PNNL

Abstract

Evaluating the corrosion of glass waste forms for nuclear waste immobilization is a key metric of their performance. Stage III behavior, the delayed acceleration of glass corrosion, remains the most potentially impactful aspect of glass corrosion behavior. Using the addition of various zeolite phases to trigger this effect, the properties of Stage III behavior were evaluated for three high-level waste glass compositions: SRL-202A, SON68, and AFCI. We show that Stage III behavior can occur at temperatures as low as 22°C, with rate acceleration observed at 90 and 70 °C for all studied glasses, and at 40 °C and 22 °C for two of the compositions (SRL-202A and SON68). Using an Arrhenius fit, the activation energy of the process was found to be highly uncertain, with values between 39 and 68 kJ·mol-1. Stage III behavior was triggered for each of the glasses studied by the addition of each of the four zeolites studied (Na-P1, Na-P2, Analcime, and Chabazite). The rates of alteration during Stage III varied very little, from 0.0058 to 0.023 g·m-2·d-1 for the accelerated region immediately following zeolite addition. The acceleration was found to be transient, with the alteration rate decreasing and then accelerating again as the experiments proceeded. The solution composition was compared to the strong base/weak acid discriminator developed by Jantzen et al. and it was found that the addition of zeolites can overcome slightly non-optimal solution conditions for zeolite formation to trigger Stage III behavior.