燃耗深度对U_3Si_2-Al弥散型燃料元件芯体中气孔的影响研究

Effect of Burnup Depth on Porosity in Core of U_3Si_2-Al Dispersed Fuel Element

辐照过程中,燃料颗粒内部会产生裂变气体形成气孔,将对其热/力学性能造成显著影响。采用带屏蔽的金相显微镜(OM)、扫描电镜(SEM)和能谱仪(EDS)对辐照后U_3Si_2-Al弥散型燃料中U_3Si_2燃料颗粒的显微组织进行了观察,统计分析了燃料颗粒内气孔的形貌、尺寸及分布,获得气孔平均尺寸及孔隙率随燃耗深度的变化规律。结果表明,裂变密度在2.34×10^(27)~3.74×10^(27)m^(-3)范围内时,U_3Si_2-Al燃料颗粒中的裂变气体气孔的形貌未发生较大改变,均呈球状。而裂变气体气孔平均尺寸以及孔隙率均随着裂变密度的增加而增大,存在两个阶段:裂变密度在2.34×10^(27)~3.19×10^(27)m^(-3)范围内,稳态增长;裂变密度在3.19×10^(27)~3.74×10^(27)m^(-3)范围内,加速增长。

Thermal/mechanical properties of the fuels are dominantly affected by the fission pores produced from fuel particles during irradiation. In this paper, the effect of U_3Si_2 fuel particle on U_3Si_2-Al dispersed fuel were studied using the optical microscope(OM), scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS). The microstructure of U_3Si_2 was observed. Additionally, the morphology, size and distribution of pores of U_3Si_2 were analyzed statistically. The results show that when the fission density increases from 2.34×10^(27)f/m^3 to 3.74×10^(27)f/m^3, the gas morphology in the U_3Si_2 fuel particles is globular and without great change. However, the average pore size and porosity caused by the fission pores increase with the fission density, which go through two stages: when the fission density of the fuel particles increases from 2.34×10^(27)f/m^3 to 3.19×10^(27)f/m^3, the average pore size and porosity are with steady-state growth; when the fission density of the fuel particles increases from 3.19×10^(27)~ 3.74×10^(27)f/m^3, the average pore size and porosity increase rapidly.