Some modifications of the Truex flowsheet for partitioning of actinides elements in high level liquid waste

PNC has been promoting actinides partitioning studies as a part of advanced reprocessing system development efforts since 1990. Concurrently, the general TRUEX process was investigated as a reference partitioning tool. A concentrated high level liquid waste (HLLW) from LWR fuel reprocessing and a highly active raffinate (HAR) from FBR spent fuel PUREX experiments were nominated as target waste solutions. A mixed solvent composed of 0.2 M CMPO - 1.0 ∼ 1.8 M TBP in n-dodecane was tested as a TRUEX solvent. Counter-current tests aimed to improve the TRUEX process, using a real HAR generated from the PUREX process, were performed in the Chemical Processing Facility (CPF), Tokai Works. In these experiments, very high α decontamination with explainable extraction profiles of tri-valent actinides and rare earth elements were obtained, but some retentions of Pu and Ru in the organic phase was recognized as a major issue of the TRUEX process. In the current investigation, however, it was found that the conventional solvent regeneration step can be an effective barrier for these nuclides retention in the waste solvent. (authors)