Generating power with ‘miniature suns’

For decades, fusion power has remained a distant dream. Now, though, miniature suns are starting to fire up


Inside a fusion reactor

It’s carbon-free, contributes to a greener future and has effectively inexhaustible fuel from seawater and lithium. So says Professor Ian Chapman, chief executive of the UK Atomic Energy Authority (UKAEA), backing nuclear fusion.

“It’s very low land use, so it doesn’t take up a lot of space, and it’s baseload, so you don’t have the intermittency you might with renewables,” he enthuses.

Nuclear fusion has long been heralded as the holy grail of power generation. So long, in fact, the industry jokes that success is permanently 30 years away.

Recently, though, all that has started to change. Now, around the world, international collaborations and private companies are making significant progress and claiming we could see the first commercial power stations come into operation by 2040.

How fusion works

Unlike nuclear fission, which generates energy through splitting atoms, fusion involves smashing two atomic nuclei – generally deuterium and tritium, both forms of hydrogen – together under great pressure, in a process that creates a heavier nucleus and releases energy. It’s the same process that goes on in the sun.

“And the important thing is that, unlike fission, it doesn’t have the same long-lived legacy waste or chain reaction,” says Chapman. “You can’t have a Chernobyl; it just can’t happen.”

In the UK, the government is currently looking for a site to trial a prototype fusion energy power plant, with councils and local authorities bidding to play host.

Unlike fission, it doesn’t have the same long-lived legacy waste or chain reaction

The design for STEP, Spherical Tokamak for Energy Production, should be completed by 2024. It will build on existing UKAEA work with tokamaks, which are compact fusion devices that use magnetic fields to contain plasma and create the high pressures required.

Finding new ways to channel waste heat

The latest step forward has been the firing up of Mast-U, a new spherical tokamak that includes a new way of exhausting the enormous amounts of waste heat.

“You must have seen videos of eruptions coming out of the sun; solar flares or mass ejections, big spirals of gas, which are thrown out,” says Chapman. “Well, we have a miniature sun and, in the same way there are events which happen at the edge where heat is thrown out, so you need to make sure none of that heat damages the wall.”

The usual way of dealing with this is to allow the heat to flow to a sacrificial surface that’s consumed. However, the new system allows materials to last much longer by channelling the heat over a longer distance.

“By the time the material gets out to the metal at the edge it’s a lot cooler, as it’s radiated heat along the path,” says Chapman. “And that takes the heat flux down from a level that’s at the melt limits of the materials that we have, down to a heat flux that’s really what would happen in a car engine.” 

You can’t have a Chernobyl; it just can’t happen

Mast-U was turned on last October and power is now being ramped up. Results should be in by the summer and, if successful, it should cut the heat which hits the wall by 90 per cent.

But STEP is by no means the only fusion project in town. ITER, the International Thermonuclear Experimental Reactor, is a fusion project involving 35 countries. Already three-quarters built, it’s due to fire up in 2025.

ITER is all about proof of concept, demonstrating that fusion can take place on a commercial scale. The findings will feed into other national initiatives around the world, including STEP and the power stations that will later be based on it.

“Despite the onset of the pandemic in 2020, the ITER project has managed to stay largely on track,” says a spokesperson. “2020 was a decisive year, with the arrival of ITER’s massive first-of-a-kind components, for example magnets weighing several hundred tonnes each, from all over the world and the start of machine assembly in mid-year.” 

Fusion in the private sector

Meanwhile, a number of independent companies are working on fusion technologies of their own. One such is First Light Fusion, spun out from the University of Oxford in 2011.

First Light has a different approach to STEP or ITER, using inertial, rather than magnetic, fusion. This involves firing a projectile at around 20 kilometres per second – 50 times faster than a bullet – at a target containing deuterium and tritium. The force generated is powerful enough for fusion to occur.

However, according to co-founder and chief executive Nick Hawker, the company has no plans to move into power generation directly, but instead will sell its targets and technology. 

“We don’t think it’s credible for a startup to build a power plant,” he says. “But we want to produce something that’s a physical product, the ultimate espresso capsule, a consumable. Each one is equivalent in energy terms to a barrel of oil.”

Chapman welcomes such initiatives, suggesting they all add pieces to the puzzle. “I think it’s also a sign that the market has an appetite for fusion and wants to invest, and that’s a really good thing,” he says. 

“These private companies are now leveraging money from oil and gas majors and venture capitalists, so that shows the market has an appetite for investment.”

In the long term, fusion is unlikely to displace other forms of power generation entirely; in many geographical areas, wind or solar power is a better bet. However, it’s widely seen as a potential major player within a portfolio of power generation techniques.

It’s also likely to need a fair level of subsidy at first, says Chapman. “To start with, with any disruptive technology, you need some subsidisation to begin with, just as we’ve seen with offshore wind, which was subsidised 20 years ago,” he says. “But now the price has come down and down, and it’s cheaper than other energy sources.”