Nuclear Chemistry Notation Nucleons • Protons and Neutrons • The nucleons are bound together by the strong force. Isotopes • Atoms of a given element with: same #protons but different # neutrons Isotopes of Carbon Radioactive Isotopes • Isotopes of certain unstable elements that spontaneously emit particles and energy from the nucleus. • Henri Beckerel 1896 accidentally observed radioactivity of uranium salts that were fogging photographic film. • His associates were Marie and Pierre Curie. Marie Curie: born 1867, in Poland as Maria Sklodowska • Lived in France • 1898 discovered the elements polonium and radium. • Winner of the sole 1911 Nobel Prize for Chemistry http://www.radiochemistry.org/nuclearmedicine/pioneers/images/mariecurie.jpg 3 classic types of radioactive decay Alpha Decay Uranium Thorium Beta Decay Thorium Protactinium Gamma decay Nuclear Fission Chain reaction! Nuclear Fission Produces: • 2 smaller atoms • 2 or 3 neutrons • Alpha, Beta, and Gamma radiation • TONS of kinetic (heat) energy Nuclear Fission • First discovered (1938) and then explained (1939) by Otto Hahn, Fritz Strassmann, Lise Meitner 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 Main project research locations of the United States University of Chicago Metallurgical Lab Enrico Fermi 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. Y-12 • Magnetic separation of 235U from 238U at Oak Ridge. • The work was overseen by E. O. Lawrence from U. C. Berkeley. K-25 • Gaseous diffusion plant at Oak Ridge for enrichment of 235U. • Based on Graham’s Law of Effusion and the oddity that UF6 is a gas. 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 neutrons 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. .