Enriched uranium
![Proportions of uranium-238 (blue) and uranium-235 (red) found naturally versus enriched grades](/Images/godic/202502/19/Uranium_enrichment_proportions.svg2001.png")
![A drum of yellowcake (a mixture of uranium precipitates)](/Images/godic/202502/19/LEUPowder2001.jpg")
![A billet of highly enriched uranium metal](/Images/godic/202502/19/HEUraniumC2002.jpg")
![A cascade of gas centrifuges at a U.S. enrichment plant](/Images/godic/202502/19/Gas_centrifuge_cascade2002.jpg")
Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% U isotope, with U only constituting about 0.711% of its weight. U is the only nuclide existing in nature (in any appreciable amount) that is fissile with thermal neutrons.