[en] A mathematical model is developed to describe the spatial and temporal distributions of radionuclides released from solid wastes dumped on a sea bed. It takes into account the field tested dependence of horizontal eddy diffusion coefficients by the '4/3 power law' and the geochemical mean residence times of these elements in oceans. Since ocean dimensions cannot be considered infinite except for very short lived nuclides (a few months), the reflections of nuclides at the boundaries and the consequent effects on the overall concentrations have been assessed. The computations indicate that the entire activity is confined to the ocean dimensions, and the integral mean concentration value over the entire depth approaches the well-mixed value at large times. The effect of using the geochemical residence time concept leads to much lower concentration levels in waters for transuranic nuclides such as ²³⁹Pu because of the much shorter geochemical residence times compared to the physical half-lives; in contrast for the majority of the other nuclides, the governing factor is essentially the radioactive decay only. (author)