Phosphate-based glasses and glass ceramics for immobilization of lanthanides and actinides

Abstract

Borosilicate glasses used to be a choice to vitrify nuclear wastes in most of the countries. However, Russian HLW vitrification plant at the Mayak Production Association (Chelyabinsk Region, Urals) uses phosphate-based glasses. Initially, Russian HLW glasses were based on sodium-aluminophosphate with the following approximate composition (mol.%): 40 Na2O, 20 Al2O3, 40 P2O5. Recently we have modified this composition by replacing of up to 50% Al2O3 with Fe2O3. Such replacement increases chemical durability and resistance to devitrification and radiation of the glasses. The phase composition and structure of these glasses containing ~ 10 wt% RE oxides and ~ 10, ~ 50, and ~ 100 wt% UO3 (over 100 wt%) were studied in details using XRD and FTIR. Glasses and glass-ceramics have high chemical durability. Thus, the glasses and glass ceramics on sodium-aluminum-iron-phosphate basis are good waste forms for lanthanide fraction of HLW generated at spent nuclear fuel pyroprocessing and minor actinides.