What is highly enriched uranium?
The other important fissile material that has been used for nuclear weapons is highly enriched uranium (HEU), usually defined as uranium whose proportion of uranium-235, the fissile isotope of uranium, has been increased to over 90%. The natural uranium mined from the earth consists of about 0.7% uranium-235 (U-235), and about 99.3% uranium-238 (U-238),, and enrichment is the process of increasing the ratio of U-235 to U-238. The half life of uranium-235 is 704 million years, while the half life of U-238 is about 4.5 billion years. It is important to note that most nuclear reactors run on low-enriched uranium (LEU), which is usually 3%-5% uranium-235. LEU cannot be used in nuclear weapons. How is highly enriched uranium made? Traditionally, uranium has been extracted from underground and open pit mines. This natural uranium is processed and then enriched. Numerous technologies have been developed to enrich uranium, such as gaseous-diffusion, centrifuges, and electromagnetic separation.
