A study of thermally induced convection near a high‐level nuclear waste repository in partially saturated fractured tuff

Abstract

We present simple estimates for velocities of buoyancy‐driven flow of liquid and gas phases near a hypothetical high‐level nuclear waste repository in partially saturated, fractured tuff. These estimates indicate that gas phase convection could take place with appreciable velocity, of the order of 20 m/year, while liquid convection is expected to be very slow, of the order of 0.1 mm/year. Detailed numerical simulations using an “effective continuum” approximation to represent fracture effects confirm these estimates and demonstrate a sensitivity of gas convection to the strength of binary diffusion.