The Atom: After 20 Years: More Hopes Than Fears

The new age began on a chill, grey afternoon 20 years ago. The site was a laboratory in a squash court beneath the stands of the University of Chicago’s old Stagg Field Stadium. Gathered there was a team of scientists and engineers headed by Enrico Fermi, a refugee from Mussolini’s Italy. They had finished building history’s first nuclear reactor. Now they were using it to produce the first controlled nuclear reaction.

The reactor was beautifully simple. It was called a “pile,” and it was literally that—a 500-ton pile of carefully machined bricks made of pure graphite. Imbedded in some of the bricks, in a precisely calculated pattern, were little cubes of uranium or uranium oxide. Long control rods, plated with the metallic element cadmium, were so set up that they could be withdrawn from, or inserted into, deep holes in the graphite.

That is all there was to it. The operation of the pile depended on natural properties of 1) uranium, which normally emits neutrons at a steady rate, 2) graphite, which slows neutrons down but does not absorb them, and 3) cadmium, which absorbs neutrons very effectively. As the control rods were withdrawn—so the experimenters figured—fewer of the neutrons from the uranium would be absorbed, and therefore more fission would occur. At some point of withdrawal, fission would be producing new batches of neutrons faster than the cadmium would be absorbing them. Result: a chain reaction.

At 10:37 on that morning of Dec. 2, 1942, Physicist George Weil stood ready to start withdrawing the final control rod.

which was marked to show how many feet and inches of the rod remained within the pile. “Pull it to 13 feet, George,” Fermi said calmly, watching the meters set up to measure the neutron emission inside the pile. As Weil withdrew the rod, the meters clicked faster and faster. Fermi did some calculating with the little slide rule he always carried with him. “This is not it,” he said. The rate of radiation leveled off as neutron emission from uranium and neutron absorption by cadmium came into equilibrium.

A Bottle of Chianti. Several times that morning, Fermi told Weil to pull the control rod out a little farther, six inches or a foot. Each time the radiation increased, only to level off again—still too much control rod. After lunch, Fermi ordered the rod withdrawn another foot. Again the radiation leveled off. Then another six inches. Still not enough. “Pull it out another foot,” Fermi called. It was precisely 3:25 p.m.

The meters clicked dizzily. “This is going to do it,” said Fermi, working his slide rule. Recalls Weil: “I had to watch Fermi every second, waiting for orders. His face was motionless. His eyes darted from one dial to another. His expression was so calm it was hard. But suddenly his whole face broke into a broad smile.” “The reaction is self-sustaining.” Fermi announced. “The curve is exponential.” Instead of leveling off, the rate of radiation was continuing to accelerate—a chain reaction was under way inside the pile.

Fermi let the reaction run on for 28 minutes, then ordered it stopped. Hungarian-born Physicist Eugene Wigner brought out a bottle of Chianti. Fermi sent out for paper cups. Nobody offered a toast—the moment was too solemn for that. Wrote Physicist Samuel K. Allison, a top Fermi assistant, in a recent article: “All of us in the laboratory knew that with the advent of the chain reaction the world would never be the same again.”

A Threat of War. A total of 42 people (including one woman, Physicist Laura Woods) were present at the squash-court experiment. Last week 27 of the survivors —Fermi and several others are dead—gathered in Washington to observe the 20th birthday of the Atomic Age. At a floodlit ceremony outside the White House, President Kennedy spoke to the group. “This development which has played a significant role in our history and in our lives,” he said, “can be either good or bad depending on the use to which it is put. It is the obligation of those who bear positions of responsibility in various governments of the world to make sure it is put to good use.” Around the world, the 20th anniversary was an occasion for contemplating the uses to which atomic energy has been put—and may be put in the future.

Less than three years after the chain reaction in Chicago, the U.S. had built atomic bombs and dropped one on Hiroshima and one on Nagasaki. The years since then have witnessed, on both sides of the Iron Curtain, a vast buildup of nuclear weapons—more than enough, it is often pointed out, to be theoretically capable of destroying every human being on earth. And the continuing deadlock of U.S. and Russian negotiators in the test-ban talks at Geneva indicates that men cannot expect in the foreseeable future a trustworthy nuclear disarmament agreement between East and West.

Peaceful Explosions. If the darkest fears of 20 years ago have not been realized, neither have the highest hopes. Sunday-supplement visions of impending universal plenty, with nuclear reactors supplying unlimited cheap power, were grossly premature. Nuclear reactors still cannot produce electric power as cheaply as thermoelectric plants fueled with coal or oil. But mankind has received a huge, unforeseen bonus from the radioisotopes created in nuclear reactors. They are used in countless applications in industry and science, from detecting tiny, hidden flaws in machinery parts to tracing physiological processes in the human body.

Last week Physicist Edward Teller, the dour genius who led the U.S. in its race to develop the H-bomb ahead of the Russians, reported on the progress of the Atomic Energy Commission’s Project Plowshare, exploring peaceful applications of nuclear explosions. He told of a Plowshare test in Nevada last summer in which a thermonuclear device with a power of 100 kilotons (equivalent to 100,000 tons of TNT) was exploded underground, creating in a few seconds a crater 1,200 ft. wide and 320 ft. deep. Such explosions, he said, could be used to make harbors and canals, remove earth and rock covering mineral deposits. Nuclear explosions, said Teller, have “the potentiality of becoming the first really important and thoroughly economic use of atomic energy.” The reasons why nuclear explosions have not already been used in practical, peaceful projects, he said, are “a lack of imagination, a lack of enterprise, and some political timidity.”

Atomic batteries to power radio transmitters have already been used in U.S. space satellites, and an AEC project is developing a special reactor for use inside space vehicles (see SCIENCE). Before many years, AEC predicts, nuclear engines will be propelling vehicles through space, as they already propel submarines, surface warships, and the nuclear merchant ship Savannah. AEC’s Project Rover is actively working toward that end.

Dispelling a Cloud. After slow beginnings, the development of power reactors has reached the point where, according to a recent AEC report to the President, atomic power is “on the threshold of competitiveness with conventional power” in parts of the U.S. where coal and oil are relatively expensive. During the 1970s, AEC predicted, nuclear power will become economically competitive “throughout most of the country.”

In its report, AEC urged heavier stress on development of “breeder” reactors, which will create more nuclear fuel than they consume. Present-model nuclear reactors operate through fission of scarce and costly uranium 235. Natural uranium is mostly U-238; less than 1% of it is U-235. Breeder reactors would convert nonfissionable U-238 into fissionable plutonium, or convert the fairly common element thorium into fissionable U-233 (neither plutonium nor U-233 is found in nature). A few days before the 20th anniversary of the first chain reaction, AEC announced that its experimental plutonium reactor had achieved a self-sustaining reaction, verifying that plutonium can be used as fuel in a power reactor.

Breeder reactors, opening up a virtually limitless supply of power, will dispel a cloud that hangs over the future of mankind—the prospect that within a few centuries the earth’s supply of coal and petroleum will be exhausted. Since modern civilization could not survive without economical sources of power, historians of the future may record that the train of atomic development beginning on Dec. 2. 1942 preserved the civilization that it sometimes seemed to threaten.