Optimization of process parameters of Zy4/TRISO composite using processing maps and breakage rate

Coated fuel particles have been developed into isotropic tristructure (TRISO) for the high-temperature gas reactors. The Zy4/TRISO composite belongs to a Zy4 matrix with distributed coated surrogated nuclear fuel particles (ZrO2 kernel). In this study, the thermal deformation behavior of a Zy4/TRISO composite was investigated at temperatures of 750–950 °C and strain rates of 0.01–1.0 s−1. Thermal compression experiments were carried out with a small deformation rate of 10% height reduction. The constitutive models and processing maps of the Zy4/TRISO composite were established, and combined with scanning electron microscopy characterization. The microstructure evolution of TRISO particles during hot compression behavior was analyzed, the breakage rates of TRISO particles under different deformation conditions were evaluated, and the optimized high-temperature deformation conditions were determined. The optimization parameters were the temperature of 900°C-950 °C with strain rates of 0.01–0.1 s−1, and TRISO particles maintained their integrity. This shows that TRISO particles under a small deformation rate will not be damaged during hot compression deformation. These stable deformation conditions are hopeful to provide valuable guidance for follow-up hot deformation processes of the Zy4/TRISO composite.