NAMMU was used to study the effects of the brine transported by groundwater outside an old salt mine which serves as a repository for the disposal of radioactive wastes, with a 2D model. The approach used combined a two-dimensional grid peclet number criteria with the two-parameter formulation and the parameter-stepping
technique of NAMMU.

The modelling results showed that, as a result of the higher density
saline groundwater in the deep hydrostratigraphic units, vertical groundwater velocities are up to two orders of magnitude lower than those predicted by constant-density freshwater calculations.

The gravitational forces on the variable-density fluid lead to the formation of convection cells and to significant changes in the flow direction in the salt-water calculations. The consequences of these results are that, due to the coupled groundwater flow and brine transport any contaminant leaving the repository would follow formerly unexpected pathways and would experience longer travel times, which is beneficial for the long-term safety of the repository.