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Notice that in each of the reactions neutrons are produced. The average number of neutrons produced in fission reactions is 2.5. Thse neutrons can then be used to produce Chain Reaction. |
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Consider reactions where 2 neutrons are produced. The first neutron causes one uranium nucleus to split into two fragments producing 2 neutrons, which in turn can cause two more uranium to fission, producing four fragments and four new neutrons. The chain reaction will continue till all the  U fuel is spent. This is roughly what happens in an atom bomb. The run away chain reaction needs to be controlled, if one is to use it for power generation. This is done by removing excess neutrons so that the chain reaction can proceed at a slow pace till all the fuel is burnt. Removing excess neutrons is achieved by inserting control rods which contain neutron absorbing material. Cadmium and boron rods are usually used for such purpose. |
