critical mass(redirected from critical masses)
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critical mass:see chain reactionchain reaction,
self-sustaining reaction that, once started, continues without further outside influence. Proper conditions for a chain reaction depend not only on various external factors, such as temperature, but also on the quantity and shape of the substance undergoing the
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the smallest mass of a fissionable substance at which a self-sustaining fission chain reaction of atomic nuclei can occur; it is characterized by the approach of the neutron multiplication factor to 1. The corresponding dimensions and volume of the device in which a chain reaction takes place are also called critical.