Effect of composition on the corrosion of simplified simulated nuclear waste glasses

Abstract

Nuclear Waste Glasses have been used for the immobilisation of nuclear wastes. A greater understanding of these materials and the way in which they interact will lead to better wasteforms design and performance. We have studied on three projects, one was on glass corrosion by investigating the effect of Al/B ratio on the Product Consistency Test (PCT) response. We have used the international simple glass ISG 3 with changes in the Al/B ratio and explored a new trend that has not been investigated so far. Our results followed established models for the Al/B ratio higher than 0.05 but the opposite trend was found below this ratio. Our second and third project are are related with development of mathematical model for product consistency test response vs. glass composition and Effect of Na2O on aqueous dissolution of glass. For this purpose, we have designed two series of glasses, one with 5% LiO2 and the other with 0% LiO2 by varying the fractions of SiO2, B2O3, CaO, Al2O3, and ZrO2, one at a time. In each of 11 baseline glasses, fractions of Na2O were increased in regular intervals. It was expected that “acceptability” limit would thus be identified in terms of the Na content for each of the 11 baseline glasses and a model could be developed for the “acceptability” limit based on PCT normalized releases (ri, g/m2) of B and Na. 146 glasses were designed and melted. We have made models for rB and rNa (the normalized B and Na PCT releases) for these two series of glasses, and then we overlapped these models to find an acceptable composition region for nuclear waste glasses in term of composition. The first-order model was fitted to data. Based on the PCT normalized B and Na releases, we made four models for Boron and four models for sodium release. In boron model, we have found 10 outliers and calculated R2 = 0.910 for B release and 0.892 for Na release. Our third project relates with further studies focused on the effect of Na2O fraction on the glass dissolution response. Because the effect of Na2O depends of the content of other oxides. In this way we have figure out the percentage of Na2O, upto which durable glasses can be made and good model fit data is achieved. Also we have calculated the temperature of all the glasses at which molten glass viscosity would be 5 Pa s.