Sunday, July 15, 2012
On the Atomic Bomb
On the Atomic Bomb: When FDR created the Office of Scientific Research and Development (OSRD) with Executive Order 8807 in 1941, he directed the U.S. government's resources at producing an atomic bomb. With calls from University of Chicago physicists (Enrico Fermi, Arthur Compton, etc.) in the late 1930s to investigate uranium-235 as a potential source of these bombs, the feasibility of producing a bomb according to the principles of nuclear fission became doable. Even designing an atomic bomb seemed relatively straightforward by the early 1940s, but separating U-235 from U-238 presented the biggest problem to physicists and chemical engineers alike. As an isotope, U-235 made up less than 1% of all naturally occurring uranium in the world (unlike U-238, which constituted 99%). On its own, U-235 was not sufficient enough to initiate a chain reaction, so it had to be enriched to at least 80% purity. The first man-made chain reaction with U-235 occurred on December 2, 1942, in a rackets court under the football field at the University of Chicago. There was no cooling system, no radiation shield, and millions of Chicagoans going about their daily routines above ground. With man-made nuclear fission reactions now possible, everything from nuclear bombs to nuclear medicine to nuclear power appeared in reach. Ultimately, through the process of gaseous diffusion, Robert Oppenheimer, Leslie Groves, and Crawford Greenewalt were able to place about a billion dollars worth of uranium into "Little Boy" (the bomb that leveled Hiroshima in August 1945).