Thin film coating of silicon carbide on zircaloy-4 tube by FCVD process and a study on its kinetics

Abstract Development of accident tolerant fuel cladding gained importance after the Fukushima-Daiichi accident with the aim of preventing hydrogen embrittlement and uranium-zirconium eutectic formation in zirconium based claddings during accidental scenarios such as reactivity insertion accident (RIA) or loss of coolant accident (LOCA). One of the considerable solutions is to obtain thin dense coatings of silicon carbide (SiC) on inner and outer surfaces of thin walled fuel cladding. Silicon carbide has several favorable properties required for the coating material, such as strength and hardness retention at high temperature, high thermal conductivity, high temperature chemical and oxidation resistance, high irradiation stability and high critical heat flux. In this work, fluidization enhanced chemical vapor deposition (FCVD) process has been used to achieve thin coatings of silicon carbide on inner and outer surfaces of zircaloy-4 fuel cladding. A parameter optimization based numerical experimentation algorithm was implemented using discrete particle method and computational fluid dynamics based open-source solvers to obtain kinetic parameter of FCVD process and individual mass deposition rates for inner and outer substrate surfaces. The coating thickness obtained by FCVD process lies in the range of 0.5-4.5 μ m for inner surface and 1.2-12 μ m for outer substrate and the total mass deposition on outer substrate surface is 2.4-2.8 times greater than that of inner substrate surface. Details of FCVD process and numerical experimentation algorithm are discussed in this paper.