Fusion research with a future

Issues in Science and Technology, Summer 1997 by Hirsch, Robert L, Kulcinski, Gerald, Shanny, Ramy

It's time for the U.S. program to abandon its deadend focus and to explore alternative paths to practical fusion power.

Major shifts are taking place in the U.S. fusion research program, driven primarily by reductions in federal funding. In the past, the program was dedicated almost completely to developing practical fusion power. Today, the program claims to be devoting roughly two-thirds of its resources to high-temperature plasma physics research and only one-third to fusion power. We believe that a significant shift back to the development of fusion power should be considered. If this shift is to be made, it must be made now, because the United States will soon decide whether or not to participate in the next stage of the International Thermonuclear Experimental Reactor (ITER) project. A commitment to ITER will claim such a large share of U.S. fusion research funds that it will essentially preclude significant exploration of other fusion concepts for at least a decade. To understand what is at stake, it helps to understand the history of the U.S. fusion program.

Fusion research was initiated in earnest in many parts of the world in the early 1950s, and there were high hopes for its early success. Outstanding physicists began to develop the science of high-temperature plasmas, and relatively quickly they conceived some ingenious magnetic bottles aimed at containing hot plasmas. Funds were readily forthcoming, and the quest for practical fusion power began. Enthusiasm and optimism were rampant. The goal was noble: a wholly new, safe, and environmentally benign energy source that would run pretty much forever on an essentially infinite fuel supply.

But in the first decade of fusion research, it became painfully clear that the nonlinear nature of the underlying plasma physics was extraordinarily complex. New plasma instabilities that destroyed plasma confinement were discovered at an alarming rate. It quickly became obvious that researchers needed to learn an enormous amount in order to develop a working fusion power system. As a result, fusion research settled down to what might be called an applied basic science program. It had a clear practical goal, but it needed to acquire a great deal of fundamental understanding before that goal could be realized.

By the late 1960s, researchers were frustrated and disheartened. At that point the Russians reported unusually good results from their tokamak experiments. [The tokamak is a toroidal (doughnut-shaped) magnetic plasma confinement configuration.] A special international team verified the Russian results, and laboratories around the world dropped most of their work on other concepts in order to build and develop tokamaks, because they seemed to provide good plasma confinement at last. Today, roughly 85 percent of the U.S. fusion program is devoted to tokamak-related research.

The good news about this stampede to tokamaks was that it led to an explosion of understanding of tokamak plasmas and dramatic increases in their performance. Practical fusion power was still the stated goal in the 1970s, so a group of scientists and engineers dedicated themselves to solving the myriad problems that had to be addressed in order to build a tokamak power reactor.

The bad news associated with this dramatic shift in emphasis was that the goal of practical commercial fusion power became confused with the goal of making fusion power from tokamaks. As we shall see, the two goals are very different. Market discipline

Any new electric power source must satisfy a set of criteria dictated by the marketplace. Today's criteria for success have evolved from those in place in the early years of fusion research. Since then, market needs have shifted somewhat, and existing energy sources have improved, some rather dramatically. Fusion technologists must anticipate future market changes as they set and adjust their program goals. Although such goal-setting has been and will continue to be somewhat uncertain, a robust and relatively timeless set of requirements for fusion reactors was developed recently to provide a sound basis for future fusion power R&D. The guide was assembled by a panel of electric utility technologists under the sponsorship of the Electric Power Research Institute (EPRI) in 1994. Their requirements fall into three categories: economics, public acceptance, and regulatory simplicity. We'll describe each of them briefly.

The cost of any new electric power source is of course critical to its acceptance. But as the EPRI report observes, "To compensate for the higher economic risks associated with new technologies, fusion plants must have lower life-cycle costs than [the] competing proven technologies available at the time of [fusion] commercialization." One important aspect of fusion economics is the system's reliability. Because fusion is likely to involve a large number of new technologies, its initial reliability will be inherently lower than that of its existing commercial competitors, which further increases the challenge of developing practical fusion power.