The safety assessment for final disposal of spent nuclear fuel has to comprehensively address the stage when containment barriers have failed and when radionuclide releases occur to the surrounding groundwater at repository depth. Essential processes for estimating risk/dose related to this scenario involve the release of radionuclide from the spent fuel surfaces due to radio-lytic oxidative dissolution of the UO2-matrix, inte- raction between radionu-clides and geologic media as well as secondary phases, and formation of intrinsic actinide colloids. This report descri- bes the outcome of a workshop about these processes that were held at Rånäs Castle north of Stockholm 7-9/6-2010
