uranium 238

English Thesaurus

1. the commonest isotope of uranium; it is not fissionable but when irradiated with neutrons it produces fissionable plutonium 239 (noun.substance)

hypernym	:	atomic number 92, u, uranium,
definition	:	a heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons (noun.substance)