Coupled neutronic–thermal–mechanical analysis of a nuclear fuel pellet using peridynamics

This study introduces a comprehensive approach for simulating cracking behavior of nuclear fuel pellets using the state-based peridynamics (PD) theory. Unlike the existing thermomechanical models of fuel pellets, this new multi-physics framework couples neutron diffusion, heat transfer and mechanical deformation. For the first time, the PD form of multi-group neutron diffusion analysis is presented and coupled with the PD thermomechanical analysis. The PD neutron diffusion coefficient is obtained in terms of the traditional neutron diffusion coefficient. The PD form equations for multi-group neutron diffusion are solved using the source iteration method, ensuring numerical stability and convergence. This approach demonstrates its effectiveness in capturing the intricate behavior of neutron diffusion. It is further extended to analyze a lattice cell of an AP1000 nuclear reactor, considering uneven distribution of neutron flux and power density for performing a comprehensive evaluation of mechanical damage. This multi-physics coupling approach enhances the understanding of fuel pellet cracking and facilitates the development of advanced reactor safety strategies.