YEARS in PROVENCE

Nuclear fusion

I can remember debating in favour of nuclear power and in particular nuclear fusion 35 years ago in Aberdeen’s Marischal College – a stance that would earn me today the tag of ‘New Environmentalist’.

Since the 1950s, fusion has offered the dream of almost limitless energy – copying the fireball process that powers the Sun, atoms forced together to form helium and release energy . Instead of splitting an atom’s nucleus, like in nuclear fission, nuclear fusion is the process of bringing together two atomic nuclei to form a new nucleus. There is no need for dangerous chemical elements like uranium or plutonium — easing the fears of nuclear proliferation. Energy derived from fusion is appealing because very few natural resources are required to create fuel.  The fuel for fusion basically comes from sea water. Every bottle of water that we drink has heavy water — deuterium — inside.

Fusion is fuelled by two readily available forms of hydrogen.

  • One litre of water contains enough deuterium, when fused with tritium, to produce the equivalent energy of 500 litres of petrol
  • A 1,500MW fusion power station would consume about 600g of tritium and 400g of deuterium a day

In Provence, southern France, the International Thermo-nuclear Experimental Reactor (Iter) is the world’s largest science experiment and the world’s largest bid to harness the power of fusion.  Iter aims to prove that fusion can be achieved on a mass scale.  The European Union, United States, China, South Korea, Japan, India and Russia have agreed to invest in building a reactor that can conduct experiments in burning plasma.  the project is receiving the first of about one million components at one of the largest construction sites in the world . Massive cost rises and long delays means the project is running two years behind schedule.

Iter’s design involves a tokamak, Russian for a ring-shaped magnetic chamber. It is based on the design of JET, a European pilot project at Culham in Oxfordshire. The plant at JET has managed to achieve fusion reactions in very short bursts, but required the use of more power than it was able to produce.  Iter will produce 500 megawatts of power for about 50 megawatts put in.  It will create a plasma of superheated gas reaching temperatures of more than 200 million C – conditions hot enough to force deuterium and tritium atoms to fuse together and release energy.

So, a future of cheap fuel, relatively little radioactive waste and no greenhouse gases emissions..  But the technical challenges of not only handling such an extreme process but also designing ways of extracting energy from it have always been immense.

Each partner first had to set up a domestic “agency” to handle the procurement of components within each member country, and there have been complications with import duties and taxes. Further delay crept in with disputes over access to manufacturing sites in partner countries. Because each part has to meet extremely high specifications, inspectors from Iter and the French nuclear authorities have had to negotiate visits to companies not used to outside scrutiny.

The main building to house the tokamak has been adjusted to leave gaps in its sides so that late components can be added without too much disruption. The route from the ports to the construction site has had to be improved to handle huge components weighing up to 600 tonnes, but this work too has been slower than hoped.  It’s thought that even a start date during 2021 may be challenging.

While one major concern is the arrival sequence of major components, another is that the components themselves are of sufficiently high quality for the system to function.

The 28 magnets that will create the field containing the plasma have to be machined to a very demanding level of accuracy. And each part must be structurally sound and then welded together to ensure a totally tight vacuum – without which the plasma cannot be maintained. A single fault or weakness could jeopardise the entire project.

Assuming Iter does succeed in proving that fusion can produce more power than it consumes, the next step will be a demo reactor. The international partners must follow up with a technology demonstration project – a test-bed for the components and systems needed for a commercial reactor.

Photograph –  http://www.forviemedia.co.uk/photo_9563214.html .

Main source and further reading/research:-

http://www.bbc.co.uk/news/science-environment-23408073

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