Phase field modeling of irradiation-induced shrinkage fracture in TRISO fuel particle

With the features in retaining fission products and maintaining structural stability, TRISO fuel particle has been widely implemented and studied in the development of advanced nuclear fuel element. During service, however, the key silicon carbide (SiC) layer of TRISO may fail due to irradiation-induced shrinkage fracture of inner pyrolytic carbon (IPyC) layer. Hence, it has great significance to analyze the fracture characteristics of TRISO for its application in engineering. This work presents a phase field model of brittle fracture for the shrinkage cracking, which is capable of simulating the propagation of IPyC crack and interfacial crack between IPyC and SiC naturally. At first, the physical model of TRISO and phase field model have been verified respectively. Subsequently, the crack evolution has been investigated under different parameters, including the Bacon Anisotropy Factor (BAF) of IPyC, fuel temperature and density of IPyC. Simulation results reveal that increasing the BAF or decreasing the density and temperature, the fracture of IPyC will be accelerated and the crack deflection may also occur subsequently. In contrast, the fracture of IPyC can be put off and relieve the stress concentration in SiC. The combination effect of shrinkage and stress relaxation from creep ultimately determines the crack evolution, which in turn influences the stress distribution within SiC.