Аннотация
In general modern nuclear power plants (NPP) use thermal reactors with enriched by isotope 235U uranium (comparing to raw uranium) in the beginning of campaign. This fuel allows having sufficient reactivity margin for obtaining burn-up more than 30-50 MW*day/kg. This reactor type is developed by itself during short period of nuclear power plants development. Raw uranium cannot supply required burn-up even in reactors with best heavy-water moderator. An effective technology of isotope separation was made for military purposes.