Progress on Fusion Research

December 25, 1993

When scientists at the Princeton Plasma Physics Laboratory in Princeton, N.J., turned on the lab's experimental nuclear fusion reactor earlier this month, the event was comparable to the Wright brothers' first flight at Kitty Hawk or the first time humans rubbed sticks together to make fire. The demonstration of nuclear fusion -- the same reaction that powers the sun's interior -- raised scientists' hopes of someday harnessing an inexhaustible, clean source of energy.

Unlike the commercial fission reactors now in use to generate electricity, a fusion reactor would produce no dangerous radioactive wastes or pose a threat to the environment in the event of a catastrophic failure. Although the concept of using nuclear fusion to generate electricity is not new, efforts to turn theory into practice have foundered for years on technical obstacles. So far, it has been impossible to design a fusion reactor that does not require more energy to operate than it generates.

The Princeton machine is based on a design first suggested by Russian researchers called a Tokamac, a doughnut-shaped chamber in which a plasma of hydrogen gas is trapped in an immensely powerful magnetic field to initiate the nuclear reaction. Previously, scientists had operated the device using only deuterium, a heavy isotope of the hydrogen atom. Last week's experiments for the first time added tritium, a radioactive isotope of the hydrogen atom, to the deuterium soup. The mixture of the deuterium and tritium in equal proportions should produce the hot gas environment needed for a self-sustaining, controlled fusion reaction.

On its first test using tritium, the Princeton reactor generated the equivalent of 3 million watts of power. Later tests produced pulses of up to 5.6 million watts -- enough to power about 1,500 homes, but still substantially less than the 24 million watts needed to run the reactor. Still, the early tests represented a momentous advance: Previous experiments have consumed several times the energy they produced.

Over the next year, scientists will use the new mixture to produce more than 1,000 brief pulses to learn how to control the hot plasma. This should help them design more advanced reactors with a goal of building commercial fusion reactors by 2035. A full-scale international reactor already is being planned jointly by the United States, Western Europe, Russia and Japan. Fusion has huge potential for providing for humanity's future energy needs. This month's success represented a small but significant step toward harnessing the power of the sun here on earth.

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