Study On The Forming Processes And Properties Of Radiation Shielding Composites Manufactured By Selective Laser Sintering

The main radiation exposure mode of nuclear power plant is gamma radiation.At present,pure lead and its composite materials are mainly used for radiation shielding in nuclear power plant.However,lead-based materials have certain toxicity,high cost of waste treatment and are easy to be oxidized.Tungsten-based composite materials have become a new research direction of radiation shielding materials.In addition,there are many kinds of pipelines,valves and complex components with various structures and sizes in the nuclear power plant.There are many kinds of radiation shielding parts and few spare parts needed,the replacement time should be as short as possible to avoid affecting the operation of the nuclear power plant.Slective laser sintering(SLS)is a rapid prototyping technology with a high degree of complexity.It is suitable for rapid prototyping of small batches of complex structural parts and very suitable for radiation shielding requirements in nuclear power plants.In this paper,radiation shielding composite powders were prepared by powder coating and mechanical mixing processes,and their SLS forming process and properties were studied.Finally,the related properties of radiation shielding applications were tested and analyzed.The main contents and conclusions are as follows:(1)The preparation technology of radiation shielding composites was studied.Based on the requirement of SLS process,tungsten carbide(WC)powder and nylon(PA)12 powder with appropriate particle size were selected as the matrix of radiation shielding composites.WC/PA12 composite powder was prepared by powder coating process and mechanical mixing process.The WC/PA12 radiation shielding composite powder prepared by the two methods was compared and analyzed,and radiation shielding composite powder with different WC-PA12 mass ratio was prepared.(2)The process of selective laser sintering radiation shielding composites was investigated.The preheating window temperature of radiation shielding composites was determined to be 165 ~170? by single factor experiment,and the process optimization of SLS forming parts of WC/PA12 composites was carried out by orthogonal test from the aspects of density,tensile strength and impact strength.The influence of different powder preparation technology and WC content on the mechanical properties of SLS moulding parts was analyzed.The effect of continuous use of powder on the mechanical properties of SLS moulding parts was analyzed.It was found that the more continuous use of composite powder,the lower the tensile strength of SLS moulding parts.(3)The properties of radiation shielding composites were studied.The gamma-ray shielding properties of SLS parts of WC/PA12 radiation shielding composites were tested,and the shielding ratios of radiation shielding composites to gamma-ray were obtained,and the effects of different WC contents on the gamma-ray shielding properties of composites were analyzed.The mechanical properties of the composites after 50 kGy and 250 kGy cumulative irradiation dose were studied.It was found that the remaining mechanical properties of the composites,except elongation at break,remained above 80%.In addition,the thermal-oxidative aging properties,flame retardant grade,high and low temperature resistance of the radiation shielding composites were also tested and analyzed.