A PHASE FIELD METHOD FOR IRRADIATION-THERMAL-MECHANICAL COUPLING FRACTURE OF THE DISPERSION NUCLEAR FUEL

Dispersion nuclear fuels have become a pivotal component in fourth-generation nuclear power technologies, and exhibit promising applications in the nuclear energy region due to their uniform fission reaction, small temperature gradients, and high burnup capabilities. With the increase of the design service life of nuclear fuel elements, a heightened demand for predicting the fracture and failure behaviors of the fuel element is proposed to avoid the leakage of nuclear fission products. The phase field fracture method is a recently developed computational fracture mechanics approach, and has achieved considerable success in predicting the fracture behaviors of complex solid media even under multi-physics conditions. In this work, we firstly propose an irradiation-thermal-mechanical coupling phase field model of dispersion nuclear fuels based on continuum thermodynamics in order to predict the fracture and heat transfer behaviors of the nuclear fuels under irradiation, thermal stress, and mechanical loadings. Subsequently, numerical simulations for the representative volume element and the entire plate of dispersion nuclear fuel in the pressurized water reactor environment are conducted. And the temperature field, the crack phase field and the hydrostatic stress field inside the dispersion nuclear fuel are obtained. The results reveal that dispersion nuclear fuels with uniform particle distribution exhibit relatively small temperature gradients. Notably, no phase field cracks are observed in the nuclear fuel matrix, and the damage of the dispersion nuclear fuel primarily manifests as the fracture of fuel particles. Many cracks nucleate at the edges of fuel particles, and then propagate inward the particle center. This work can provide an effective simulation method and numerical analysis basis for predicting the fracture behavior of dispersion nuclear fuel element. © 2025 Chinese Society of Theoretical and Applied Mechanics. All rights reserved.