基于COMSOL的全陶瓷微封装燃料元件建模与传热分析

Modelling and Heat Transfer Analysis of Fully Ceramic Microencapsulated Fuel Pellet Based on COMSOL Software

采用COMSOL软件构建了全三维全陶瓷微封装(FCM)燃料元件模型,提出了一种FCM燃料元件内TRISO颗粒随机分布的高效建模方法,可以实现较高填充率的颗粒弥散填充。分析了不同颗粒填充率(35%、40%和45%)下以及不同颗粒随机分布下FCM燃料元件的温度分布特性。结果表明:FCM燃料元件中心区域温度高,沿径向温度降低;TRISO燃料颗粒特别是燃料核芯的温度明显高于周围基体的温度,温差可达130 K甚至更高,其中最大的温度梯度出现在Buffer层;在相同线功率下,随着颗粒填充率的增加,燃料芯块的最高温度降低,平均温度略有升高;受到颗粒分布随机性的影响,当颗粒填充率减小时,平均温度和最高温度分布的离散程度均增加,但总体上颗粒随机分布对燃料芯块平均温度的影响较小。

A full three-dimensional model for fully ceramic microencapsulated(FCM)fuel pellet was constructed using COMSOL software.An efficient modelling method for the random distribution of TRISO particles in FCM fuel pellet was proposed,which could achieve a particle dispersion with high packing fraction.The temperature distribution characteristics of FCM fuel pellets under different packing fractions(35%,40%and 45%)and various random particle distributions were analyzed.Results show that the temperature in the central region of FCM fuel pellet is high,and the temperature decreases gradually along the radial direction.The temperature of TRISO fuel particles,especially in the fuel core,is significantly higher than that of the particles in the surrounding matrix and the temperature difference can reach 130 K or even higher.The maximum temperature gradient appears in the Buffer layer.Under the same linear power,with the increase of particle packing fraction,the highest temperature of fuel pellet decreases and the average temperature increases slightly.Influenced by the randomness of particle distribution,the scatter degrees of both the average temperature and the maximum temperature distributions increase with the decrease of particle packing fraction.In general,the random distribution of particles has an inconsiderable effect on the average temperature of fuel pellets.