Modeling of the irradiation-induced multi-scale mechanical behaviors for surrogate FCM pellets with interfacial cracking

Abstract

The simulation method and analysis code to investigate the irradiation-induced thermo-mechanical behaviors of surrogate FCM pellets are established, incorporating the cohesive model at the interface of the surrogate kernel with the buffer layer. The innovative volume growth strain model is adopted to correlate the anisotropic shrinkage and creep deformations of the solid skeleton with the macroscale volumetric growth of the buffer layer under external hydrostatic pressures. The predictions of the pellet swelling and the microstructure information agree well with the experimental results, validating the developed models and simulation strategy. It is indicate that: (1) a gap with a width of ∼22.98 μm is generated at the fast neutron fluence of 7.50 × 10²⁵ n/m²; (2) the predicted maximum tensile stress of ∼1894 MPa for the SiC layer implies that its tensile strength is particularly high; the tensile strength of the SiC matrix might exceed ∼289 MPa; (3) the volumetric swelling of the surrogate TRISO particle is mainly contributed by the outward displacements of the buffer layer after interfacial cracking; (4) without considering the anisotropic skeleton creep contribution on the macroscale volumetric growth of the buffer layer, the peak shrinkage strain of the buffer layer could be twice higher due to the enhanced hydrostatic pressure, accompanied by the reduced current porosity and the enlarged gap width; the maximum skeleton tensile stress will increase by ∼60.37 %. This study offers insights into the irradiation-induced thermo-mechanical behaviors of surrogate FCM pellets, supplying a foundation for further research on FCM fuels.