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

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.