Physics214Week16 - This Week Fission and fusion What made...

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This Week Fission and fusion What made our world Atomic and Hydrogen bombs Big bangs in small packages Nuclear power plants The solution to the energy problem? Enrichment What does it mean and why is it necessary? Toxic Disposal Radiation in everyday life Limit your exposure (same for the stock market) Fusion: The Holy Grail 10/13/2011 Physics 214 Fall 2011 1
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10/13/2011 Physics 214 Fall 2011 2 Fission and fusion If we make an atom from it’s constituents energy is released. This is called the binding energy. Iron is the most tightly bound so if we can make elements up to Iron by the fusion of light elements energy is released. Similarly if we can break a very heavy atom into lighter elements we also have energy release. E = mc 2 Mass is another form of energy a nucleus is lighter than the sum of the constituent particle masses Fusion processes are how the sun produces energy and fission processes are how nuclear reactors produce energy
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10/13/2011 Physics 214 Fall 2011 3 Chain reaction If a U 235 atom is broken into two lighter elements energy is released. This is accomplished using a neutron. The process produces 3 neutrons which can then cause 3 more atoms to undergo fission. Without any control this chain reaction produces an enormous amount of energy in a fraction of a second. It is an atomic bomb. This process was first observed by Enrico Fermi in a laboratory under the Chicago University football stadium U 235
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10/13/2011 Physics 214 Fall 2011 4 Manhattan project and the bomb In the early forties all the top scientists were taken to Los Alamos to design the atomic bomb. In order for a bomb to work there had to be sufficient Uranium but it could not be in one piece because it fission would spontaneously occur. The main challenges were to obtain enough U 235 and to design a system to bring the uranium together with a neutron source when the bomb was dropped.
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10/13/2011 Physics 214 Fall 2011 5 The hydrogen (fusion) bomb Fusion gives a much bigger energy release than fission , Hydrogen bombs are designed to use an atomic bomb to provide the temperature and pressure so that fusion takes place. There is a central core of light elements surrounded by plutonium or uranium.
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10/13/2011 Physics 214 Fall 2011 6 Enrichment Naturally occurring uranium is nearly all U 238 U 235 is the fissionable material. Complicated processes have been developed to increase the fraction of U 235, this is enrichment. For a reactor the final fraction of U 235 is about 3.5%. For the original bomb several kilograms were required. In a reactor some of the U 238 is turned into plutonium which is also a fissionable material that is used in atomic bombs. Plutonium is produced and can be obtained from the spent fuel rods
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10/13/2011 Physics 214 Fall 2011 7 Nuclear reactors In order to produce energy we need to have controlled fission. Fuel rods are inserted into a
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This note was uploaded on 12/07/2011 for the course PHYS 214 taught by Professor Staff during the Fall '08 term at Purdue University-West Lafayette.

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Physics214Week16 - This Week Fission and fusion What made...

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