Research Progress on Chromium-Based Accident-Tolerant Coatings for Zirconium Alloy Cladding

The Fukushima nuclear accident revealed the serious safety hazards of zirconium alloy cladding under both design-basis and beyond-design-basis accident conditions, primarily stemming from its rapid oxidation reaction and hydrogen embrittlement risk at high temperatures. Consequently, the development of accident-tolerant fuel (ATF) has become a significant research direction in the nuclear fuel field, with the aim to enhance the safety margin of fuel assemblies during both normal operation and accident scenarios. Among various ATF technology solutions, applying protective coatings on the surface of zirconium alloy cladding is considered one of the most promising near-term strategies. Chromium (Cr)-based coatings, in particular, have attracted considerable attention due to their low thermal neutron absorption cross section, excellent high-temperature oxidation resistance, and thermal expansion coefficient compatible with zirconium alloys.This article systematically reviews the corrosion behavior, mechanical properties, oxidation resistance, and primary failure mechanisms of Cr-coated zirconium alloys under normal operation and accident conditions. It further discusses recent research progress in enhancing the oxidation resistance of chromium coatings through heterogeneous element doping and the introduction of intermediate diffusion barrier layers. Additionally, it points out key unresolved issues in the current research and provides an outlook for future research directions for optimizing the performance and reliability of chromium-based coatings in nuclear applications.