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 (llLLW) 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 1.01.8 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 a 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 m effective ‘“barrier” for these nuclides’ retention in the waste solvent. 1NTRODUCTION PNC has been carrying out basic experiments for the purpose of separating actinides from I-ILLW since 1990, as a part of an effort to increase the fuel utilization efficiency and to widen the options for waste management in the. future~). Due to its high compatibility to the present PUREX process, PNC’S current strategy is to apply the general TRUEX process, originally developed by Horwitz, et al.2] to the actinides partitioning process.. The concept of an “Advanced reprocessing system” (Fig. 1) shows that the PUREX and TRUEX processes should be developed in parallel. The PUREX especially should be improved by focusing on lightening the load on the succeeding partitioning process. Generating simpler compositions with smaller amounts of HLLW is a major goal for improving the process. For this purpose, the methods using sodium-based reagents should be avoided, and Np should be co-extracted into the product Pu-streams in the Purex process. One 140