Abstract:
In order to investigate the influence of residual pores that may appear in SiC layer on the in-pile performance of TRistructural ISOtropic (TRISO) particle, and find the critical size of residual pores, in this paper, the in-pile performance of TRISO particle with residual pores was numerically simulated by using the multi-physical field coupling COMSOL software, and the effects of fission gas, CO release, internal pressure and residual pore size on the stress distribution of TRISO particle coating were analyzed. The results show that in the later stage of irradiation, the ratio of CO release is much higher than that of fission gas atoms, and the internal pressure of the particle can reach 49.5 MPa in the later stage. The existence of residual pores makes the stress of silicon carbide (SiC), inner dense pyrolytic carbon layer (IPyC) and outer dense pyrolytic carbon layer (OPyC) increase rapidly, especially in the SiC layer. When the size of residual pore reaches 9 μm, the maximum stress of SiC layer reaches 600 MPa, which is much higher than its intrinsic strength. When the residual pore size is 5 μm, the maximum stress of SiC layer is about 450 MPa, which is equivalent to its intrinsic strength. Therefore, in order to ensure the structural integrity of SiC layer in the preparation process, the residual pore size of SiC layer should be less than 5 μm.
