Redox behavior of ruthenium in nuclear glass melt: ruthenium dioxide reduction reaction

Among platinoid fission products, ruthenium is a key element during the vitrification of high-level waste because it poorly soluble in glass matrix. It occurs mainly as RuO 2 particles and sometimes Ru 0 melt final cooled glass. Because physical properties are very different from those glass, change such rheology, thermal conductivity electrical conductivity. In addition, even more distinct properties, melts can be sensitive to presence particles. Thus, speciation, specifically reduction into , was investigated air environments, experimental results were compared thermodynamic calculations (Calphad method). Under conditions, modeling good agreement. They show at 1403 °C 1405 ± 7 °C, respectively. The indicate that particle formation may result an autocatalysis mechanism, which involves gaseous species ruthenium. first appear approximately 1280 °C. At ° C < T 1400 only few observed attributed minor phenomena: local redox reaction with iron or disproportionation reaction. higher temperatures ( > °C), much significant takes place. This one decomposition under temperature oxygen pressure predicted by calculations. Based on obtained assumed mechanism dissolved species.