[en] The computer program GARD is being used to calculate the rate of movement of radionuclides from a proposed deep underground vault to the surface or near surface environment. The conceptual model represents a deep underground vault in igneous rock, and a system of fissures which connect the vault with the surface of the geologic formation. After a certain initial period (container integrity time), during which there is assumed to be no release, the radionuclides are assumed to be released from a vault within a certain time (leach time) and transported as dissolved species by groundwater. Important phenomena influencing their transport are convection, radioactive decay and physicochemical processes such as sorption, ion exchange and precipitation. From the material balance a set of partial differential equations has been formulated. Simultaneous solution of these equations by the Laplace transform technique leads to expressions for the discharge rates of radionuclide chains as a function of time and distance. (author)