b'C H A P T E R 3T H E U RA N I U M T RA I L L EA DS T O I D A H Oin December 1942. After that, an bomb might also be made with pluto- The proposal came from Walter Zinn,unprecedented collaboration of military, ni uone of the physicists who had beenm .scientific, and corporate resources man- with Enrico Fermi in Chicago. Theaged to build a weapon. A version of The government built huge atomic Manhattan District had organized athe Navy scientistsidea for separating piles (later called reactors) of ura- Metallurgical Laboratorythe light from the heavy isotope of ura- nium and graphite at there, a name intended tonium was built at Oak Ridge, Hanford, Washington, to disguise its true pur-Tennessee. The technique produced the manufacture plutoni- pose. After the war,few pounds of enriched uranium um. The procedure the governmentneeded for one bomb. was extremely cost- assignedly. Despite the weapons workmassive size of the to other labora-Hanford reactors, tories, and thetheir daily output of Met Lab ceasedplutonium was rarely to exist. Its assetsenough to fill a shot were reorganized asglass. Once plutonium the Argonne Nationalatoms had been created, they Laboratory with a missionhad to be separated from the uranium to develop reactors, supported bymatrix in which they had originated research in chemistry, physics, metal-and from the fission and other activa- lurgy, and other fields. Zinn became itstion products. Chemists devised ways first director. 9to do this. The Manhattan District builttwo bomb designs, each using one of Zinn could see that the nations firstthe two fuels. On July 16, 1945, the priority for uranium would continue toteam at Los Alamos, New Mexico, test- be for weapons. Any use of it for othered a plutonium device. On August 6 purposes would have to promoteand 9, 1945, respectively, the United defense goals or make extremely effi-States dropped Little Boy, a uranium- cient use of uranium. He proposedcharged bomb on Hiroshima and Fat therefore to design and build atMan, containing plutonium, on Argonne an experiment to prove that aNagasaki. Hiroshima received the reactor could generate electricity anddestructive power equivalent to 12,500 manufacture plutonium at the sameChicago Historical Society P&S-1964.0521 tons of TNT; Nagasaki, 22,000 tons. 7 time.Uranium had another useful quality. Ina chain reaction, it could manufacture During the war and immediately after- It was an astonishing idea. The reactoranother fissionable element. Some of ward, the assumption that uranium was would be built so that the non-fission-the liberated neutrons entered the scarce continued to influence the way ing U-238 would be tucked in close tonuclei of uranium-238, not splitting it governments and scientists regarded it. fissioning U-235 fuel rods and also sur-but eventually changing it into plutoni- The scarcity was felt to be so serious round them like a blanket. During theum, a new element not found, it was that General Groves, who continued to chain reaction, one liberated neutronthought at the time, in nature. T h isadminister the Manhattan District after would keep the chain reaction goingplutonium activation product, upon the war, approved a proposal in 1946 to and another one or two would hit thebeing bombarded with neutrons, build a reactor that would help solve U-238 and create new atoms of plutoni-proved to be fissionable. Therefore, a the uranium shortage. 8 um fuel. It would solve the scarcity of2 3'