Influence of Flow-Field Structure on Uranium Isotope Separation in the Separation Nozzle

In the separation nozzle process, uranium isotope separation is based on the mass dependence of the centrifugal forces in a fast curved flow consisting of uranium hexafluoride and a light auxiliary gas that is admixed in a high molar excess. The objectives of this investigation are to determine the dependence of the separating characteristics of a centrifugal flow field on its spatial structure. Calculations were carried out for small UF₆ mole fractions in the light auxiliary gas, so that the complicated ternary diffusion equations are reduced to two simple binary diffusion equations. The calculations show that isotope separation increases with the radial displacement of the UF₆ streamlines relative to the auxiliary gas. Favorable initial distributions for a large radial shifting of UF₆ exist when the flux, at the beginning of deflection, is high for small deflection radii, whereas at the end of deflection, the UF₆ should be concentrated at large radii near the outer deflection wall. Consequently, a radial decrease of flow velocity, a high ratio of nozzle width to deflection radius, and high centrifugal fields at the end of deflection yield high separation effects. Taking into account the interdependence between the gas flow rate, the viscous losses, and the diffusion coefficient, the model developed can predict the influence of geometric parameters on the separating characteristics of the nozzle.