Fermi had originally designed his first full-scale pile as a 76-layer sphere. Some 250 tons of better graphite from National Carbon now promised to reduce neutron absorption below previous estimates; more than 6 tons of high-purity uranium metal in the form of 2¼-inch cylinders began arriving from Iowa State College at Ames, where one of the Met Lab’s chemistry group leaders, Frank Spedding, had converted a laboratory to backyard mass production. “Spedding’s eggs,” dropped in place of oxide pseudospheres into drilled graphite blocks that were then stacked in spherical configuration close to
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