Hydrothermal Corrosion of PVD and Cold Spray Cr-Coatings on Zircaloy-4 in Different LWR Coolant Environment

Accident-tolerant fuel (ATF) cladding materials aim to improve fuel reliability and safety during accident scenarios in water-cooled reactors. These ATF cladding should also perform comparable or better than the current zirconium alloy cladding under reactor normal operating conditions. The deposition of coatings on the current Zircaloy has shown to be a feasible alternative as coating technologies can be readily implemented in current manufacturing facilities. In this regard, different protective coatings and coating methods are being studied to replace the current cladding with reliable ATF systems. Cr-coated claddings have emerged as one of the best candidates for ATFs for light water reactor (LWR), particularly for applications in pressurized water reactor (PWR). However, limited data or no data available on stability of Cr-coated cladding in boiling water reactor (BWR). In this study, surface-modified Zircaloy-4 was produced by depositing a protective coating of chromium by two different coating techniques, Physical Vapor Deposition (PVD) and Cold Spray (CS). The aim of this work is to investigate the hydrothermal corrosion protection offered by the Cr-coating. Coated samples have been tested in both hydrogen and normal water chemistry at simulated BWR conditions. The preliminary data confirmed poor corrosion protection of Cr-coating. A comparison of their corrosion behavior with current fuel cladding of Zircaloy-2 and Zircaloy-4 will be provided. Wide range of analysis methods are used for this scope, such as scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).