Numerical study of functionally graded material models for evaluation of thermomechanical loading on nuclear fuel particles

Functionally graded materials (FGMs) are well suited for analyzing the thermomechanical behavior of dispersed fuel particles under severe thermal and mechanical conditions, due to their capability to exhibit continuously varying properties in the radial direction. In this study, the primary focus is placed on the numerical analysis of an FGM hollow sphere subjected to thermal loading and internal pressure, as this configuration is more relevant to higher burnup conditions and the associated buildup of internal gas pressure. Within this framework, the radial distribution of material properties is assumed to be continuous, and the influence of the inhomogeneity parameter, β, on the temperature field, radial displacement, and radial and circumferential stresses is investigated. The results show that variations in β play a decisive role in the thermomechanical response of the hollow sphere and can alter both the magnitude and the radial location of stress concentration. Accordingly, an appropriate choice of β can be used to optimize the mechanical response of the fuel particle and reduce stress concentration in critical regions. The FGM solid-sphere formulation is included as a complementary theoretical formulation representing a physically relevant configuration for the early stage of irradiation; however, the parametric numerical results and quantitative discussion of the present study are restricted to the hollow-sphere configuration.