The steps in the production of nuclear fuel for power reactors are: mining, milling of uranium into "yellow cake" (U₃O₈), conversion into UF₆ for feed, enrichment, and fuel fabrication. Except for the enrichment step, which is a Government monopoly, the industry is in private hands.

Uranium enriching is the process of increasing the proportion of the isotope U₂₃₅ relative to the isotope U₂₃₈ in the uranium. Natural uranium consists of about 0.0711 percent of U₂₃₅, while light water reactors need uranium enriched to between 2 and 4 percent U₂₃₅. Of the cost of fuel fabrication, including mining, approximately half is attributable to enriching at current prices.

All major enrichment facilities in the free world currently use the gaseous diffusion method of enriching uranium. This method pumps the gas UF₆ through permeable barriers. A slightly higher portion of U₂₃₅ goes through the barrier than the heavier U₂₃₈. The enriched gas is then sent through another stage where again it filters through a barrier becoming slightly more enriched, while the depleted gas is recycled through another stage. This process can continue until the desired proportion of U₂₃₅ is achieved.

The work done in separating the isotopes U₂₃₅ from U₂₃₈ is called separative work. It takes approximately one kilogram of separative work applied to 2.35 kilograms of natural uranium to produce one kilogram of uranium containing 1.4 percent of U₂₃₅ while stripping the uranium tails to 0.2 percent U₂₃₅. The separation factor by gaseous diffusion is 1.00429 which means that 600 metric tons of UF₆ must be pumped so that about 300 metric tons permeates through the barrier in order to accomplish one kilogram of separative work. This huge pumping requirement is responsible for the vast power needs of the gaseous diffusion process.