Out-of-pile RandD on chromium coated nuclear fuel zirconium based claddings for enhanced accident tolerance in LWRs

Abstract : In the framework of the CEA/AREVA/EDF French nuclear institute, coatings (with thicknesses of a few microns up to $\sim$20$\mu$m) on zirconium alloy cladding have been studied with the objective to provide a significant reduction in the embrittlement of the cladding in accidental conditions, such as the lossof-coolant accident (LOCA). Early studies performed at CEA on several types of coatings obtained by a physical vapor deposition (PVD) process, including ceramic nitride and metallic multi-layered coatings, are discussed in a first part of this paper. The results of this screening analysis showed that chromium coatings have exhibited the best compromise between oxidation resistance and adhesion of the coating. In a second part, the present paper gives an overview of out-of-pile results obtained so far on Cr-coated Zircaloy 4 cladding in both nominal and accidental (LOCA) conditions