单词 | criticality |
释义 | criticalitynoun crit·i·cal·i·ty ˌkri-tə-ˈka-lə-tē : a critical quality, state, or nature The true criticality of that basic political rationale is being demonstrated in the 1990s. But the inspector general of the Department of Homeland Security, in a report released Tuesday, found that the list was not child's play: all these "unusual or out-of-place" sites "whose criticality is not readily apparent" are inexplicably included in the official federal antiterrorism database. specifically, physics : the state in which a mass of fissionable material sustains or is able to sustain a nuclear chain reaction Criticality can be achieved by increasing mass (adding more plutonium) or … by compressing a barely subcritical mass to increase its density. How big is a critical mass? That depends on the proportion of fissile material and on its shape and configuration. Surrounding the mass with a neutron-reflecting substance further reduces the size needed for criticality, by returning neutrons that would otherwise escape. |
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