Just before the beginning of World War II, Albert Einstein wrote a letter to President Franklin D. Roosevelt. Urged by Hungarian-born physicists Leo Szilard, Eugene Wingner, and Edward Teller, Einstein told Roosevelt about Nazi German efforts to purify Uranium-235 which might be used to build an . Shortly after that the United States Government began work on the Manhattan Project. The Manhattan Project was the code name for the United States effort to develop the Atomic bomb Essay before the Germans did.
"The first successful experiments in splitting a uranium atom had been carried out in the autumn of 1938 at the Kaiser Wilhelm Institute in Berlin"(Groueff 9) just after Einstein wrote his letter. So the race was on. Major General Wilhelm D. Styer called the Manhattan Project "the most important job in the war . . .
an all-out effort to build an atomic bomb."(Groueff 5) It turned out to be the biggest development in warfare and science’s biggest development this century. The most complicated issue to be addressed by the scientists working on the Manhattan Project was ;the production of ample amounts of ‘enriched’ uranium to sustain a chain reaction.;(Outlaw 2) At the time, Uranium-235 was hard to extract. Of the Uranium ore mined, only about 1/500 th of it ended up as Uranium metal. Of the Uranium metal, ;the fissionable isotope of Uranium (Uranium- 235) is relatively rare, occurring in Uranium at a ratio of 1 to 139.
;(Szasz 15) Separating the one part Uranium-235 from the 139 parts Uranium-238 proved to be a challenge. ;No ordinary chemical extraction could separate the two isotopes. Only mechanical methods could effectively separate U-235 from U-238.;(2) Scientists at Columbia University solved this difficult problem. A ;massive enrichment laboratory/plant;(Outlaw 2) was built at Oak Ridge, Tennessee. H.
C. Urey, his associates, and colleagues at Columbia University designed a system that ;worked on the principle of gaseous diffusion.;(2) After this process was completed, ;Ernest O. Lawrence (inventor of the Cyclotron) at the University of California in Berkeley implemented a process involving magnetic separation of the two isotopes.;(2) Finally, a gas centrifuge was used to further separate the Uranium-235 from the Uranium-238. The Uranium-238 is forced to the bottom because it had more mass than the Uranium-235.
;In this manner uranium-235 was enriched from its normal 0.7% to weapons grade of more than 90%.;(Grolier 5) This Uranium was then transported to ;the Los Alamos, N. Mex., laboratory headed by J. Robert Oppenheimer.
;(Grolier 5) ;Oppenheimer was the major force behind the Manhattan Project. He literally ran the show and saw to it that all of the great minds working on this project made their brainstorms work. He oversaw the entire project from its conception to its completion.;(Outlaw 3) Once the purified Uranium reached New Mexico, it was made into the components of a gun-type atomic weapon. ;Two pieces of U-235, individually not large enough to sustain a chain reaction, were brought together rapidly in a gun barrel to form a supercritical mass that exploded instantaneously.;(Grolier 5) ;It was originally nicknamed ‘Thin Man'(after Roosevelt, but later renamed ‘Little Boy’ (for nobody) when technical changes shortened the proposed gun barrel.
;(Szasz 25) The scientists were so confident that the gun-type atomic bomb would work ;no test was conducted, and it was first employed in military action over Hiroshima, Japan, on Aug. 6, 1945.;(Grolier 5) Before the Uranium-235 ;Little Boy; bomb had been developed to the ;point of seeming assured of success,;(Grolier 5) another bomb was proposed. The Uranium-238 that had been earlier ruled out as an option was being looked at. It could capture a free neutron without fissioning and become Uranium-239. ;But the Uranium-239 thus produced is unstable (radioactive) and decays first to neptunium-239 and then to plutonium-239.
;(Grolier 5) This proved to be useful because the newly created plutonium-239 is fissionable and it can ;be separated from uranium by chemical techniques,;(6) which would be far simpler than the physical processes to separate the Uranium-235 from the Uranium-238. Once again the University of Chicago, under Enrico Fermi’s direction built the first reactor. "This led to the construction of five large reactors at Hanford, Wash., where U-238 was irradiated with neutrons and transmuted into plutonium."(6) The plutonium was .