criticality accidentJoe Segen2016-12-03T20:10:03+00:00
Definition An uncontrolled nuclear chain reaction resulting from the unintended aggregation of a critical mass of fissile material–e.g., enriched uranium or plutonium, in an unprotected (unsafe) environment.
While criticality accidents are dangerous and often lethal to humans within the immediate area, the critical mass formed cannot produce a fission bomb-type nuclear explosion given that the explosive supercriticality of a bomb requires specific engineering elements not present in accidents.
Well-known accidents at nuclear power plants–e.g., Three Mile Island, Chernobyl, Fukushima I and others, are not regarded as criticality accidents.
Synonyms Critical excursion, critical power excursion, criticality event