Enrichment and SWU
Fluorinated uranium in the form of UF6 is shipped for further processing into “low enriched uranium” (LEU) at enrichment facilities. The enrichers use either gaseous diffusion or centrifuge technologies to increase the relative abundance of the fissile isotope U-235. The energy-intensive gaseous diffusion process is considered obsolete and is being replaced globally by centrifuge technologies.
Enrichment services are priced by the Separative Work Unit, or SWU, which is a measure of the work effort required to physically concentrate fissile U-235 in the “product stream” while depleting it from the “tails stream.” As a rule of thumb, eight to ten kilograms of unenriched (“natural”) uranium “feed” enter the enrichment process for each kilogram of enriched UF6 that exits the process and is shipped on to a fabrication facility.
As with conversion facilities that act as commercial delivery and pick-up points for U3O8, enrichment facilities play a comparable role in the commercial market for UF6. Thus, a utility that needs conversion services may buy conversion directly from a converter or it may buy UF6, taking delivery at an enrichment facility. A common arrangement is a swap, in which the utility delivers U3O8 to a converter and takes delivery of UF6 at an enricher, paying only for the embedded conversion value.
The Russian Federation is the world’s largest operator of enrichment plants, followed by URENCO (the British-Dutch-German consortium with facilities in the U.K, Netherlands, Germany and the U.S.A.). AREVA/Eurodif is next (with a gaseous diffusion plant being replaced by centrifuges in France, and another planned in the U.S.A.), followed by USEC in the U.S.A. a gaseous diffusion operator. (USEC is in the process of trying to upgrade to a centrifuge facility of its own design.) China has more modest-sized enrichment facilities, but is believed to be adding to them. Brazil also has a modest enrichment program that covers part of the local requirement.