Alpha and gamma radiolysis of nuclear solvent extraction ligands used for An(III) and Ln(III) separations

Effect of Metal Complexation on Diglycolamides Radiolysis: A Comparison between Ex-Situ Gamma and In-Situ Alpha Irradiation

Radiolytic degradation is an important aspect to consider when developping a ligand or a complexant for radionucleides. Diglycolamide extractants (DGAs) have been playing an important role in many partition processes...

Curium(iii) radiation-induced reaction kinetics in aqueous media

Insight into the effects of radiolytic processes on the actinides is critical for advancing our understanding of their solution chemistry because the behaviour of these elements cannot be easily separated from the influence of their inherent radiation field. However, minimal information exists on the radiation-induced redox behaviour of curium (Cm), a key trivalent transuranic element present in used nuclear fuel and frequently used as an alpha radiation source. Here we present a kinetic study on the aqueous redox reactions of Cm(iii) with radicals generated through the radiolysis of aqueous media. In particular, we probe reaction kinetics in nitric acid solutions that are used as the aqueous phase component of used nuclear fuel reprocessing solvent systems. Second-order rate coefficients (k) were measured for the reaction of Cm(iii) with the hydrated electron (e_aq^-, k = (1.25 ± 0.03) × 10¹⁰ M^-1 s^-1), hydrogen atom (H˙, k = (5.16 ± 0.37) × 10⁸ M^-1 s^-1), hydroxyl radical (˙OH, k = (1.69 ± 0.24) × 10⁹ M^-1 s^-1), and nitrate radical (NO₃˙, k = (4.83 ± 0.09) × 10⁷ M^-1 s^-1). Furthermore, the first-ever Cm(ii) absorption spectrum (300-700 nm) is also reported. These kinetic data dispel the status quo notion of Cm(iii) possessing little to no redox chemistry in aqueous solution, and suggest that the resulting Cm(ii) and Cm(iv) transients could exist in irradiated aqueous solutions and be available to undergo subsequent redox chemistry with other solutes.

A review of the alpha radiolysis of extractants for actinide lanthanide separation in spent nuclear fuel reprocessing

Radiation stability is one of the key properties to enable the efficient use of extractants in spent nuclear fuel with high radioactivity. The last several decades have witnessed a rapid progress in the radiation chemistry of extractants. A variety of studies and reviews pertinent to the radiation stability of extractants have been published. However, a thorough summary for the alpha radiolysis results of extractants is not available. In this review, we survey the development of alpha radiolysis of extractants for actinide lanthanide separation and compare their radiolysis behaviors induced by alpha particles and gamma rays. The discussion of alpha radiolysis of extractants is divided into three parts according to the functional groups of extractants (i.e., phosphine oxide, amide and bis-triazinyl bipyridines). Given the importance of radiation source to carry out alpha irradiation experiment, we first give a brief introduction to three practicable alpha radiation sources including alpha emitting isotopes, helium ion beam and reactor. We hope this review will provide useful information and unleash a broad palette of opportunities for researchers interested in radiation chemistry.

An experimental and computational look at the radiolytic degradation of TODGA and the effect on metal complexation

A combination of Fukui function calculations with experimental characterization gives an improved understanding of the behaviour of TODGA solutions after radiolysis.

Radiolytic stability of N,N-dialkyl amide: effect on Pu(iv) complexes in solution

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 ⁶⁰Co 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.