The international fusion project has been in limbo for two years, ever since funding governments balked at the original price tag of 7 billion euros. Researchers have since drastically scaled down their ambitions.

Speaking at a fusion conference organised by the International Atomic Energy Agency in Sorrento last week, Evgenii Velikhov, Russia's leading fusion scientist, says that if a decision to begin construction is not made soon, "our future is very bleak".

Umberto Finzi, the European Commission's coordinator for energy and the environment, warns that if governments fail to back the new design, practical fusion energy research will fade away.

The US, Europe, Japan and the Soviet Union began working together on fusion in 1986, but by the time the design for the International Thermonuclear Experimental Reactor (ITER) was finalised in 1998 the political climate was very different. US support for fusion had dwindled and Russia had little money to put on the table.

The US pulled out of the project last year, and fusion researchers in Europe, Japan and Russia have since been reworking the design, cutting the original capital cost in half.

Finzi points out that the cost of building the reactor, if spread over 10 years, is only 25 per cent of the 1.4 billion euros already spent on fusion research worldwide every year. Behind the scenes at Sorrento, Finzi was busy preparing the ground for negotiations next year on a funding package between Europe and Japan.

The principle of the revamped ITER is the same as before: inside a large doughnut-shaped vessel known as a "tokamak", powerful magnetic fields contain a plasma of the hydrogen isotopes deuterium and tritium.

When heated to over 100 million degrees, the deuterium and tritium nuclei fuse to form alpha particles and neutrons. The alpha particles reheat the plasma while the energy of the neutrons can be extracted.

Many of the key parameters of the new design have shrunk. The amount of power to be generated has been reduced from 1500 to 500 megawatts, while the volume of plasma has dropped from 2000 to 837 cubic metres.

Crucially, the reactor is no longer aiming to "ignite" the plasma. Ignition occurs when the alpha particles provide enough energy to sustain the reaction, and no further input of heat is needed.

The aim now is to provide 67 per cent of the plasma's energy from alpha particles, a figure that cannot be achieved by any of the existing small research tokamaks.

Despite the need to input energy, the reduced ITER should produce ten times as much energy as it consumes. No other tokamak has yet produced surplus power, though the JET fusion reactor at Culham in Oxfordshire has come close.

Experiments at JET over the past few months have for 5 seconds reached the levels of plasma pressure, density and confinement required for ITER. "We have made steady progress on all fronts," says JET's leader, Jerome Pamela. "I'm sure ITER will work."

Apart from the design, the other burning question for ITER researchers is where it will be built. Possible sites include Cadarache in southern France and three locations in Japan. But Canada, an associate ITER member, has proposed building the reactor next to an existing nuclear complex at Clarington, west of Toronto.

This has the advantage that tritium is already produced there, and it would also be an acceptable compromise between Europe and Japan. In addition, ITER scientists hope this location may entice the US to rejoin the project.

This article appeared in the October 14 issue of New Scientist New Scientist. Copyright 2000 - All rights reserved. The material on this page is provided by New Scientist and may not be published, broadcast, rewritten or redistributed without written authorization from New Scientist.

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