What is enriched uranium and how does it differ from natural uranium?
Natural uranium is mined directly from the earth. It contains two types of uranium called U-235 and U-238. The concentration of U-235 in natural uranium is always 0.7 percent. The other 99.3 percent is U-238. U-235 is responsible for the energy released in nuclear reactors and atomic bombs. For this reason, bomb-makers and reactor-owners want to increase the concentration of U-235 using a process called uranium enrichment. The result is enriched uranium. U-235 is more radioactive than U-238; therefore, the greater the enrichment of the uranium, the greater the radiation levels, and the greater the toxicity to humans and other living things. Moreover, because U-235 is more energetic than U-238, enriched uranium can sometimes undergo a spontaneous chain reaction, releasing a sudden burst of energy and a shower of neutron radiation the deadliest type of atomic radiation. The effect can be catastrophic. In the jargon of the industry, this kind of unplanned chain reaction is called a critic
