ITER is an experimental fusion device being built at Saint-Paul-lez-Durance in southern France. Under the current project baseline, research operation is expected to begin in 2034, with deuterium–tritium operation starting in 2039. ITER is designed to produce 500 MW of fusion power from 50 MW of external plasma-heating power, corresponding to a plasma gain factor of Q ≥ 10. It will not generate electricity, but the knowledge gained from its experiments will support the development of future demonstration fusion power plant such as DEMO. In such plants, fusion heat would be converted into electricity through an appropriate power-conversion system.

Tokamak

ITER will operate with deuterium-tritium plasma at temperatures of around 150 million kelvin, about ten times hotter than the core of the Sun. The plasma will be confined in a toroidal, doughnut-shaped vacuum vessel by a combination of powerful magnetic fields generated by superconducting coils and the electric current flowing through the plasma.

The ITER plasma will have a major radius of about 6.2 metres and a minor radius of about 2.0 metres. During full-power operation, the plasma current will reach up to 15 MA. The toroidal magnetic field at the plasma major radius will be about 5.3 T, while the maximum field on the toroidal field coils will reach 11.8 T.

Vacuum Vessel

The ITER vacuum vessel will measure 19.4 metres across and 11.4 metres high and will have a distinctive D-shaped cross-section. Its interior volume will be about 1,400 m³, accommodating approximately 840 m³ of plasma. The vessel itself will weigh about 5,200 tonnes, increasing to around 8,500 tonnes after installation of the blanket and divertor.

Magnetic Coils

The main toroidal magnetic field will be produced by 18 superconducting Nb₃Sn toroidal field coils, each about 17 metres high and 9 metres wide and weighing roughly 330 tonnes. Together they will store about 41 GJ of magnetic energy and produce a maximum field of 11.8 T. The coils will operate at cryogenic temperatures of about 4 K. At the centre of the machine, a six-module Nb₃Sn central solenoid about 13 metres high and 4 metres wide will induce and drive a plasma current of up to 15 MA. With its support structure, the completed solenoid will weigh about 1,000 tonnes and generate a maximum field of 13 T.

External Heating

ITER will use three complementary external-heating systems: neutral beam injection, electron cyclotron resonance heating and ion cyclotron resonance heating. Two heating neutral beam injectors will provide a total of 33 MW, while the radiofrequency systems are planned to provide up to about 67 MW of electron cyclotron heating and 20 MW of ion cyclotron heating in later operating phases. Not all of this installed heating capacity would be used simultaneously in the Q ≥ 10 reference scenario.

Fusion Reaction

ITER is designed to produce fusion power of about 500 MW in long plasma pulses lasting 400 to 600 seconds. The first wall, blanket systems and divertor will be exposed to intense neutron and heat loads and will provide important data for the design of future fusion reactors. Because naturally available tritium reserves are insufficient for large-scale fusion energy production, ITER will also test lithium-containing Test Blanket Modules. These experiments will investigate how fusion neutrons can be used to breed tritium for the fuel cycle of future power plants.

The ITER tokamak.

Cost

ITER is one of the world’s most ambitious international science and engineering projects. Large components manufactured in different member countries must be transported to France and assembled with millimetre- and sub-millimetre-scale precision. Its cost is difficult to express as a single figure because much of the project is funded through in-kind contributions from the seven ITER Members, and the budget has evolved as the design and schedule have been revised.