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 able to provide positive energy balance 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 2), 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 the European Union, Japan, the Russian Federation, China, India, South Korea and the USA.

ITER will allow the study of plasmas in conditions similar to those expected in an electricity-generating fusion power plant. It is designed to generate 500 MW of fusion power for extended periods of time, ten times more than the energy input needed to keep the plasma at the right temperature. It will therefore be the first fusion experiment to produce net power (although the device will not produce electricity). 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.

ITER will be built in 10 years. A large part of the construction cost will be awarded in the form of contracts to industrial companies. Europe will contribute a major share of the costs (around 45%). The contributions of the partners will form the largest part consisting 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. The 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 international ITER agreement was signed in November 2006 by the 7 partners and the ITER Organisation was formally established in October 2007 (although it was operational already before that). The ITER construction works have started. The first plasma operation is expected in 2018.

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". Parts 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 power that is generated by the fusion reactions, divided by the amount of external heating power. 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 produce Q=10 for hundreds of seconds, and Q larger then 5 during longer periods, possibly one hour or more.

The plasma produced in ITER will be "burning", which means that most of the heating from the plasma comes from the fusion reactions themselves. Producing, studying and controlling this burning plasma constitute the new scientific frontier that ITER will explore.

ITER should also 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.