(V) Development of PVD Coatings for Hydrothermal Corrosion Mitigation of SiC-SiCf Cladding in Light Water Reactors

SiC-SiC_f composites are being investigated as advanced fuel cladding materials with enhanced accident tolerance for the light water reactors (LWRs) due to their high temperature stability and resistance to irradiation. SiC-SiC_f cladding offers excellent safety performance in a loss-of-coolant accident scenario compared to the currently used zirconium-alloy cladding. One challenge in the implementation of this composite for LWR cladding application is the hydrothermal corrosion of SiC at normal reactor operating conditions. This corrosion can lead to gradual recession of the cladding tube and detrimental silica buildup in the coolant.

In this work, a variety of environmental barrier coatings and coating technologies are being investigated to mitigate the corrosion of SiC. Of particular interest is the use of physical vapor deposition (PVD) processes to deposit a range of metallic and ceramic coating. Deposition processes under consideration include sputtering techniques and cathodic arc deposition. The effect of deposition parameters on microstructure will be presented and discussed. Data from a variety of characterization methods will be presented including TEM microstructural analysis, stress measurements using x-ray diffraction, and mechanical testing via nanoindentation. Autoclave corrosion testing was used to evaluate corrosion performance under prototypical hydrothermal conditions to screen out candidate coating materials. The effect of coating microstructure on corrosion performance will be presented.