Influence of the Monovalent M Cation on the M2+xTh2-xNdx(C2O4)5 nH2O Solid Solution Domain

An optimized fuel cycle option for Generation III/IV systems could be co-management of the minor actinides in an integrated closed fuel cycle. This approach implies separating these actinides from the fission products, and then converting them to solid forms to re-fabricate fresh fuel. Oxalate compounds are well known for this purpose. Co-management process is based on the oxalic co-precipitation of An(IV) and An(III) in a mixed oxalate as, for example, the hexagonal phase, M+2+xAnIV2-xAnIIIx(C2O4)5 nH2O with M+ representing a singly-charged cation. A study of the Th-Nd-M+ hexagonal oxalate systems has been carried out in order to understand the charge compensation mechanisms implicated in the formation of mixed oxalates systems.