Redox effects on the durability and viscosity of nuclear waste glasses

Iron oxide is one of the major components in West Valley nuclear waste glasses (about 12%). The authors report studies of the effect of the redox state of iron oxide on the viscosities and chemical durability of West Valley waste glasses that were prepared with Fe(II)/ΣFe ratios between 0.0 and 0.8 by melting in a controlled atmosphere of CO and CO2. Durabilities were determined using modified MCC-3 tests and viscosities were measured between 950 degrees C and 1150 degrees C. It is found that the redox effects on durability are strongly dependent on glass composition; e.g., the leach rate differs by a factor of 12 from the most oxidized to most reduced glass at low alumina compositions, while this factor falls to below 2 for similar, but more durable, glass compositions with higher alumina contents. The viscosities of these glasses decrease by about 30% over the range of redox states investigated