Development of an Experimental Design to Investigate the Effects of R7T7 Glass Composition on the Residual Rate of Alteration

A mixture design method is developed to investigate the effects of R7T7 glass composition on the residual rate of alteration in di-ionized water at 50 °C. The 12 variables are SiO2, B2O3, Na2O, Al2O3, CaO, ZnO, NiO + CoO, Fe2O3, MoO3, ZrO2, FP remaining (Fission Products and actinides remaining) and platinoïds. The method is detailed in this paper and a following publication will deal with the results of its implementation. This experimental design involves 27 glass compositions (with 29 oxides in each glass composition) which are used as training data to estimate the composition effects and to build the predictive alteration models. Three additional glass compositions were formulated to validate the models and to compare the results with other studies. Leaching experiments were planned in residual regime conditions with a monthly monitoring of the pH and the concentrations in solution. Normalized mass loss and alteration rate are calculated and linear regressions were carried out to statistically treat the experimental data.