Uranium used in most nuclear power plants needs to be enriched to a level of 3 to 5 percent 235U. [4] X Research source [5] X Research source [6] X Research source (A few nuclear reactors, such as the CANDU reactor in Canada and the Magnox reactor in the United Kingdom, are designed to use unenriched uranium. [7] X Research source ) Uranium used for atomic bombs and warheads, in contrast, needs to be enriched to 90 percent 235U. [8] X Research source

Uranium dioxide used as fuel in nuclear reactors is made into centered ceramic pellets encased in metal tubes to make 4m (13. 12-foot) long rods[11] X Research source

Because of the number of passes required, this process is energy-intensive and is being phased out. In the United States, only one gaseous diffusion enrichment plant remains, located in Paducah, Kentucky. [13] X Research source

The gas centrifuge process was first developed in the 1940s, but was not brought into significant use until the 1960s, when its lower energy requirements for producing enriched uranium became important. [15] X Research source At present, a gas centrifuge processing plant exists in the United States in Eunice, New Mexico. [16] X Research source In contrast, Russia currently has four such plants, Japan and China have two each, while the United Kingdom, the Netherlands, and Germany each have one. [17] X Research source

One method being developed in South Africa injects the gas into the cylinder on a tangent. It is presently being tested with light isotopes such as those in silicon. [18] X Research source

This process was investigated in 1940 as part of the Manhattan Project, but was abandoned while still in an early stage of development when the more efficient gaseous diffusion process was developed. [19] X Research source [20] X Research source

This method was used to process uranium for the atomic bomb dropped on Hiroshima in 1945 and was also the enrichment method Iraq used in its nuclear weapons program of 1992. It requires 10 times more energy than gaseous diffusion, making it impractical for large-scale enrichment programs. [21] X Research source