Solubility of uranium oxide in ternary aluminosilicate glass melts

Abstract

Uranium solubility was measured in melts belonging to the CaO-Al2O3-SiO2 (CAS) and MgO-Al2O3-SiO2 (MAS) systems using the Pt wire loop technique, enabling independent control of the temperature (1400 °C), glass composition, and oxygen fugacity (-16.1<log(fO2)<-0.7). The low sample masses allowed the equilibrium state to be reached quickly and rapid quenching of the glasses was performed in order to immobilize each system as close as possible to the molten state. The compositions of the different quenched glasses were analyzed by EDS. Uranium solubility decreased with decreasing oxygen fugacity, highlighting the lower solubility of uranium at reduced oxidation states. For each system, uranium solubility was constant from log(fO2)<-9.7. Moreover, different uranium behavior was evidenced between the two ternary systems. Modification of the Al content affected only uranium solubility in the CAS compositions, while uranium volatilization for oxidizing conditions was noted in the MAS system. This difference in behavior may be attributed to structural changes and probably to the variable proportions of [5]Al in each glass system.