【作者】 刘逸波； 张宇； 刘博； 张云； 邵友林； 马文军；

【Author】 LIU Yi-bo;ZHANG Yu;LIU Bo;ZHANG Yun;SHAO You-lin;MA Wen-jun;China North Nuclear Fuel Co.,Ltd;Institute of Nuclear and New Energy Technology,Tsinghua University;

【机构】 中核北方核燃料元件有限公司； 清华大学核能与新能源技术研究院；

【摘要】 包覆颗粒是高温气冷堆核燃料元件的重要组成部分,每个球形燃料元件中含有约12 000个包覆颗粒,包覆颗粒由UO₂核芯、疏松热解炭层、内致密热解炭层、SiC层、外致密热解炭层几部分组成,其中SiC层是包覆颗粒最主要的压力壳,是防止压力壳式破坏的关键层,其制造质量决定了包覆颗粒的破损率,进而影响球形燃料元件的质量。包覆颗粒的制备采用化学气相沉积法,即在CVD沉积炉中,加入直径为（500±50）μm的UO₂核芯颗粒,在气体冲力与重力的作用下,形成特殊的流态化状态,通过改变工艺气体种类、流量、沉积温度,连续完成疏松热解炭层、内致密热解炭层、SiC层、外致密热解炭层的包覆。流态化的状态对于SiC层的厚度均匀性、密度、球形度及破损率都有较大程度的影响。本文通过对包覆颗粒SiC层制备过程中流态化控制影响因素的研究,确定了适合的工艺控制方法及最佳的工艺控制参数,使SiC层破损率控制在较好的合格率水平,保证了包覆颗粒的产品质量。更多还原

【Abstract】 Coated particle is an important part of HTGR nuclear fuel elements,each of the spherical fuel element contains about 12000 coated particles.The coating process is to add 4 layers on the surface of UO₂ kernel,the 4 layers from inside to outside are porous carbon buffer layer,inner pyrolitic carbon layer,SiC layer and outer pyrolitic carbon layer.And the SiC layer is the main pressure vessel to prevent the particles from damage by high pressure.So the breakage of coated particles is mainly influenced by the manufacturing quality of SiC layer.Coated particles are fabricated in fluidized-bed with chemical vapor depositing（CVD） method.During this process UO₂ kernels with a diameter of（500±50）μm are charged into the furnace,and particles are fluidized under the action of gas and gravity.Then porous carbon buffer layer,inner pyrolytic carbon layer,SiC layer and outer pyrolytic carbon layer are deposited orderly,through control the different kinds of gas,gas concentration,deposition temperature and so on.The state of fluidization has a great influence on the thickness uniformity of SiC layer,density,roundness and breakage.Here we make a deeply research on the factors which may influence the fluidization during the SiC layer preparation,and suitable control method and parameter are obtained,thus the breakage of SiC layer is controlled and the quality of coated particles are improved.更多还原