| With the rapid development of nuclear power station in our country, more attention is payed to howto deal with spent fuels. More than1000t spent fuels will be unloaded every year until2020.Aluminum matrix reinforced with B4C is an ideal neutron absorber and shielding material,with goodproperties displayed as light weight、high strcture strength、high melting point、good heatconduction、steady size、good plasticity、low heat inflation、excellent mechanic property、good neutronabsorber ability、the less second radioactive pollution and so on. in this paper, MCNP program wasimplyed to calculate the shielding property of B4C/Al composite material, and Al powder reinforcedwith B4C was employed to fabricate it with powder metallurgy. The mechanical property、corrosionand radiation resistance、shielding performance were valued. The main conclusions show as follows:(1)The shielding performance of B4C, low density of B4C/Al composites and high density B4C/Alcomposites was calculated. The results show all materials have a good shielding property to neutronsespecially to thermal neutrons. They are suitable for shielding neutrons under1MeV. The higher theneutrons energy, the poorer the shielding effect is. A “reversal” phenomenon is presented in theshielding effect curve with a series of “reversal” energy0.5,0.8,1.2MeV. At the thermal neutronregion, the shielding effect of material can be obviously improved with increasing weight content ofB4C, at the fast neutron region, the effect is not obvious; the relationship between material thicknessand transmission coefficient is a negative exponent.(2)The neutron transmission coefficient of neutron absorber material B4C/Al composites wascalculated, when they were in air, water,200-1400ppm H3BO3solution, at the thickness of0.3-9cm,5%-40%B4C content, faced to200eV-20MeV neutrons and235U thermal neutron fission source. Theresults show that under the same neutron energy, the neutron-shielding qualities of simulatedspecimens are more better than polyethylene boron carbide at the same weight content of B4C andwater、copper and concrete at the same thickness. The transmission coefficient of B4C/Al compositesis reduced with the increasing content of B4C and the thicknesses of material, increased with theincreasing neutron energy, and have a little change on the varied concentration of H3BO3solution. Abetter shielding effect of B4C/Al composites is displayed in water than in H3BO3solution, anda“reversal”characteristic is showed when in air, of which the transmission coefficient is almost steadyfaced to the5-15MeV neutrons. A lower transmission coefficient of B4C/Al composites is performedunder the fission source irradiation than to be irradiated by20MeV neutron source. The ranking shielding performance of media is H3BO3solution＞water＞air, and an exponential fell relationship isfound by the neutron transmission coefficient and thickness of media, which can be expressed ase-0.71xand e-0.669x, where x is thickness of media(cm).(3)B4CP/Al composites produced by Powder metallurgy was employed to test its bending strength、irradiation and corrosion resistance、neutron shielding performance and copper、iron was taken tomeasure its neutron transmission coefficient. The results show that lower sintering temperature withlonger sintering time is helpful to improve mechanical property of B4Cp/Al composite. Under theoxygen condition, samples could generate reinforced alloy phases and finally increase its mechanicalperformance. γ irradiation almost has no effect on the mechanical performance of samples. Corrosionstress cracking takes place in the erosive process. The cracks grow wider and its numbers add with thetime goes.The variation of H3BO3solution’s concentration has a small influence on the bendingstrength of B4Cp/Al composite. With the increasing concentration of H3BO3, the corrosion ability isstronger but its increasing trend is not obvious. There is no passivation appearance in the corrosionprocess. B4CP/Al composite displays a good corrosion resistance with its polarization electric icorstaying at10-6A cm-2quantity magnitude.15%wt.B4Cp/Al composite display a perfect shieldingperformance, the transmission coefficient was almost0.2with0.8cm material thickness.When it’s B4Ccontent is15%-20%, the shielding effect improve evidently and it is better than copper、iron at thesame thickness. |
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