Uranium is found in nature, containing ).7 percent of uranium-235, 99.3 percent of uranium-238, and a trace of uranium-234.
Uranium containing 0.711 per cent by weight of uranium 235 and no other isotope of uranium except uranium 238 and trace quantities of uranium 234.
Uranium whose constituent isotopes have an isotopic abundance equivalent to that found in nature. The naturally-occurring isotopic abundance for 235U is approximately 0.711% and for 238U it is approximately 99.289%. Reference: 10CFR71. Related to depleted uranium. Related to enriched uranium.