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What is ITER?

ITER, the next-step machine. Click on the image to enlarge.

ITER (the International Thermonuclear Experimental Reactor) is designed to be a tokamak capable of generating 500MW of fusion power for up to 50 minutes, it representing an experimental step between today's studies of plasma physics and tomorrow's electricity-producing fusion power plants. The machine's name is not only an acronym: "iter" signifies "the way" in Latin, an appropriate appellation for a machine paving the road to the commercial exploitation of fusion. ITER is an international project involving the People's Republic of China, the European Union (represented by the European Atomic Energy Community, commonly referred to as EURATOM), Japan, the Republic of Korea, the Russian Federation, and the United States of America, under the auspices of the International Atomic Energy Association. India and Brazil have also shown interest in joining the project. With construction scheduled to start soon in Cadarache, France, the first plasma operation is expected in 2015.

Computer-aided picture of ITER's implementation in the CEA research centre of Cadarache. Click on the image to enlarge.

The ITER project started at the end of the 80's as an initiative of Ronald Reagan and Mikail Gorbachev, at that time the respective presidents of the USA and Russia. The ITER Engineering Design Activities (EDA) were carried out between July 1992 and July 2001 within the framework of the ITER agreement signed by the - then - four parties, namely EURATOM, Japan, the Russian Federation and the United States of America. During the EDA, the ITER Joint Central Team worked out a reference design, including in particular a set of requirements to be satisfied by any proposed site. In 2001, negotiations started on the joint implementation of the project, including such issues as location, cost partitioning, production of the various components and the setting up of a framework for the practical management of the project. At the outset of the negotiations four locations were suggested for ITER. On June 7, 2001 Clarington (near Toronto) was proposed as a host site by Canada. About a year later, on June 5, 2002, the Japanese site of Rokkasho-Mura as well as two European locations (one in Valdellos near Barcelona in Spain, and one at Cadarache near Aix-en-Provence in the south of France) were proposed. An international team of experts judged the various sites for their suitability to host the project. After a period of several years during which they had withdrawn from the project, the USA rejoined in 2003. At that time Korea and China joined the enterprise as well. On November 26, 2003, the European Union opted for the Cadarache as the sole European candidate site for ITER. On January 9, 2004, Canada withdrew from the project. Since then long and painstaking negotiations have been undertaken to decide which of the two remaining proposed sites would be selected for ITER. On June 28, 2005 the decision was taken that the machine would be located in Cadarache, France.

ITER will be the first machine in which fusion reactions will take place abundantly and for a long time. Even in the best performing present-generation tokamak, the Joint European Torus or JET at Culham in the United Kingdom, the fusion fire has only been kept alive for a few seconds in relatively brief experimental campaigns during which tritium fuel was used. Aside from showing that the fusion reactions can be maintained for prolonged periods of time, ITER should demonstrate whether the materials developed for its construction resist radioactive activation. Indeed, materials proposed for fusion reactors are currently tested only by placing samples in fission reactors and checking their behavior under the bombardment of fission - not fusion - neutrons. As the latter are more energetic than the former, the presently proposed materials can ultimately only be tested in a fusion environment. In sum, JET has delivered the "proof of principle" that we can light the fusion fire, but ITER is needed provide the physics and technology basis for the construction of a demonstration electricity-generating power plant ("DEMO").

ITER will have superconducting magnetic field coils. Such coils are necessary for sustained economical operation of a future fusion power station. The tokamak vessel and superconducting magnets are located inside a thermally shielded shell to maintain the cryogenic temperatures needed for superconductivity. While the near-vacuum of the cryostat minimises convective heat transfer, thermal shields placed between the cold magnet structure and the warm vessel minimise radiative heat transfer. These shields consist of stainless steel panels cooled by helium gas at 80° K (Kelvin). The temperature of the superconducting coils themselves needs to be kept at 4° K (the "absolute zero" of temperature corresponds to 0° K which is -273° Celsius).

The cost of building ITER is estimated to be 5 billion EUR, most of which will be paid "in kind" by the partners taking responsibility for building the various components of the machine (superconducting coils, heating systems, diagnostics, ...) and for shipping them to the construction site. Of the total cost, 80% will go to industry. The European Union will shoulder 50% of the expense for ITER, with the other five partners contributing 10% each. Japan will produce 20% of the machine components, half of which will be financed by the European Union in the form of industrial contracts. Moreover, Japan will provide 20% of ITER's scientific staff.

The subsequent running of the device during 20 years of operation will equally require an amount on the order of 5 billion EUR. The host location will see an influx of one to two thousand highly qualified researchers. Building and running the machine will indirectly provide employment for thousands of people in the Cadarache region.

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