The UK government announced this week its invitation to local communities to put forward proposals to host the country's prototype fusion energy power plant. The successful site will be home to the construction of STEP - the Spherical Tokamak for Energy Production - that is targeted for completion by 2040. At a media briefing ahead of the government's announcement, Professor Ian Chapman, CEO of the UK Atomic Energy Authority, explained why this is an exciting prospect for the whole world.

Ian Chapman at the media briefing on 25 November

"Globally, we burn 50% more fossil fuels now than we did in 2000, when there was already very clear evidence of climate change. That's a really depressing statistic.

There's a lot of focus about tackling net zero in the UK, but it's a global problem. It's a bit like COVID in that there's no point tackling it locally, you have to tackle it globally. It's no surprise that in response to COVID, it's the science superpowers that will come to the world's rescue with a vaccine. In the same way, those science superpowers have to step up and deal with climate change.

Roughly, in terms of gas, oil and coal, or their equivalent, there's 11,000 Mtoe [million tonnes of oil equivalent] burned today and around 11,000 days to go until 2050. So, a big simplification of 'net zero by 2050' means that we have to displace a megatonne of oil each day, for 30 years.

What does that mean? A megatonne of oil equivalent is about the size of a conventional nuclear power station or about the size of Hornsea, which is the world's largest offshore wind farm. So we'll need to build one of those every day for 30 years to displace all the carbon we currently burn. This is a huge challenge and we need to throw everything at it.

How are we going to solve that challenge?

In Stephen Hawking's last book, published posthumously, he was asked which world-changing idea he would like to see implemented by humanity and his answer was: "This is easy. I would like to see the development of fusion power to give an unlimited supply of clean energy."

Developing fusion power is not easy, of course, but in many ways - and Hawking realised this - fusion is the ultimate energy source. It doesn't produce carbon; it's baseload, which means it's working all the time; there is essentially unlimited fuel as it comes from seawater; it's inherently safe as our challenge is getting the reaction going, not stopping it and, although it does produce some waste, it's low level, manageable waste.

What's actually happening at the heart of the fusion reaction is that we take very light things - these are isotopes of hydrogen called deuterium and tritium. You force them close together and, when they fuse, they release an enormous amount of energy, much more energy than you would get from a coal station or a gas station or a nuclear fission station. We use this energy to ultimately produce electricity, with the other product of the fusion reaction being helium, which is an inert gas.

Now, tritium - one isotope of hydrogen - is radioactive and does need careful handling, but tritium has a very short radioactive half-life (about 12 years). In fact, you don’t find tritium naturally because it's all long since decayed. So, it's a complication in the process but it's not a big legacy problem.

Fusion is enormously high yield, so for the rest of my life, even if I burned much more electricity than I do at the moment, all the fuel I need comes from the water that you can put in one bathtub and the lithium that you'd find in two laptop batteries.

Fusion is happening in the core of our sun and all of our stars right now. The enormous mass of the sun means that gravity forces the isotopes of hydrogen close enough to fuse. We obviously cannot recreate the mass of the sun here on earth, so instead we have to give the fuel more energy, heating it 10 times hotter than the centre of the sun, which just sounds ridiculous.

When you have a fuel that is 10 times hotter than the centre of the sun, you obviously cannot let that fuel touch the walls, and so we hold it away from the walls using very large magnets. This was a concept invented back in the 1970s and we've been working on perfecting it since then.

So if that was known then, why isn't fusion working now? Well, fusion needs three things: market pull, technical demonstration of an energy gain and private investment.

It needs the market to want it and right now the consciousness of the climate emergency is as high as ever. It also needs a technical demonstration that it works here on earth. We have done fusion, but to date we've had to put more energy into getting the fuel hotter than the sun than [the energy] we've got out.

That will soon change with a machine called ITER, which will demonstrate that putting 50 megawatts in to heat the fuel can produce 500 megawatts of energy. That's the energy consumption of Leeds or Liverpool, for example. So, it's showing that fusion works on a commercial scale.

You also need the market to want to invest; to date fusion has been almost entirely funded by the public sector, as it's in pre-competitive phase, but the market is beginning to invest now. There are 40 or so start-up companies that have raised nearly GBP2 billion [USD2.7 billion] of investment over the last 10-15 years, so you can see that the appetite of the market is really exponentiating because of these other two conditions.

The largest fusion device operating in the world today is a machine called JET, which is in the UK. This is the only machine in the world of its scale, and the only machine in the world that is capable of operating with genuine fusion fuels (deuterium and tritium). It's also the only machine in the world that has the same mixture of metals that you'll put on the inside of a power plant, essential for proving ITER's technology, and it's the only fusion machine in the world that has to deal with genuine nuclear conditions.

Operating JET has given the UK unique experience. Indeed, the UK happens to have the largest fusion organisation in the world - the UKAEA - with the breadth of capability you need to design a fusion power station.

First of all, you need to understand how to control a fuel which is 100 million degrees, and that we do in JET. Then you need to understand how you extract that enormous heat. We've just completed a machine called MAST Upgrade, designed to test exactly that, how you exhaust the heat from a fusion energy plant.

You also need to understand how the neutrons produced in the reaction affect the machine's materials and test those components on a metre-by-metre scale so that you can qualify them to put into power stations. The UK has two unique facilities for doing that.

In addition, you need to understand how to process and store the tritium fuel and we are building the largest tritium research facility in the world for doing exactly that.

Of course, you don’t want to send people into this environment, because there are big magnetic fields and neutrons, so you use large robots for going in and fixing parts of the plant. We have the biggest centre of nuclear robotics in Europe right now - a facility called RACE.

And, finally, you need to put all of those things together in an integrated design.

I am confident that ITER will work. It will demonstrate that fusion works on a commercial scale. However, if you take the ITER design and try to build bigger versions of that design, you have to raise a lot of money to do it.

The cost of ITER is about GBP20 billion. We see from fission plants that trying to raise GBP20 billion every time you build one will slow down the penetration into the market. The UK realised this 30 years ago and so we pursued the idea of the so-called spherical tokamak.

The major cost in ITER actually lies in the massive magnets you need to hold the fuel, and then the big building that you have to put that magnetic bottle inside. So, if you can strip out costs by making the machine smaller and using the magnets more efficiently, you can strip out billions of cost.

And that is the genesis of the spherical tokamak, which is a much more compact design that, in principle, produces the same power output. It makes much more efficient use of the magnets and really drives down the price.


The boundary condition - the fuel in the middle - still has to be 150-200 million degrees, which is hotter than the sun and if you put that heat into a much smaller volume, the chances of melting the walls are obviously a lot higher, so you need a clever way of exhausting the heat from that fusion device.

We came up with a design in the mid-2000s, started building around seven years ago, and just a couple of weeks ago we completed the build and turned it on. By next summer we'll know whether this new exhaust system really works. No one else in the world has built one of these; it is unique.

If it works, it takes a heat flux challenge, which is like a space shuttle re-entering the earth's atmosphere, and takes it down to a level which is in a car engine, and we've known how to build car engines for 100 years; we know how to deal with that kind of heat. If it does what it says on the tin, it's a complete step-change for fusion because, all of a sudden, you really can conceive of building these much more compact plants.

A year ago, we began an endeavour to design and build a fusion power plant, a device that we're calling STEP. We're aiming to produce net energy and to have a much lower capital cost than other fusion power plants. There are other fusion power plants designs being undertaken and most of them use technology like ITER.

We're aiming to use a different technology that is much more compact, and hopefully much cheaper. The government has made a GBP220 million investment so far into the concept design, and as part of that concept design we're getting on with tackling some of the technical challenges.

Alongside this we're also looking for a site as well as working with government to develop a regulatory environment for how these power stations will be regulated in the future. At the same time, we’re also working on the delivery vehicle to take this design to market. As I said before, the question is, how do we provide a global solution to climate change.

STEP is a hugely ambitious programme, targeting to be the first in the world to produce a prototype fusion power plant, and then to export that technology round the world. The UK wants to be at the forefront of addressing climate change - it's a global problem and we need to be spearheading this new technology."

Date: Saturday, 05 December 2020
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