ITER: A Thermonuclear Reactor That Scientists Will Tidy Up When It’s Done

July 17, 2012 — Leave a comment

Yesterday I toured the site of ITER, the nuclear fusion plant under construction near Cadarache, France. A multinational collaboration is pumping 150 billion Euros into this experimental fusion reactor, which aims to create 500 mega-watts of power, for every 50 that are pumped into.

ITER, which sort of means International Thermonuclear Experimental Reactor but is actually just a nice, trans-national word, is an enormous project spanning generations. First conceived in the 1980s, the idea is to create mostly clean, virtually limitless energy through the process of fusing Hydrogen atoms together. This is a process we see at work in the universe in stars and it seems technologically feasible that with a lot of work we can reproduce the conditions on Earth and set ourselves free of not only a limited fossil fuel supply, but also of the cost of using those fuels long term (i.e. climate change).

ITER grew as a collaboration during the 1990s and the decision to locate the experimental plant in France was made early in this century. Europe currently funds the bulk of the project (45%) with Russia, Japan, Korea, the USA, China and India all participating in other major roles, currently they are building many of the reactor components.

The ITER fusion reactor at Cadarache is purely experimental, it will never be used to generate energy for the French grid. The site chosen was a 180 hectare forest and 90 hectares of it will remain as such, to surround the site and keep it looking green. The site is also somewhat seismically active, and earthquakes can occur here. The structure is being built to withstand a 7.2 Richter magnitude earthquake, though such an event has never been recorded in the area, with the biggest being. 6.1 quake over a hundred years ago. To accomplish this the whole site is being built atop 500 special columns, that allow the entire facility to pitch and bend during tremors. It is all very impressive.

ITER is due to be completed in 2020, at which point full-scale nuclear fusion experiments will begin. The reactor itself is a Tokamak: a donut-shaped ring of plasma, contained within intense magnetic fields. This plasma reaches temperatures of 150 million degrees (10 times as hot as the Sun!), and incredible pressure. Under such conditions it is believed that fusion can occur at large scales. Large is necessary in this game, and the aim of the project is to be able to output 10x as much energy as was input to the reactor. Such a multiple of energy return makes fusion a viable power source for the world, and in this case will mean transforming 50 mega-watts into 500.

After 25 years of experiments, the ITER project will be complete and a second reactor will be built, based on the results of the research done in Cadarache. This second reactor, DEMO, will be a functional power station and will lead the way for widespread nuclear fusion for the world.

If all goes according to plan it will have taken a little over a century for the dream of nuclear fusion to become a global reality.

Today, that dream is very much still under construction (see photo below). The place is mostly a levelled building site. A couple of the buildings have gone up, and the power grid is in place. It would be good to return and tour it again in a few years.

One amazing fact about ITER has stood out for me in particular: after the experiments are complete, the whole site will be deconstructed and the location will be turned back into forest.

This decision seemed utterly bizarre to me at first. After thinking about it though, I’m not sure how else you can responsibly plan for something as long term and large-scale as ITER. A century from now, it is hard to know if fusion will have turned out to be the best route to take and rather than leave our descendants with an ageing reactor to deal with, at least this plan means we leave things as we found them. Also, since the successor to ITER (DEMO) is part of the larger plan, it seems prudent to factor in the concept of cleaning up phase 1 as phase 2 ramps up. Perhaps this is how more big ideas should be planned? On the other hand, it seems ridiculous that the first industrial-scale fusion reactor will never be used for civil energy generation, and will not be kept for even the sake of history.

Learn more about ITER here and here.

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