Nuclear Reaction
The reaction of a nuclear bomb takes place when neutrons are thrown at very high speeds at uranium - 235 or putonium - 239. This causes a reaction to happen by the atoms splitting, which would have half the protons and half the neutrons of the original atom. When this is done the reaction releases a great amount of thermal energy and gamma rays. This happens continuously and uncontrollably.
Hiroshima Bomb - "Little Boy"
The Hiroshima bomb was made from enriched uranium-235. This was prepared by diffusion enrichment techniques using the very small differences in mass of the two main isotopes: U-235 and U-238, the majority. A sphere of U-235 is made around the neutron generator and a small bullet of U-235 is removed. The bullet is placed at the one end of a long tube with explosives behind it, while the sphere is placed at the other end. About 60 kilograms of highly-enriched uranium was used in the bomb which was released over Hiroshima, Japan's seventh largest city. Some 90% of the city was destroyed because of this bomb by the following sequence of events:
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Nagasaki Bomb - "Fat Man"
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Better known as "Fat Man", the bomb dropped on Nagasaki 3 days later from the Hiroshima bomb, was one of these so-called "implosion-triggered bombs". Early bomb designers faced several problems, particularly how to control and direct the shock wave uniformly across the sphere since this bomb was not easy to build. Their solution was to create an implosion device consisting of a sphere of U-235 to act as the tamper and a plutonium-239 (about 8 kg) core surrounded by high explosives. When the bomb was detonated, it had a 23-kiloton yield with an efficiency of 17 percent. This is what happened:
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