THE FIGHT FOR FUSION
How Tokamak Energy compares to other nuclear fusion projects…
“Unlike fission, fusion can be switched off in an instant. It’s a lot safer”
2 superconductors (HTSs) to create the magnetic fields in their machine. These materials, discovered in the 1980s, can superconduct at higher temperatures than ordinary superconductors and so can be relatively easily cooled using liquid nitrogen. Crucially, they can also carry bigger currents and so generate stronger magnetic fields. Kingham thinks that using HTSs for nuclear fusion magnets could be their ‘killer app’.
“There’s a growing recognition that HTS magnets are a boost to fusion,” says Tokamak’s senior commercial manager Dr Ross Morgan, pointing out that Commonwealth Fusion Systems, a spinout company from the MIT Plasma Science and Fusion Center in the US, also considers this to be the key enabling technology. If it’s to work, the materials will need to be made in large quantities, and right now there are few suppliers – one reason why using HTSs is much more feasible for smaller machines. If HTSs became a central component of fusion reactors, they would surely be mass-produced, making them cheaper.
This is only one of the many engineering challenges that must be solved if mini-tokamaks are to become tomorrow’s power sources. Tokamak Energy also places its faith in an unusual tokamak shape: spheres, rather than the usual cylindrical devices favoured by the bigger projects such as ITER and JET. Spherical tokamaks have “significant physics advantages but greater engineering challenges,” says Kingham.
This is a view that’s echoed by Chris Warrick, the communications manager at the UK Atomic Energy Authority (UKAEA) in Culham. “We have known for decades that more compact, ‘spherical’ tokamaks have great potential,” he says. “They are inherently more efficient than conventional tokamaks, requiring less magnetic field to confine the plasma of fuels.” The UKAEA has been developing its own small spherical tokamak, called the Mega Amp Spherical Tokamak (MAST), since the late 1990s. But Warrick adds that they have drawbacks too, especially the challenges of removing the tremendous amount of heat from the reactor, because it is more intensely concentrated in the compact design.
POWERING THE FUTURE
Tokamak Energy is just one of the small players in this game. In the United States alone there has been
over $1bn of private venture capital put into fusion projects, and there are now about 25 such companies worldwide. One is AGNI Energy, a Washington-based start-up pursuing an unconventional version of scaled-down fusion in which a beam of high-energy deuterium atoms is fired at a target of lithium and tritium. However, the company’s CEO Troy Dana says it is not seeking to use nuclear fusion for power generation. “We have identified commercial applications for our device that do not require net energy gain,” he says. The company hopes to have a proof of concept device operating by mid-2019.
Meanwhile, General Fusion, based in Burnaby, Canada, is aiming to develop the world’s first commercial fusion power plant using a new technique called ‘magnetised target fusion’. This, explains CEO Christofer Mowry, combines aspects of the magnetic confinement of plasma in a tokamak with the alternative approach to fusion called ‘inertial confinement’, in which lasers are used to cause sudden, high compression of the fuel to trigger fusion. In the General Fusion device it happens in a pulsed manner, rather like the compression cycles of an internal combustion engine. Mowry argues that the bigger fusion projects aren’t trying to make cost-effective, commercially viable forms of fusion – which, he says, is precisely why the smaller private enterprises can complement those efforts.
If small-scale commercial nuclear fusion reactors were to become a reality, it wouldn’t just transform the way we make energy, it would also alter the whole infrastructure. Unlike fission, fusion can be switched off in an instant. “In a fusion reactor at any one time, you have only a few seconds’ worth of fuel, whereas in a fission reactor you have 25 years’ worth,” says Kingham. “It’s inherently a lot safer.”
That means fusion reactors wouldn’t need to be far from centres of population or industry. It’s possible to imagine towns or companies having their own dedicated machines, making energy generation much more distributed and local.
But will the little guys really achieve where the giants have so far failed? “They [the larger projects] were rather taken aback five years ago when we started to look serious,” says Kingham. According to Morgan, the ability of start-ups to build small devices rapidly – in three to four months – is crucial. It means they can learn quickly and build that knowledge into the next generation. In contrast, says Kingham, the large-scale projects “tend to be quite risk-averse and conventional.”
Tokamak Energy says that they hope to have a practical device that achieves industrial-scale heat by around 2025, which could become commercialised by 2030. That’s ambitious. But as Kingham says, “to make progress, we’ve got to have bold plans.”