目前所使用的累积因子是在无限大介质模型下计算得到的，与现实模型差异较大。为了提高累积因子在实际计算中的精度，基于Monte Carlo方法和圆柱模型对水中的γ射线吸收剂量累积因子随介质尺寸的变化进行了研究。结果显示：水中的累积因子值会随着圆柱半径的变大而先增大，后趋于稳定。其在趋于稳定值时对应的圆柱半径数值与能量和介质厚度无关，仅与点源和测量点到介质表面的距离有关。在累积因子达到稳定值之前，其大小随圆柱半径的变化较大，在一定自由程数范围内符合线性变化规律，并且随着介质厚度的增大，符合线性规律对应的自由程数范围也会增大。该研究可为使用点核积分方法进行屏蔽设计时分析计算误差提供参考。
Abstract
γ-Ray buildup factors calculated using an infinite medium model can differ greatly for actual finite models. The precision of the buildup factors used in the actual calculations is improved using Monte Carlo simulations to study the variation of the energy absorption buildup factors as a function of the medium size for water using a cylindrical model. The results show that as the cylinder radius increases, the buildup factors in water first increase up to a maximum. The corresponding radius values for the maximum buildup factors are not influenced by the γ-ray energy or the medium thickness, but are only related to the distance from the point source to the measured point on the medium surface. The differences between the buildup factors as the cylinder radius increases are larger than for the maximums, and the variation is linear for some mean free paths. As the medium thickness increases, the corresponding range of the mean free paths where the variation is linear also increases. This work provides a reference for analyzing calculational errors in shielding designs.
关键词
辐射防护 /
累积因子 /
介质尺寸 /
影响因素
Key words
radiation protection /
buildup factor /
medium size /
influence factors
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参考文献
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