A Direct Method of Calculating the Optimum Operating Conditions of Isotope Separation Columns

Abstract

The separative power of an infinitesimal counter current element is expressed in terms of radial parameters. It is shown that the separative power is independent of the value of the radial product stream; arbitrarily chosing this to be zero (i. e. “balanced diffusion”) makes it possible to calculate the optimum radial isotope velocities and the axial profile directly from the diffusion and continuity equations. As an illustration of the method, the optimum axial flow profiles and maximum separative powers of gas centrifuges and thermal diffusion columns are calculated, and compared with known results. In the case of the gas centrifuge, the effect that axial back diffusion has on the optimum profile and maximum separative power, is calculated. The variation of the separative power with different axial profiles is determined for the thermal diffusion column. It appears that the natural convection induced axial profile, which is used presently in thermal diffusion columns, gives a small fraction of the maximum separative power. Calculations indicate that a column with a static separative region (and boundary flows) will approach the maximum separative power and will be well suited for measurements of collision parameters.