| Deep space exploration work is the key research direction of space power countries,and space nuclear reactor power supply(space reactor)has the advantages of high power density,high adaptability and long working life compared with traditional power supply,which improves stable power support for deep space exploration missions.However,the γ-rays and neutron produced by space nuclear reactors will cause radiation damage to materials and devices in spacecraft,resulting in in-orbit service failures and even accidents.Exogenous radiation shielding of space reactor is an important prerequisite to ensure the safety and longterm operation of spacecraft in orbit.In this thesis,a new radiation shielding material based on Gd2O3/Bi2O3/epoxy resin is simulated by Monte Carlo method for γ-rays and neutron shielding generated by space reactor.Developing lightweight external radiation protection technology,which has important scientific value and engineering practical significance.In this paper,Geant4 and WinXCom software are used to calculate the radiation shielding effect of γ-rays,neutron shielding materials used in aerospace and rare earth elements.The enhancement ability of each element to each other γ-rays weak absorption region and the neutron absorption cross section of the elements are compared,and selection and optimization of functional fillers are completed,a new radiation protection material Gd2O3/Bi2O3/epoxy resin with excellent radiation resistance and comprehensive properties was determined.Monte Carlo method was used to simulate the effects of the ratio and amount of functional fillers on the neutron and γ-rays shielding properties of composite protective materials.Simulation for 1 MeV neutron and γ-rays,the results show that the radation shielding effect of the composite material on rays is almost the same trend when the content of Bi2O3 or Gd2O3 is increased separately.Therefore,Bi2O3 and Gd2O3 are added in equal proportions.It is also found that the shielding effect of the material on neutron and γ-rays increased significantly with the increase of functional filler content,but when the content of functional fillers is too large,the neutron shielding rate decreases instead,and the functional filler content is set to 50%for the best overall consideration.Geant4 is used to simulate the shielding effect of composite shielding materials on neutron and γ-rays in each energy band.It is found that the shielding effect of the shielding material on thermal neutrons,slow neutrons,intermediate neutrons and low to medium energyγ-rays is better,while the shielding effect of the high energy γ-rays and fast neutrons needed to be increased by the thickness of the material.With the increase of ray energy,the γ-rays and neutron shielding rates of composite shielding materials show different decreasing trends,especially when the γ-rays energy is 50.5 keV and 90.5 keV and the neutron energy is 100 eV,the shielding effect of the materials rises suddenly.By changing the radius of the functional fillers,the effect of filler size on the shielding performance of the material is investigated.the results show that for low-energy neutron andγ-rays,the shielding effect is better when the particle size of the filler is smaller,and the effect is especially obvious for low-energy γ-rays and less for high-energy rays.This is mainly due to the fact that the larger the projected area of the filler in the incident direction of the radiation source,the higher the probability of collision between the radiation and the filler particles,the better the neutron and γ-rays shielding performance of the material,and this conclusion is further verified by changing the arrangement of the filler. |
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