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The radiolytic degradation of di-ethylhexyl-isobutyramide (DEHiBA) was examined by subjecting the compound to gamma irradiation, measuring the remaining concentration of the intact compound, identifying the degradation products and measuring uranium distribution ratios. The combined effects of radiation dose, contact with aqueous solutions of HNO 3 , and aeration were also examined. The DEHiBA displayed significant stability at doses up to 1000 kGy, undergoing a slow exponential concentration decrease that was accompanied by the appearance of multiple degradation products. The most abundant compounds that were formed by radiolysis resulted from cleavage of the C carbonyl-N and C ethylhexyl-N bonds, generating di-ethylhexylamine, and mono-ethylhexyl-isobutyramide. Acid contact did alter the radiolytic pathways, with acid favoring cleavage of the C carbonyl-N bond, while a more diverse array of compounds were formed in the absence of acid. Pulsed radiolysis experiments were also conducted, in which picosecond bursts of energetic electrons were used to irradiate solutions of dodecane containing DEHiBA; formation of the dodecane radical cation was implicated, which serially reacted with DEHiBA to form radical or radical cation species intermediate in the formation of the observed products. The 2 slow degradation kinetics suggests that DEHiBA possesses good potential for selective extraction of uranium in fuel cycle extraction operations.

The radiolytic degradation of three N,N-dialkyl amide ligands relevant to nuclear fuel reprocessing was studied. The degradation of these ligands: N,N di-2-ethyhexylbutyramide (DEHBA), N,N di-2-ethyhexylisobutyramide (DEHiBA) and N,N di-2-ethyhexyl-3-dimethylbutanamide (DEHDMBA) was examined to evaluate the effect of the structure on the formation of degradation products as well as to compare alpha induced degradation to gamma induced degradation. In situ alpha radiolysis by introduction of plutonium(iv) as the alpha source in the solution and ex situ gamma radiolysis with Co as the gamma source were compared. Upon identification of the main degradation products, a degradation scheme was proposed. The effects of radiation on the stability of Pu-monoamide complexes were discussed. Theoretical calculations were also performed to determine bond dissociation energy and estimate the relative strength of the bond in the molecule. The results show that neither the type of radiation (alpha vs. gamma) nor the structure modification (introduction of branching on the alkyl chain off the carbonyl carbon) of the molecule significantly impact the formation of degradation products under the conditions studied. Moreover, it was observed that the overall stability of the monoamide remains good and that Pu complexation is not greatly affected by either alpha or gamma irradiation.

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This study reports the gas phase complexation behavior of Pu(IV) with N,N-dialkylamide ligands and tributylphosphate by electrospray ionization mass spectrometry. In-source collision induced dissociation (CID) and ion trap collision induced dissociation were used to investigate the kinetic stability of Pu species in the gas phase. With both class of ligands, N,N-dialkylamide and trialkylphosphate, oxidation of Pu from the tetravalent state to the hexavalent state was observed at both high skimmer voltages and during ion trap CID. The results suggest that oxidation is due to the presence of a nitrate group in the coordination sphere of the metal and is independent of the ligand.

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