Alternative Solvent Wash Process Using Tetramethylammonium Hydroxide Solution as Salt-Free Wash Reagent

Abstract

A solvent wash procedure employing tetramethylammonium hydroxide (TMAH) as an alternative to sodium carbonate was investigated in order to minimize the volume of radioactive waste resulting from solvent regeneration in the Purex process. The wash efficiency of tetramethylammonium base solutions was measured in comparison with sodium carbonate solution on a 30% TBP-70% dodecane mixture containing zirconium-dibutyl phosphate complex. The experimental evidence showed tetrametylammonium base solutions to be as effective as sodium carbonate solution. In particular, addition of oxalic acid which complexes strongly with zirconium enhanced the wash efficiency. The 31P NMR spectra of dibutyl phosphate (DBP) indicated that the cleanup of DBP depended mainly on ionization of DBP. As tetrametylammonium hydroxide can be decomposed by heating at about 200°C, it is considered to have good applicability as a salt-free wash reagent. © 1989, Atomic Energy Society of Japan. All rights reserved.