The impact of alternative spent fuel dissolution models on calculated releases from the EBS - some insights from the opalinus clay safety case

The impacts of uncertainties involving radionuclide release from spent fuel have been examined in the context of Swiss studies of a repository for spent fuel in Opalinus Clay. There are significant uncertainties in both the quantities of radionuclides available for rapid release (the IRF or instant release fraction) and the rate of long-term matrix dissolution. The reasons for these uncertainties are described and a range of cases for modelling both these processes are described. The impact of these alternative models on releases from the near field and on biosphere doses are evaluated for a repository in Opalinus Clay, to provide some insights regarding the relative importance of the uncertainties and to provide some guidance in relation to future research required. (authors)