Dissolution of uranium metal into molten LiCl-KCl-UCl4

A study has been made on the kinetics of dissolution of uranium metal into molten LiCl-KCl eutectic with some UCl4 as an oxidizing agent under static and dynamic conditions at temperatures ranging from 4000 to 5000C. The static dissolution rates have been determined by the weight losses of the metal, and were shown to obey a first order kinetic equation. The measurements of the dynamic dissolution rates have been carried out by a rotating disc method, and the concentration changes were measured by an emf method. The dynamic dissolution rates were also confirmed to follow a first order kinetic equation, and were proportional to the 1/2 power of rotating speeds. The dissolution process is concluded to be controlled by the diffusion of U(IV). The activation energies were 9.3+-1.0 kcal/mol for the static dissolution and 6.6+-0.6 kcal/mol for the dynamic dissolution. These values are compared with the value of 7.43 kcal/mol of the activation energy for the diffusion coefficients of U(IV) determined in the previous work. The differences between the values could be explained by the temperature dependence of the thickness of the diffusion layer. (auth.)