Chemical durability and performance of assessment of spent fuel and high level waste forms under simulated repository conditions - Spanish contribution to IAEA project

Chemical durability of spent fuel under repository conditions is one of the main topics of interest in national and international projects from the last two decades. During the last decade there have been growing the activities in Enresa related to the deep disposal concept with the aim of developing a spent fuel alteration model for the understanding of the behaviour of this nuclear waste under repository conditions. In this context, the development and utilisation of models and sub-models based on experimental work have been of great importance. Experimental studies with spent fuel(in Collaboration Agreement with ITU) and spent fuel analogues in several environmental conditions have been carried out into Enresa R+D Programmes in order to reach a better knowledge of the relevant processes and to quantify the spent fuel chemical durability under repository conditions. In this work, it is showed the utility of data provided from experiments with spent fuel analogues to test the mechanisms and the influence of relevant parameters in the spent fuel alteration under repository conditions. The evolution of irradiated fuel under interim storage conditions and in deep geologic storage and its oxygen to metal ratio (O/M) before the water access to the fuel is another factor of great influence on enhanced spent fuel leaching. This effect has been also studied by means of spent fuel analogues and by using simulated (artificially) aged fuel. (author)