MICADO : model uncertainty for the mechanism of dissolution of spent fuel in nuclear waste repository

Direct geological disposal of spent fuel from nuclear energy production is a waste management strategy of many European member states. Disposal safety must be ensured for hundreds of thousands to millions of years. If one wants to put the highly radioactive used nuclear fuel within a thick-walled metallic canister directly into a repository, corrosion of the canister will occur and access of deep groundwater will eventually take place. What happens if deep groundwater comes into contact with the fuel? Research has been ongoing for more than 25 years to create a large experimental data base to simulate the long-term performance of the fuel. Furthermore, there has been a substantial effort to develop descriptive and predictive modeling procedures. The evaluation of the long term performance of the spent fuel relies on the development of theoretical and sometimes semiempirical models which can be combined with more general safety assessment models allowing repository barrier performance predictions for overall repository performance assessment (PA). The coordinated action MICADO assesses the uncertainties in models describing the dissolution processes of spent nuclear fuel in a repository for geological time periods. The objective is to find out whether international research has now provided sufficiently reliable models to assess the corrosion behaviour of spent fuel in groundwater and by this to contribute to answering the question whether the highly radioactive used fuel from nuclear reactors can be disposed of safely in a geological repository.