Gaseous diffusion plant waste

Researchers used the 1998 demonstration of the DeHg process on wastes from the DOE s Portsmouth Gaseous Diffusion Plant to estimate the unit costs associated with the treatment... 

A cascade tiiat has the same number of units (i.e., the same capacity) in all stages of a group is known as a squared-off cascade. A cascade in which the number of units, or the capacity, in each stage decreases as the produce and waste ends of the cascade are approached is called a tapered cascade. A single multiplate distillation column is an example of a squared-off cascade a gaseous diffusion plant for uranium separation is an example of a tapered cascade. 

U.S. Department of Energy. (2002). Final Remedial Action Report for Lasagna Phase Ilb In-Situ Remediation of Solid Waste Management Unit 91 at the Paducah Gaseous Diffusion Plant, Paducah, Kentucky, http //www.rtdf.org/public/lasagna/lastechp.htm. 

Uranium oxide [1344-57-6] from mills is converted into uranium hexafluoride [7783-81-5] FJF, for use in gaseous diffusion isotope separation plants (see Diffusion separation methods). The wastes from these operations are only slightly radioactive. Both uranium-235 and uranium-238 have long half-Hves, 7.08 x 10 and 4.46 x 10 yr, respectively. Uranium enriched to around 3 wt % is shipped to a reactor fuel fabrication plant (see Nuclear REACTORS, NUCLEAR FUEL reserves). There conversion to uranium dioxide is foUowed by peUet formation, sintering, and placement in tubes to form fuel rods. The rods are put in bundles to form fuel assembHes. Despite active recycling (qv), some low activity wastes are produced. 

Eq. 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. 

It is interesting to compare the economics of gas centrifugation to gaseous diffusion, albeit crudely. London (1961) divides enrichment cost into two principal categories (1) specific investment, i.e., capital cost per separative work unit (SWU) amortized over the plant life, and (2) power cost per SWU. (SWU, which is a function of quantities and concentrations of feed, product, and waste provides a quantitative measure of the isotope separation task for any conceivable process.) The latter comprises the bulk of operating costs. The estimates, which are crude, clearly demonstrate an advantage for gas centrifugation. 

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