Figure 3. Three Faces of Fusion Deuterium-Tritium (Stefano Coledan).

The Basics of Limitless Power. Albert Einstein’s famous E=MC² equation reflects the enormous energy that can be released by fusing atoms. Hydrogen atoms fusing together to create helium powers the sun.

1. First Generation: Scientists have duplicated solar fusion on Earth by using two “heavy” hydrogen atoms—deuterium and tritium—which fuse at lower temperatures than ordinary hydrogen. A first-generation deuterium-tritium fusion reactor operated experimentally for 15 years at the Princeton Plasma Physics Laboratory in New Jersey.

2. Second Generation: While useful for studying fusion, reactors operating with deuterium-tritium fuel are impractical for commercial use. Among other things, the reaction produces large amounts of radiation in the form of neutrons. Substituting helium-3 for tritium significantly reduces neutron production, making it safe to locate fusion plants nearer to where power is needed the most, large cities. This summer, researchers at the University of Wisconsin Fusion Technology Institute in Madison reported having successfully initiated and maintained a fusion reaction using deuterium and helium-3 fuel.

3. Third Generation: First-generation fusion reactors were never intended to produce power, and, even if they are perfected, they would still produce electricity in much the same way as it is created today; that is, the reactors would function as heat sources. Steam would then be used to spin a massive generator, just as in a coal- or oil-fired plant. Perhaps the most promising idea is to fuel a third-generation reactor solely with helium-3, which can directly yield an electric current—no generator required. As much as 70 percent of the energy in the fuels could be captured and put directly to work.