出典:Wiktionary
出典:Wikipedia
出典:『Wikipedia』 (2011/06/13 15:59 UTC 版)
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 (e.g. the nuclear fission cross-section), its density, its shape, its enrichment, its purity, its temperature and its surroundings.