Partitioning of minor actinides from HLLW using the DIAMEX process. Part 2- "Hot" continuous counter-current experiment

Among several processes proposed world-wide, the French DIAMEX (DIAMide EXt raction) process seems to be very efficient for the removal of Minor Actini des (MA) from genuine High Level Liquid Waste (HLLW). The MA are in this pr ocess directly extracted from the PUREX (Plutonium Uranium Redox EXtraction ) raffinate together with fission lanthanides using the completely combusti ble diamide extractant. In this work a hot demonstration of the DIAMEX proc ess using genuine high-level PUREX raffinate is reported. The continuous co unter-current experiment was carried out in a 16 stage centrifugal extracto r battery, installed in a hot cell. In order to produce a representative HL LW a PUREX process was applied on dissolved fuel using the same equipment. In the DIAMEX process up to 6 extraction stages were sufficient to achieve feed decontamination factors between 100 and 230 for lanthanides and above 300 for minor actinides. Go-extraction of molybdenum and zirconium were eff iciently prevented using oxalic acid scrubbing. The back extraction proved to be very efficient, yielding in 4 stages more than 99.9 % recovery of bot h the lanthanides and the actinides. Go-extracted ruthenium, technetium, pa lladium and neptunium are less efficiently back-extracted requiring further process development.