14 MeV快中子照相准直屏蔽系统的设计与优化

基于强流氘氚中子源科学装置HINEG设计了一套快中子照相准直屏蔽系统。采用中子输运设计与安全评价软件系统SuperMC和ENDF/B-Ⅶ.0数据库计算了准直中子束的中子能谱及注量率、γ射线能谱及注量率、直射中子注量率与γ射线注量率比值（φ_d/φ_γ）、直射与散射中子注量率比值（φ_d/φ_s）、准直束中子注量率的不均匀度等特性参数，并采用MCNP5程序进行了对比验证。研究了准直屏蔽系统的内衬材料、尺寸等对特性参数的影响规律，并通过优化获取了最优设计方案。计算结果显示，在同等计算条件下，SuperMC计算结果与MCNP计算结果相对偏差小于1%，准直屏蔽系统的φ_d/φ_γ为50.1，φ_d/φ_s为5.7，在Φ30 cm视野范围内的中子注量率为4.80×10⁷ cm^-2•s^-1，其中直射中子注量率为4.09×10⁷ cm^-2•s^-1，中子注量率不均匀度为5.8%，满足快中子照相对准直束特性参数的要求。

Design and Optimization of Shielding Collimator System for 14 MeV Fast Neutron Radiography

A shielding collimator system of fast neutron radiography was designed based on High Intensity D-T Fusion Neutron Generator. The beam characteristic parameters of the shielding collimator system, including neutron energy spectrum and fluence rate, γ-ray energy spectrum and fluence rate, direct neutron fluence rate and gamma fluence rate ratio (φ_d/φ_γ), direct neutron fluence rate and scattered neutron fluence rate ratio (φ_d/φ_s) and neutron fluence rate uniformity were calculated by SuperMC code coupled with ENDF/B-Ⅶ.0 library, and the MCNP5 code was used to verify the results. The lining material and its thickness of the shielding collimator system were studied aiming to acquire the optimal design. The results show that the deviation between the calculated results of SuperMC and MCNP is less than 1% under the same condition, and theφ_d/φ_γ,φ_d/φ_s, the total neutron fluence rate withinΦ30 cm,φ_d and its uniformity are about 50.1, 57,4.80×10⁷ cm^-2•s^-1,4.09×10⁷ cm^-2•s^-1 and 5.8% respectively, which can meet the need of fast neutron radiography facility.