Abstract
The exchange rate of uranium isotopes was investigated in a mixed system of natural U(VI) solution and cation exchange resin containing depleted U(IV) and U(VI) ions at various acid concentrations and temperatures. The experiments showed the presence of two isotopic exchange paths: (1) a first exchange process- "U(IV)-U(VI) exchange occurring within the resinous phase", and (2) second exchange process- "U(VI)-U(VI) exchange between the resinous and solution phases".
Based on the experimental results, it was found that
(1) The exchange rate constant for the first process is very sensitive to hydrogen ion concentration in the resinous phase.
(2) The exchange rate constant for the second process is almost independent of hydrogen ion concentration in the system.
(3) The apparent activation energy is 13.9 kcal/mol for the first process, and 5.84 kcal/mol for the second.
(4) The cation exchange resin used is an ideal material as adsorbent of U(IV), because U(IV) is stable in the resinous phase and complete mixing of U(IV) and U(VI) is prevented by using this system.
