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The Fusion Reaction

How an environmentally friendly power source can solve the fossil-fuel supply-and-demand gap.

Fortnightly Magazine - August 2005
Figure 2 - Tokamak Fusion Test Reactor

An electromagnetic field coil configuration provides the magnetic fields to contain a plasma with temperatures in the 100 million degrees centigrade range required for fusion reactivity. Various methods have been developed to heat the plasma, producing temperatures up to 30 times hotter than the center of the sun.

The Tokamak Fusion Test Reactor (TFTR) at the Princeton Plasma Physics Laboratory (PPPL) and the Joint European Torus (JET) at Culham, England, were constructed in the early 1980s with the capability to operate with a deuterium/tritium fuel mixture. In the mid-1990s, both of these devices demonstrated a significant production of fusion power. The TFTR, shown in Figure 2, achieved a temperature of 370 million degrees centigrade. A discharge lasting about one-half second reached a peak fusion power production of 10 MW. 3 The JET produced a peak of 16 MW of fusion power with a discharge of about three times that time scale. 4 In addition, JET made 4 MW for 5 seconds. The TFTR was decommissioned in 1997 due to U.S. fusion budget constraints, while the JET is continuing to produce excellent experimental results.

The fusion energy produced in an individual magnetic confinement fusion experiment has risen by a factor of more than 1 trillion over the last 30 years (see Figure 3) . As a comparison, computer speed has risen by a factor of one hundred thousand during this same time period.

These achievements stimulated the technical and political development of the International Thermonuclear Experimental Reactor (ITER). The ITER is planned as a joint international project among six partners (Japan, the European Union, Russia, South Korea, China and the United States). A decision has been made to site ITER at Cadarache in southern France, with experimental operations scheduled to begin in 2014.

The ITER device, shown in Figure 5, would be the first full-scale fusion reactor, although not a prototype power plant. The experiment will aim to produce up to 500 MW of fusion power for up to 400 seconds, with the reacting fuel almost fully self-heated by the alpha particles produced in the fusion reaction. The experimental program will include test blanket modules to develop and demonstrate heat transfer and tritium breeding. The ITER configuration features superconducting magnets for long-pulse operation. Full remote handling will be required because of activation of the structure.

A demonstration U.S. power plant would enable the commercialization of fusion energy in about 35 years. Early in its lifetime, it would show net electric power production, and ultimately would demonstrate the commercial practicality of fusion power. The basic configuration of the demo could be similar to ITER. However, the physics and technology development preceding the demo would determine its final configuration and facilitate steady state operation, producing about 1 GW of electrical power.

Figure 3 - Progress in Fusion Energy Production

Advances in steady state magnets, tritium breeding blankets, remote maintenance, and fusion materials are required for construction and operation of a demonstration power plant. In addition, these technologies must be integrated with a reacting plasma.

ITER will advance steady state magnets, remote maintenance, and technology systems integration. While some blanket testing will occur during