A Big Step For Fusion Power But Not That BigJohn Carey
For more than 40 years, scientists have chased the dream of fusion energy. Hoping to harness the same reactions that power the sun, they have built giant machines and run hundreds of tests. But not until Nov. 9 did they finally experiment with the fuel that would actually stoke a real power plant. On that Saturday evening, European scientists injected tritium, a heavy form of hydrogen, into the Joint European Torus (JET), a research reactor 50 miles west of London. And for a second, the reactor produced 1.7 megawatts worth of speeding neutrons, enough energy to power 600 homes. "Our aim is to show the scientific feasibility of fusion," says JET physicist Karl J. Dietz. "What we did was the necessary first step."
To fusion proponents, the European experiment was welcome news. "It's an important milestone," says Richard D. Petrasso, a physicist at the Massachusetts Institute of Technology's Plasma Fusion Center. But while fusion could someday live up to its promise -- a cheap, abundant energy source that produces little hazardous waste -- don't sell your oil stocks yet. For one thing, the reaction generated only one-tenth of the power used to produce it. Moreover, the experiment merely confirms what scientists' calculations had long predicted -- that adding tritium to the lighter hydrogen fuel used in past tests dramatically speeds up the fusion reaction and boosts the power output. That proves, in theory anyway, that fusing atoms could generate as much commercial power as existing nuclear-fission plants.
But the experiment didn't answer a number of crucial scientific questions. Without answers, researchers can't reach the key stage called ignition, when the fusion reaction makes enough heat to keep itself going. One worry, for example, is whether the soup of electrically charged atoms that swirls inside a fusion reactor will become unstable, shutting the reaction down. Another uncertainty: Will the reaction heat the soup as much as some calculations show? If it doesn't, the reaction won't sustain itself and reach ignition.
The JET experiment didn't use enough tritium to resolve these doubts. If scientists had used more of the material, the walls of their reactor would have become too radioactive for researchers and technicians to work inside it. Both JET and a similar test reactor at Princeton University are building systems to handle the radioactivity, but the next stage of experiments won't begin until 1993 at Princeton and 1994 in Britain.
Even if scientists clear all those hurdles, though, a prototype power plant is at least 40 years away (table). And fusion boosters admit that fusion can't compete economically with coal, oil, or fission reactors at today's prices.
The experiment comes at a crucial time for fusion research. Support has been shaky, especially in the U. S. "In the past decade, our progress has been limited by budgets, not technical problems," says Ronald C. Davidson, director of Princeton's Plasma Physics Laboratory. The Energy Dept., for example, recently axed plans for an ambitious next-generation reactor, Princeton's $1.4 billion Burning Plasma Experiment.
MAMMOTH MACHINE. Scientists, however, are determined to push ahead. They are calling for the U. S., Europe, and Japan to commit more than $5 billion for the International Thermonuclear Experimental Reactor (ITER), a mammoth machine that's a necessary step to a prototype commercial reactor. While support in Japan and Europe remains strong, fusion boosters worry that wrangling over the site of the reactor could derail the effort. So the news about progress in fusion comes at an especially good time. "To keep the momentum for ITER going, they have to show they are moving ahead," points out physicist John M. Soures of the University of Rochester, who is working on a competing form of fusion power.
JET spokesman John Maple insists that the experiment was planned and scheduled on scientific grounds alone. Still, he readily admits the value of publicity. "I suspect it will increase confidence in our work by those outside the field," he says. Not in Congress. Staffers say that because the results were long expected, they won't boost political support for fusion. It will take more than this small step on the long path to fusion energy to persuade governments to shell out the billions needed to finish the journey.
A LIKELY TIMETABLE FOR FUSION POWER
1993-97 Tests with large amounts of tritium at the Joint European Torus and
Princeton's Tokamak Fusion Test Reactor
1992-97 Designing the International Thermonuclear Experimental Reactor
(ITER), a $5 billion to $6 billion machine jointly funded by
the U.S., Japan, and Europe
1997-2006 Building the ITER
2007-20 Designing a prototype power plant
2020-25 Building the prototype power plant
2030 Large-scale fusion-power generation