Calculations of nuclide migration in rock and porous media, penetrated by water

Some physical and mathematical models are given for migration of nuclides in rock and porous media penetrated by water. The cases considered are thermal convection due to the decay heat from radioactive sources and transport due to the hydraulic gradient connected with the geographic structure. The model for thermal convection is highly simplified but is conservative compared to the often made adiabatic assumption which limits convection effects to a region characterized by a high ratio between buoyant and viscous forces. The piezometric head and corresponding gradients are calculated by analytic methods. It is shown that the solutions are strongly dependent upon the variation of the permeability with depth. The special features of migration in cracks are studied. A computer program, MINUTE, was developed for numerical calculations. Times for transport of some important nuclides to the ground surface were calculated using appropriate input data for representative Swedish deposition sites. Error margins are discussed