In-situ monitoring of seeded and unseeded stage III corrosion using Raman spectroscopy

摘要

Stage III glass dissolution, the occasionally observed tendency for accelerated aqueous corrosion after extensive time spent at lowreaction rates, is a major area of technical uncertainty in long-term glass performance modeling for vitreous nuclear waste forms.Stage III dissolution behavior is thought to be caused by the precipitation of zeolite phases that lower the activity of the ratecontrolling orthosilicic acid ion and cause the acceleration of glass dissolution. The uncertainty lies mainly in a poor understandingof the growth kinetics of these key crystalline phases. It is particularly important to understand the impact of temperature and pHconditions on Stage III behavior. Accurate analysis of this phenomenon is complicated by the typically very long (e.g., years), andvariable length of the induction period preceding the onset of Stage III behavior. In this study of a high-sodium aluminoborosilicateglass, we demonstrate the ability to initiate the onset of Stage III behavior in a controllable fashion so as to both reduce the timedelay of the incubation period, and to also be able to initiate Stage III dissolution in controlled conditions. In this case, wedemonstrate that Stage III glass corrosion behavior is possible at 70 °C, a lower temperature than previously observed (90 °C), evenin an unseeded experiment. We confirm, through a comparison study, that seeded and unseeded Stage III corrosion rates areequivalent. This enables wide-scale testing of Stage III corrosion rates for many glass compositions in relatively short times throughthis technique. We also report further development of the use of in situ Raman spectroscopy monitoring of boron concentrationand pH through simple and chemometric analysis methods.