The excess of neutrons produced.
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The first time a fission chain reaction was produced was in 1942
another name for nuclear fission is: E=MC squared
In actuality, a spontaneous fission event begins a nuclear chain reaction. It kick starts a nuclear chain reaction. And a neutron from that fission will initiate another fission to continue and rev up that nuclear chain reaction.
It is called nuclear chain fission reaction.
To sustain a fission chain reaction, each fission reaction must result in one more fission reaction. And that one should result in one more, and so on.
Nuclear fission
Not of itself, but it can be made to be.
Neutrons released during a fission reaction trigger other fission reactions.
Fissile, that is they will split on capturing a neutron, releasing energy. Also if the fission releases more neutrons, as with U-235 and Pu-239, this gives the possibility of a chain reaction.
A nuclear chain reaction nuclear fission
Fission and fusion reactions are chain reactions but in different ways. In fission reaction a heavy nuclei is bombarded with a slow moving neutron and this nuclei breaks to produce more such neurons along with generation of new elements. These slow moving neutrons are further used to carry out fission of more such nuclei. This is chain reaction. Fusion reaction are a different class of nuclear reaction in which small nuclei fuse together to produce bigger nuclei along with the generation of energy due to mass defect.. In fusion reaction lot of energy is produced and this energy is used to carry out further reaction. Thus both can be called series reaction.