types of uranium
Uranium naturally occurs as two isotopes: 99.3% 238U and 0.7%235U, of which only 235U will burn in a nuclear reactor. Although it is difficult to separate the two isotopes, nuclear reactors can use enriched uranium rather than pure 235U.
Low enriched uranium contains more than 0.7% but less than 20% of 235U. This is usually used in nuclear reactors with the 235U content between 3 and 5%. High enriched uranium contains more than 20% 235U, this is most commonly used in research reactors, naval propulsion reactors and weapons.
Depleted uranium contains less than 0.7% 235U, this is a by-product of nuclear weapons and nuclear power. It has been also linked to gulf war syndrome and higher incident rates of cancer near nuclear power sights. Depleted uranium must be stored safely for hundreds of years until their radiation has decreased to a safe level. This is processed in the Uk at THORP.