Domnanich Katharina A, Severin Gregory W
Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.
National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, United States.
ACS Omega. 2022 Jul 12;7(29):25860-25873. doi: 10.1021/acsomega.2c03540. eCollection 2022 Jul 26.
At the Facility for Rare Isotope Beams (FRIB), interactions between heavy-ion beams and beam-dump water will create a wide variety of radionuclides which can be accessed by a technique known as "isotope harvesting". However, irradiation of water is always accompanied by the creation of numerous radical, ionic, and molecular radiolysis products. Some of the radiolysis products have sufficiently long lifetimes to accumulate in the irradiated water and affect the harvesting chemistry. Here we investigate the formation of hydrogen peroxide, molecular hydrogen, and molecular oxygen during a high-intensity proton irradiation of a flowing-water isotope-harvesting target and compare the experimental results to simulations. The simulations kinetically model the chemical reactions occurring in the homogeneous phase of radiolysis in flowing water and establish an "effective yield". In both the experiment and simulations, the bulk quantities of H, HO, and O are considerably lower than predicted by primary radiolysis yields (escape yields), meaning that in the high beam intensity regime the homogeneous phase reactions have a considerable impact on the overall chemical composition of the water. Further, it could be shown that for radiation which is characterized by a limited linear energy transfer, such as the here applied protons, the bulk outcome of the microscopic kinetic modeling could be estimated by a simplified steady-state model.
在稀有同位素束流装置（FRIB）中，重离子束与束流卸料水之间的相互作用会产生各种各样的放射性核素，这些核素可以通过一种称为“同位素采集”的技术获取。然而，水的辐照总是伴随着大量自由基、离子和分子辐射分解产物的产生。一些辐射分解产物具有足够长的寿命，能够在辐照水中积累并影响采集化学过程。在此，我们研究了流动水同位素采集靶在高强度质子辐照过程中过氧化氢、分子氢和分子氧的形成，并将实验结果与模拟结果进行比较。模拟对流动水中辐射分解均相阶段发生的化学反应进行动力学建模，并确定了一个“有效产额”。在实验和模拟中，H、HO和O的总量均远低于初级辐射分解产额（逃逸产额）的预测值，这意味着在高束流强度条件下，均相反应对水的整体化学成分有相当大的影响。此外，可以证明，对于以有限线能量转移为特征的辐射，如本文所应用的质子，微观动力学建模的总体结果可以通过一个简化的稳态模型来估算。
