| Accelerator driven sub-critical system (ADS) has a neutron energy spectrum hard,large flux, energy distribution width and strong transmutation long-life nuclide ability,which is recognized to be the most safe and effective way to disposal nuclear waste.Lead Bismuth Eutectic (LBE) is a preferred material as coolant and spallation target ofADS, because of its good neutron properties, radiation resistance and heat transferperformance and inherent safety, etc. The main purpose of the coolant is bring therelease heat of nuclear fission reaction as far as possible safety and economical outputof the reactor. In order to improve the cooling efficiency of liquid lead bismuth alloyand guarantee the safety of the reactor core, we have to research the flow and heattransfer characteristics of lead bismuth alloy. However, thermophysical properties oflead bismuth alloy, such as density, surface tension, heat capacity and thermalconductivity, are key factors influencing the flow and heat transfer characteristics. Theresearch of thermophysical properties of liquid lead bismuth alloy is scientific basis tosolve these problems, such as the compatibility of structural material, lead bismuth alloycomposition control and purification technology, etc.In this paper, we researched thermophysical properties including density, surfacetension, heat capacity and thermal conductivity of lead bismuth alloy comprehensivelyand systematically by experimental methods, analyzing thermophysical properties oflead bismuth alloy the cause of the abnormal changes versus temperature and exploringthe influence law and the influence mechanism of thermophysical properties of leadbismuth alloy versus bismuth content.Firstly, the density and surface tension of five kinds of lead-bismuth alloys(Pb100Bi0,Pb80Bi20, Pb70Bi30, Pb60Bi40, LBE) were measured range from melting temperature to873K by Static Drop method. The results showed that the density of Pb80Bi20and LBEwas abnormal near melting point, because covalent bond to metallic bonding is notinstantaneous in the process of Bi metal melting. The surface tension of lead-bismuthalloys deviated from the theoretical value in low temperature area, because of the highoxygen partial pressure on the surface of the liquid metal droplet.Secondly, the specific heat capacity of lead-bismuth alloys were measured range from313K to773K by DSC method, obtaining the law curve of specific heat capacity oflead-bismuth alloys with temperature. The results showed that the specific heat of theliquid lead-bismuth alloys were stable range from623K to700K, in other words, the influence of temperature on specific heat capacity could be ignored.Finally, thermal conductivity of lead-bismuth eutectic was measured range from423K to873K by laser flash diffusivity apparatus. The results showed that thermalconductivity of lead-bismuth eutectic increased with temperature raise gradually.The experimental results of this study provided basic reference for compositionoptimization of lead-bismuth alloy and the design of lead-based cooled reactor,evaluating hypo eutectic lead-bismuth alloy as coolant material, which is of greatsignificance for the development of spallation targets and the coolant materials ofaccelerated driven sub-critical system. |
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