Atomistic modeling of sodium borosilicate glasses containing uranium

Safe and effective management of high-level nuclear waste (HLW) is of considerable interest to ensure the sustainable utilization of nuclear energy. One method of long-term storage and disposal involves the processing and transformation of the spent fuel into a glass, a technique known as vitrification. Sodium borosilicate glasses are generally accepted as a proper HLW isolating media. Understanding the microstructure and migration of heavy cations in these glasses provide insights in mechanisms of delocalization of actinides from the radioactive wastes during long-term storage. To fully exploit these glasses for applications, fundamental insights about the atomic structure is needed. The x-ray and neutron diffraction experiments have provided the average structure of these glasses, but these methods alone are insufficient to determine the atomic structure, which are comprised of several atomic pair distributions overlapping with each other. I will briefly describe a method to obtain realistic computer models of these glasses containing uranium by jointly exploiting the experimental information (diffraction data) and the density functional theory approach. I will then discuss on the atomic structure of these glasses for varying glass-former concentrations.