In aqueous reprocessing, SACSESS will work at optimising the chemical systems selected within ACSEPT. For each chemical system, parameters involved in safety case analysis will be studied, such as radiolytic solvent stability, solvent clean-up, management of the secondary wastes, physico-chemical solvent stability, loading capacity and kinetics. 

The behaviour of the extractants, complexants, diluents all together (solvent stability) will be studied in process conditions, but also out of these operation ranges (mal-operation) in order to identify the weak points and find solutions to assess the safety of the processes. 

The work will be organised by chemical systems selected for each tested process options, including, when accurate, the alternative system. Furthermore, a list of transversal key issues has been established.

The simulation of these systems will be developed from the chemistry to the process, allowing a better and safer management of the plant in the longer term. This includes multiscale modelling, radiolysis modelling and process modelling. In addition, new online monitoring techniques will be developed, allowing a fine tuning of the plant operation parameters.

In parallel, an alternative process to those already developed will be studied, allowing the partitioning of americium alone, reducing the hazards related to the handling of curium in fuel for enhanced safety. As far as possible, the most promising systems already identified will be adapted to meet the requirements of such a process and optimised.

All the new generated data will be integrated thanks to flowsheeting and system studies to allow a feedback to the R&D programme and an assessment of the global safety of the designed processes.

In pyrochemistry, SACSESS will focus on the recovery of minor actinides from metallic fuels and inert matrix transmutation targets. Within ACSEPT and former European projects, two processes were identified and further developed at the lab scale (the electrorefining process on aluminium and the liquid-liquid reductive extraction process in molten fluoride/liquid aluminium). Specific salt treatment for recycling and waste conditioning were also proposed.

However, at this stage, some safety issues have to be addressed. The first ones are those related to the use of molten salts and liquid metals at high temperature.          The physico-chemical behaviour that impacts the chemical safety (solubility, volatility, influence of oxygen ingress, heat capacity, viscosity, etc) both in chloride and in fluoride will be studied. Online monitoring development will be continued.

In addition, parameters that can impact the safety will be identified and studied. This includes risks of accumulation of an element in liquid or solid phase, of precipitation, of formation of volatile species… Molten salt modelling will also be developed, first to help to calculate physico-chemical parameters and reduce the number of necessary complex experiments and second, to develop the modelling of pyrochemical processes in the longer term.

The conditioning of the used molten salts (chloride and fluoride) and/or or other process chemicals (metals…) into waste streams suitable for a safe storage/repository will also be considered, including the impact of matrix material.

 With the above studies, being driven by safety considerations, a specific domain will be dedicated to global safety and integration whereby safety case studies will be performed on each process concept to identify the weak points in order to give feedback and reorient the experimental program. Integration studies will gather all the results to deliver optimised process flowsheets.

With the help of TSOs and with feedback from safety analyses, specific methodologies will be developed and applied to these processes in order to identify safety issues and then to optimise these processes. In addition, all the results will be integrated to optimise the flowsheets, to perform system studies and will ensure the link with other projects and initiatives to ensure the relevance of the SACSESS research programme.