Introduction to ITER

While significant progress has been made with JET and other fusion experiments, it was clear from an early stage that a larger and more powerful device would be needed to create the conditions expected in a fusion reactor and to demonstrate its scientific and technical feasibility. ITER is an international research and development project with the aim to demonstrate the scientific and technological feasibility of fusion energy.

Figure 1:The ITER machine. The man
in the bottom shows the scale.

ITER has twice the size of JET in its linear dimensions (see figure 3), which means it has a plasma volume that is almost ten times larger. ITER is truly a global project: the current partners in the ITER project are Europe, Japan, the Russian Federation, China, India, Korea and the USA.

ITER will allow the study of plasmas in conditions similar to those expected in a electricity-generating fusion power plant. It is designed to generate 500 MW of fusion power for extended periods of time, ten times more then the energy input needed to keep the plasma at the right temperature. It will therefore be the first fusion experiment to produce net power. It will also test a number of key technologies for fusion including the heating, control, diagnostic and remote maintenance that are expected to be needed for a real fusion power station.

Figure 2:The size of the plasma in
different fusion experiments across
Europe. The ITER plasma is twice the
size of JET in its linear dimensions.

The construction costs of ITER are estimated at 4.7 billion Euro over 10 years, a large part of which will be awarded in the form of contracts to industrial companies. Another five billion Euros are foreseen for the 20-year exploitation period. Europe will contribute a major share of the costs. The contributions of the partners will for the largest part consist of components for the machine, so-called in kind contributions.

ITER will be a machine of the tokamak type in which the torus-shaped fusion plasma is confined by strong magnetic fields ( see illustration). The device´s main aim is to demonstrate prolonged fusion power production in a deuterium-tritium plasma. Compared with current conceptual designs for future fusion power plants, ITER will include most of the necessary technology, but will be of slightly smaller dimensions and will operate at about one-fifth of the power output level.

In June 2005, the partners in the project decided unanimously to choose the European site at Cadarache, in the South of France, as the location for the construction of ITER. The design of ITER is ready for the start of construction to begin, and the first plasma operation is expected in 2016.

Figure 3:Countries participating in the ITER project.
The dots indicate fusion research institutes.

ITER objectives

The official goal of ITER is "to demonstrate the scientific and technological feasibility of fusion power for peaceful purposes". Part of this general goal are a number of specific goals, all concerned with developing a viable fusion power reactor.

First of all, ITER should produce more power than it consumes. This is expressed in the value of Q, which represents the amount of thermal energy that is generated by the fusion reactions, divided by the amount of external heating. A value of Q smaller than 1 means that more power is needed to heat the plasma than is generated by fusion. JET, presently the largest tokamak in the world, has reached Q=0.65, near the point of "break even" (Q=1). ITER has to be able to momentarily produce Q=10, and Q larger then 5 during a longer period.

Secondly, ITER should maintain a fusion plasma up to 8 minutes, and to sustain a "burning plasma", which means that most of the heating from the plasma comes from the fusion reactions themselves.

Thirdly, ITER should implement and test technologies and processes needed for future fusion power plants - including superconducting magnets and remote handling (maintenance by robots).

Lastly, ITER should test and develop concepts for breeding tritium from lithium inside the blanket surrounding the plasma.