裂变气体气泡尺寸对弥散燃料颗粒内部特征的影响规律

Effect of Fission Gas Bubble Size on Internal Characteristics of Dispersion Fuel Particles

在前期均匀裂变气体气泡尺寸弥散燃料颗粒开裂模型基础上,基于不同尺寸气泡压力作用于燃料相的米塞斯(Mises)应力相等这一假设条件,建立了非均匀气泡尺寸的燃料颗粒开裂模型,并通过模型计算了裂变气体气泡尺寸对燃料相等效层厚度、气泡中气体原子数、气泡压力、燃料相最大张应力等内部特征的影响规律。计算结果表明:当气泡半径较大时,燃料相等效层厚度与气泡半径近似呈线性关系,当气泡尺寸较小时,等效层厚度与气泡半径之比随气泡半径减小急剧增加;随着气泡半径减小,气体原子数浓度增加;在升温过程中气泡内壁最大张应力的增大速率明显高于开裂阻力,气泡半径越小,燃料颗粒开裂温度越低。

On the basis of the fuel particles cracking model of bubble size homogeneity, the cracking model with bubble size heterogeneity was proposed according to stress equilibrium condition that the equivalent effective stresses applied by the gas bubble are identical. The effect of the fission gas bubble size on the internal characteristics, such as equivalent fuel thickness, gas atom number, bubble pressure and maximal tensile stress, was analyzed through this proposed model. The results show that the equivalent thickness is linearly dependent with the bubble radius when the bubble radius is larger, while the ration of equivalent thickness to bubble radius increases rapidly with bubble radius decreasing when bubble radius is smaller. The gas atom concentration increases as the bubble radius decreases. The increasing rate of maximal tensile stress at bubble wall is larger than that of cracking resistance during heating process, and the cracking temperature of fuel particle decreases with bubble radius.