ITER

ITER is an international research and engineering project based in southern France and organized around the construction and operation of a very large experimental tokamak. Its purpose is to investigate whether a controlled deuterium-tritium plasma can produce substantially more fusion power than the external heating power required to sustain it, while also testing the technologies, materials, systems, and operating methods that a future fusion power plant would need. ITER is not a commercial electricity-generating station and is not intended to supply power to the grid. The project grew out of international fusion cooperation initiated during the Cold War. The United States, the Soviet Union, the European Community, and Japan began discussing a major collaborative experiment in the 1980s. Engineering design work continued through the following decades, with China, India, South Korea, and other participants joining the developing project. The ITER Agreement entered into force in 2007, creating the ITER Organization as an intergovernmental entity. The European Union hosts the facility and provides the largest share of its contributions, while the other members contribute through a mixture of cash, components, personnel, and in-kind procurement. The core machine is a magnetic-confinement tokamak. Powerful superconducting magnets are designed to confine an extremely hot plasma in a doughnut-shaped vacuum chamber. ITER is designed for a plasma volume of approximately 840 cubic metres and a nominal deuterium-tritium operating target in which about 500 megawatts of fusion power would be generated from roughly 50 megawatts of plasma-heating input. This frequently cited ten-to-one figure is a plasma-performance objective, not an expected net-electricity output. ITER will not convert its experimental fusion heat into commercial electricity. The facility is being assembled at the Cadarache site in Provence. Its major systems include the vacuum vessel, superconducting magnet system, cryostat, heating and current-drive equipment, tritium-handling systems, cooling infrastructure, remote-maintenance equipment, diagnostics, and extensive radiation-shielding and safety systems. Member governments and domestic agencies manufacture many of these components in their own territories and deliver them to the site for integration. This distributed procurement model is central to the project's political and industrial structure but also creates demanding interfaces, transport, quality-control, and schedule-management challenges. ITER's scientific goals include demonstrating long-duration burning-plasma behavior, studying self-heating by alpha particles, testing plasma-control methods, and improving understanding of the conditions needed for sustained fusion. Its engineering goals include validating superconducting magnets, remote handling, nuclear-grade vacuum and cooling systems, tritium-related technologies, and materials exposed to intense neutron and heat loads. The project's results are intended to inform the design of DEMO-type plants, which would be subsequent facilities aimed at demonstrating electricity production. The program has experienced significant schedule revisions, technical difficulties, inflationary pressure, and changes to the planned installation sequence. Welding and dimensional problems affecting components of the vacuum vessel and thermal-shield systems, along with broader manufacturing and integration issues, contributed to a reassessment of the original first-plasma plan. In 2024, ITER announced a revised baseline that moved away from the earlier first-plasma milestone toward a later start with a more complete machine and a deuterium-tritium phase targeted for the 2030s. The organization remains active, but its ultimate technical value will depend on successful assembly, commissioning, plasma operation, and publication of reliable experimental results.

ITER's origins lie in the effort to make fusion research a sustained international enterprise. At the 1985 Geneva summit, the leaders of the European Community, Japan, the Soviet Union, and the United States supported cooperation on a major international fusion project. The International Atomic Energy Agency subsequently helped coordinate conceptual work, and the four parties began the Conceptual Design Activities in 1988. Engineering Design Activities followed in the 1990s, producing progressively more detailed specifications for a large tokamak. The project was initially conceived as a four-party collaboration. China, South Korea, and India later became members, while the European Union represented the European host and contributed through the European domestic agency. Russia remained a founding participant through the post-Soviet transition, and the United States participated in the design and later construction phases. Japan also remained a principal partner. The broad membership made ITER one of the largest scientific collaborations ever attempted, but it also created a complex governance and procurement structure. France was selected as the host in 2005, and the Cadarache site in Provence became the location for the machine and supporting facilities. The ITER Agreement was signed in 2006 and entered into force in 2007. The agreement established the ITER Organization as an intergovernmental entity with responsibility for designing, assembling, commissioning, operating, and decommissioning the facility. The European Union, as host, undertakes approximately 45 percent of the project's in-kind contribution, while the other members each provide smaller shares. Contributions are commonly delivered as manufactured components rather than simple cash payments. The construction phase involved major civil works, site preparation, manufacturing contracts, and the creation of a supply chain extending across the member countries. The machine's scale is unprecedented for a tokamak: its superconducting magnet structures, cryostat, vacuum vessel, blanket modules, heating systems, cooling networks, diagnostics, and remote-maintenance equipment must be integrated to extremely tight tolerances. Components are built by national domestic agencies and industrial suppliers before being shipped to France. This approach distributes industrial benefits and technical responsibility but increases the number of interfaces that must be managed. The original schedule anticipated an early first-plasma milestone followed by later installation of systems required for deuterium-tritium operation. As construction and manufacturing progressed, however, the schedule changed repeatedly. Component production, quality assurance, transport, site integration, and the effects of the COVID-19 period and supply-chain disruption added pressure. Inspection later identified dimensional and welding issues in sections of the vacuum vessel and thermal-shield assemblies. These problems required corrective work and contributed to the decision to reconsider the planned assembly sequence. In 2022, Pietro Barabaschi became Director-General after Bernard Bigot, who had led the organization during a major construction period. Under the subsequent planning process, ITER moved toward a strategy that emphasizes more complete machine assembly and testing before the first plasma rather than pursuing the earlier limited first-plasma milestone. The revised baseline announced in 2024 targeted a later initial operation and a deuterium-tritium phase in the 2030s. The precise timing remains dependent on manufacturing, repair, integration, regulatory, and commissioning progress. ITER's historical importance rests on its role as a bridge between present-day fusion experiments and future demonstration reactors. It is intended to show that a burning plasma can be controlled at reactor-relevant scale and to test technologies needed for sustained operation. It will not produce commercial electricity, and its success would not by itself prove that fusion power is economically competitive. Instead, its scientific and engineering results are expected to guide later DEMO programs and the wider development of fusion-energy systems.

• 2024

  New baseline and installation strategy announced

  [3]New ITER baseline and project strategyiter.org

  ITER announced a revised approach centered on completing more of the machine before initial operation and targeting deuterium-tritium operations in the 2030s.

• 2022

  Pietro Barabaschi becomes Director-General

  [4]ITER Director-General Pietro Barabaschiiter.org

  Pietro Barabaschi succeeded Bernard Bigot and took responsibility for the next stage of assembly, integration, and commissioning.

• 2016

  Revised project baseline approved

  [5]ITER project baselineiter.org

  The ITER Council approved a revised baseline intended to align the construction program with a more realistic staged schedule.

• 2015

  Bernard Bigot becomes Director-General

  [7]Bernard Bigot becomes Director-Generaliter.org

  Bernard Bigot assumed leadership as the project moved through intensive construction and component-procurement work.

• 2010

  Osamu Motojima becomes Director-General

  [6]Osamu Motojima becomes Director-Generaliter.org

  The organization entered a major construction phase under its first Director-General, Osamu Motojima.

• 2007

  ITER Organization established

  [1]ITER: In a few linesiter.org

  The ITER Agreement entered into force, creating the intergovernmental organization responsible for the project.

• 2005

  France selected as host

  [1]ITER: In a few linesiter.org

  The Cadarache site in southern France was selected to host the ITER facility.

• 1988

  Conceptual Design Activities begin

  [1]ITER: In a few linesiter.org

  The participating parties began coordinated conceptual design work for the future tokamak project.

• 1985

  International fusion project proposed

  [1]ITER: In a few linesiter.org

  Leaders of the European Community, Japan, the Soviet Union, and the United States backed the idea of a major collaborative fusion experiment.

A public, intergovernmental flagship research program positioned between laboratory-scale fusion experiments and future demonstration power plants. ITER is a research facility rather than a commercial energy brand or operating power station.

• Fusion research facility

  ITER tokamak

  The central experimental machine is a large magnetic-confinement tokamak designed to contain a deuterium-tritium plasma. Its superconducting magnets create the magnetic configuration needed to confine the plasma, while the vacuum vessel, blanket, divertor, heating systems, diagnostics, and cooling systems support reactor-scale experiments. ITER is designed around a nominal objective of approximately 500 megawatts of fusion power from about 50 megawatts of plasma-heating power. It will not generate electricity for commercial distribution.

• Tokamak subsystem

  Superconducting magnet system

  ITER's magnet system includes toroidal-field, poloidal-field, central-solenoid, and correction coils. The magnets are cooled to cryogenic temperatures so they can carry high currents with minimal electrical resistance. Together they shape, control, and confine the plasma. Their manufacture is distributed among ITER members, making them both a core scientific asset and a major test of international industrial coordination.

• Fusion technology

  Plasma heating and current-drive systems

  ITER combines several plasma-heating approaches, including neutral beam injection, electron-cyclotron heating, and ion-cyclotron heating. These systems must raise the plasma to fusion temperatures, help control its shape and stability, and support experiments over a range of operating conditions. Their performance is important to testing whether alpha-particle self-heating can dominate the energy balance in a burning plasma.

• Fusion engineering

  Remote handling and diagnostics systems

  Because components inside the machine will become radioactive during deuterium-tritium operation, ITER relies on remote maintenance equipment and extensive diagnostic instruments. Remote systems are intended to inspect, remove, and replace in-vessel components without direct human access. Diagnostics will measure plasma temperature, density, impurities, stability, and confinement, providing the data needed to operate and evaluate the experiment.

• 2024

  Adopt a revised machine-assembly and commissioning strategyGeneration change

  Background

  Problems involving vacuum-vessel sectors and thermal-shield components, together with broader integration and supply-chain pressures, required the organization to reconsider the earlier first-plasma sequence.

  Action taken

  ITER adopted a plan focused on completing and testing more of the machine before initial operation, with a later first-plasma target and deuterium-tritium operations planned for the 2030s.

  Aftermath

  The strategy is intended to reduce the risks of operating an incomplete machine, but it extends the timetable for experimental results and increases the importance of repair, manufacturing, and integration execution.

  Source

• 2016

  Approve a revised project baselineStrategy

  Background

  Construction progress, component procurement, and the complexity of integrating an unprecedented number of internationally manufactured systems made the original schedule difficult to maintain.

  Action taken

  The ITER Council approved a revised baseline for staged construction and assembly.

  Aftermath

  The revision provided a new program framework, although later technical and manufacturing issues led to further schedule reassessment.

  Source

• 2005

  Select Cadarache as the host siteStrategy

  Background

  The members needed to choose a permanent location for the international facility and associated construction program.

  Action taken

  France was selected to host ITER at the Cadarache research site in Provence.

  Aftermath

  The decision established the project's French construction base and made the European Union the host member responsible for the largest share of the in-kind contribution.

  Source

1. 1ITER: In a few linesiter.org
2. 2ITER official websiteiter.org
3. 3New ITER baseline and project strategyiter.org
4. 4ITER Director-General Pietro Barabaschiiter.org
5. 5ITER project baselineiter.org
6. 6Osamu Motojima becomes Director-Generaliter.org
7. 7Bernard Bigot becomes Director-Generaliter.org