FARF31 - a far field radionuclide migration code for use with the PROPER package

The far field radionuclide migration computer code FARF31 has been developed as a submodel to the probabilistic package PROPER, and can be considered a refined and less CPU-time consuming version of the far field models used in the KBS-3 study. FARF31 constitutes the numerical equivalent of a dual porosity model for radionuclide migration along a stream tube in fractured rock. It calculates the migration rate of the radionuclide chains at the exit of the tube given the input rates at the entrance. Advection, dispersion and one dimensional matrix diffusion is taken into account as well as chain decay. The underlying equations are formulated in terms of groundwater travel time and Peclet number, thus allowing for the groundwater travel time to be computed outside FARF31 by a separate submodel fitted to handle Darcy velocities and kinematic porosities which vary in space. Input migration rate boundary conditions are arbitrary. (authors)