Although most isotope separation problems involve only two components, it is occasionally necessary to consider the effect of one or more additional components on cascade design or performance. Examples are the effect of the 0.0058 percent 234 U present in natural uranium, the 236 U present in uranium recovered from a nuclear fuel reprocessing plant, the three isotopes found naturally in oxygen, or the five isotopes occurring in natural tungsten, de la Garza and co-workers have extended the theory of the close-separation, ideal cascade to multicomponent mixtures. In this section, their development is used to derive equations that describe the effect of small amounts of 236 U on the performance of a cascade designed to separate 235 U and 238 U. For extension of the theory to systems containing large amounts of a third component and to multicomponent systems, de la Garza’s papers [Dl, D2] and Pratt’s [P2] summary of them may be used.

Figure 12.27 Nomenclature for stage processing mixture of 23SU, 236U, and 238U.