Nuclear Fusion Receives Boost From Design Effort

SOME of the scientists and engineers who want to harness the nuclear fusion process that powers the stars are tackling a new challenge. They are fusing the efforts of several nations to design an advanced research reactor.Last month, negotiators from the European Community, Japan, the Soviet Union, and the United States agreed on terms for the partnership. The signature, this November, of a treaty embodying those terms will trigger a six-year, billion-dollar design program that is as much an experiment in international technical cooperation as in physics. It also reflects an emerging maturity in this research field. Three decades of work have brought researchers to the point where they now see their way clear to igniting a self-sustaining fusion reaction - in essence, a miniature "star here on Earth. They expect that, within a decade, they will have to begin thinking in detail about how to use this "star" in a practical electric power station. The program to design an International Thermonuclear Experimental Reactor (ITER) aims to blueprint a facility that will produce the engineering data needed for this practical planning.

Truly international Alexander J. Glass of the Lawrence Livermore National Laboratory in Calif., who leads the US ITER home team, says designing such a facility internationally, with work sites in Japan, Europe, and the United States, "is complex." Yet, he adds, the project has had the advantage of being truly international from its start four years ago. Unlike the "international" space station or "international" space telescope, this not a project conceived by one nation which then invited others to join it. The four partners shared equally in ITER's conception and will share equally in its work and cost. Dr. Glass explains, "We have to reach decisions by consensus. We have to discuss matters until there is agreement." This may slow the program down. But, once consensus is reached, each partner has made a solid commitment to it, Glass adds. Glass's Livermore colleague, David Baldwin, who led a US Department of Energy ITER concept review, notes that the partners are willing to accept the complexity of cooperation to cut costs. He explains that it costs more totally to design ITER this way. But each nation individually pays less than if it tried to do the job alone. This is an important consideration for a facility that costs $1 billion to design and may cost $5 billion to build, according to a preliminary estimate.

Wave of future Glass says he thinks the ITER arrangement is pioneering a cooperative style that represents "the future of large international scientific projects." Another factor encouraging cooperation is the realization that this project that no one wants to fund alone has, nevertheless, become essential to progress in controlled fusion research. That means magnetic confinement fusion, in which the hot reacting gas is confined by magnetic fields. The other type of fusion research, in which laser beams crush fuel pellets until they undergo nuclear reactions, has been largely a United States interest. Globally, magnetic confinement has been the main line of research in several countries, especially the four ITER partners. They have been supporting it at a total annual cost of nearly two billion dollars, according to the International Atomic Energy Agency. The challenge in magnetic confinement is to hold together a mass of gas, at temperatures up to several hundred million degrees, long enough for significant fusion to occur. At such temperatures, atoms of deuterium (doubly heavy hydrogen) whiz around at speeds of several million miles an hour. When two of them collide, they fuse to produce an atom of helium and release energy. Several research teams, especially in the United States and Europe, have progressed far enough in doing this that they are confident that machines now being planned can ignite a self-sustained fusion reaction using deuterium and tritium (triply heavy hydrogen). John Maple, of the Joint European Torus fusion project at Culham, England, has compared the current situation to putting a lighted match under a pile of fuel for a bonfire. Researchers can study the smoke. But the fire goes out when the match is withdrawn. When ignition is achieved in fusion reactors now being planned, the bonfire will be set to smoldering. Eventually, in later generations of machines, it will blaze brightly. Then engineers will need to know how to use it in practical electric power plants. This is where the kind of research the ITER machine is designed to do will help. Startup of a practical fusion power plant is a next-century prospect. But that prospect now seems brighter than in past decades. Both the official United States energy strategy document and the report of a European Community fusion evaluation board consider fusion power will likely be a realistic energy option a few decades hence.