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The History of Nuclear Research1919 June - Rutherford creates oxygen from nitrogen. 1920 Rutherford speculates on the existence of the neutron at the Royal Society. 1931 November - Urey discovers deuterium. 1932 James Chadwick proves the existence
of neutrons, using alpha particles striking a beryllium foil. He
determines their mass by measuring the recoil tracks of known atoms
of the rarified gas in his cloud chamber. 1933 Leo Szilard, a Hungarian physicist who took refuge in London from Nazi Germany, reads about a speech in which Lord Rutherford ridiculed the idea of using the transformation of atoms as a source of power. Szilard realizes that, "if we could find an element which is split by neutrons, and which would emit two neutrons when it absorbs one neutron, such an element could sustain a nuclear chain reaction." 1934 Frederic and Irene Joliot-Curie of France discover artificial radioactivity, i.e. the radioactivity of atoms produced in transmutation experiments. Enrico
Fermi of Italy irradiates
uranium with neutrons. He believes he has produced the first transuranic
element, but unknowingly achieves the world’s first nuclear fission. 1935 1936 1938 Otto Hahn and Fritz Strassmann
of Germany split the uranium atom by bombarding it with neutrons
and show that the elements barium and krypton are formed. 1939
Hans A. Bethe, a German-born physicist, recognizes that the fusion of hydrogen nuclei to form deuterium releases energy. He suggests that much of the energy output of the Sun and other stars results from energy-releasing fusion reactions in which four hydrogen nuclei unite and form one helium nucleus. First experimental fission
in U.S. takes place at Columbia University. Einstein and Szilard warn Roosevelt
The fear of a German atomic bomb troubled Leo Szilard. On August 2, 1939, he and Edward Teller drove to Long Island, New York. They went to ask Albert Einstein to sign a letter to President Roosevelt outlining the dangers of a German bomb project. September 1
It was not until July 13, 1942, in the midst of World War II, that the United States undertook the Manhattan Project to develop an atomic bomb. By December 2, a Manhattan Project team headed by Enrico Fermi produced the first artificial fission reaction at the University of Chicago. Three years after its inception, the Manhattan Project achieved its goal of developing an atomic weapon.
Construction of CP-1, or Chicago Pile Number One, was done under the football stadium in an abandoned squash court. On December 2, 1942, mankind first harnessed the energy of the atom. Fermi's pile produced only 1/2 watts of power. But that was all the power the United States needed to start the next phase of the bomb's development. The pile contained 771,000 pounds of graphite, 80,590 pounds of uranium oxide and 12,400 pounds of uranium metal when it went "critical." It cost about $1 million to produce and build. The pile took the form of a flattened ellipsoid which measured 25 feet wide and 20 feet high. 1940 June 3 - German scientists fail to observe neutron multiplication in the reactor in Hamburg. 1941 January - Based on experiments
with a natural uranium reactor, the Germans reject graphite
as a moderator. 1942 May - Heisenberg and Dopel observe
the first multiplication of neutrons. 1943 March 15 - Oppenheimer moves the bomb development to Los Alamos. 1944 August 26 - Bohr presents his memorandum
on intentional control of nuclear weapons to Roosevelt. 1945 January - First Pu reprocessing
production run at Hanford Trinity Test
On July 16, 1945, at 5:29:45 AM, a light "brighter than a thousand suns," filled the valley. As the now familiar mushroom cloud rose in to the sky, Oppenheimer quoted from Hindu scripture, the Bhagavad-gita, "Now I am become death, the destroyer of worlds." The world had entered the nuclear age. The "Gadget" had a yield equivalent to 19 kilotons of TNT. "Fat Man," the bomb dropped on Nagasaki was identical in design to the "Gadget." August 6,9 - Atomic bombs dropped on Hiroshima and Nagasaki. Little Boy Bomb
In essence, the Little Boy design consisted of a gun that fired one mass of uranium 235 at another mass of uranium 235, thus creating a supercritical mass. A crucial requirement was that the pieces be brought together in a time shorter than the time between spontaneous fissions. Once the two pieces of uranium are brought together, the initiator introduces a burst of neutrons and the chain reaction begins, continuing until the energy released becomes so great that the bomb simply blows itself apart. This is a replica of the bomb that was dropped over Hiroshima, Japan on August 6, 1945.
Fat Man
The rapid spontaneous fission rate of plutonium 239 necessitated that a different type of bomb be designed. A gun-type bomb would not be fast enough to work. Before the bomb could be assembled, a few stray neutrons would have been emitted, and these would start a premature chain reaction leading to a great reduction in the energy released. Seth Neddermeyer, a scientist at Los Alamos, developed the idea of using explosive charges to compress a sphere of plutonium very rapidly to a density sufficient to make it go critical and produce a nuclear explosion. This is a replica of the bomb that was dropped over Nagasaki, Japan on August 9, 1945. Fat Man Specifications
The Atomic Bomb Cloud over Nagasaki
On August 9, 1945, the American B-29 bomber, Bock's Car left Tinian carrying Fat Man, a plutonium implosion-type bomb. The primary target was the Kokura Arsenal, but upon reaching the target, they found that it was covered by a heavy ground haze and smoke, pilot Charles Sweeney turned to the secondary target of the Mitsubishi Torpedo Plant at Nagasaki. Of the 286,00 people living in Nagasaki at the time of the blast, 74,000 were killed and another 75,000 sustained severe injuries.
World War II ended in Europe on May 8, 1945, less than a month after the death of President Franklin Roosevelt, but plans for the development and use of atomic weapons continued. At at 5:29 a.m. on July 16, 1945, the United States conducted the world's first nuclear test explosion at Alamogordo, New Mexico. The Nuclear Age was born, a product of the fear, violence, and suffering of World War II. J. Robert Oppenheimer, director of the Los Alamos Laboratory, recalled the following passage from the Bhagavad Gita upon witnessing the explosion: "I am become death, the destroyer of worlds" Within a month, nuclear weapons were used to destroy the Japanese cities of Hiroshima and Nagasaki. When he received word of the bombing of Hiroshima, President Truman exclaimed, "This is the greatest day in history!" | ||||||||
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A
QuickTimeVR model of the Little Boy Bomb
