Tokamak fusion power

Just as putting a man on the moon was the impossible dream of the early 1960s, achieving nuclear fusion – thereby unlocking the promise of limitless clean energy – is one of the great unsolved mysteries that persists today. Despite decades of research, breakthroughs on the long path to fusion have been thin on the ground.

Such are the formidable challenges involved, and the years of work put into it, that there is a well-known saying in scientific circles that goes along the lines of: commercial nuclear fusion is just 30 years away, and always will be.

A significant number of major experimental fusion projects – including massive public collaborations such as ITER in southern France and JET in the UK – are hard at work to prove the saying wrong. For major projects like these, hope rests on the construction and operation of huge tokamaks – doughnut-shaped magnetic confinement devices that contain the superheated plasma in which fusion can occur.

But is there a smaller, faster way to achieve fusion reactions that produce more power than went into their creation? That’s what numerous groups around the world are arguing. One such proponent of small-scale fusion is Tokamak Energy, a British company that traces its origins to Oxfordshire’s Culham Laboratory in the 1990s. Alongside JET, two Culham scientists – tokamak pioneer Alan Sykes and fusion physicist Mikhail Gryaznevich – developed START, a small spherical tokamak, with a tiny budget and using spare parts from around the lab.

START demonstrated great efficiency in sustaining high plasma pressure for a given magnetic field, but it became increasingly clear to Gryaznevich and Sykes that Culham’s focus was firmly on JET, and the prevailing consensus was that while START’s science was good, it would be impossible to provide enough power to such a small device to reach the high fields necessary for fusion.

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Sykes retired from Culham in 2009 and a frustrated Gryaznevich soon followed suit, and the pair established Tokamak Energy to pursue spherical tokamaks as a route to fusion. Today, the company has discovered that route through the combination of small spherical tokamaks and high-temperature superconducting magnets.

Tokamak Energy’s work was validated this summer when it was nominated by the World Economic Forum as one of the world’s 49 Technology Pioneers. We spoke to the company’s chief executive Dr David Kingham to discuss the progress made so far with the ST25 prototype tokamak, milestones for the future and unlocking the investment required to make the impossible dream of fusion energy a reality.

Chris Lo: How does Tokamak Energy’s spherical tokamak approach to fusion differ from more conventional international projects like ITER?

David Kingham: The spherical tokamak has this high efficiency; it uses the magnetic field very efficiently to get high plasma pressures, and that essentially means instead of going to very large devices, we can see how to get to fusion energy gain in a small device. So instead of 35 metres across, as ITER is, we’re thinking of a few metres across. If you can make that reduction in size, then things can go a lot quicker, and it’s certainly a lot cheaper.

CL: Do you have a timeframe in mind to hit certain milestones?

DK: Yes, the key milestones are five years to get to an energy gain in one of these compact devices, by around 2020. Ten years to get to first electricity production, even if it’s only on a relatively modest and possibly short timescale, and then 15 years to get to electricity in the grid. It will require very substantial investment, but if we make progress along that path, then we’ll be in a position to raise that investment. We can only hope to do that if we collaborate around the world with people who have got complementary expertise to the expertise that we have.

Amec Foster Wheeler will develop a remote handling system for the ITER fusion reactor in France.

CL: Why do you think 2015 is the year that the company has been recognised as a Technology Pioneer by the World Economic Forum?

DK: We came to the attention of their Global Agenda Council on Decarbonising Energy, which is one of the nominators for this Technology Pioneer award. I think that council was looking around the world for technologies that could possibly have an impact on climate change well before 2050. I don’t know for sure, but I imagine it was stimulated by the Paris climate change conference that’s coming up later this year. I think the World Economic Forum was looking for technology options, as it were – things that might be relatively high-risk but could have a huge impact if successful.

CL: Is this award an important validation for your work thus far?

DK: It is, absolutely. Until 2015 we were keeping quite quiet. We hadn’t really publicised what we were doing for about four years, but we thought towards the end of 2014, we’ve got enough evidence that we should start publishing. So we published a couple of papers very early in 2015. One was basically showing that tokamaks don’t have to be huge to be powerful – quite a groundbreaking physics paper. The second was on the engineering challenges of these compact spherical tokamaks.

Basically you need a lot of shielding around the magnet to protect the material in the magnet against neutron damage and to stop heat getting into the magnet. We have pretty well cracked the problem – we know what material we’d like to use, we know roughly the scale of the shielding. We don’t know exact lifetimes of the magnet material, but we know it’s going to be good enough to get us to a first electricity device without the device getting so huge.

CL: What challenges are you currently addressing with the ST25 tokamak, and what important tests do you have coming up?

DK: We in fact have two ST25 tokamaks: one using conventional copper magnets, and the other using high-temperature superconducting magnets.

On those devices, the main thing we’re doing is developing techniques to heat the plasma and to drive a plasma current, which is important in tokamaks. We’re also developing control systems that will be used on the next device that we’re currently building, the ST40. It’s really from the ST40 that we are expecting to produce significant results late next year, and that will be hot plasmas in a high magnetic field device. The ST25s are the prototypes for the ST40, one in particular. The ST40 will use copper magnets. The second of these ST25s is our prototype for high-temperature superconducting magnets.

CL: Are there recent achievements by other projects that you’ve found particularly exciting?

DK: There have been three very interesting things recently. MIT has come out with an advanced reactor concept using the same type of high-temperature superconducting magnets that we’re planning to use. We agree with MIT’s assessment that these high-temperature superconductors are the key to rapid development of fusion power.

"We agree with MIT’s assessment that these high-temperature superconductors are the key to rapid development of fusion power."

We collaborate with Princeton Plasma Physics Lab quite closely, and they are just recommissioning their spherical tokamak device, NSTX, after a very substantial upgrade. So we’re off to present papers at a conference in Princeton in about a month’s time. We can learn from what they’re doing; we can tell them what we’re doing. We’ve actually commissioned them to do some engineering design checks on our ST40 device, because they have the expertise to do that.

And just in the last few days, the consortium from Durham University and Culham Centre for Fusion Energy has published a paper on the economics of fusion using high-temperature superconducting magnets. That’s just come out and we basically agree with them that high-temperature superconducting magnets are the way forward. Their study is very theoretical and our approach has been a bit different, it’s been more about early-stage prototyping and filing patent applications of the engineering of the magnets, while they’ve gone for longer-term economics and longer-term benefits. It’s all helpful.

CL: Are you aware of Lockheed Martin’s efforts to develop a compact fusion reactor, with a similar goal of using a small reactor to accelerate development?

DK: That’s really fascinating. It’s really interesting to see Lockheed Martin’s approach to fusion energy. They’re basically saying, ‘This is a hugely exciting opportunity, if only we could find the right technology, then we could see how to scale it up, develop it quickly and deploy it at huge scale.’ However, the technology that they’re looking at most closely at the moment, at least as far as what they’ve said publicly, looks highly speculative. Most people who’ve worked on tokamaks and other magnetic confinement devices would be pretty sceptical about whether the specific technology that Lockheed Martin have announced is a good way forward.

That leaves two possibilities: one is they actually have something else that they’re not telling the world about, or they might turn their attention to the sorts of things we’re doing, which have many of the features that Lockheed Martin is looking for – the compactness and the ability to develop the technology quickly. So it’s exciting to see Lockheed Martin getting interested in this area. It’s a validation of the value of the goal, and of the potential method of getting there.

CL: In July you gave evidence to the House of Lords Science and Technology Committee on the future prospects for fusion in the UK – what’s your opinion on the level of public support for fusion in this country?

DK: There’s latent public enthusiasm. We exhibited at the Royal Society Summer Science Exhibition in June and early July this year, so we had about 10,000 visitors to our stand, and there was lots of enthusiasm, as well as some healthy scepticism. I think fusion is exciting for people, and a lot of people recognise that it’s an important challenge that we have to tackle.

However, there haven’t been many very exciting results for the last 15 years. I mean, JET achieved its huge goal of 16MW of power back in 1997, and nothing really spectacular has happened since then. So we know as a business that to keep investors, the public and perhaps politicians interested, we have to produce results every year or two and they’ve got to be exciting.