Behavior of plasma sprayed Cr coatings and FeCrAl coatings on Zr fuel cladding under loss-of-coolant accident conditions

To fabricate the oxidation resistance accident tolerance fuel cladding, Cr layer and FeCrAl alloys were deposited on Zircaloy-4 using atmospheric plasma spraying technology. The specimens were exposed under a simulated loss-of-coolant accident condition. XRD, SEM and EDS techniques were carried out to explore their high temperature behavior. According to the analysis results, both Cr coating and FeCrAl coating were successfully prepared by atmospheric plasma spraying system. Cr coating had superior oxidation resistance. Compact Cr2O3 scale forming on Cr coating acted as an oxygen diffusion barrier, whereas FeCrAl coating degraded due to inter-diffusion, leading to its poor protection for the cladding. Difference in standard Gibbs free energy of formation of Fe and Zr caused the prior oxidation of Zr. Accordingly, Zr-rich and Zr-depleted zones occurred in FeCrAl-coated specimens.