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THE ULTIMATE WEAPON TAKES SHAPE
Enrico Fermi designed a device that could eventuate in a chain reaction. It consisted of layers of graphite, alternated with chunks of uranium. The uranium emitted neutrons, and the graphite slowed them down. Holes were left for long cadmium safety rods. By withdrawing those control rods Fermi could speed up the production of neutrons, thus increasing the number of uranium atoms that would be split (fission). When the rods were withdrawn to a critical point, then the neutrons would be produced so fast that the graphite and cadmium could not absorb them. In that manner a chain reaction would result. Slowly, Fermi’s first atomic pile began to grow in a subterranean room at Columbia University. The big question remained-was it viable?