FIFTY years ago today, Italian-born physicist Enrico Fermi led the experiment that "fired up" the first nuclear reactor. He demonstrated beyond doubt what many atomic physicists already believed theoretically - humans can ignite and control the sustained release of nuclear energy.
His experimental setup was crude. Precisely placed graphite bricks piled 57 layers high and supported by a wooden frame dominated a squash court beneath the University of Chicago's Stagg Field football stadium. Fifty tons of uranium spheres were distributed at precisely determined locations throughout the 400 tons of graphite in what Dr. Fermi and his colleagues called an "atomic pile." Neutron-absorbing rods were inserted in this "pile" to control the rate of nuclear-fission reactions. The rods - all bu t one of which were operated by hand - were withdrawn to start the reaction and pushed in to stop it.
This setup was not a prototype for a working nuclear reactor. Yet it demonstrated basic principles that underlie the design of the most advanced nuclear-power reactor today. Its successful operation was one of those rare events that change the world.
As Fermi recalled 10 years later in an article in the Chicago Sun-Times: "The event was not spectacular, no fuses burned, no lights flashed. But to us it meant that release of atomic energy on a large scale would be only a matter of time."
But the world at large did not learn of its new destiny for several years. Secrecy cloaked the experiment as part of the United States atomic-bomb program. Even authorized officials could learn of its success only in guarded terms. Hence the now famous phone call from Nobel laureate Arthur H. Compton, who headed the Chicago phase of the program, to Harvard University chemist James B. Conant.
Dr. Compton reported, "The Italian navigator has landed in the New World." Dr. Conant asked, "How were the natives?" "Very friendly," Compton replied.
Like the arrival of the geographical Italian navigator Columbus 500 years ago, this scientific landfall has turned out to be a mixed blessing. Fermi spoke for many of his fellow atomic scientists when he noted in his Chicago Sun-Times article, "We hoped that perhaps the building of power plants, production of radioactive elements for science and medicine would become the paramount objects." But, given the cold-war hostilities of that time, he sadly acknowledged that "fabrication of weapons still is and m ust be the primary concern."
In spite of the military emphasis of the early atomic age, many nuclear experts also talked optimistically of the potential benefits of what they called "the peaceful atom." They foresaw an era of abundant energy. But Conant warned of the atom's darker side.
He told the American Chemical Society's 1951 diamond jubilee dinner: "I see ... neither an atomic holocaust nor the golden-age abundance of the atomic age. On the contrary, I see worried humanity endeavoring by one political device or another to find a way out of the atomic age." He added that holocaust would be avoided "only by the narrowest of margins.... And only because ... the military advisers could not guarantee ultimate success."
Looking back over the first half century of this atomic age in which he has played a leading role, nuclear chemist and Nobel laureate Glenn Seaborg of the University of California at Berkeley concludes that "probably, on the whole, it's been for the good of mankind."
Conant's prophecy is being fulfilled as the nuclear powers work together to reduce their weapons stockpiles. Plenty of those weapons still exist. But efforts to control them now proceed in an international climate in which the United States is buying fissionable material from Russian warheads to be diluted and burned in nuclear-power plants.
Fermi's hopes also have been at least partly fulfilled. This is especially true in the case of "production of radioactive elements for science and medicine." Some are radioactive forms of naturally occurring elements such as iodine. Others are forms of man-made elements, such as the plutonium that is burned in power plants and exploded in nuclear weapons.
Virtually every country now uses radioisotopes, which are generally produced in nuclear reactors. Because their radioactivity makes them easy to spot, biologists and chemists use them to trace complex chemical processes. Physicians use them in certain kinds of treatment and analyses. Their radioactivity helps process a variety of materials, such as shrink wrap. They appear in antistatic devices that keep copy-machine paper from sticking. One of them - americium-241 - is used in some types of smoke detect or.
Dr. Seaborg, who is co-discoverer of more than a dozen radioisotopes and man-made elements, cites this wide usage to support his belief that the nuclear age has developed "beneficially." He particularly notes the impact that radioisotopes such as iodine-131 and technetium-99m, which he discovered, have on medicine. More than 10 million nuclear medical procedures and 100 million tests are performed annually in the US alone.
Seaborg also discovered plutonium in 1941. Asked if humanity can safely use this dangerous, bomb-powering material, he says he believes "we can safely use it." He notes that 40 percent of a typical nuclear-power plant's energy comes from plutonium. The element is produced by transformation of some of the uranium fuel and also undergoes energy-releasing fission. He also notes that many space missions "wouldn't be possible" without something like the plutonium-powered generators that provide electricity at
distances where solar cells are useless.
While Fermi's hopes for radioisotopes have been abundantly fulfilled, nuclear-power development lags. According to the International Atomic Energy Agency (IAEA), 29 countries were operating or building 497 nuclear-power plants at the end of last year. Some nations use nuclear power as the dominant source of electricity - France: 72.7 percent, Belgium: 59.3 percent, and Sweden: 51.6 percent. About 110 nuclear plants supply 21.7 percent of US electricity. That makes the atom second only to coal as a US ele ctrical-energy source.
Overall, the atom now accounts for about a sixth of the world's electricity. Public concern for safety and radioactive-waste disposal, however, have slowed nuclear-power development in some countries (see story at right). US nuclear-plant builders haven't had a new order for a domestic plant in more than a decade.
SEABORG, who served as chairman of the old Atomic Energy Commission, says he expects nuclear power to return to favor, because "it's an energy source with the least impact on environmental and human health." But John N. Schock, energy-program leader at the University of California's Lawrence Livermore National Laboratory, says he isn't sure how much the world can count on nuclear power.
For the atom to return to favor, the public would have to be convinced that plants will be safely run and radioactive waste safely stored. Nuclear Regulatory Commission Chairman Ivan Selin has called waste disposal "the most pressing problem facing the industry" in the United States.
Many people have wondered if humanity should have probed the atom's awesome secrets at all. Seaborg explains that "it was inevitable that we would uncover this knowledge and use it."
Dr. Schock agrees, saying: "It's something that happened. It's good in that it's an energy source ... if we're willing to use it and accept the risks of using it."