Oxidation Behavior of Platinum Group Alloys in Molten Glass

The composition of platinum group alloys in insoluble residue liquid waste produced during spent nuclear fuel reprocessing depends on the type of fuel and the degree of burn-up. Consequently, for disposal of this waste by its vitrification in borosilicate glass, robustness of the vitrification process is necessary. It is very important in this process whether the platinum group alloy contained in the undissolved residue remains as a metal or blends into the glass. In this paper, the local structure and chemical state of each type of atom in borosilicate glass have been analyzed by SEM-EDS and EXAFS to evaluate the behavior of platinum group alloys in the glass. The SEM-EDS results showed that molybdenum migrate into the glass phase easily, while ruthenium, rhodium, and palladium atoms tend to stay in the alloy phase. The EXAFS showed that molybdenum (VI), ruthenium (IV), and palladium (0) were present in the same chemical form regardless of compositional change, while rhodium (III or IV) varied depending on the composition of the alloy.