The mechanisms controlling the migration of uranium in crystalline rocks such as granites or granodiorites are insufficiently well understood to arrive at a quantitatively defensible safety case for deep disposal of radioactive waste. To help further our knowledge of the relevant processes, a controlled column experiment was undertaken using a disc of metallic (depleted) uranium as a source and granodiorite samples from a former candidate disposal site for spent uranium fuel, Sievi in Finland, as the host medium. The experiment ran for approximately 500 days. This report summarises efforts made to simulate the uranium migration observed during the experiment. The model was developed from blind predictions to an inverse model that attempted to reproduce the measured effluent data. In the absence of independently derived kinetic data for uranium precipitation and dissolution it is difficult to arrive at a truly unique solution. Nevertheless, the exercise has been instructive in highlighting the principal areas of uncertainty and the pit falls that await those seeking to represent far more complex hydrogeochemical systems than that investigated here.JRC.F.7-Energy systems evaluatio
