Predicting solute transport in fractured rocks- processes, models and some concerns

Abstract

Abstract Flow and solute transport in fractured crystalline rocks has gained increasing interest in the last decades because several countries plan to site final repositories for high level nuclear waste at large depths in rock formations. Water flow and solute transport by the seeping groundwater are slow and it is not possible to make experiments over the thousands of years and hundreds of meters of interest. Instead one has to rely on models that describe the processes and mechanisms that will be dominant over long times. It is found that most nuclides of interest are strongly retarded in relation to the water velocity because they enter the slightly porous rock matrix by molecular diffusion and sorb on the micropore surfaces in the rock matrix. One of the key questions is how large is the contact surface between the seeping water and the fractured rock.