ITER (International Thermonuclear Experimental Reactor) is at this time one of the most ambitious, complex and costly[1] energy projects in the world. Its promoters chose this acrostic to express the beginning of a path (iter is also a Latin term meaning route) to develop a new form of energy for peaceful and innovative uses.

Artistic representation of the ITER plant with the tokamak and associated systems.

In Cadarache, an enclave in Saint Paul-lès-Durance (in southern France’s Provence-Alpes-Côte d’Azur region), seven partners (from 35 countries[1]) are working together to build the world’s largest tokamak, designed to demonstrate the feasibility of nuclear fusion as a source of massive energy, based on the same principle that makes our sun and other stars shine. A carbon-free process and therefore without the harmful effects of greenhouse gases.

The experiments to be carried out at ITER are decisive in broadening scientific knowledge in the field of fusion and flagging the way for future fusion power plants. The objective of ITER, which will be the first machine to bring together and contrast the technologies, materials and physical processes needed to produce commercial fusion-based electricity, is therefore to achieve a positive energy balance by maintaining this production over long time periods.

Thousands of scientists and engineers have worked and are working on the design of ITER since the idea of a joint international fusion project was conceived in 1985. And since then, the ITER partners —China, the European Union, India, Japan, Korea, Russia, and the United States— have laboured closely together to build this important experimental device, to get it up and running, and to show the world that it is possible to build a commercial demonstration fusion reactor.

R. Reagan and M. Gorbachev at the 1985 Geneva Summit. Among the different issues, it was decided there to start an international project on thermonuclear fusion.


Scientists know that the energy amount produced in a tokamak depends on the number of fusion reactions that take place in it. In principle, therefore, the larger the machine, the more energy it can generate. Consequently, ITER, which is ten times the volume of plasma in the largest tokamak in existence today, will be a unique experimental device with a more efficient containment capacity. Indeed:

  • ITER has been designed to produce 500 MW of fusion energy.- In 1997 the European JET broke the world record for fusion energy production, which it still holds. It then obtained a total of 16 MW, starting from an input heating power of 24 MW (Q=0.67). However, with ITER, the energy return will be tenfold, generating 500 MW of fusion energy from 50 MW of input heating power (Q=10). This energy will certainly not be transformed into electricity, but ITER will clear the way for other machines to do so.
  • ITER will mature the interaction of the different technological systems involved in a fusion power plant.- ITER is halfway between today’s smaller-scale experimental reactors and future demonstration fusion power plants. ITER will allow scientists and technologists to address not only the study of plasmas under conditions analogous to those expected in the fusion power plants of tomorrow, but also to test innovative technologies for heating, cryogenics and remote control, diagnosis and maintenance.
  • ITER will generate a deuterium-tritium plasma whose reaction will be maintained by internal heating.- The physics and technology of nuclear fusion are already exploring the threshold of the so-called “burning plasma”, with sufficient confinement efficiency to incite a significant number of fusion reactions. Scientists are confident that, with ITER, not only will much more energy be produced, but plasmas will remain stable for longer periods of time.
  • ITER and the regeneration of tritium.- Planetary reserves of tritium (an isotope used along with deuterium to fuel the fusion reaction) are insufficient to meet the needs of future fusion power plants. An important task for ITER is to show the feasibility of tritium regeneration by testing multiple prototype lithium loops in a realistic fusion environment.
  • ITER will test safety specifications.- ITER covered a significant stage on the road to fusion when, in 2012, it was granted a nuclear operator’s licence by the French government after a careful and pondered examination of its safety files. One of the main purposes of ITER, then, is to show that during its operation the environmental and health effects are harmless.


The ITER project is, as already mentioned, an international collaboration of China, the European Union, India, Japan, Korea, Russia and the United States. These seven partners have harmonised their resources to crown one of the greatest summits in science: reproducing on Earth the processes that take place in the Sun and the other stars to produce their light and heat.

Signatories of the ITER Agreement (2006) together with Jacques Chirac, President of France and host. From left to right: Vladimir V. Travin, Deputy Head of Rosatom (Russia); Takeshi Iwaya, Senior Vice-Minister for Foreign Affairs (Japan); Xu Guanhua, Minister of Science and Technology (China); José Manuel Durão Barroso, President of the European Commission; Jacques Chirac; Kim Woo Sik, Vice-Prime-Minister of the Ministry of Science and Technology (South Korea); Anil Kakodhar, Government Secretary in the Department of Atomic Energy (India); Raymond L. Orbach, Under-Secretary for Science at the Department of Energy (USA), and Janez Potočnik, European Commissioner for Science and Research.

Together, ITER represents half of the world’s population, three continents, more than 40 languages and 85% of the planetary GDP. In daily practice thousands of people are working for the success of ITER.

As signatories to the ITER Agreement, reached in 2006, the costs of building, operating and dismantling the project are shared by all the partners. But the experimental results and any intellectual property obtained during the manufacture, construction and operation of the device will also be distributed among all of them.

Most of the construction costs (45.6%) are assumed by the EU. The rest is shared equally by China, India, Japan, Korea, Russia and the US. (9.1% each). It should be noted that the partners will contribute hardly any money. 90% of the contributions will be made in kind (components, systems and finished buildings).

The ITER signatories have also concluded technical cooperation agreements with third countries and institutions: with Australia (through the Australian Nuclear Science and Technology Organisation, ANSTO, in 2016), with Kazakhstan (through the Kazakh National Nuclear Centre, in 2017), with Canada (with which it has signed a Memorandum of Understanding to explore future cooperation), with Thailand (by signing a cooperation agreement with the Institute of Nuclear Technology, in 2018), and with other international organisations, national laboratories, universities and schools. Altogether, more than 70 cooperation agreements.


Aerial photo of the terrains (180 Ha) on which the ITER plant is being built.

In 2010, the construction of ITER started in Cadarache, a land of about 42 hectares in the south of France, near the French Riviera. The main building is almost finished and the beginning of the tokamak assembly is scheduled for 2020.

The exact sequence of each assembly phase has been carefully orchestrated and coordinated. In fact, assembling as a whole the more than ten million components, manufactured in different parts of the world by each ITER member and delivered to Cadarache is, in itself, a huge logistical and engineering challenge.

In November 2017, the project covered half of the route to the first plasma, for which less than 30% of the stages currently remain.


2005 Decision to locate ITER in France
2006 Signature of ITER Agreement
2007 Official establishment of the ITER Organization
2007-2009 Cleaning and levelling of the land
2010-2014 Ground support structure and seismic foundation for the tokamak
2012 Nuclear licensing (ITER is already a Nuclear Facility under French law)
2014-2021 Construction of tokamak building (access for assembly activities in 2019)
2010-2021 Construction of ITER plant and auxiliary buildings for the first plasma
2008-2021 Manufacture of the main components of the first plasma
2015-2023 The largest components are transported along the ITER Itinerary
2020-2025 Main assembly phase I
2022 Toroid Termination
2024 Cryostat closure
2024-2025 Integrated start-up phase (system start-up begins several years earlier)
Dec 2025 First plasma
2025-2035 Progressive machine start-up begins
2035 Deuterium-tritium operation begins


The dramatic planetary spread of SARS-CoV-2 has been a severe test for the management of an international project like ITER. However, those involved in the project, whatever their level of responsibility, have done everything possible to respond to this unprecedented set of challenges, putting security at the forefront as always.

In order to preserve the health of the people involved in the ITER project, all the precautionary measures recommended by the WHO and the Government of France, as ITER’s host, have been taken since the first outbreaks of Covid-19. The main objective has been to ensure the safety and health of people, while maintaining as far as possible the timetable for critical activities. This is being achieved through individual responsibility (by scrupulously complying with health and safety recommendations), the solidarity of all the people (who have worked like a well-oiled orchestra), the advance planning of multiple scenarios, and clear guidance from the President of the Council and the senior management of the ITER Organization as the situation has evolved.

[1] With an investment of some 24 billion euros, it is the fifth most expensive project in the history of science and technology, after the Apollo Program, the International Space Station, the Manhattan Project and the GPS system development.

[2] [Note updated 31 January 2020]: The United Kingdom, formally withdrawn from the European Union and Euratom, has expressed interest in continuing to participate in the ITER Project. This will require a further arrangement, the terms of which will be agreed during the so-called transition period. However, until the signature of the new Agreement, the ITER Council has decided to terminate the existing contracts with the staff and suppliers.

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