Subsurface transport modelling of long-lived nuclides

The behaviour of radionuclides with very long half-life (129I,99Tc,226Ra) was examined in the subsurface environment of a Hungarian low and intermediate level shallowland waste repository. Previous measurements of water levels, conductivity distribution, saturation, tritium content and other parameters of ground water have been conducted for hydrological characterisation of the site. Migration in clayey media has been assessed based on these measurements and on calculated hydrological data of the groundwater flow. Subsurface transport has been followed from the repository to two nearby creeks through the unsaturated and saturated zones. How errors of model parameters influence the computed results in the case of subsurface transport, was also investigated.