Thermo-mechanical behavior of helical cruciform fuel with dispersed TRISO particles: A multiphysics simulation study

The helical cruciform fuel with dispersed TRISO particles exhibits inherent safety and enhanced heat transfer characteristics in a fluoride-salt-cooled high-temperature reactor. This fuel design can be fabricated using additive manufacturing technology. This study investigates its thermo-mechanical behavior through Multiphysics numerical simulation to elucidate mechanical failure and deformation mechanisms. Three-dimensional analyses include a matrix with a single TRISO particle, a helical cruciform matrix segment with stochastically dispersed TRISO particles, and a 1/8 symmetrical matrix with multiple regularly arranged TRISO particles. For a single TRISO particle, the temperature effects on both the buffer/IPyC gap gas pressure and tangential stress in the SiC layer are analyzed. The thin elastic layer model, which accounts for the interfacial bonding strength at the OPyC-matrix interface, is applied to simulate four cases with different debonding strengths and spring constants. The results show that when the bonding strength increases from 80 MPa to 100 MPa, the failure probability increases by a factor of six. For the helical cruciform matrix segment, stress distributions are analyzed at different packing fractions. The peak failure probability of the matrix drops from 1.2 × 10-4 to 3.2 × 10-6 when the interfacial bonding strength is reduced from 80 to 50 MPa. For the symmetrical matrix, contour plots of Von Mises stress and radial displacement distribution are provided. Overall, this study indicates that the interfacial bonding strength between the OPyC and the matrix is a critical factor impacting the failure probability of both the matrix and the SiC layer.