Fission and the • First discovered (1938) and then explained (1939) by , Fritz Strassmann, and Otto Frisch

Nuclear Fission and Einstein Concept was first considered by Einstein when he developed his theory of relativity after the work of the above scientists

Einstein wrote a letter convincing Roosevelt to start work on an atomic bomb.

Einstein was never asked to work on the bomb because the FBI worried about his association with socialists

The Manhattan Project

• Run by Major General Leslie Groves • Robert J. Oppenheimer was director of the Los Alamos Laboratory where the bombs were designed • Building and testing bombs, but also procuring fissile materials-enrichment of and Uranium

• Natural uranium consists of 99.3% uranium-238 and 0.7% uranium-235 -only the latter is fissile. • Uranium-235 has to be physically separated from the more plentiful . • Various methods were considered for uranium enrichment, most of which was carried out at Oak Ridge. Plutonium

• Only small amounts of plutonium (239) exist in nature • The best way to obtain large quantities of the element is in a • Only a small amount of the uranium-238 will be transformed, so the plutonium must be separated from the remaining uranium, and other products Main project research locations of the United States University of Chicago Metallurgical Lab built the first nuclear reactor, CP-1, in a squash court under the football stadium. The first sustained chain reaction occurred on Dec. 2, 1942. Oak Ridge

X-10 n Secret City on the Clinch River near Knoxville, Tennessee. n Primary purpose was to enrich 235U. n Also built a graphite reactor at X-10 to study the production of plutonium.

Hanford

• Secret City on the Columbia River in Washington State. • A series of nuclear reactors designed to produce plutonium. • A chemical plant to purify plutonium. Los Alamos

• Secret City in the Sangre de Christo Mountains in New Mexico. • The purpose was to design and build the bombs. Gun Design

• This design worked with uranium. • A 2000 lb TNT Blockbuster bomb was used as the “trigger”.

Implosion Design

• This design was required for plutonium. • Impurities of 240Pu would release too many and cause premature detonation in the gun design. This would lower the yield. Trinity Site

• The gun design was simple and the scientists did not feel that testing was necessary. • The implosion device was much more complicated and needed to be tested. • The chosen site was in the Jornado del Muerto Valley near Alamogordo New Mexico and code named Trinity. Gadget -July 16th 1945 6.2kg of Plutonium 239 Explosion equivalent to 18.6 kilotons of TNT Little Boy Hiroshima - August 6th 1945

• 64 kg of 80% Uranium 235 • Resulted in blast equivalent to 15 kilotons of TNT Little Boy- Gun Design A barometric-pressure sensor determines the appropriate altitude for detonation and triggers the following sequence of events: • The explosives fire and propel the bullet down the barrel. • The bullet strikes the sphere and generator, initiating the fission reaction. • The fission reaction begins. • The bomb explodes. Fat Man Nagasaki August 9th 1945

• 6.2 kg of Plutonium 239 • Resulted in a blast equivalent to 21 kilotons of TNT Fat Man Nagasaki August 9th 1945 • The explosives fired, creating a shock wave. • The shock wave compressed the core. • The fission reaction began. • The bomb exploded.