Modeling of irradiation-induced thermo-mechanical coupling and multi-scale behavior in a fully ceramic-microencapsulated fuel pellet

Abstract

Fully ceramic microencapsulated (FCM) fuels with enhanced accident tolerance can provide an increased retention of fission products. In this study, a new method to model their irradiation-induced thermo-mechanical behavior is established. A fuel performance code called Thermo-mechanical Analysis of Inert Matrix Fuels (TMAIMF) is developed based on ABAQUS platform to enable the researchers to allow for all the irradiation effects in the three-dimensional large-deformation constitutive models of the involved materials. Especially, the important gas-release-induced thermal-mechanical effects are considered for the porous carbon layer. Finite element analysis is implemented for the thermo-mechanical coupling and multi-scale behavior in a FCM pellet, with the non-spherically symmetric thermal-mechanical interactions among all the coating layers in a TRISO particle, the TRISO particles and the matrix taken into account. Numerical simulation results indicate that (1) the irradiation shrinkage and gas-induced effective expansion strain in the porous carbon layer are responsible for the accommodation of kernel swelling, so the deformations of FCM pellets are dominated by the thermal expansion and irradiation swelling of SiC matrix; (2) the gas-induced effective expansion strains in the porous carbon layer together with the irradiation creep strains occurred in various materials protect the pellet from cracking during the whole irradiation process, with highly efficient heat transfer maintained. This study supplies a fundamental basis for advanced fabrication and optimization of FCM fuel pellets.