| In recent years,with the rapid development of nuclear energy and nuclear technology,the important influence of radiation shielding materials on system safety has been widely valued.In the domain of nuclear energy,nuclear power and nuclear medicine,the demand for high performance neutron shielding materials is increasing rapidly.The design and preparation of advanced neutron shielding materials have important significance for improving operational efficiency and safety of nuclear facilities.In this paper,a kind of nickel metal foam neutron shielding composite is designed characterized and researched.1)By using Monte Carlo Method,the geometric model of nickel foam metal composite material was established.A Am-Be neutron source and a small nuclear reactor neutron energy spectrum was chose,then the influence of porosity,chemical composition of fillers and foam structure on shielding performance was discussed.Simulation results show as follows: under the condition of different neutron source,neutron shielding properties have different relationship with porosity;The secondary gamma dose increased firstly and then decreased as the porosity increased in different energy spectra.The gamma-rays shielding performance is monotonically decreasing as the porosity increased.When the boron carbide were added in fillers,the neutron dose and gamma dose both decrease with the adding of the content of boron carbide.thus the 30wt% was best choice for boron carbide content.the shielding ability of nickel foam(porosity of 0.89)composite material containing 30wt% carbide boron were 50% higher than non-foam structure.2)The preparation process of two kinds of composite materials was designed and studied by filling paraffin and polyethylene into nickel foam.Firstly,this experiment determined the supplement cycle of additives in electroplating process and selected 0.89 and 0.96 as the porosity of nickel foam.The preparation process of boracic paraffin/nickel foam composites was designed.The preparation process of boracic polyethylene /nickel foam composites was designed.by studying the relationship between the filling rate and the polyethylene content in fillers,the content of polyethylene is determined as 50% mass fraction.the dispersion of boron carbide was improved by surface modification.3)Characterization and analysis of neutron shielding performance,gamma shielding performance,mechanical properties and thermal conductivity of nickel foam composite materials of two systems are carried out.The results show that the neutron shielding performance of the 6 cm thick nickel foams matrix composites is about 5% higher than that of fillers under the condition of Am-Be neutron source.For different energy gamma source,the gamma-ray shielding capability of the nickel-base foam composite material is better than that of polymeric fillers.Compression test result shows that the mechanical properties of paraffin/ nickel foam are well above that of paraffin or nickel foam,and the compressive strength of composites is about 30% higher than that of foam nickel.For the polyethylene/ nickel foam,when porosity of nickel foams were 0.89,the mechanical properties of composite materials were 20% higher than that of polyethylene,when the porosity of nickel foams were 0.96,the difference between mechanical properties of composite materials and polyethylene is very small;The energy absorption efficiency of all composite materials increased by 30% compared with that of polyethylene.The heat flow test results show that the thermal conductivity of nickel foams composite materials were more than twice that of polymer.In this paper,the research provides an important reference for neutron shielding materials of advanced small-sized and movable nuclear facilities.it also provides a technology basis of theoretic and testing research for the next generation of neutron shielding materials with higher performance,higher reliability and more wildly application field. |
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