Separation of U(VI) from Zr(IV) with tri-n-butyl phosphate (TBP) as the extractant by using an ejector mixer-settler

A solution of Tri-n-Butyl Phosphate (TBP) diluted with n-alkane diluents (1.1M) has been utilized as a versatile solvent for the reprocessing of thermal and fast reactor fuels (PUREX process) for the past several decades. TBP has also been employed in various separation processes such as separation of ²³³U from irradiated thorium by THOREX/Interim-23 process, for monazite processing, Zr/Hf separation, Nb/Ta separation etc. Earlier, preliminary studies such as dissolution and solvent extraction aspects were carried out with U-Zr and U-Pu-Zr alloy fuels in our laboratory. In the present study, TBP has been examined as the extractant to separate U (VI) from Zr (IV) from nitric acid medium. Continuous SX runs in counter-current mode were carried out with a U-Zr feed solution with 1.1M TBP/DD as the solvent by using an ejector mixer-settler (16 stage). Prior to the mixer-settler runs, the feed solution was prepared by dissolving U-6wt% Zr alloy in conc. nitric acid (~16M) in the presence of 0.05 M HF under reflux conditions. Required quantity of nitric acid was mixed with the above U-Zr solution to generate 3 liters of U-Zr feed solution containing ~102 gpl U (VI) and ~5.5 gplZr (IV) in 4M HNO₃