Early studies on Cr-Coated Zircaloy-4 as enhanced accident tolerant nuclear fuel claddings for light water reactors

Abstract

Coatings with thicknesses between a few microns and ∼10 μm deposited on a Zircaloy-4 substrate have been studied with the objective to provide a significant reduction in the oxidation-induced embrittlement of the nuclear fuel cladding, especially in accidental conditions, such as LOss-of-Coolant-Accident (LOCA) conditions. This paper deals with the early studies carried out at CEA, several years before the Fukushima-Daiishi events, on different types of coatings obtained by a physical vapor deposition process. The studied coatings included ceramic, nitride and metallic multi-layered ones. The results of this screening analysis showed that the first generation of chromium-based coatings exhibited the most promising behavior: good compromise between oxidation resistance and adhesion to the metallic substrate, good fretting resistance and improved resistance to oxidation in steam at high temperature (Design Basis Accident LOCA conditions and slightly beyond).