Irradiation performance and modeling of HTR-10 coated fuel particles

The irradiation test of HTR-10 spherical fuel elements was carried out in the Russian IVV-2M research reactor with the irradiation temperature of 1000 ± 50 °C. After the burnup reached 100,000 MWd/t, the irradiation temperature was raised to a higher temperature. The high R/B levels observed during the normal irradiation test were due to manufacture defects of one to four coated particles. Post-irradiation examination indicated that at normal irradiation condition, the pyrolytic carbon (PyC) and silicon carbide (SiC) layers of particles kept their integrity. However, after irradiation at higher temperatures, several types of defects including radial and tangential cracks in SiC layers, cracks in buffer layers, and through coating failure were found, and the failure fraction reached 5.8 × 10−2. These defects were most likely caused by the higher thermal stresses generated. In this study, PANAMA fuel performance code was used to estimate the heating temperature in the irradiation test. The calculated results showed that when the heating temperature is much higher than 1850 °C, the failure fraction of coated particle can reach the level of 1%.