Separation of Gaseous Isotopes by Diffusion

Abstract

The behavior of a set of mercury diffusion pumps has been investigated and the separation factors for a number of isotopic mixtures have been determined. Formulae have been derived which give the dependence of enrichment on the choice of reservoirs. In addition, Barwich's theory for the fractionation process has been extended to the case of finite reservoirs. The solution for this problem is a slowly converging series, but a qualitative picture of the dependence of equilibrium time on various factors is obtained. The separation factors which have been found for the Hertz diffusion pumps for bromine in CH₃Br, carbon in CH₄, oxygen in O₂ and H₂O, Ne, and A are 1.005, 1.107, 1.045, 1.073, 1.198, and 1.154 per unit, respectively. Twelve pumps of the Hertz design, and seventeen modified units were used. The modifications were made in an attempt to improve the original design, but the factors obtained for these units are smaller. Auxiliary experiments indicate that the performance of the new units is seriously impaired by the presence of back diffusion and that increased factors can be obtained by eliminating the latter effect.