The compact reactor: a shortcut on the road to nuclear fusion?

16 December 2014 (Last Updated December 16th, 2014 18:30)

Lockheed Martin has raised eyebrows with the announcement of a small reactor that it claims will provide a shortcut to revolutionary nuclear fusion energy. But with dozens of research teams around the world working to a much longer timescale to achieve fusion, is the defence company's project more PR stunt than scientific revelation?

The compact reactor: a shortcut on the road to nuclear fusion?

fusion reactor

There’s no argument that nuclear fusion, if realised, would bring about a total revolution in global energy, a solution to the environmental, geopolitical and economic challenges of modern power generation. The focus for decades has been on making this grand atomic vision a reality, which has proven an elusive goal, plagued by false dawns and a shifting timescale in which, like the Greek myth of Tantalus and his divine punishment, the fruit remains constantly out of reach.

Multinational defence company Lockheed Martin’s secretive development division Skunk Works, which has previously been responsible for the design of sophisticated military aircraft, made a noteworthy left turn in October this year by announcing its entry into the nuclear fusion race.

The company’s compact fusion reactor (CFR) project aims to carve out a shortcut on the path to fusion by dramatically reducing the size of the doughnut-shaped fusion reactor (also called a tokamak) used to contain the heat of the fusion process. While the tokamak at the multinational fusion project ITER in France will be a 23,000-tonne behemoth, the Skunk Works team is confident it can build a 100MW reactor, capable of powering a city of up to 100,000 people, small enough to fit on to the back of a truck.

Bold claims: accelerating fusion development
Skunk Works believes the reduction in size will accelerate the pace at which it can test its concept through multiple iterations as it works towards a working prototype within the next five years and the first operational reactor in the next 10. "Our compact fusion concept combines several alternative magnetic confinement approaches, taking the best parts of each, and offers a 90% size reduction over previous concepts," said Skunk Works’ compact fusion lead Dr Tom McGuire. "The smaller size will allow us to design, build and test the CFR in less than a year."

In a publicity video for the project, McGuire was bullish about the development momentum afforded by the CFR’s diminutive size, first as a power source for military aircraft and ships, then as a revolutionary clean energy device. "Ten years, we have great military vehicles," he said. "Twenty years, we have clean power for the world."

Given that the main milestones on the way to fusion have not yet been crossed and many fusion specialists speculate that fusion is unlikely to become a part of the world’s energy mix before 2050, this is a staggeringly bold claim.



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Creating fusion: a daunting challenge

The challenges for dozens of research teams around the world are significant. For successful fusion, the reactor must be able to achieve a temperature of at least 100 million degrees Celsius – far hotter than the core of the sun – and then have a confinement time long enough to create a self-sustaining reaction, thought to be around three seconds.

The closest anyone has come to achieving this confinement time is the Joint European Torus (JET) reactor at the Culham Centre for Fusion Energy in Oxfordshire, UK, which has hit a milestone of one second. And beyond that, there is the central quandary of releasing more energy through the fusion reaction than was used to create it in the first place.

This has never been done; again, the closest attempt was made by JET, where in 1997 a reaction yielded 16MW of fusion power from an input of 25MW. Given this kind of incremental progress, and the massive scale of projects like ITER, which intends to build a 30m tall experimental reactor by 2020 at a ballooning cost of around $50bn, it has become increasingly clear that the path to nuclear fusion will be a long, costly and high-risk endeavour. Unless, of course, the process can be disrupted by a team like Skunk Works.

Traditional wisdom in modern fusion science emphasises the need for large-scale tokamaks to improve the confinement time for the reaction because if the plasma touches the reactor wall, it quickly cools and the reaction is lost. Back in the ’60s and ’70s when smaller units were more commonly used for fusion experiments, the longest confinement time achieved was around one millisecond. Thus modern projects like ITER use much larger reactors to allow more time before energy can escape and improve the efficiency of the reaction.

Lockheed’s compact fusion: scientists remain sceptical

"Skunk Works believes the reduction in size will accelerate the pace at which it can test its concept."

So how can Skunk Works’ small-scale CFR produce a viable result? In broad terms – because broad terms are all the company is offering for now – the compact reactor’s proprietary design strengthens its field as the plasma gets closer to the wall, allowing higher pressures than can be achieved in other tokamaks so there are more collisions between nuclei and the efficiency increases.

Somewhat unsurprisingly, the wider nuclear fusion community has reacted to Skunk Works’ announcement with something approaching a collective eye-roll. Central to the scepticism that has met the project is the complete lack of concrete data on what the CFR has achieved. Of course, as a private company Lockheed Martin is perfectly within its rights to withhold sensitive information; indeed it might be unwise to make public data that could be used by its rivals.

Nevertheless, there have been too many false starts and disappointing fusion ‘breakthroughs’ for expert observers to start getting excited about a five-paragraph press release. Writing for The Conversation in the aftermath of Skunk Works’ October announcement, Matthew Hole, senior research fellow at the Australian National University’s Plasma Research Laboratory, echoed a common suspicion among scientists in the field.

"Lockheed Martin will need to show a lot more research evidence that it can do better than multinational collaborative projects like ITER," Hole wrote. "So far, its lack of willingness to engage with the scientific community suggests that it may be more interested in media attention than scientific development."

Indeed, in its press release Lockheed openly notes that the project will be looking for partners to "help further the technology", and its slickly produced marketing material uses language more closely aligned with an investor pitch – phrases like "restarting the atomic age" abound – than the kind of detailed report, subject to peer review, that makes scientists sit up and take notice.

Other researchers have expressed reservations about the basic science behind Skunk Works’ claim. In an interview with the MIT Technology Review, Ian Hutchinson, one of the leads on MIT’s own magnetic confinement fusion project, didn’t mince words when describing his impressions of the CFR.



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"It seems purely speculative, as if someone has drawn a cartoon and said they are going to fly to Mars with it," he said. "Of course we’d be delighted if a real breakthrough were possible, but when someone who shows no evidence of understanding the issues makes a bald claim that they will just make a small device and therefore it will be quicker [to develop], we say, ‘Why do they think they can do that?’ And when they have no answers, we are highly sceptical."

There is every chance that Skunk Works has the data to properly validate the potential of its CFR, and the project could well have a meaningful impact on the field of nuclear fusion. But in making its announcement, it is joining a wide world of scientific endeavour, from the massive ITER and California’s National Ignition Facility to JET, which even now is gearing up for an attempt to break its own fusion output record in 2017.

It’s an exciting time for the fields of fusion and plasma physics, with important discoveries being made around the world year after year. But there is still no compelling evidence to suggest the long road to commercial nuclear fusion is getting any shorter, and Lockheed Martin will need to make a much more detailed case to persuade anyone otherwise.

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