Monte Carlo simulation study of the effects of acidity and LET on the primary free-radical and molecular yields of water radiolysis - Application to the Fricke dosimeter
Monte Carlo simulation study of the effects of acidity and LET on the primary free-radical and molecular yields of water radiolysis - Application to the Fricke dosimeter
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DOI：
10.1139/v07-021
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发表时间：
2007-03-01
影响因子：
1.1
通讯作者：
Jay-Gerin, Jean-Paul
中科院分区：
文献类型：
--
作者：
Autsavapromporn, Narongchai;Meesungnoen, Jintana;Jay-Gerin, Jean-Paul
蒙特卡罗模拟用于研究酸度 (pH) 对从中性溶液到 0.4 mol/L H2SO4 范围内的脱气硫酸水溶液辐射分解中产生的各种化学物质的初级产率的影响。还研究了以线性能量转移 (LET) 衡量的辐射质量的影响，在环境温度下，LET 的变化范围约为 0.3 至 15 keV/μm。我们的结果表明，酸度增加 ( 1 < pH < 4) 会导致 G(eaq)(+H)(-) 产量增加。 “还原”自由基（水合电子和 H 中心点原子）的增加，G（中心点 OH）和 G（H2O2）略有增加，而 G（H2）略有减少。当pH < 1时，(OH)-O-中心点自由基与HSO4-阴离子反应形成SO4中心点自由基，导致G(中心点OH)急剧下降。相比之下，在 pH 值约为 4 至 7 的范围内，计算出的产率值与硫酸浓度无关。在中性水和 0.4 mol/L H2SO4 (pH 0.46) 溶液中，当 LET 增加到大约 15 keV/μm 时，初级分子产率增加，同时自由基的产率减少。作为例外，G（H 中心点）首先随 LET 增加，在 6.5 keV/μ m 附近达到最大值，然后在更高的 LET 下急剧下降。所获得的结果通常与所研究的整个酸度和 LET 范围内的现有实验数据非常一致。最后，作为一个应用，我们模拟了硫酸亚铁溶液在曝气水溶液中的辐射诱导氧化。 0.4 mol/L H2SO4（弗里克剂量计）作为时间的函数，长达约 50 秒，并解决了 LET 对 25 摄氏度下产生的三价铁离子产率的影响。Fe3+ 离子的产生对自由基产率高度敏感，特别是 H 中心点原子（通过形成 HO2 中心点），导致 G(Fe3+) 随着 LET 的增加而显着下降。我们计算的 Fe3+ 离子产额值很好地再现了观察到的 G(Fe3+) 随辐射质量变化的总体趋势。
Monte Carlo simulations are used to investigate the effects of acidity ( pH) on the primary yields of various chemical species produced in the radiolysis of de-aerated aqueous sulfuric acid solutions over the range from neutral solution to 0.4 mol/L H2SO4. The effects of the quality of radiation, measured in terms of linear energy transfer ( LET), have also been studied for LET varying from similar to 0.3 to 15 keV/mu m at ambient temperature. Our results show that an increase in acidity ( 1 < pH < 4) leads to an increase in the yield G(eaq)(+H)(-). of the "reducing" free radicals ( hydrated electron and H-center dot atom) and a slight increase in G(center dot OH) and G(H2O2), while there is a slight decrease in G(H2). At pH < 1, (OH)-O-center dot radicals react with HSO4- anions to form SO4 center dot- radicals, resulting in a steep decrease in G(center dot OH). By contrast, in the range of pH from similar to 4 to 7, the calculated yield values are independent of sulfuric acid concentration. In both neutral water and 0.4 mol/L H2SO4 (pH 0.46) solutions, the primary molecular yields increase upon increasing LET to similar to 15 keV/mu m with a concomitant decrease in those of free radicals. As an exception, G(H center dot) at first increases with LET, reaching a maximum near 6.5 keV/mu m before decreasing steeply at higher LET. The results obtained are generally in good agreement with available experimental data over the whole acidity and LET ranges studied. Finally, as an application, we have simulated the radiation-induced oxidation of ferrous sulfate solutions in aerated aq. 0.4 mol/L H2SO4 (Fricke dosimeter) as a function of time up to similar to 50 s and addressed the effects of LET on the resulting ferric ion yield at 25 degrees C. The production of Fe3+ ions is highly sensitive to free-radical yields, especially H-center dot atoms ( via formation of HO2 center dot), resulting in a marked decline of G(Fe3+) with increasing LET. The general trend of the observed variation of G(Fe3+) with radiation quality is well reproduced by our computed Fe3+ ion yield values.