Exposure buildup factors up to 40 mean free paths in ranging from 0. 015 MeV to 15 MeV photon energy were calculated by using the Monte Carlo simulation code EGS4 for light concrete used in certain nuclear power plant. The calculation took into account effect of bremsstrahlung, fluorescence and coherent (Rayleigh) scattering on the buildup factor. Then, the corresponding fitting parameters of the G-P fitting formula were presented by the geometrical progression approximation fitting formula. The method can get the γ shielding buildup factors for any shielding thickness of the concrete and any photon energy.%使用蒙特卡罗程序EGS4计算了光子能量范围0.015～15 MeV、屏蔽厚度达40个平均自由程的某核电厂中使用的轻混凝土的γ照射量积累因子,程序计算中考虑了轫致辐射、荧光效应和相干(瑞利)散射对积累因子的影响.使用G-P近似拟合公式对γ屏蔽积累因子计算结果进行拟合计算,给出了相应的积累因子G-P拟合公式的拟合参数.利用此方法可得到此种轻混凝土的任意光子能量和屏蔽厚度的γ屏蔽积累因子.
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