Numerical analysis of effective thermal conductivity of FCM with multilayer TRISO particle

Abstract

Fully Ceramic Microencapsulated (FCM) fuel, consisting of tristructural-isotropic (TRISO) and SiC matrix, has engaged significant attention owing to its unmatched accident tolerance and excellent heat transfer efficiency. The effective thermal conductivity (ETC) is of great significance when evaluating the thermal efficiency and safety of nuclear fuel. In this study, the finite element method (FEM) is used to model the ETC of full 3D FCM pellets. The effects of several factors on the ETC of the FCM were mainly investigated, such as the volume fraction, components properties, and the distribution of TRISO particles. The numerical ETC was compared to analytical models in the literature, the most appropriate analytical model was recommended and the accuracy of the developed numerical model was verified. The performed calculation showed that the ETC of the pellet is negatively correlated with the volume fraction of the TRISO particles. In addition, we found that the distribution of particles has a noticeable effect on the ETC of the pellet, and the relationship is fitted by data mining. Based on the results of the calculations, two routes to improve the ETC of the FCM pellet are proposed, one is to increase the thermal conductivity of the buffer layer and the matrix in the TRISO particle and the other is to disperse the TRISO particles by optimizing the preparation process. The present study provides theoretical support for the analysis and improvement of the FCM design and fabrication in the future.

Keywords

• Effective thermal conductivity
• Fully ceramic microencapsulated (FCM) fuel pellet
• Tristructural-isotropic (TRISO) fuel particle
• Finite element method
• Data mining