SiC_f-SiC composite fuel cladding for light water reactors

The use of silicon carbide (SiC) and SiC fiber reinforced composites (SiC_f-SiC) for reactor fuel cladding have seen increased interest since the accident at Fukushima. In particular SiC is being investigated as an accident tolerant fuel due to its retention of strength at high temperature, good stability under irradiation, and low rates of hydrogen production in loss of coolant accident conditions. However, for SiC to be a viable option it must be shown that an all ceramic cladding can maintain low permeability and that rates of corrosion are acceptable throughout the entire fuel lifetime. In this paper, details in the design and development of a General Atomics permeability rig will be discussed and data will be presented showing that a SiC-based cladding can attain leak rates less than or equal to 5x10^-12 atm cc/s that surpass existing leak rate requirements imposed for light water reactor applications. Corrosion data was obtained in collaboration with Westinghouse and show rates lower than that present for Zircaloy cladding under normal operating conditions. This data will be presented in the context of computer modeling that has been used to develop an all ceramic cladding design that is expected to retain adequate strength and permeability performance throughout the entire fuel lifetime, from startup to end of life storage conditions. (author)