What is highly enriched uranium? What is enrichment?
Highly enriched uranium is uranium that contains 20 percent or more of the isotope uranium-235 (U-235 for short). Because it easily fissions, uranium-235 is useful in powering nuclear reactors or nuclear bombs. Natural uranium mined from the ground contains only 0.7 percent U-235 and cannot sustain the explosive nuclear chain reaction needed for a nuclear bomb. To make HEU, the uranium has to be “enriched” — that is, the concentration of U-235 has to be increased. Separating the atoms of U-235 from the atoms of U-238 (which make up more than 99 percent of natural uranium) requires complex and difficult technology, since these atoms have the same chemical properties and differ only slightly in weight. Terrorist groups would almost certainly not have the technical or financial means to enrich their own uranium. Unfortunately, the same technologies used to make LEU for peaceful reactor fuel can also be used to make HEU for nuclear weapons — which is why Iran’s pursuit of uranium enrichme
