Advanced Monte Carlo method for simulating glass alteration: Application to aluminoborosilicate glasses

Understanding the alteration mechanisms of nuclear glasses is paramount for safety assessment of deep geological disposal of nuclear waste. This endeavor poses significant challenges due to the experimental limitations in observing atomic-scale mechanisms, which are essential for developing macroscopic alteration models. Consequently, a novel Monte Carlo approach has been developed to simulate the alteration process of simplified nuclear glasses at the atomic level. This approach employs a dual lattice to represent both the solid material and the solution, thereby facilitating the incorporation of diffusion and hydrolysis-recondensation mechanisms. Preliminary findings underscore the critical influence of alteration conditions on glass behavior and elucidate the interplay between rate of hydrolysis at the gel-solution interface and the morphology of the outer layer formed within the gel. Intense hydrolysis promotes the formation of a porous, low-density layer, whereas slower hydrolysis fosters the development of a dense, cross-linked layer. The figure depicts the morphologies of alteration gels simulated by Monte Carlo with various values of hydrolysis and redeposition probabilities. Depending on the intensity of the hydrolysis rate, the morphology of the surface of the gel changes. At a low hydrolysis rate, a passivating layer enriched in Si and Al forms, and this layer disappears as the hydrolysis rate increases, giving way to a more rough and porous layer. image