冷中子三轴谱仪屏蔽体的蒙特卡罗模拟

Monte-Carlo Simulation for Shielding of Cold Neutron Triple-axis Spectrometer

冷中子三轴谱仪(CTAS)的屏蔽体对于保障工作人员安全、降低散射大厅本底及提高信噪比具有重要的意义。采用蒙特卡罗程序MCNP5对谱仪各部分屏蔽体进行了计算,并结合Mcstas程序确定了CTAS入口处的中子源,大大提高了计算效率。经过模拟计算和优化表明:单色器后端使用厚350mm、密度4.6 g/cm3的重混凝土,衔接屏蔽体使用厚300 mm、密度3.6 g/cm3的重混凝土,生物屏蔽采用厚150 mm、密度3.6 g/cm3的重混凝土可保证屏蔽体外表面的剂量率满足散射大厅的剂量要求。

The shielding of Cold neutron Triple-Axis Spectrometer（CTAS ） is important for radiation safety of workers, and reduce the background of scattering hall as well as enhancing the ratio of signal-to-noise. In this study, Monte-Carlo simulation was performed to conduct the calculation on the shielding of CTAS. To increase the calculation efficiency, neutron source was obtained by using Mcstas code. The results indicate that, in the case of heavy concrete （ density 4.6 g/cm3） with thickness of 350 mm for the shielding behind the monochromater, and heavy concrete （density 3.6 g/cm3） with thickness of 300 mm for the other monochromater shielding, as well as the heavy concrete （density 3.6 g/cm3） with thickness of 150 mm for biological shielding, the dose rate outside shielding may meet the requirement of national standard of China.