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Final design element completed at ITER fusion reactor in France

28 May 2013

In late April, ITER nuclear fusion project team leaders gave final approval for the design of the most technically challenging component – the fusion reactor’s ‘blanket’ that will line the inside of ITER’s doughnut-shaped 500MW tokamak reactor chamber, which will contain the super-heated nuclear fuel.

Photo: ITER
Photo: ITER

ITER will be the first experimental nuclear fusion reactor to generate more energy than it consumes, with the aim of creating a power source that produces an unlimited supply of clean, cheap energy with no carbon dioxide or radioactive waste.

It is the largest scientific collaboration in the world, with 34 countries representing half the world’s population contributing to the £13bn cost of the project.

The blanket has to absorb some of the 150 million °C heat and extreme electromagnetic loads generated by the fusion reaction. It is the last major component to be designed and completion will allow the project to move to the main manufacturing stage, with procurement due to start later this year and eventual assembly of the reactor lining scheduled to begin in May 2021.

ITER uses the same type of nuclear reaction that powers the sun, with two isotopes of hydrogen heated to extreme temperatures until they become plasma and are fused together, releasing a fast-travelling neutron that transfers energy as heat.

The blanket will capture this energy, comprising 440 four-tonne modules covering a total surface of 600m2, each comprising a beryllium ‘first wall’ containing a water-cooling system to contain the plasma and absorb the heat, and a water and steel shield block to absorb the neutrons themselves.

Six other modules will be located in ports around the middle of the chamber that will test ways of releasing tritium, one of the hydrogen isotopes used in the fusion reactor, by reacting the plasma with lithium.

The building site in Cadarache, southern France, has also passed the crucial stage where some 493 seismic bearings – giant concrete and rubber plinths – have been set into the reactor’s deep foundations to protect against possible earthquakes.

Over the next few years about a million individual components of the highly complex fusion reactor will be delivered to the site There will be at least another decade of building work and a further decade of testing before the reactor will be allowed to go nuclear.

A fission reactor meltdown like those at Chernobyl or Fukushima will be impossible at ITER because the fusion reaction is fundamentally safe. If there is any disturbance from ideal conditions the reaction stops automatically.

The ITER tokamak is twice the length and 10 times the volume of the previous European experimental fusion reactor, JET, at Culham in the UK, where much of the science underpinning ITER was carried out.

ITER is the first experimental fusion reactor to receive a nuclear operating licence because of its power-generating capacity. For every 50 megawatts of electricity it uses, it should generate up to 500mw of power output in the form of heat.

If everything goes to plan, the reactor will have proven the technology’s viability by the 2030s, meaning commercial reactors could be built later in the century.

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