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5 November 2015

Too cool for fuel: inside the nuclear fusion reactor Wendelstein 7-X stellarator

The new machine is designed to release energy in the same manner as the atoms in the sun.

By Michael Brooks

The “stellarator”. It is a brilliant term for a nuclear fusion reactor: futuristic-sounding and yet perfectly accurate. The machine mimics stellar processes in order to generate energy. This November, if clearance from the regulatory authority is forthcoming, engineers will fire up the Wendelstein 7-X stellarator (W7-X) in Greifswald, Germany.

Construction of the W7-X cost €1bn. It is a ring-shaped chamber, 16 metres in diameter. Inside, electrically charged gas known as plasma will circulate at temperatures of 100 million degrees Celsius. The plasma is held in place by magnetic fields and the pressure is such that the atomic nuclei it contains fuse together, releasing energy in the same manner as the atoms in the sun.

We already have fusion reactors in various parts of the world. Most are standard doughnut-shaped “tokamaks”. Stellarators are tokamaks with a set of twists and turns in their geometry that make it easier to keep the plasma under control. Japan has been operating a stellarator since 1998. The idea with all of these machines is that they will eventually lead to power stations that generate cheap, zero-carbon electricity. Alluring as the promise is, it is unlikely to be fulfilled in the first half of this century.

Engineers have been designing and building fusion reactors since the 1940s. They have never worked reliably. Creating and maintaining the extreme conditions for fusion to occur costs more energy than we can get out. If not managed carefully, the radiation, heat and pressure can also destroy the machines.

The hope with the W7-X is that its fusion reactions will be stable and the design will point the way to building a commercially viable fusion reactor. Yet even that would be a double-edged sword.

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In the south of France, engineers are currently building a huge, tokamak-style fusion reactor called Iter that will serve as a prototype for a commercial fusion power generator. If the W7-X is successful, however, it will force Iter’s funders and designers to rethink their plans, if not abandon them. Iter is not expected to be turned on for another decade at least; it is hard to see how it will make sense to carry on with the construction of a second-rate reactor that won’t even give us energy we can purchase.

Even so, we have done similar things with nuclear fission. The current, failing set of UK nuclear reactors was not optimised for electricity generation: this was compromised so that they could also produce fissile material for nuclear weapons.

The next generation – of the type that the government wants the French and Chinese to build for us – is much better-designed. However, the European Pressurised Reactor (EPR) is not only more efficient; it is also much more complicated and expensive. Existing projects to build EPRs in Europe are way over budget and behind schedule.

How long can this go on? While we tinker with these grand engineering projects, we ignore the low-hanging fruit. According to a report recently issued by the Committee on Climate Change, improvements in technology, coupled with measures to reduce carbon emissions, will make energy from wind and solar comparable in price with gas-sourced electricity in just a few years. Then there is the dull but sensible pursuit of energy efficiency measures. These we can do. Difficult technology has its place in the pantheon of long shots – but it is not the solution to bank on, however cool its name. 

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This article appears in the 28 Oct 2015 issue of the New Statesman, Israel: the Third Intifada?