ITER (International Thermonuclear Experimental Reactor)

ITER is the world’s largest tokamak fusion experimental reactor, under construction in southern France through a seven-party international collaboration. Its goal is to demonstrate a burning plasma, in which the fusion reaction sustains itself.

Simple Definition (High School)

ITER is a giant experimental machine that tests whether we can produce, here on Earth, the same fusion energy that makes the Sun shine. It is too large and too expensive for any single country to build, so the world’s major nations and regions are joining forces to construct it. The goal is to show, in a real large-scale device, a state in which the reaction keeps going vigorously once the fuel is loaded and ignited. It is not yet a power plant; rather, it is positioned as an experimental reactor for verifying the science and technology needed to build one.

Precise Definition (Undergraduate and Above)

ITER (International Thermonuclear Experimental Reactor) is an international collaboration involving seven parties: the European Union, Japan, the United States, Russia, China, South Korea, and India. It is under construction at Cadarache, France. It is a tokamak-type experimental reactor fueled by deuterium and tritium, and it has two main performance goals.

The first is to achieve $Q \geq 10$ for the energy gain factor $Q = P_\text{fus} / P_\text{in}$, which is the ratio of the fusion power output $P_\text{fus}$ to the injected heating power $P_\text{in}$. This corresponds to obtaining 500 MW of fusion output from 50 MW of heating.

The second is to realize and demonstrate the physics of a burning plasma, in which heating by the alpha particles produced in fusion becomes the dominant source of plasma heating. ITER does not generate electricity; it is an experimental reactor that demonstrates the scientific and engineering feasibility of this burning plasma.

Role in Fusion Research

ITER is a key device that bridges fusion, which has been verified at laboratory scale, to the large-scale, long-duration burning plasmas that come closer to a power plant. The knowledge gained here on burning plasma control, superconducting coils, the divertor, tritium handling, and more feeds directly into the design of the next-stage prototype reactor, DEMO. It can be called a central milestone for determining, on a global scale, whether fusion energy can become practical.

Learn More

• ITER
• Tokamak
• DEMO

Related Terms

• Tokamak - The confinement scheme ITER adopts
• Tritium - One of ITER’s fuels
• Divertor - ITER’s heat and particle exhaust device
• Lawson Criterion - An indicator for achieving a burning plasma