Development and demonstration of innovative partitioning processes (i-SANEX and 1-cycle SANEX) for actinide partitioning

• We report the development of two new actinide separation processes.
• A selective separation of trivalent actinides from PUREX raffinate was demonstrated.
• SO3-Ph-BTP shows a very high selectivity towards trivalent Actinides.
• Very high recovery of An(III) from PUREX raffinate was achieved.

Two full continuous countercurrent processes for the recovery of trivalent actinides (An(III)) from a simulated PUREX raffinate solution (HAR) were developed and demonstrated using miniature laboratory-scale centrifugal contactors: the innovative SANEX and the 1-cycle SANEX processes. The innovative SANEX process was successfully demonstrated in a 16 + 16 stage flow sheet. In the first 16 stages, Am(III), Cm(III), and Ln(III) were quantitatively co-extracted from the HAR by a TODGA-based extractant. The decontamination factors (DFs) for the major non-lanthanide fission products were >103. The loaded extractant was then subjected to two stripping steps using the second 16 stages of the flow sheet. The first stripping step concerned the selective stripping of Am(III) + Cm(III) at fairly high acidity (0.35 ML−1 HNO3) with the new hydrophilic N-chelating selective ligand SO3-Ph-BTP. High An(III) recoveries >99.8% were achieved with high decontamination factors toward the trivalent lanthanides. In the second step, the residual stripping of Ln(III) from loaded organic phase was carried out quantitatively using 0.5 ML−1 citric acid solution at pH 3. However, Ru proved to be the only exception and remained to a large extent (12.8%) in the spent extractant. A more challenging route also studied at our laboratories is the 1-cycle SANEX process, i.e. direct An(III) separation from HAR using an extractant mixture of CyMe4BTBP and TODGA in 1-octanol/TPH diluent. A demonstration process was also successfully implemented using a 16 + 16 stage flow sheet on the above-mentioned laboratory-scale centrifugal contactor rig. It was demonstrated that a selective extraction and high recovery of >99.8% of Am(III) and >99.4% Cm(III) was achieved with low contamination of fission products. Both new processes are major contributions to the field of partitioning and important steps forward toward the industrial implementation of MA partitioning.