Technischer Bericht NTB 80-05

A onedimensional radionuclide chain transport model is developed taking into account sorption, dispersion and arbitrary repository concentrations. For piecewise constant parameters a semianalytical solution can be written down when mass conservation is considered rigorously and flux conservation to a good approximation at the layer boundaries. The solution consists of a superposition of terms which are easily interpreted and is invariant under layer permutation and parameter scaling. A corresponding computer code RANCH has been developed. It's structure and some experience in numerical calculations are discussed. As an example the results of a three layer, four chain members calculation are given.