Cascade Theory:
Within the operation of a diffusion cascade, it is frequently essential to charge the plant along with feed material of different assays or concentrations of U235F6. These feeds have to be fed within the cascade at a point where the assay of the gas already being processed is the similar as in which of the feed to be charged.
To selection this feed point, thus, it must be probable to calculate the concentration of U235F6 in the process gas at any point in the cascade. These calculations can be made by knowing two things: first, the concentration of U235F6 in the process gas at several points in the cascade (determined through laboratory and instrument analysis); and second, the increase in the concentration of U235F6 accomplished through every stage. This is known as the stage enrichment and should not be confused along with the separation accomplished through a stage previously discussed. Therefore, by knowing the stage enrichment and the U235F6 concentration at a few points in the cascade, it is probable to determine the concentration at other points.
The feed material ordinarily charged into a plant contains a very small percentage of U235F6 with the remainder being U238F6. In the other words, a far greater amount of the feed flows downward within the cascade and is erased as tails than is removed at the top of the cascade as U235F6 or product. By this reason, as we progress upward within the cascade from the feed point, the total flow by the converters becomes progressively smaller. It follows, thus, which in the ideal design each stage would be different in size from the adjacent stages. Therefore, because the cost of construction of a production cascade is of great importance, a lower cost might be achieved through the use of several identical units. For this purpose, the cascade is composed of a series of sections, every of that holds a large number of identical stages. The modification in equipment size is accomplished within a step-wise manner through varying the equipment size of every so-called section.