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Uranium ""_(92)U^(238) is not suitable for chain reaction . Why ?

Answer»



Solution :Natural uranium consists of three isotopes namely `U^(233), U^(235)` and `U^(238)`. The energy required for breaking up `U^(238)` is more than 1.2 MeV, and the energy required for breaking up `U^(235)` is about 0.03 eV. The energy of emitted neutrons in a nuclear fission is of the order of 0.03 eV, thus it can produce a chain reaction with `U^(235)` and not with `U^(238)`. And EVEN if a neutron of energy more than 1.2 MeV is used to produce fission of `U^(238)`, the secondary neutrons get slowed down after colliding with `U^(238)` nuclei and unable to cause further fission. Thus `U^(238)` is not suitable for chainreaction. [The percentage of `U^(233)` in natural uranium is negligibly SMALL `~=0.006%` and `U^(235)` is `~=0.7%` and `U^(238)~=99.3%`]


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