Uranium in which the content of the isotope uranium-235 has been increased above its natural value of 0.7% by weight. Typical low-enriched uranium for commercial power reactors is enriched in uranium-235 to the range of 3% to 5%. In highly enriched uranium, the uranium-235 has been increased to 20% or more.
uranium in which the naturally occurring proportion of uranium which can be readily split (fission ) is increased. For use as fuel in a nuclear power plant, it is increased from less than 1 percent to between 3-5 percent. To produce an atomic bomb requires enrichment to 90 percent.
Uranium in which the proportion of uranium 235 to total uranium of all isotopes is increased from 0.72% to a higher value.