What the Fusion-Power Breakthrough Means

FOR over four decades, nuclear-fusion scientists have tried to learn how to tap the power of a man-made ``star.'' Over the past weekend, some of them finally cleared the first major hurdle on the way to that goal.

The hurdle is labeled the ``scientific feasibility'' of hydrogen-fusion power. That's techno-speak for the point at which researchers know enough about the star-hot gas in which fusion occurs to build a reactor that will ignite and control a self-sustaining fusion reaction.

Deputy laboratory director Dale Meade of the Princeton (University) Plasma Physics Laboratory says he and his colleagues have reached that point with a series of experiments begun Dec. 9. Using the laboratory's Tokamak Fusion Test Reactor, they have reached power levels never attained before while, for the first time, burning the kind of hydrogen fuel mix that a future commercial fusion power plant might use. This is a mix of deuterium (doubly heavy hydrogen) and tritium (triply heavy hydrogen). It has enabled the Princeton reactor to reach power outputs of 4 to 5 megawatts - the goal Dr. Meade wanted to meet before shutting down for the holidays.

Meanwhile, Europe, Japan, Russia, and the United States are preparing to make a run at the next major hurdle on the path to commercial fusion power - building a fusion reactor that produces more power than it consumes. They are equal partners in the International Thermonuclear Reactor (ITER) project. With this machine, they hope to demonstrate ``engineering feasibility'' - techno-speak for finding out what it takes to build a practical power plant.

The Princeton experiments should provide the final pieces of basic scientific knowledge the ITER project needs. These have to do with how the deuterium-tritium mix behaves at temperatures of several hundred million degrees while being confined and controlled by strong magnetic forces. Reaching this stage of scientific feasibility is a significant achievement for the world effort to develop fusion power. It also is a triumph of humility over arrogance and of cooperation over rivalry.

Britain, the Soviet Union, and the United States cloaked their early fusion work in secrecy. Each hoped to beat the others in demonstrating a fusion reactor that produced net power. Many scientists thought they could do it in a few years. After all, they produced the hydrogen bomb in less than a decade. Shouldn't controlling fusion be just as easy?

They soon learned a humbling lesson. They were dealing with a new form of matter that didn't behave as their simplistic theories expected. This is plasma - a gas so hot the electrons are stripped from its atoms, leaving a mixture of negatively charged electrons and positively charged hydrogen nuclei. This is star stuff. The fusion researchers soon discovered they didn't know how to handle it. It's too hot for any material container to hold. Magnetic forces can confine it. But it easily wriggled out of the crude magnetic ``bottles'' of the 1950s.

Frustrated, the rivals took down the secrecy walls in 1958 and discovered that their scientific teams were all equally baffled. Thus began the world quest for fusion power.

The technical challenge has been tough. The ups and downs of political and budgetary priorities have slowed national research programs. It will likely take 10 to 15 years to demonstrate engineering feasibility. After that, there's the challenge of commercial feasibility - designing practical fusion reactors that electric utilities will buy and run.