Highly enriched uranium. Used in nuclear weapons and some types of research and submarine propulsion reactors. Defence and Security
(Highly enriched uranium). HEU is an important fissile material used in nuclear weapons. It is uranium whose proportion of uranium-235 has been increased to over 90%. Uranium as it exists in its natural state consists of 0.7% uranium-235. Uranium-235 has a half life of 704 million years.
Uranium that has been enriched to greater than 20-percent U-235.