Iron phosphate glass waste forms for vitrifying Hanford AZ102 Low Activity Waste (LAW), part II: Property-composition model

Abstract Mathematical models for the chemical durability–composition relation for 5-component iron phosphate glasses, containing a nuclear waste similar to that of the high sulfate (~17 wt%), high soda (~80 wt%) Hanford AZ 102 LAW, have been developed using statistical analysis. The dissolution rate (DR) in deionized water at 90 °C was used as a representative property for the chemical durability. These waste forms contained P2O5, Fe2O3, Al2O3, Na2O and SO3. This 5-component system was used previously to develop mathematical models for predicting the dependence of glass formation on composition. The results from this study can potentially be used to develop other properties-compositions models for iron phosphate glasses containing nuclear wastes. Two separate statistical models, based on Backward Elimination and Stepwise procedures, were developed and both models produced similar results. The DR-values calculated from both models were in good agreement with the experimentally measured values. The DR-composition models developed for the present iron phosphate glass waste forms (containing Hanford AZ102 LAW), are shown to be valid for predicting DR-values for similar waste forms containing other types of nuclear wastes as well. The chemical durability for a few selected glasses whose compositions were generated by the models was also measured by the Vapor Hydration Test (VHT). The model predicted DR-values qualitatively confirmed the measured VHT-values, which provides further support for validating the model.