critical mass is the minimum mass of a sample of fissionable material necessary to sustain a nuclear chain reaction.
the minimum mass of a sample of fissionable material necessary to sustain a nuclear chain reaction?
critical mass
critical mass









































a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. the critical mass of a fissionable material depends upon its nuclear properties (specifically, the nuclear fission cross-section), its density, its shape, its enrichment, its purity, its temperature, and its surroundings. the concept is important in nuclear weapon design.









































section::::explanation of criticality.









































when a nuclear chain reaction in a mass of fissile material is self-sustaining, the mass is said to be in a "critical" state in which there is no increase or decrease in power, temperature, or neutron population.
critical mass
an alternative definition defines fissile nuclides as those nuclides that can be made to undergo nuclear fission (i.e., are fissionable) and also produce neutrons from such fission that can sustain a nuclear chain reaction in the correct setting. under this definition, the only nuclides that are fissionable but not fissile are those nuclides that can be made to undergo nuclear fission but produce insufficient neutrons, in either energy or number, to sustain a nuclear chain reaction. as such, while all fissile isotopes are fissionable, not all fissionable isotopes are fissile. in the arms control context, particularly in proposals for a fissile material cutoff treaty, the term "fissile" is often used to describe materials that can be used in the fission primary of a nuclear weapon. these are materials that sustain an explosive fast neutron nuclear fission chain reaction.
fissile material