Thermal conductivity estimation of fully ceramic microencapsulated pellets with ZrO2 as simulated particles

Abstract Fully ceramic microencapsulated (FCM) fuel is manufactured by replacing the graphite matrix of conventional high-temperature gas-cooled reactor tristructural isotropic (TRISO) fuel compact with silicon carbide (SiC) matrix, because of the tremendous merits of SiC. Most of the previous studies on FCM fuel thermal conductivity focused on the parameters of the SiC matrix and particle volume fraction. The present work deals with the estimation of fuel thermal conductivity of the FCM, considering not only the particle size and volume fraction but also the matrix-particles interaction such as the interfacial layer and gap formation between the matrix and particle. ZrO2-3mol%Y2O3 particles were used to simulate the TRISO-coated particle and SiC nanopowder as the matrix. An estimation of thermal conductivity was performed with the Maxwell-Eucken model and Hasselman-Johnson model, and further correction was done employing the Knudsen effect. The calculation result showed that correction with the Knudsen effect provided the values that were closest to the measured thermal conductivity.