Property Measurment and Improved Strength of Duplex Sic/Sic Ceramic Composites for Fast Reactor Fuel Cladding

78329 Generation IV advanced reactors [such as the gas cooled fast reactor (GFR) and the Lead Cooled Reactor (LFR)], selected for development by the Gen IV International Forum, require core outlet temperatures up to 900¿C. Most metals, including refractory alloys, loose much of their strength at these temperatures, and cannot survive core overheating accidents should they occur. Monolithic ceramics, retain strength at these high temperatures, but are too brittle to serve as a robust fuel cladding material. Ceramic composites, such as those made from silicon carbide fibers and matrices, can meet the temperature and toughness requirements, but are not impermeable to fission gases. This project will develop an improved duplex silicon carbide ceramic tube that combines the features of the composite (toughness at very high temperatures) with the impermeability of a monolithic fuel cladding. In Phase I, test specimens, containing an inner core of monolithic silicon carbide and an outer sheath of filament SiC infiltrated composite, will be designed and fabricated. A new, high temperature, mechanical strength testing method will be developed, and materials will be tested under simulated exposure conditions. Commercial Applications and Other Benefits as described by the awardee: A very high temperature fuel cladding material is an essential prerequisite to the eventual design and deployment of advanced generation IV fast spectrum nuclear reactors, which will be required later in this century to meet both the environmental and energy needs of the nation.