A breakthrough in nuclear fusion

Described as a landmark achievement known as “ignition” or “energy gain”, earlier this week, researchers at the US National Ignition Facility in California said fusion experiments had released more energy than was pumped in by the high-powered laser they were using to kickstart their experiments. So why is this an exciting outcome. With us to explain are nuclear physicist Brian Applebe from Imperial College, and Richard Dinan, who’s the author of the book, “The Fusion Age” and CEO of Pulsar Fusion, a company developing fusion reactors…

Brian - Fusion has the potential to be a revolutionary energy source because essentially it's a form of nuclear energy. But unlike nuclear fission, which our current power plants are based on fusion energy would produce very little radioactive waste. It would not be using fossil fuels, therefore would contribute very little to, say, greenhouse gas emissions. And finally the fuel that we use for fusion is readily available. We can extract a lot of the fuel from seawater and then we can breed the other fuel that we need for fusion in the reactors themselves. So it has the capability of being really revolutionary in terms of being an energy source. It's just tremendously difficult to do. And last week's experiment was essentially a landmark milestone where we've ticked one box on some of the many challenges that we need to have a commercial fusion power source.

Chris - Clearly we know it works because that's how the sun works and the sun has been there for billions of years and we think it's gonna be there for a few billion more. So what are the challenges then that we need to overcome to realize what the sun is doing down here on earth?

Brian - Yes, so that's true. So we know it works, but what we've been striving to do for about 50 years is to do it in a controlled manner in a laboratory whereby we can get out a precise amount of energy and we can essentially control all the stages of the experiment. So what we did last week, or what was done in Livermore in California, was that more energy came out of the fusion fuel than was used to heat it up in the first place. However, that energy is coming out in the form of high energy neutrons. So what we have to do is we first of all have to scale up that experiment such that we can produce a naturally useful amount of energy. And then secondly, we have to find ways of taking the energy from high energy neutrons and generating electricity, which is a useful form of energy.

Chris - Richard, I suppose we've entered into this era now where we actually regard this not as something that's pie in the sky. People don't hear that you are running a company building fusion reactors and roll their eyes, I presume.

Richard - A few weeks ago, I was at a conference in Switzerland and I mentioned nuclear fusion as a possible technology. And one person in the audience actually laughed. They were saying, 'ah, as if that will ever happen'. So the skepticism around fusion technology has been very real. So for everybody in the industry, this is really vindicating and I think a lot of people are advising their paradigms now.

Chris - What sort of timescale are businesses like yours working towards? So when you are asking for investment, when you are getting people to come and put money into a venture, what is the timescale on the business plan?

Richard - Well, I mean, as we just said, fusion is what the sun is doing, but we don't have a sun. You know, as people are mentioned, this is an amazing achievement, but there's still quite a lot to do. So with investment horizons, you're not talking about three to five year horizons until you get profit. It's for people who are making conscientious investments that they want their children to enjoy and it's not something that a lot of venture capitalists do, it doesn't fit their model still.

Chris - So Brian, when we actually are, are trying to surmount these challenges, what we are hearing about from California, they're using a laser to kickstart a reaction and measuring how much energy comes out. That presumably is one approach because we've got other people doing similar experiments in the UK. At Jet in Oxfordshire, we've got this reactor that's an international collaboration ITER, which is being built in France and I think they're up to 23 or 24 billion they've spent on that so far, haven't they? But are all of these things working in a similar sort of direction or are they all solving problems in different ways, and this is all incremental knowledge? How does this actually all add up?

Brian - At a very basic level, they're all trying to tackle the same problem, which is that, in order to have a successful fusion experiment, you need to make the plasma, which is the fusion fuel, extremely hot. It needs to be hotter than the center of the sun, such that the fusion reactions can actually occur. And then secondly, you must somehow contain that plasma for a sufficiently long time, such that you get enough reactions to produce a useful amount of energy. So then there is a whole spectrum in different ways in which you can approach this heating plus confinement or containment problem. On the one end in Livermore they're using lasers where essentially they don't really do any actual containment. They essentially slam the plasma together, they compress it, make it, you know, 10,000 times more dense than water and that whole experiment is over in less than a billionth of a second. On the other scale, you've got something like Jet whereby you're essentially taking something plasma that's really low density and using magnetic fields to confine it and to do the containment. And then between these two ends of the spectrum, there are a lot of different approaches.Several of the startup companies are looking at different ways in which you can do some sort of mixture of these sort of confinement and heating approaches. I think it's a rising tide that lifts all boats in that, you know, if one experiment is successful, we learn about how the plasma behaves, which can be relevant to other experiments.

Chris - Richard, one of the missions of your company is gonna be propulsion systems for space. How does fusion fit into that?

Richard - Well, I mean, as you just said, there are several ways of doing this and what they've just done at NIF, which is called inertial confinement with these big lasers. A lot of scientists, you know, have been very much focused on how we can do fusion rather than how we should do fusion. Because we've got to contain that, we've gotta be able to use that and harness those neutrons for power. And I agree that electromagnetic confinement, like what you were talking about at Jet or at ITER, are very, very suited for power station fusion. But there's another promise that fusion gives us. It's not just the ability to power our planet indefinitely, it's the ability to leave our solar system because the same reaction that we just saw happen in America would give us exhaust speeds a thousand times faster, if you like, than conventional space thrusters, which means Mars in two weeks. It's an incredible potential if it can harness propulsion. So it's harnessing that same power for more than one application.