No-remixing separation cascade

Almost 60,000 moles of natural abundance uranium flow through the cascade, at the feed stage for each mole of 90% 235u withdrawn. 

ACS Symposium Series American Chemical Society Washington, DC, 1975. 

9 Is of major Importance for estimating the size and cost of an Isotope separation plant. It Indicates that the total flow Is a product of two factors the first of these, proportional to l/(a-l) Is a function only of the elementary separation factor which Is determined by the separation process used. The second factor [In square brackets], which Is usually called the separative duty or separative work units (S.W.U.) Is a function only of quantities and concentrations of feed, product, emd waste. It has the same dimensions as those used for the quantities of material, and Its value Is Independent of the process used to accomplish the separation task. The significance of the magnitude of the elementary factor Is Immediately apparent a two-fold reduction In (a-1) requires an Increase In the total flow by a factor of 4. Since for a gaseous diffusion process, the total flow rate Is closely related to the total area of porous barriers, the total pumping capacity and the total power consumption required, all the associated costs vary proportionately. 

Now let us examine deuterium enrichment—first the scale of the current effort, and a projection of the deuterium requirements in the future. The United States has constructed two plants, each capable of producing 500 tons of D2O per year. One of these plants Is dismantled, and the second plant Is currently operating at about one third of Its capacity, producing 180 tons of D2O per year. In Canada, two plants with a combined output of 1600 tons D2O per year have recently been completed (21). 

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