ModelMuse USGS MODFLOW 6.5 MT3DMS Near-Field Model for a Deep Geological Repository in Georgian Kaolin (White Clay)
A study of the hydraulic, advection, mass transfer, porosity, diffusion, and dispersion properties inside of a natural lens of Kaolin (white clay) in the state of Georgia as a potential location for a deep geological repository (DGR) was performed. Crushed clay rock engineered barriers were modeled to determine if spent nuclear fuel (SNF) could be contained for 10,000-y using ModelMuse and MODFLOW 6.5 software. At approximately 150 m depth a 20m x 10m x 10m concrete vault containing 675 vitrified spent nuclear fuel (SNF) rods inside of carbon steel canisters were simulated with a single rupture at the center of the vault’s bottom at step one (zero-y) for each contaminant’s model. Both engineered barriers of crushed clay rock (Collova-Oxfordian and Opalinus) were mixed homogenously with hexadecyl pyridinium. The SNF contaminants of iodine, neptunium, plutonium, uranium, and technetium were each modeled separately. For iodine, a metal organic framework (MOF) was emulated by modeling the removal of most of the iodine during the vitrification process. Above the crushed clay rock engineered barriers exist a natural shale rock; and, below the crushed clay rock engineered barriers resides a mud stone foundation of undefined depth. The model’s-colored visualization of the data showed the hydraulic head contours and the contaminant’s concentrations in 2-D and 3-D. Using a 30-m hydraulic gradient across the model with an injection well (simulated contaminant leaching) and an ejection well (simulated ground disturbance to ground water), a 10,000-y progression of the plume demonstrated that it would be feasible to build a DGR in clay rock and clay formations east of the Mississippi River. Each contaminant’s model demonstrated that the contaminant would not enter the ground water at concentrations greater than EPA’s Drinking Water Standards and Regulations. From this research, future studies can be made to further investigate the significance of other factors such as multiple ruptures; similar barriers; chemical and biological reactions with canister, rock, and clay variations; different pressures and temperatures; higher and lower PH; vitrification processes with extraction of contaminants; and technologies to increase the partition factors. Furthermore, factorial, or other robust engineering designs can show the most optimal (smallest plume migration) engineered material barriers beyond 10,000-y.
Author Bio
Mr. Weyant is a PhD CEE student at Old Dominion University (ODU) and currently works as a physical scientist for the Department of Energy (DOE) at Germantown HQ, Maryland. He earned a MS CEE at ODU and a BS Mathematics at Excelsior University. His professional experience stems from the Naval Nuclear Power Program (reactor panel operator), Penn E & R Consultants (Environmental Project Management), Department of Defense (health Physicist) and Department of Energy (Physical Scientist). His subject matter expertise covers radiological and chemical contaminant fate and transport for surface and groundwater modeling.
