Mathematical modeling of sorption immobilization and dehydration of saline liquid radioactive waste using expanded perlite M100

Saline liquid radioactive waste (LRW) can be generated during the operation and decommissioning of nuclear facilities, requiring safe treatment and long-term isolation. Conventional treatment methods require high energy consumption and complex infrastructure. For facilities with large accumulated inventories of LRW, such as the BN-350 reactor plant, low-energy approaches enabling conversion of waste into a non-flowable state are highly relevant. Sorption immobilization using porous mineral sorbents represents a promising option; however, its practical implementation requires a quantitative description of kinetically limited sorption and subsequent moisture removal processes. In this work, two complementary computational modules were sequentially developed. At the first stage, a mathematical description of water sorption from an LRW solution by expanded perlite M100 was formulated based on a hybrid model that accounts for temperature dependence and salt precipitation during solution concentration. At the second stage, a two-dimensional model of diffusion-controlled dehydration of the “perlite-salt precipitate” system was implemented using numerical simulation and validated against the results of two independent laboratory experiments. The obtained results confirm the applicability of sorption immobilization as a low-energy and technologically simple approach for the treatment of large volumes of LRW, while the developed model can be used to estimate processing timeframes and support process scale-up for industrial implementation.