A Doughnut for Power

A long step was taken last week toward the still-distant goal of providing the U.S. with a virtually limitless source of energy. In Washington, the new Energy Research and Development Administration issued a draft "environmental statement"* detailing the environmental impact of a large, advanced fusion test reactor. ERDA's action made it clear that the U.S. is determined to harness nuclear fusion, the process that feeds the fires of the sun and gives H-bombs their awesome power. If all goes well, the $215 million test reactor, to be built on the Forrestal campus of Princeton University, will go into operation in the early 1980s.

Repulsive Charges. To meet that deadline, U.S. scientists, starting with a technique devised in the Soviet Union, will have to develop an almost entirely new technology. Unlike nuclear fission --the splitting of a heavy atom into two lighter ones--fusion occurs when two light atoms collide and merge into a heavier one. The reaction releases considerably more energy than fission. Starting the chain reaction that causes fission (Abomb) explosions and powers today's nuclear reactors is relatively easy; basically, all that is required is the bringing together of enough fissionable uranium or plutonium in the right shape. The neutrons emitted by these naturally radioactive elements then begin the self-sustaining chain reaction.

Fusion, on the other hand, requires extreme pressure and temperatures as high as 100 million degrees. Under these conditions, the nuclei of light atoms are energized (or speeded up) enough so that they can overcome their mutually repulsive electrical charges, collide and fuse. In the hydrogen bomb, the necessary pressures and temperatures are produced by first setting off a fission explosion. Controlling and containing fusion will be vastly more difficult, but scientists believe that the Russian-invented Tokamak (for "Toroidal Kamera Magnetic") system can be developed into a practical and safe reactor.

Inside the Princeton doughnut-shaped Tokamak, deuterium and tritium (both isotopes, or different forms, of hydrogen) will serve as fusion fuel. In the form of a plasma (a high-temperature, ionized gas), the fuel will be suspended within powerful magnetic fields. Thus the gas will be supported by nothing but magnetic force and will be insulated from the steel walls of the reactor. If the plasma touched the wall, the wall would be heated, the plasma would be contaminated and its temperature lowered. The powerful magnetic fields will be manipulated to squeeze the plasma, raising its temperature and increasing the pressure upon it. The plasma will be made even hotter by an electric current generated inside it by another magnetic field and by a beam of deuterium atoms shot into it. These combined effects should raise temperature and pressure high enough in about a tenth of a second to begin fusion of the deuterium and tritium nuclei. The scientists' major goal: to come close to producing as much fusion energy during one of these periods as is used to power the Tokamak during the same time.

Once that has been done, ERDA officials hope to build more advanced experimental reactors, followed by a 500-megawatt demonstration power plant in the 1990s, and working fusion power plants that use only deuterium as a fuel by the end of the century. If that scenario can be successfully followed, the term "energy crisis" will become obsolete. There is enough deuterium in the world's oceans to fill mankind's energy needs for untold centuries to come.

*Required by the National Environmental Policy Act before any federal construction project can be started.

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