| Abstract Scope |
TRISO particles are considered one of the most reliable and technologically ready advanced fuel forms. Despite TRISO’s demonstrated robustness, major gaps exist in understanding the underlying mechanisms which produce fuel failure. Irradiated particles have shown that the buffer layer stochastically fractures in two distinct modes, radial fracture and internal tearing, and their mixture. It has been shown that internal tearing can be more favorable than radial fracture, as internal tearing relieves adjacent layers of their mechanical stress, while also allowing the buffer layer to remain as an intact barrier against fission products. While not much is known about what causes these two failure-modes, previous experimental work has shown that TRISO layers contain mechanically relevant features which are artifacts of manufacturing conditions. For example, it has been observed that the buffer layer contains a stochastic and heterogeneous porosity distribution, and a distinct buffer-IPyC interlayer region, hypothesized to be a result of manufacturing conditions. Additionally, computational studies have shown that the buffer layer likely contains significant residual stresses as a result of deposition temperature. Lastly, residual porosity is found within the UCO fuel kernel, which can allow for densification. In this study, we coupled statistical BISON fuel-performance modeling with smeared cracking to study the impact of manufacturing condition on failure-mode. It was found that an interlayer region, a heterogeneous porosity distribution and residual stress have a significant impact on fracture morphology. Furthermore, kernel densification promoted internal-tearing and is thus a candidate for triggering the internal-tearing observed in experimental works. |