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与传统的地雷探测技术相比,热中子分析(Thermal Neutron Analysis,简称TNA)探雷技术具有准确率高、虚警率低和对环境适应性强的特点,但探测速度较慢,制约了其广泛应用。为了提高地雷位置处的慢热中子通量,缩短探测时间,提出了一种基于252Cf的中子源慢化装置设计构型,主要包含中子慢化层、中子反射层、本底γ屏蔽层和侧向中子吸收层4个部分。采用数值模拟的方法比较了4种常用中子慢化(反射)材料的性能,优选高密度聚乙烯作为慢化材料,石墨作为反射材料。同时,为了满足辐射安全要求,对屏蔽材料的结构进行了优化计算。按照设计构型搭建了TNA探雷实验平台。在104n/s中子源强下优化了慢化层和反射层的厚度,测试了装置慢化效能,在107n/s中子源强下评估了装置辐射安全性能。结果表明,采用该装置可使地雷位置处的慢热中子通量提升11倍以上,并能有效保障辐射安全。
Compared with the traditional landmine detection technology, thermal Neutron Analysis (TNA) detection technology has the characteristics of high accuracy, low false alarm rate and good adaptability to the environment. However, the detection speed is slower and restricts Its wide range of applications. In order to improve the slow thermal neutron flux at the mine site and shorten the detection time, a design scheme of 252Cf-based neutron source moderator is proposed, which mainly includes neutron moderator, neutron reflector and background γ Shielding and lateral neutron absorption layer 4 parts. The performance of four commonly used neutron moderating (reflecting) materials is compared by numerical simulation. High density polyethylene is preferred as the moderating material and graphite as the reflecting material. Meanwhile, in order to meet the radiation safety requirements, the structure of the shielding material has been optimized and calculated. According to the design configuration TNA mine detection platform. The thickness of the moderator layer and the reflector layer were optimized under the 104n / s neutron source intensity. The device moderation effectiveness was tested. The radiation safety performance of the device was evaluated under a 107n / s neutron source intensity. The results show that using this device can increase the slow thermal neutron flux at the mine site by more than 11 times and effectively ensure the radiation safety.