Dynamic stabilization of heat-generating liquid waste plume in a sloping aquifer

Contaminant transport by groundwater in a sloping aquifer is considered in the case when contaminant plume has a salinity (and density) different from that of the groundwater, and is heat generating. Forced convection is present due to regional groundwater flow and natural convection is also expected to develop due to concentration differences and thermal changes. Such a situation takes place in deep-well disposal of liquid radioactive waste, in which the heat generation is caused by the radioactive decay. Flow and contaminant transport in the aquifer were calculated in 2D approximation in the plane of the aquifer, and the process of heat conduction in confining rocks was described by a 3D model. The set of equations governing flow, heat and mass transfer in the system was solved numerically with use of finite differences technique. Accuracy of numerical solution was checked by comparison with an original analytical solution of the flow problem for concentration-driven convection. It was shown that the influence of the natural convection component could cause acceleration as well as slowing down of the contaminant plume movement depending on system parameters. Results of numerical solution were approximated by a dimensionless analytical expression, which can be used for estimation of the relative impact of different driving forces exerting influence on the contaminant plume movement.