Yellowcake, or uranium concentrate, produced by mines cannot be used directly as a nuclear fuel. Specialized processing and fuel bundle fabrication are required before that can occur. First the uranium concentrate is refined to remove impurities and change its chemical form to UO3. Then the UO3 is chemically converted into one of two different uranium compounds, UO2 or UF6, depending on the type of reactor to be fuelled. UF6 moves on to enrichment for use in light water reactors, while UO2 moves directly to manufacturing where fuel assemblies for heavy water reactors are constructed.
Typical nuclear reactors hold about 18 million uranium fuel pellets.
