Center for Radiation Chemistry Research, Idaho National Laboratory, 1955 N. Freemont Ave., Idaho Falls, 83415, USA.
Phys Chem Chem Phys. 2020 Nov 21;22(43):24978-24985. doi: 10.1039/d0cp04310a. Epub 2020 Oct 25.
To mitigate third phase formation in next generation used nuclear fuel reprocessing technologies, the addition of 1-octanol has been trialed. However, contradictory reports on the radiolytic effect of 1-octanol incorporation on separation ligand degradation need to be resolved. Here, 50 mM N,N,N',N'-tetraoctyldiglycolamide (TODGA) dissolved in n-dodecane was gamma irradiated in the presence and absence of 1-octanol (2.5-10 vol%) and a 3.0 M HNO aqueous phase. Radiation-induced TODGA degradation exhibited pseudo-first-order decay kinetics as a function of absorbed gamma dose for all investigated solution and solvent system formulations. The addition of 1-octanol afforded diametrically different effects on the rate of TODGA degradation depending on solvent system formulation. For organic-only irradiations, 1-octanol promoted TODGA degradation (d = 0.0057 kGy for zero 1-octanol present vs.∼0.0073 kGy for 7.5-10 vol%) attributed to a favourable hydrogen atom abstraction reaction free energy (-0.31 eV) and the ability of 1-octanol to access a higher yield of n-dodecane radical cation (RH˙) at sub-nanosecond timescales. This was rationalized by determination of the rate coefficient (k) for the reaction of 1-octanol with RH˙, k = (1.23 ± 0.07) × 10 M s. In contrast, irradiation in the presence of 1-octanol and a 3.0 M HNO aqueous phase afforded significant radioprotection (d = 0.0054 kGy for zero 1-octanol present vs.≤ 0.0044 kGy for >2.5 vol%) that increases with 1-octanol concentration, relative to the single phase, organic-only solutions. This effect was attributed to the extraction of sufficiently high concentrations of HNO and HO into the organic phase by TODGA and 1-octanol as adducts which interfere with the hydrogen atom abstraction process between the 1-octanol radical and TODGA. Our findings suggest that the addition of 1-octanol as a phase modifier will enhance the radiation robustness of TODGA-based separation technologies under envisioned solvent system conditions in the presence of aqueous HNO.
为了减轻下一代核燃料后处理技术中第三阶段的形成，已经尝试添加 1-辛醇。然而，关于 1-辛醇的加入对分离配体降解的辐射分解作用的矛盾报告需要解决。在这里，50 mM N，N，N'，N'-四辛基二甘醇酰胺（TODGA）溶解在正十二烷中，在存在和不存在 1-辛醇（2.5-10 体积%）的情况下用γ射线辐照，并在 3.0 M HNO 水相中。在所有研究的溶液和溶剂体系配方中，辐射诱导的 TODGA 降解表现出与吸收的γ剂量呈准一级衰减动力学。添加 1-辛醇对 TODGA 降解的速率产生了截然不同的影响，这取决于溶剂体系配方。对于仅有机的辐照，1-辛醇促进了 TODGA 的降解（对于零 1-辛醇存在，d = 0.0057 kGy，对于 7.5-10 体积%，约为 0.0073 kGy）归因于有利的氢原子提取反应自由能（-0.31 eV）和 1-辛醇在亚纳秒时间尺度内获得更高产率的正十二烷自由基阳离子（RH˙）的能力。这是通过确定 1-辛醇与 RH˙反应的速率系数（k）来合理化的，k =（1.23 ± 0.07）×10 M s。相比之下，在存在 1-辛醇和 3.0 M HNO 水相的情况下进行辐照会提供显着的辐射防护作用（对于零 1-辛醇存在，d = 0.0054 kGy，对于> 2.5 体积%，≤0.0044 kGy），与单相有机溶液相比，随着 1-辛醇浓度的增加而增加。这种效应归因于 TODGA 和 1-辛醇作为加合物将足够高浓度的 HNO 和 HO 萃取到有机相中，这干扰了 1-辛醇自由基和 TODGA 之间的氢原子提取过程。我们的发现表明，在存在水合 HNO 的情况下，作为相改性剂添加 1-辛醇将增强基于 TODGA 的分离技术在预期溶剂体系条件下的辐射稳定性。
