Reprocessing and Dissolution
Due to the various stages for the different fuel types, the ASGARD project will have different goals for the different fuels. However, in principle, the aim is to reach an understanding of the manufacturing and recycling of the different kind of fuels to a scientific level approaching that for oxide fuels. If, during the course of the project, decisions are taken for a selection of a specific fuel, the focus will shift towards the problems associated with that particular fuel. However, the research on the other types of fuel will continue although the effort will be reduced. The broad scope of ASGARD ensures that relevant knowledge is generated regardless of which of the fuel alternatives will be the dominating one in the future.
The oxide dissolution and separation strategy is a fairly mature process being dealt with and optimised in the FP7 ACSEPT project. New separation strategies have been tested on genuine spent fuel and the selected processes will be evaluated for industrial implementation. Whereas the above is valid for actinide oxide fuels, such as MOX and / or Minor Actinide containing MOX, the dissolution and separation issues for inert matrix fuels containing ceramic MgO or metallic molybdenum (Mo), has not been investigated coherently. The ASGARD project focuses therefore mainly on the Inert Matrix Fuels (IMF) with molybdenum or magnesium-oxide. It is of crucial importance to take into account the behaviour of the matrix elements in the dissolution and separation processes and to check their compatibility with the future vitrification (impact on the stability of the waste and amount of generated waste).
Results from carbide fuel production and reprocessing will provide an insight into the safest and most economical carbide fuel design and establish the safest way to process carbide fuel whilst minimizing waste production.
Concerning nitride fuels, the impact of carbon and oxygen impurities on the dissolution rate in nitric acid will be clarified. As data from the literature are ambiguous, these results will be of particular importance for industrial application of nitride fuels in Gen-IV systems. From the industrial perspective, an even more important result will be the ability to enrich N-15 at a sufficiently low cost, as well as to recover N-15 during the dissolution process. Considering that nitride fuels contain 5 weight percent nitrogen, a specific cost of 10 € per gram nitrogen consumed in the process is deemed to be acceptable. The feasibility of reaching this goal will depend on the required N-15 enrichment, the corresponding cost of enrichment, losses of N-15 in the fabrication process and the efficiency of N-15 recovery during dissolution. The ASGARD project will provide industrial objectives for the combined performance of these aspects.