Fusion, the nuclear reaction that powers the stars, may be the most efficient energy source in the universe, but the dream of converting its enormous potential into electricity on Earth has frustrated some of the best minds of science.
Scientists succeeded long ago in generating electricity with heat released when atoms are split in a process called fission, but not without serious limitations. The current generation of nuclear power plants uses fuel that is scarce and costly, and many fear that nuclear accidents will lead to catastrophic releases of radiation.
Those problems would go away, fusion researchers contend, if reactors could be built that would fuse atoms rather than split them. When atoms combine, enormous amounts of energy are released. Theoretically, at least, it should be possible to do that with fewer worries over safety--because if a fusion reactor failed, the reaction would simply stop. A fission reactor, on the other hand, could melt down because of loss of control of the nuclear reaction.
But the greatest dream of fusion lies not in safety as much as in its promise of unlimited fuel.
Fusion reactors would use a form of hydrogen--called deuterium--as fuel, and hydrogen is the most abundant element in the universe. The oceans, so the theory goes, would supply all the fuel the Earth would ever need if fusion reactors could be developed, and the amount of seawater used would scarcely be missed.
One cubic foot of seawater contains enough deuterium to produce as much energy through fusion as 10 tons of coal burned in a conventional power plant.
For nearly four decades, hundreds of millions of dollars has been spent in the quest for fusion, so far with very limited results.
It is hard to make fusion work because hydrogen atoms are positively charged, and thus they repel each other, just as the poles of magnets push each other away.
To get around that problem, the atoms must be pushed together into an intensely dense material, and they must be heated to the point that they overcome the repulsion of the electrical charge. That, however, requires temperatures of several hundred million degrees.
Until Thursday, at least, that was the conventional wisdom. It remains to be seen whether the reported results in Utah at room temperature significantly alter the course of research.
Most of the research around the world has centered on the use of a very dense, superheated tritium and deuterium gas, called a plasma. This year, the U.S. Department of Energy is funding $350 million in research in this area.
The nation’s lead research institution in plasma fusion is the Princeton Plasma Physics Laboratory, where some success has been achieved. Scientists there have generated temperatures 10 times hotter than the core of the sun, about 360 million degrees Fahrenheit, but they were able to hold it there for only a fraction of a second. For the experiment to work, the temperature must be maintained continuously.
Furthermore, it has taken far more energy to keep the experiment working than has been released through fusion. Ideally, of course, scientists want to reverse that and put out more energy than they put in. Scientists at Princeton hope to reach the “break-even” point within the next couple of years.
U.S. scientists told an international fusion conference in Nice, France, last year that they are about three-tenths of the way to breaking even. A similar program in Europe was reported about a quarter of the way.
One of the main barriers in plasma fusion is simply keeping the fuel closely compacted during the experiment. Obviously, temperatures that great would melt any container, so the plasma has to be contained in a “magnetic bottle” created by a powerful magnetic field. But that is difficult to control for long periods, and requires enormous amounts of energy.
Scientists elsewhere, particularly at the Lawrence Livermore Laboratory, have taken a different approach--the use of lasers to zap solid pellets containing hydrogen. The lasers serve two functions: they heat the fuel to hundreds of millions of degrees, and they compress the hydrogen.
The Lawrence process “implodes” the fuel capsule, and scientists there have succeeded in compressing the pellet to 100 times the density of liquid. Scientists at Osaka University in Japan have reported similar success. However, compressions of about 1,000 times the density of liquid are required for the “ignition” that would lead to fusion.
There is a third approach to fusion that has been studied extensively, and it is more similar to the work done by the Utah scientists than either plasma or laser fusion. Some of that research was done by Steven E. Jones of Brigham Young University, just down the road from the University of Utah.
Jones was one of the pioneers in the field of muon fusion. In a 1986 article in the Journal of Physics, Jones reported on his work. He argued in the technical piece that it is possible to achieve fusion by firing muons into a gas of deuterium and tritium. Muons are subatomic particles created in atom smashers.
The concept has some merit, according to other researchers, but muons are very costly to produce.
More recently, Jones has concentrated his research in the “cold fusion” process like that announced Thursday by his colleagues at the University of Utah. Jones, interviewed by telephone, was reluctant to describe his results because a professional journal is about to publish his report and if he discusses his work now it could jeopardize publication.
He described his work, as well as that by the University of Utah researchers, as “a scientific success.”
He said, however, that it is far too early to know if the results will lead to practical applications, particularly in the production of energy.
“We have shown that nuclear fusion can be achieved . . .” by the cold fusion process, he said.
The next step, he said, is for the experiments to be repeated by many other scientists at many other locations.