交替多层分布中子流屏障构建与中子流屏蔽特性及相关机理研究

The structurally optimized design of the composites is an effective method and important trends to enhance the shielding performance of the composites for radiation. Recently, the shielding composites for the neutron radiation are designed as a three-layered structure. However, the composites have the limited layer number and poor protection efficiency, and it also cannot effectively protect secondary radiation induced by neutron. Moreover, the attenuation law of the neutron flux in the layered composites is unclear so that the theoretical development of the neutron radiation shielding is limited. The composites are designed as the multi-layered and alternating distribution structure through co-extrusion, and the thickness and layer number of the composites are flexible and controllable. The neutron flux and secondary radiation induced by neutron flux are multiple scattered, decayed and absorbed between the alternating multilayered interfaces of the composites. Eventually, the harmful rays dissipate between the multilayered interfaces. In order to reveal the radiation shielding mechanism of the alternating multilayered composites, the influence of the ratio of the thickness between adjacent layers, layer numbers, the filler loading and its dispersion state on the performance of radiation shielding are investigated. Meanwhile, the structure and properties of the polymer matrix of the multi-layered composites are also investigated so as to reveal neutron flux attenuation law. The completion of the research will provide a new thought for designing and fabricating shielding composites with high performance, multifunction and play a very significant role in both academic and industrial fields.

中子辐射作为核辐射的主要射线之一，对人体健康的损害极为严重。已有的工作将防中子辐射复合材料设计为三层结构，但其层数有限，防护效率有待提高，且不能有效防护中子流引发的次级放射，中子流在层状复合材料中的衰减规律尚不清楚。本项目用共挤的方法，将防中子流辐射和 X、伽马射线辐射有机结合起来，并将其设计为交替多层分布结构，保证总厚度不变的情况下，层数达成百上千层。中子流经层界面间多次散射、慢化、吸收，中子流引发的次级放射经X、伽马射线防护层多次衰减、吸收，如此在层界面间多次进行，最终将有害射线耗散在层间，同时解决中子流辐射和中子流引发次级放射的问题，探索构建高效中子流屏障的方法，为制备新型、高效防中子辐射复合材料提供思路。经一定剂量中子流辐射后，通过研究交替层状复合材料聚合物基体微观结构与性能的变化，揭示中子流在交替层状复合材料中衰减规律，对促进防中子辐射复合材料的发展和应用具有重要意义。

中子辐射作为核辐射的主要射线之一，对人体健康的损害极为严重。已有的工作将防中子辐射复合材料设计为三层结构，但其层数有限，防护效率有待提高，且不能有效防护中子流引发的次级放射，中子流在层状复合材料中的衰减规律尚不清楚。本报告用共挤出的方法，将防中子流辐射和X、伽马射线辐射有机结合起来，并将其设计为交替多层分布结构，保证总厚度不变的情况下，层数达几百层。中子流经层界面间多次散射、慢化、吸收，中子流引发的次级放射经X、伽马射线防护层多次衰减、吸收，如此在层界面间多次进行，最终将有害射线耗散在层间，同时解决中子流辐射和中子流引发次级放射的问题，探索构建高效中子流屏障的方法，为制备新型、高效防中子辐射复合材料提供新思路和新方法。与此同时，通过测试聚合物基体纳米尺度的熔点间接反映中子流在交替层状复合材料中衰减规律。通过交替多层复合共挤出系统制备的层状分布复合材料，相比于非层状分布复合材料的屏蔽率、质量衰减系数、线性衰减系数都有所提高。与此同时，中子流的次级放射对聚乙烯的结晶有破坏作用，并且能引起聚乙烯基体的交联，随着层数增加，这种交联得到有效的削弱，这也反向证明了交替层状复合材料对聚乙烯基体有保护作用，是有效削弱次级放射的有力证据。经一定剂量中子流辐射后，沿厚度方向可以观察到纳米尺度的熔点略有向上增加的趋势，即聚合物基体纳米尺度的熔点有梯度变化。交替多层复合材料（都以高密度聚乙烯为基体，一层加入氮化硼，另一层加入硫酸钡）纳米尺度的熔点略高于一层为纯高密度聚乙烯另一层为高密度聚乙烯/氮化硼的交替多层复合材料，由此说明硫酸钡的加入对次级放射有一定的屏蔽作用，次级放射对聚合物基体的破坏作用被削弱。