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Under the cover name of "The Metallurgical Laboratory," some of the most important discoveries were made at the University of Chicago directed by famed Dr. Arthur Holly Compton. His leading associate: Italian-born Dr. 'Enrico Fermi, whom many consider the world's foremost nuclear physicist. But there were also scores of other laboratories where the work went on: Columbia, University of California, Iowa State, industrial research centers.
Processes & Places. There were many possible ways of separating U-235 from natural uranium. Two processes at least were found to work well. In the first (mass spectrograph), uranium particles were electrically charged, fired through a huge electromagnet, sent into a curving course. The lighter U-235 swung more widely on the curve. Traps were set at the end of the turn, and U-235 was caught there, while U-238 was discarded.
In the second, as incredibly delicate as the first, a gaseous uranium compound was pumped through the finest of sub-microscopic filters. The faintly more volatile U-235 passed through more easily. Result: a higher percentage of U-235 beyond the filters.
The experimental work of the electromagnetic method was done at the University of California under blond, boyish Dr. E. O. Lawrence; on diffusion, at Columbia under Dr. H. C. Urey. By 1943, before the experiments were completed, vast plants to carry out both processes were being constructed at Oak Ridge, a sparsely inhabited region near Knoxville, Tenn.
Into that brand-new city (called Dogpatch) flooded weird equipment: thousands of powerful, new-type pumps, gigantic electromagnets, innumerable other machines and instruments. Amid oceans of mud and battlefront confusion, they finally found their places. Both plants were successful, produced effective quantities of precious U-235.
Squash Court Pile. Production of plutonium was probably no more important, but vastly more dramatic. On a squash court under the stands of University of Chicago's football field, a strange apparatus took form. It was an oblate spheroid (doorknob shape), built up of graphite bricks with lumps of uranium or uranium oxide imbedded in their corners. This was the world's first chain reaction "pile"—a uranium "lattice" and a graphite "moderator." If it worked according to Dr. Fermi's theories, it would produce the first chain reaction ever set up on earth. .
With care, and great trepidation, the physicists laid the bricks. They knew they were deep in unknown territory; anything might happen. Around them hummed southside Chicago. Nearby, students passed on their way to classes.
By theory, the chain reaction should start spontaneously when nearly all the bricks were laid. Then it could be stopped short of a disastrous explosion by inserting strips of cadmium to break the chain.
But far below the "critical size" of the theory, instruments gave the alarm. The reaction was starting to cook. Luckily, the cadmium strips had been inserted at "retard" position. Slowed down by their influence, the reaction was easily stopped. "This," commented Dr. Smyth dryly, "was fortunate."