that ‘activate’ other reactor materials produce large amounts of radioactive waste that will remain hazardous for hundreds of thousands of years, and its disposal creates problems that the nuclear industry is still wrestling with.
In principle, nuclear fusion offers a better alternative. The products in this case are not radioactive, so there is little hazardous waste. And the energy release in fusion can be greater, as illustrated in thermonuclear hydrogen bombs where the process is unleashed in an uncontrolled outburst. But whereas fission happens naturally in stuff like uranium that can be dug from the Earth, fusion is harder to trigger – even though it powers the stars.
An atom of hydrogen has one proton and no neutrons in its nucleus. The easiest way to fuse hydrogen atoms involves two of the element’s forms. One of these is called deuterium, which has a neutron in its nucleus as well as the proton, and tritium, which has two neutrons and a proton. Deuterium occurs naturally – it makes up about 1 in every 6,000 hydrogen atoms in seawater, so its supply is virtually limitless. But tritium decays radioactively, and needs to be produced in situ to fuel a fusion reactor.
To spark the fusion process and overcome the particles’ natural repulsion, the deuterium 2
2 and tritium must be heated to extremely high temperatures and either squeezed to tremendous pressures or kept hot for a long time. Such conditions exist in the Sun, and can be created artificially in experimental fusion reactors. But it’s immensely hard to sustain and control those conditions, and for decades efforts to produce nuclear fusion in this way have consumed more energy than they generate.
The leading candidate for a fusion device is the so-called tokamak, first developed in the Soviet Union in the 1960s (the word is a Russian acronym). Here, a doughnut-shaped ring of hot plasma is suspended in space using strong electromagnetic fields – the plasma is too hot to simply ‘bottle’ in a way that brings it in contact with material walls. But the plasma is difficult to control, and easily becomes unstable in ways that destroy the intense conditions needed to keep fusion going.
In other words, it’s not getting controlled fusion underway that’s the problem, but sustaining it to produce net energy gain. “It’s a problem of engineering,” explains Close. “Fusion has been demonstrated back in 1947, and has been going on in tokamaks for decades.” But it still hasn’t given us commercial fusion as a ‘clean’ source of energy.
THINKING SMALL
Global investment in nuclear fusion research (not including weapons-related research) is around $2bn (£1.56bn approx), says Kingham. More than 40 experimental tokamaks are being tested and developed at many large centres and projects worldwide, such as the International Thermonuclear Experimental Reactor (ITER) in southeast France and the Joint European Torus (JET) in Culham, Oxfordshire, close to Tokamak Energy’s headquarters. The EU’s Roadmap to Fusion Energy predicts that a demonstrator plant based on the ITER reactor (called DEMO, and still under design) will put electricity into the grid around 2050, and that commercial plants will appear in the following decades.
It’s a long wait, but the Tokamak scientists think they can get there quicker. In 2015, one of the company’s consultants, physicist Dr Alan Costley, proposed that tokamaks small enough to fit onto the back of a truck might have significant advantages over big ones in producing energy gain. The conventional view is that tokamaks have to be huge to keep the plasma hot enough for long enough, but Costley argued that small tokamaks can operate at higher plasma densities, making them more efficient without needing to get larger.
The idea caused much debate and controversy in the fusion community, but Tokamak is counting on smaller reactors being the key to success. Devices of this scale are within the means of private investment – which in Tokamak’s case has come from companies such as Oxford Instruments and Legal & General, as well as from initial seed funding from the UK government and private investors.
To generate tritium fuel, Tokamak plans to use ‘tritium-breeding blankets’, in which neutrons generated in deuterium-tritium fusion hit lithium atoms in the blanket and convert them to tritium. The fuel ingredients are continually fed into the plasma as fusion proceeds.
But the crucial innovation, according to the Tokamak team, is the powerful magnets used to generate the fields that confine the plasma. Most tokamaks use either conventional ‘supermagnets’ made from special metal alloys, or electromagnets made from coils of superconducting materials, which lose all electrical resistance when cooled and can therefore carry large currents. But Tokamak goes one better by using so-called high-temperature 2