Design And Performance Of Gd/Sm-containing Polymer Neutron Shielding Materials

Fourth-generation advanced reactors are characterized by strong neutron flow,high operating temperature and small footprint.The current commercial polymer neutron shielding materials are mainly boron-containing polyethylene,whose neutron shielding performance and high temperature resistance can hardly meet the demanding service requirements of advanced nuclear energy systems,and the shielding effect of a single shielding nuclide is not uniform in the face of the complete thermal neutron energy spectrum.Accordingly,this paper prepares polyimide(PI)-based and trifunctional epoxy resin(AFG-90H)-based shielding materials and investigates the effects of different shielding nuclide treatment methods on the performance of the composites;meanwhile,to address the shielding limitations of single shielding nuclide,the optimal value of double shielding nuclide is obtained through simulation and experiment.The main research of this paper includes the following aspects:(1)Design,preparation and performance analysis of modified Gd2O3/PI and Gd-MOF/PI shielding materialsIn this paper,modified gadolinium oxide(M-Gd2O3)was prepared by surface modification treatment of Gd2O3 with silane coupling agent;Gd-MOF(Gd4(1,2,4,5BTEC)3)was synthesized by hydrothermal method.In terms of neutron shielding performance,When the Gd content is 4 wt%,the composite shielding of 1 cm thickness can achieve 99.9%thermal neutron requirement.In terms of thermal stability performance,all samples maintained good thermal stability at experimental temperatures below 300℃.Under the same shielding performance,when the mass loss is 5%,The thermal decomposition temperatures of Gd-MOF/PI,Gd2O3/PI,and M-Gd2O3/PI were 500℃,500℃,and 489℃,respectively.In terms of mechanical properties,the fracture strength of pure PI was 30.98 MPa.compared with pure PI,the tensile strength of the composites with low concentrations were all improved.At the concentration of Gd content of 4wt%,Gd2O3/PI improved by 15.78%,modified Gd2O3/PI improved by 4.76%,and Gd-MOF/PI improved by 4.99%compared to pure PI.2)Composition design and performance analysis of epoxy resin composites containing gadolinium-samarium double shielding nuclidesThe optimal ratio of shielding nuclides in the composite:When the energy is in the higher energy range(0.4-leV),the shielding effect of Sm and Gd elements will appear"oscillation".When Sm:Gd=1:3,the composite has the lowest half-value layer thickness variance,which is 86.9%and 76.8%lower than that of Sm-only and Gd-only composites,respectively.composites with different concentrations of Sm:Gd=1:3 were prepared and their mechanical properties were analyzed to conclude that the appropriate amount of nanoparticle fillers could improve the tensile properties of the materials,with 1%wt Sm2O3/3%wt Gd2O3/AFG-90H having the best tensile properties(62.5MPa)and elongation(6.1%),and the tensile properties and elongation were increased by 48.8%and 56.4%,respectively,compared with pure AFG-90H.