Temperature dependence of the Fricke dosimeter and spur expansion time in the low-LET high-temperature radiolysis of water up to 350°C: A Monte-Carlo simulation study
Temperature dependence of the Fricke dosimeter and spur expansion time in the low-LET high-temperature radiolysis of water up to 350°C: A Monte-Carlo simulation study
复制标题
在高达 350°C 的低 LET 高温水辐射分解中，Fricke 剂量计和杂散膨胀时间的温度依赖性：蒙特卡罗模拟研究
DOI：
10.1039/c1cp20293f
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
Y. Katsumura and J-P. Jay-Gerin
中科院分区：
文献类型：
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作者：
S. Sanguanmith;Y. Muroya;T. Tippayamontri;J. Meesungnoen;M. Lin;Y. Katsumura and J-P. Jay-Gerin
利用低线性能量传递（LET）辐射（如60Co γ射线或快速电子）对硫酸亚铁（Fricke）剂量计进行了蒙特卡罗模拟，并将其作为温度从25°C到350°C的函数。Fe2+氧化的预测产率随着温度的升高而增加，达到~ 100-150℃，然后在更高的温度下趋于基本保持不变，与实验结果非常吻合。利用直接应用得到的铁离子产率G（Fe3+）与和{3 [G（e−aq + H˙）+ G（HO2˙）]+ G（˙OH） + 2g (H2O2)}之间的化学测量关系的简单方法，其中G（e−aq + H˙）、G（HO2˙）、G（˙OH）和G（H2O2）是脱氧后0.4 M H2SO4水溶液辐射分解的主要自由基和分子产率，并确定了其寿命τs及其温度依赖性。在马刺模型的精神中，τs是重叠马刺的重要指标，给出了体溶液中从非均匀马刺动力学到均匀动力学转变所需的时间。计算表明，在25 ~ 350℃的温度范围内，τs减小了约一个数量级，从25℃时的~ 4.2 × 10−7 s减小到350℃时的~ 5.7 × 10−8 s。τs随温度升高而减小主要是由于所涉及的单个物种的扩散速度加快所致。此外，G（Fe3+）对温度的依赖性在很大程度上反映了温度对辐射分解初级自由基产率的影响，特别是对H˙原子产率的影响。在~ 200 ~ 250℃以上，H˙原子与水的反应越来越明显的干预也导致了G（Fe3+）的变化，根据反应速率常数的选择，G（Fe3+）可能会略微减少或增加。本文报告的所有计算都使用Elliot（加拿大原子能有限公司）和Bartels（圣母大学）的放射性分解数据库，该数据库包含了目前在20至350°C范围内有关速率常数、反应机制和g值的所有最佳信息。
Monte-Carlo simulations of the radiolysis of the ferrous sulfate (Fricke) dosimeter with low-linear energy transfer (LET) radiation (such as 60Co γ-rays or fast electrons) have been performed as a function of temperature from 25 to 350 °C. The predicted yields of Fe2+ oxidation are found to increase with increasing temperature up to ∼100–150 °C, and then tend to remain essentially constant at higher temperatures, in very good agreement with experiment. By using a simple method based on the direct application of the stoichiometric relationship that exists between the ferric ion yields so obtained G(Fe3+) and the sum {3 [g(e−aq + H˙) + g(HO2˙)] + g(˙OH) + 2 g(H2O2)}, where g(e−aq + H˙), g(HO2˙), g(˙OH), and g(H2O2) are the primary radical and molecular yields of the radiolysis of deaerated 0.4 M H2SO4 aqueous solutions, the lifetime (τs) of the spur and its temperature dependence have been determined. In the spirit of the spur model, τs is an important indicator for overlapping spurs, giving the time required for the changeover from nonhomogeneous spur kinetics to homogeneous kinetics in the bulk solution. The calculations show that τs decreases by about an order of magnitude over the 25–350 °C temperature range, going from ∼4.2 × 10−7 s at 25 °C to ∼5.7 × 10−8 s at 350 °C. This decrease in τs with increasing temperature mainly originates from the quicker diffusion of the individual species involved. Moreover, the observed dependence of G(Fe3+) on temperature largely reflects the influence of temperature upon the primary free-radical product yields of the radiolysis, especially the yield of H˙ atoms. Above ∼200–250 °C, the more and more pronounced intervention of the reaction of H˙ atoms with water also contributes to the variation of G(Fe3+), which may decrease or increase slightly, depending on the choice made for the rate constant of this reaction. All calculations reported herein use the radiolysis database of Elliot (Atomic Energy of Canada Limited) and Bartels (University of Notre Dame) that contains all the best currently available information on the rate constants, reaction mechanisms, and g-values in the range 20 to 350 °C.