Simulation of the migration behavior of nuclides Sr and Cs in integrated buffer/backfill materials based on COMSOL

This study examines attapulgite-bentonite-pyrite (AB 7 Fe) and zeolite-bentonite-pyrite (ZB 7 Fe) mixtures as buffer and backfill materials for nuclide migration using soil column experiments and COMSOL modeling. The results indicated that ZB 7 Fe possessed higher adsorption capacities for cesium (Cs) and strontium (Sr) compared to AB 7 Fe. Conversely, AB 7 Fe demonstrated superior retardation performance, more effectively slowing nuclide migration. After 1000 years, Cs and Sr concentrations in AB 7 Fe surpassed those in ZB 7 Fe. Additionally, nuclide migration increased with higher initiation pressure, dispersion, and diffusion coefficients. This research is crucial for improving the long-term safety of nuclear waste repositories.