Low Enriched Uranium (LEU) is the basic material to fabricate nuclear fuel. It consists of uranium hexafluoride that is a white-grey, waxy solid at standard temperature and pressure. LEU is made by enriching naturally occurring uranium to improve its ability to produce energy. Enrichment increases the concentration of uranium atoms that can split to produce heat. This heat in turn is used to generate electricity.

The LEU that is stored in the IAEA LEU Bank has enrichment levels up to nominally 4.95%, suitable to make fuel for a typical light water reactor, the most widely used type of nuclear power reactor worldwide. LEU is safely stored and transported in strong steel cylinders.

LEU does not deteriorate and can be safely stored for many years. LEU is not a nuclear waste, nor is any waste generated by simply storing it.