Refractory Composites for Reactor Applications (PSI-7266-290)

Generation IV, Gas-Cooled Fast Reactor (GFR) nuclear systems require the development of new high strength materials capable of operating at 1000 C. Ferritic/martensitic steels, previously used as reactor materials, cannot be used successfully in this temperature regime. This project will develop a new family of moldable, nanofiber-reinforced, refractory ceramic composites, which possess high strength (70 MPa) at 1000 C and fracture toughness. The materials, which primarily comprise Hf and Si, will minimally moderate the fast spectrum, while maintaining thermal conductivity greater than 10 W/m-K. The refractory component makes these materials robust to high-rate, high-temperature helium gas flows and provide oxidation resistance. In Phase I, prototype, nanofiber-reinforced composite panels will be fabricated. The composition of the composite will be optimized to produce a material system that provides strengths greater than 70 MPa at 1000 C. Thermal conductivity measurements will be used to demonstrate that the materials possess high thermal conductivity (> 10 W/m-K). Erosion and oxidation testing will show that the materials undergo no erosion in high-temperature helium flows up to 40 m/s and retain their mechanical properties after oxidation at 1000 C. Commercial Applications and Other Benefits as described by the awardee: In addition to the nuclear reactor application, high-strength, high-temperature ceramic composites should find use in gas turbine engines and in high temperature fuel cells. In addition, military engines could take advantage of higher temperature operation to produce greater thrust-to-weight ratios than possible with superalloys.