Deuterium permeability and diffusivity in FeCrAl alloys for LWR cladding application

FeCrAl alloys, one of the promising ATF (Accident Tolerant Fuel) claddings, have been widely researched because of their superior oxidation resistance. However, compared with zirconium-based cladding, the higher tritium permeability of FeCrAl alloys could result in a higher tritium concentration in the primary coolant water. Deuterium transport through ferrite FeCrAl alloys compared with 316L-SS was investigated using a permeation apparatus. Deuterium permeability, diffusivity and solubility in FeCrAl alloys were measured. A 2D finite element method model was built based on updated test results to analyze the tritium release from LWRs fuel rods. Deuterium diffusivity in FeCrAl alloys is more than one order of magnitude higher than 316L-SS, but the solubility is much lower. In addition, the impact of all these data on LWRs operation was discussed. The diffusion rate significantly affects the time to reach steady state. Still, even if the diffusion rate is reduced by a factor of 0.01, it does not affect the steady-state tritium permeability from the fuel rods. FeCrAl fuel rods would experience a considerable tritium flux release rate because of the high diffusivity.