Temperature dependence of the Fricke dosimeter and spur expansion time in the low-LET high-temperature radiolysis of water up to 350C; A Monte-Carlo simulation study

フリッケ線量計の低LET放射線分解のモンテカルロ計算による水分解におけるスパー拡散時間の評価

Sanguanmith, S.*; 室屋 裕佐*; Tippayamontri, T.*; Meesungnoen, J.*; Lin, M.; 勝村 庸介*; Jay-Gerin, J.-P.*

Sanguanmith, S.*; Muroya, Yusa*; Tippayamontri, T.*; Meesungnoen, J.*; Lin, M.; Katsumura, Yosuke*; Jay-Gerin, J.-P.*

硫酸第一鉄水溶液(フリッケ線量計)の低LET放射線分解のモンテカルロ計算を25から350Cの温度範囲で実施した。Feの酸化の予測量は温度上昇に従い、100-150Cまでは増加し、それ以上の温度ではほぼ一定になり、実験報告と良い一致を示した。また、G(Fe)の温度依存性は水分解の初期収量、特にH原子の収量、を反映するが、200-250C以上ではH原子の水分子との反応の寄与がさらに顕著となり、この反応速度定数の選択によってG(Fe)が増減した。

Monte-Carlo simulations of the radiolysis of the ferrous sulfate (Fricke) dosimeter with low-linear energy transfer (LET) radiation have been performed as a function of temperature from 25 to 350C. The predicted yields of Fe oxidation are found to increase with increasing temperature up to 100-150C, and then tend to remain essentially constant at higher temperatures, in very good agreement with experiment. Moreover, the observed dependence of G(Fe) 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 200-250C, the more and more pronounced intervention of the reaction of H atoms with water also contributes to the variation of G(Fe), which may decrease or increase slightly, depending on the choice made for the rate constant of this reaction.