TerraPower HT9 Mechanical and Thermal Creep Properties

TerraPower has revitalized the manufacturing of HT9, and optimized its heat treatment to be used as fuel claddings in the Traveling Wave Reactor. TerraPower initiated a comprehensive test program to compare the mechanical and thermal creep properties of the optimized TerraPower HT9 to the historical HT9. The uniaxial tensile tests show TerraPower HT9 has improved yield strength compared to historical HT9 across all temperatures. Charpy impact toughness tests on TerraPower HT9 show lower upper shelf energy compared to historical HT9, but the ductile to brittle transition temperature (DBTT) between the steels remain similar. Three point bend tests between room temperature and 400 °C show comparable fracture toughness to those of historical HT9. Thermal creep test data suggest TerraPower HT9 have improved creep strength compared to historical HT9.