Understanding gel maturation processes in simplified nuclear glasses through experiments and Monte Carlo simulations

Modeling glass alteration is essential for understanding the mechanisms that govern its long-term behavior. A newly developed Monte-Carlo model introduces a dual-network approach that explicitly represents both the solid glass and the surrounding solution, enabling the simulation of interfacial processes such as hydrolysis, gel formation, and structural reorganization. Previous applications of this framework reproduced how changes in hydrolysis rate affect the evolution of the gel–solution interface and the emerging surface morphology. The current version extends these capabilities to capture gel maturation, where the progressive reorganization of the gel network leads to the closure of transport pathways. This channel blocking reduces the mobility of dissolved species, and the model reproduces the experimentally observed drop in boron diffusivity as the gel becomes denser and its pore network loses connectivity. This mechanism naturally drives the system toward the residual alteration rate. To validate these processes, we carried out experiments designed to probe gel evolution directly in the long-term alteration regime. The measurements show a marked decrease in boron transport through the gel as it matures, consistent with the model prediction that pore shrinkage and reduced connectivity progressively limit diffusive pathways. By combining experimental evidence with the improved Monte-Carlo framework, this work provides a coherent picture of how gel maturation governs transport, controls boron mobility, and ultimately determines the long-term alteration behavior of borosilicate nuclear glasses.