Thermomechanical modeling of pellet-cladding interaction using state-based peridynamics

Abstract

Pellet-Cladding Interaction (PCI) is a significant concern for the safe and reliable design of nuclear fuel rods. This study presents a modeling approach for investigating PCI employing the Ordinary State-Based PeriDynamics (OSB-PD) while considering irregular discretization to improve the modeling of curved boundaries of fuel rods with geometric precision. Unlike the existing PD models for fuel pellet, the present study considers contact and heat transfer between fuel pellet and cladding. Also, it presents a new frictional contact model with stick and slide friction. The heat conduction is modeled through gas, contact and radiation between pellet and cladding. In order to capture complex fragmentation and failure in pellet, material variability is considered by applying randomized critical stretch values with normal distribution. Specifically, it presents the effects of friction coefficient, gap size, and power level on crack patterns in fuel pellets while considering PCI. The PD predictions show that the number of major radial cracks remains constant as the friction coefficient increases; however, the number of circumferential cracks increases significantly. As the gap size increases, both the temperature in fuel pellet and the temperature difference across the gap increase. Also, the number of cracks in fuel pellet increases with the increasing value of gap size. The power level has a strong influence on the temperature gradient of the fuel rod, and the number of cracks in fuel pellet directly correlates with the power level.