Investigation on thermo-mechanical performance of fully ceramic microencapsulated fuel

Abstract

Abstract Fully ceramic microencapsulated (FCM) fuel is a promising ATF concept with extraordinary fission product inclusion capacity, excellent oxidation and corrosion resistance, and high thermal conductivity. The thermo-mechanical performances are of great significance when evaluating the safety and applicability of a nuclear fuel. In this study, a finite element method (FEM) model for FCM thermo-mechanical performances analysis was presented. The thermo-mechanical behaviors, coupled with irradiation behaviors (including irradiation-induced dimensional change (IIDC), heat generation, conduction, thermal expansion, creep, burnup, and gap/plenum pressure, etc.), were developed to investigate the thermal and mechanical characteristics of TRISO-based FCM Fuel. A simplified model of TRISO fuel particles was established and validated. After that, a full 3D modeling of FCM fuel pellet with typical packing fractions was realized by an optimized stochastic strategy. A numerical method was validated and successfully applied to realize the simulations of a FCM fuel pellet. Two different thermal boundaries, namely fixed particle power and fixed pellet power, were performed to investigate the irradiation behavior of FCM fuel. Moreover, the effects of burnup, particle spacing, no fuel zone width and other key parameters were well studied and investigated. The performed calculation showed that temperature and stress in matrix and TRISO are both positively correlated with the packing fraction. It s worth noting that compared with the cases of fixed particle power, cases of fixed pellet power may lead to higher fuel temperature and higher stress. The results also implied that from the perspective of probability evaluation, most of the TRISO particles in FCM fuel can maintain the structural integrity under different packing fractions, but some of the particles with higher stress may crack or damage, especially in the cases of high burnup and high packing fraction.