The radiolysis/hydrolysis test loop, located at theIdaho National Laboratory (INL), was designed to allowthe investigation of the possible impacts of radiolytic andhydrolytic degradation processes upon the efficacy of asolvent extraction process flowsheet. Recently researchersat the INL have studied the impacts of gamma radiolysison the Actinide Lanthanide Separation (ALSEP)extraction process. This process uses an organic solventconsisting of a neutral extractant, N,N,N’N’-tetra-2-ethylhexyl-diglycolamide (T2EHDGA) and an acidicextractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) dissolved in n-dodecane.The actinides and lanthanides are co-extracted fromrelatively high concentration nitric acid and the actinidesare selectively stripped from the loaded organic phaseusing a carboxylic acid buffered aminopolycarboxylicacid solution. In order to evaluate possible solventwashing approaches, a combination of 31P NMR andbatch contact experiments were performed on unirradiatedALSEP solvent, solvent containingoctylphosphonic acid, and ALSEP solvent irradiated inthe INL test loop in contact with 3.0 M nitric acid. Thedifferent solvent systems were examined in an attempt todetermine the relative importance of neutral products ofthe radiolytic degradation of the ALSEP solventcomponents. The results of these studies suggest thateither a sodium carbonate or ammonium carbonatesolvent wash would be effective for the removal of acidicimpurities from the ALSEP solvent.
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