Abstract
A numerical analysis is presented on the diffusive separation behavior of a three-component gas mixture of 235UF6, 238UF6, and light gas in a gas centrifuge. The purpose of analysis was to examine the isotope separation performance of the centrifuge in the presence of light gases such as N2 and HF, which inevitably leak in from the atmosphere or accumulate from impurities contained in uranium hexafluoride.
An approximate basic equation is used, which is almost the same as derived by T. Kai for a ternary system from a generalized form of the Stefan-Maxwell equations, taking account of the pressure diffusion in a rapidly rotating cylinder. The method has previously been proposed for application to counter-current centrifuges, which are characterized by stable axial flow in two concentric streams, assuming that the gas mixture is in thermo-dynamical equilibrium between the light gas and UF6 mixture.
Calculations made using the above basic equation indicated that the separative power of the centrifuge is significantly lowered with increasing penetration of the light gas into the separative zone between the two concentric streams. The results of calculation are in fairly good agreement with previously reported theories over a wide range of light gas concentration.
Measurements made using an experimental centrifuge equipped with scoop substantiated the foregoing trends indicated from calculation up to about 1 ??, average concentration of light gas in the centrifuge cylinder. At higher concentrations, a more significant lowering of separative power by the presence of light gas was indicated from measurement than from calculation.
