6.1 Introduction

Processes in which isotopic composition changes are produced when a flowing gas mixture experiences large linear or centrifugal acceleration are termed aerodynamic processes. Of the many aerodynamic processes that have been proposed or investigated experimentally, only two have been carried through large-scale pilot-plant experiments to intended commercial deployment. These are the separation nozzle process, developed by Becker and his associates of the Nuclear Research Center at Karlsruhe, West Germany, and the UCOR process, developed by the Uranium Enrichment Corporation of South Africa. The separation nozzle process has passed through a number of development stages, which have been described in detail by Becker and his associates [B5-B12, G1 ]. These will be summarized in Sec. 6.2. The South African process is subject to considerable industrial secrecy; a brief summary of three published articles on this process [G2, HI, R3] will be given in Sec. 6.3.

Numerous other schemes for separating isotopes in flowing gas streams have been conceived and subjected to small-scale test, but none has appeared sufficiently promising to enlist the major development support given the nozzle and UCOR processes. Summary descriptions of other aerodynamic processes are in references [T2] and [М2].