From the acquisition of basic data to the processes for the treatment of spent fuels

In the continuation of PYROREP (FP5), the pyrochemical domain of EUROPART (FP6) involves today seven European participants and two international partners in order to assess treatment processes which could be used in a broad variety of fuel cycles (MSR spent fuel, metallic, oxide, carbide or nitride fuels from any reactors). Indeed, a pyrochemical process is not sensitive to radiolysis, and obviously to temperature effects, and could afford to treat fuels after a short cooling period, even at high concentrations. Within EUROPART, the chemistry of actinides and of some fission products was studied in depth in either chloride or fluoride molten salts. Laboratory-scale demonstration experiments were used in order to assess electrolytic processes in molten chlorides and liquid-liquid reductive extraction in molten fluoride/liquid aluminium. An electrolysis process is also under development in molten fluoride. To complete the studies, the development of devices and the modelling of processes are taken into consideration. In order to be fitted for acceptance, a process has to produce minimal quantities of wastes, compatible with storage constraints. Therefore, decontamination techniques, as well as materials suitable for disposal, have to be developed. Fission products precipitation by carbonate and phosphate, and filtration on zeolites were studied. Some original confinement matrices such as sodalite or pollucite were also studied. Integration studies have been carried out in order to evaluate and to compare some selected process flow sheets and possibly to redirect R and D programmes. (authors)