Structural characterization of uranium and lanthanide loaded borosilicate glass matrix

Borosilicate glass is a potential candidate for high-level radioactive waste conditioning, thus understanding the effects caused by the combined presence of uranium and actinides within these matrices is of great importance. The glass matrix was simultaneously loaded with UO₃ and lanthanide oxides (CeO₂, Nd₂O₃, and Eu₂O₃) as chemical surrogates for actinides. Neutron diffraction in combination with Reverse Monte Carlo simulation confirmed that the basic glass structure is comprised of tetrahedral SiO₄, and BO₃/BO₄ units. X-ray absorption spectroscopy indicated the presence of Ce mainly as Ce^III and the co-existence of U^V and U^VI. U acts as an intermediate oxide and reduces the number of four-coordinated B, lanthanide ions serve as modifiers, with their increasing concentration shifting the B-O coordination from 3 to 4. X-ray photoelectron spectroscopy revealed a depth-dependent variation in the U^IV/U^VI ratio. Leaching tests showed increased dissolution of Si, B, and Na, compared to the glass matrix.