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The Manhattan Project, or more fully, the Manhattan Engineering District Project, was an effort during World War II to develop the first nuclear weapons by the United States with assistance from the United Kingdom and Canada. Its research was directed by American physicist J. Robert Oppenheimer, and overall by General Leslie R. Groves after it became clear that success was possible and that Germany was also investigating that possibility. Though it involved over thirty different research and production sites, the Manhattan Project was largely carried out in three secret scientific cities that were established by power of eminent domain: Hanford, Washington, Los Alamos, New Mexico, and Oak Ridge, Tennessee. Some families in Tennessee were given two weeks notice to vacant the family farm lands they had had for generations. The existence of these cities was offically secret until several years after the war.
The industrial problem was centered around the production of sufficient fissile material, of sufficient purity. This effort was two-fold, and is represented in the single test and two bombs that were dropped.
The Hiroshima bomb, Little Boy, was based on uranium-235, a minor isotope of uranium that has to be physically separatedIsotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes. While in general chemical elements can be purified through chemical processes, isotopes of the same element have nearly identical chemic from more prevalent uranium-238, which is not suitable for use in an explosive device. The separation was effected mostly by gaseous diffusion of uranium hexafluorideUranium hexafluoride or UF, is a compound used in the uranium enrichment process that produces fuel for nuclear reactors and bombs. It forms solid grey crystals at standard temperature and pressure (STP), is highly toxic, reacts violently with water and i ( U FFluorine (from L. Fluere meaning "to flow"), is the chemical element in the periodic table that has the symbol F and atomic number 9. It is a poisonous pale yellow, univalent gaseous halogen that is the most chemically reactive and electronegative of all6), but also by other techniques, such as a series of centrifuges, and the calutronA Calutron was a mass spectrometer used for separating the isotopes of uranium developed by Ernest O. Lawrence during the Manhattan Project. Its name is a tribute to the University of California, Lawrence's institution. In a mass spectrometer a vaporised method, using the cyclotron principle of magnetic separation. The bulk of this separation work was done at Oak RidgeOak Ridge National Laboratory (ORNL is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle, LLC. ORNL is located in Oak Ridge, Tennessee, near Knoxville. Scientists and engineers at O.
The first and only test, and the Nagasaki bomb, Fat ManThe nuclear weapon nicknamed Fat Man was detonated over Nagasaki, Japan, on August 9, 1945. It was the second and, so far, the last known nuclear weapon to be used in assault. The 10-foot 8-inch (3. 25 metres) long, five-foot (1. 52 metres) diameter, 10,0, in contrast, consisted primarily of plutoniumPlutonium is a radioactive, metallic, chemical element. It has the symbol Pu and the atomic number 94. Its atomic weight is 244. 06, its density 19,800 kg/m3. It is the element used in most modern nuclear weapons. The most important isotope of plutonium i-239, a synthetic element which even in pure form too readily undergoes fission to be used in a gun type device as can Uranium 235. The design of an implosion device was at the center of the efforts by physicists at Los Alamos during the Project. The property of uranium-238 which makes it less suitable directly for use in an atomic bomb is used in the production of plutonium -- with sufficiently slow neutrons, uranium-238 will absorb neutrons and transmute into plutonium-239. The production and purification of plutonium was at the center of wartime, and post-war, efforts at the Hanford Site, using techniques developed in part by Glenn Seaborg.
The choice of civilian instead of military targets has often been criticized. However, the U.S. already had a policy of massive incendiary attacks against civilian targets in Japan. They dropped 20% explosives, to break up wooden structures and provide fuel, and then dropped 80% (by weight) small incendiary bombs to set the cities on fire. The resulting raids devastated many Japanese cities, including Tokyo, even before atomic weapons were deployed. The allies performed such attacks because Japanese industry was extremely dispersed among civilian targets (with many tiny family-owned factories operating in the midst of civilian housing), and in order to break the will of the Japanese population to back the war.
