摘要: 中子照相是一种重要的无损检测技术，它能用于火工产品、毒品和核燃料元件等的检测。基于紧凑型D-T中子发生器，完成了一个用于快中子照相的准直屏蔽体系统（BSA）的物理设计。根据D-T中子源的能谱和角分布建立了中子源模型，采用MCNP4C蒙特卡罗程序，模拟了准直屏蔽体系统中中子和γ射线的输运，准直中子束相对于单位源中子的中子注量可以达到9.30×10^-6 cm^-2，准直中子束中主要是能量大于10 MeV的快中子；在设置的样品平面直径14 cm的照射视野范围，准直束中子注量的不均匀度为4.30%，准直束中中子注量与γ注量的比值为17.20，中子通量和中子注量比值J/Φ为0.992，说明准直中子束有好的平行性；准直屏蔽体外的泄露中子注量率与准直束中子注量率相比降低了2个量级。所设计的准直屏蔽体能满足快中子照相的要求。


Neutron radiography is an important nondestructive testing technique. It can be used to detect the explosive devices, drug and the nuclear fuel element, etc. A beam-shaping-assembly (BSA) based on a compact D-T neutron generator is designed for fast neutron radiography in this paper. D-T neutron source model is constructed based on the neutron energy spectrum and angular distribution data. The transportation of neutron and γ-ray in the BSA is simulated using MCNP4C code. The neutron fluence of the collimated neutron beam with respect to the neutron source of the unit source is 9.30×10^-6 cm^-2. The collimated neutron beams is mainly fast neutrons with energies greater than 10 MeV. In the irradiation field range with a diameter of 14 cm, the neutron fluence uniformity of the collimated beam is 4.3%, the ratio of the neutron fluence to the gamma fluence in the collimated beam is 17.20, and the neutron flux and the neutron fluence ratio (J/Φ) is 0.992 which indicates that the collimated neutron beam has good parallelism. The leakage neutron fluence in outside of BSA is two orders of magnitude lower than that of the collimated neutron beam. The designed BSA can meet the need of fast neutron radiography.