Comparison of thermal-hydraulic calculation in 100 MWt thorium-based HTGR using SiC and ZrC TRISO coated fuel particle

The High-Temperature Gas-cooled Reactor (HTGR) uses Tri-structural Isotropic (TRISO) coated fuel, the first barrier to fission products with unique ruggedness. One of the layers of TRISO is a SiC layer, which maintains the fuel's dimensional stability and mechanical integrity and acts as a fission product barrier. At extremely high temperatures, the SiC layer in the TRISO coating system tends to decompose, vaporizing silicon elements and forming a porous carbon structure. The weakness of the SiC layer leads to more expensive and difficult main-tenance processes. ZrC is considered the primary alternative to replace the SiC layer due to its superior stability at high temperatures and more resistance to fission products especially palladium. Previous research has shown that from a neutronic perspective, the performance of ZrC and SiC layers is equally good with insignificant differences. The following research step analyzes the temperature distribution in the hot spot channel of the fuel and the overall core using both types of layers. The temperature analysis is essential to ensure that the maximum fuel temperature during normal operation does not exceed the thermal design target of 1495 degrees C. This research also simulates the temperature of both layers above the fuel design limit of 1600 degrees C. In addition to thermal --hydraulic analysis, calculations were also conducted to determine the coolant pressure drop caused by friction, elevation and form. The calculation showed that the peak temperature value during normal operation for TRISO with SiC and ZrC layer is below the thermal design target value. Both temperatures are not significantly different, with the TRISO (ZrC) temperature being higher during normal operation and the TRISO (SiC) temperature being higher during accident/high-temperature conditions. The pressure drop profile indicates that both coated fuel particles do not exhibit significant differences.