Because of the lack of the corresponding electrochemical data, the rad ioisotope method, a modification of the moving-boundary
method for measuring transforence numbers by use of radioisotopes, was applied to determine the mobility of UO
in aqueous solution in a concentration range 0.1–5.10−4M. It is an example of the investigations of the transport processes of actinides in aqueous and non-aqueous electrolyte solutions
in favour of conventional analytical methods and separation processes with60Co as indicator. In order to suppress hydrolysis the majority of measurements were made in solutions of nitric acid at constant
pH 2. The results on the transference number, conductivity and mobility of the UO2-ion constituent is transferred to the standard aqueous system by van RYSSEL-BERGHE's theory. Measurements of Th-, Np-,Pu-
and Am-constituents are in progress.