Development of oxalate precipitation process for the partitioning of long-lived nuclides from the high level liquid waste

A new oxalate precipitation process was developed for separating the long-lived nuclides from high level liquid waste (HLLW). The process consists of oxalate precipitation, the dissolution of oxalate precipitate and the destruction of oxalate ion in the filtrate. The oxalate precipitation was carried out by the addition of oxalic acid to a simulated solution at room temperature. A precipitation condition was first designed by an inactive test followed by Am precipitation. The resulting oxalate slurry was filtered to obtain the oxalate precipitate and the filtrate. The oxalate precipitate was then dissolved by nitric acid at 90 degrees C and the resulting solution was treated with H2O2. The optimum conditions for the complete partitioning of Nd and Am in an oxalate form from the simulated solution were 0.5 M of nitric acid and 0.5 M of oxalic acid. H2O2 was not appropriate for the destruction of oxalate ion in the filtrate because hydrogen peroxide was explosively decomposed by transition elements such as Ru and Fe in the filtrate. The problem has been solved by the semi-batch feeding of H2O2 into the filtrate.