Experimental Study Of Shield γ-ray And Neutron By Thermal Sprayed Coating

The main task that the nuclear shielding design is shieldγ–rays and neutrons. Middle-and high-dose irradiation of the whole body against the most, has long aroused sufficient attention. Excessive low dose of irradiation would cause people's gonads, red bone marrow, bone, lung, thyroid, breast, skin, eye diseases occurred. These pathological change incubation period is long, the effect appear late, very easy to be neglected. Therefore, excessive low dose of irradiation on the human body lead to chronic injury and late effects should arouse people's more sufficient attention. In order to reduce low dose of irradiation to the human body on greater degree, the paper selected WC-12Co powder, B4C powder, used subsonic flame spraying process to prepared shielding coating. The shielding result was calculated and protection effect experiment was done. The irradiation effect (100 days) of the coating was tested.B4C melting point up to 2450℃, subsonic flame can not melt powder, can not directly sprayed B4C coating. So B4C powder was coated certain thickness of nickel alloy by means of chemical nickel plating pretreatment process and used to prepared coating directly. Pass the sieve method, about 90% of the B4C powder diameter increase 5-20μm. SEM and EDS analysis show that part of a powder coating appeared leakage phenomenon. Commercial WC-12Co powder was directly sprayed.Simulation results show that WC-12Co coating protection effect drops suddenly with the increase ofγ–rays photon energy. WC-12Co coating (1mm) can shield 100% Gamma Rays (below 0.1 MeV ). Whenγ–rays photon energy rised to 3MeV, the protection effect is minimum(about 7.2%). WC-12Co coating is suitable for shield smallerγ-rays photon energy.Simulation results of neutrons shield show that the protection effect of B4C coating to thermal neutrons is very good. B4C (99.8% of the 10B) Coating with thickness of 0.15mm can shield 100% thermal neutrons. WC-12Co coating(1mm) can shield 12% thermal neutrons while 2mm thickness of WC-12Co coating can only shield 3.5% fast neutrons. B4C coating is not fit for shield fast neutrons. The shielding experiment indicates that the protection effect of the coating conforms with the simulation results.Before and afterγ–rays and neutrons irradiation to WC-12Co coating, the microstructure,surface morphology and elements composition has not taken place obvious change. After irradiation of the fast neutrons, the bonding strength of WC-12Co coating increased about 20%-50%. EDS analysis showed that the coating and substrate interface does not occur diffusion phenomenon within the scope of micro-elements. Perhaps it is due to improvement of yield strength and tension strength of the material.SEM analysis show that after the fast neutrons irradiation, B4C coating internal crack, EDS analysis did not detect B. B neutron capture will become H,He and fled the material, resulting in material cracking.