REMOVL OF ACTINIDE ELEMENTS FROM HIGH LEVEL RADIOACTIVE WASTE BY TRIALKYLPHOSPHINEOXIDE (TRPO)--CASCADE EXTRACTION VERIFICATION WITH SYNTHETIC HAW SOLUTION

The modified TRPO process for removing actinide elements from synthetic solution, which was taken from reprocessing of power reactor nuclear fuel, was verified by cascade experiment. Neptunium valence was adjusted in the process for improving neptunium removing efficiency. At 1 mol/L concentration of HNO3 of feed solution and after a few stages of extraction with 30% TRPO kerosene, over 99. 9% of Am, Pu, Np and U could be removed from HAW (high level radioactive waste) solution. The stripping of ac-tinides loaded in TRPO are accomplished by high concentration nitric acid, oxalic acid and sodium carbonate instead of amminocarboxylic complexing agents used in previous process. The actinides stripped were divided into three groups, which are Am + RE, Np + Pu, and U, and the cross contamination between them is small. Behaviours of F. P. elements are divided into three types which are not extracted, little extracted and extracted elements. The extracted elements are rare earth and Pd, Zr and Mo which are coextract-ed with actinides. The separation factor between actinides and other two types of F. P. elements will increase if more scrubbing sections are added in the process. The relative concentration profile of actinide elements and Tc in various stages as well as the distribution of actinides and F. P. elements in the process stream solutions are also presented.