Summarizing Fission

Fission Summary

  • Nuclear fission is a reaction in which a nucleus is split.
  • Fission releases energy when heavy nuclei are split into medium-mass nuclei.
  • Self-sustained fission is possible, because neutron-induced fission also produces neutrons that can induce other fissions, \(n+{}^{A}X\to {\text{FF}}_{1}+{\text{FF}}_{2}+\text{xn}\), where \({\text{FF}}_{1}\) and \({\text{FF}}_{2}\) are the two daughter nuclei, or fission fragments, and x is the number of neutrons produced.
  • A minimum mass, called the critical mass, should be present to achieve criticality.
  • More than a critical mass can produce supercriticality.
  • The production of new or different isotopes (especially \({}^{\text{239}}\text{Pu}\) ) by nuclear transformation is called breeding, and reactors designed for this purpose are called breeder reactors.


breeder reactors

reactors that are designed specifically to make plutonium


reaction process that produces 239Pu


condition in which a chain reaction easily becomes self-sustaining

critical mass

minimum amount necessary for self-sustained fission of a given nuclide

fission fragments

a daughter nuclei

liquid drop model

a model of nucleus (only to understand some of its features) in which nucleons in a nucleus act like atoms in a drop

nuclear fission

reaction in which a nucleus splits

neutron-induced fission

fission that is initiated after the absorption of neutron


an exponential increase in fissions

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