Uranium cannot be used as a fuel or weapon in its natural state. To
be used as reactor fuel or bomb manufacture, U-235 must be separated from natural
U-235 is the only fissile isotope in natural Uranium (U), therefore Uranium must
be "enriched" to have a higher percent concentration of U-235.
U-235 Concentration needed for:
- 3-5% of U-235
- This level of uranium is called Low Enriched Uranium (LEU)
- 90% of U-235
- Referred to as Weapons Grade or Highly Enriched Uranium (HEU)
All of the uranium isotopes are fissionable materials that can undergo nuclear fission reactions (see http://www.paducahvision.com/nuclear-energy ). Uranium-235 is a "fissile" material meaning that it is capable of undergoing a self-generated and self-sustained nuclear fission reaction. Uranium-234 and U-238 are capable of a fission reaction only when their fission reaction is initiated by an outside energy source such as bombardment by neutrons.
Use of uranium as a reactor fuel or weapons component requires the U-235 isotope to be "enriched" until the U-235 abundance exceeds that of natural uranium (see http://www.paducahvision.com/uranium-enrichment ). Typical U-235 enrichment abundance for use as a nuclear fuel is 2 – 5%. One kilogram of enriched uranium-235 has the capacity to produce as much energy as 1,500,000 kilograms (1,500 tons) of coal.