Peridynamics for multi-physics coupling to simulate cracking in fuel rods

This study presents a new coupled multi-physics model based on Bond-Associated Non-Ordinary State-Based Peridynamics (BA-NOSB PD) to investigate the mechanical behavior and crack patterns of fuel rods. Unlike the existing PD coupled multi-physics models, this novel PD model for the first-time accounts for the irradiation-induced behaviors such as densification, swelling, and creep. Also, it captures the Pellet and Cladding Interaction (PCI) under realistic boundary conditions. Furthermore, random critical stretch values with normal distribution within the fuel rods lead to realistic crack pattern of fuel rods during prolonged irradiation. The crack pattern of fuel rods with irradiation is compared with those without irradiation. The results show that the fuel pellet initially shrinks and then expands as burnup rises, while cladding consistently shrinks inward until gap closure, with its compressive state relieved by PCI. Associated with the damage in fuel rods, radial cracks occur during the power rise, while circumferential cracks mainly form during the densification stage, and only few secondary circumferential cracks occur during power ramp-down. The displacement of damaged pellet increases slowly as burnup rises, and the gap closure time is greatly delayed compared with that of an undamaged pellet.