Thermal gradient migration of brine inclusions in salt

An apparatus was used to measure velocities of inclusions in synthetic single crystals (NaCl and Kcl) and in natural rock salt under various conditions of temperature gradient and uniaxial stress. The migration velocities of the inclusions were found to be dependent on temperature, temperature gradient, and inclusion shape and size. The velocities were also dictated by the interfacial mass transfer resistance at the brine/solid interface. This interfacial resistance depends on the dislocation density in the crystal, which, in turn, depends on the axial compressive loading of the crystal. At low axial loads, the dependence between the velocity and temperature gradient is non-linear. At high axial loads the interfacial resistance is reduced and the migration velocity depends linearly on the temperature gradient. Intragranular inclusions move under the influence of the temperature gradient only as far as the boundary of the grain in which they are contained. At the grain boundary, the migrating inclusions are trapped and deliver their brine and their volume to the interconnected porosity. VAPMIG, which combines brine inclusion migration and vapor transport and bulk diffusion in interconnected porosity, has been developed to predict the release of water and brine to a drillhole in rock salt heated by nuclear wastes