Transport mechanism of uranium in the iodide process

Abstract

The possibility of uranium transport by the van Arkel-de Boer process is discussed in terms of a thermodynamical calculation, and the operating conditions are theoretically deduced. Experimentally it was observed that the uranium was successfully transferred under some of these conditions but not under others. The kinetics of the process were studied under the optimum condition (in a closed transport system with the two temperature regions arranged stepwise). From the deposition rate of uranium the rate-controlling stages, dependent on the total pressure of the system, were determined and it was concluded that the uranium transport was only via the tetra-iodide while the formation rate of the tri-iodide was so slow that it did not substantially participate in the process. The standard diffusion constant of the gaseous tetra-iodide was found to be 3.1 × 10^–3 cm²/sec, and the dependence of the natural convection velocity on the total pressure in the system was evaluated from the experimental data.