| Abstract Scope |
The Fuel-Cladding Chemical Interaction (FCCI) phenomenon presents a challenge to the longevity and performance of steel-clad metallic fuels in sodium-cooled fast reactors (SFRs), especially under high burnup and elevated operating temperatures. While pure Y2O3 barriers have historically been used to prevent molten uranium interactions with crucibles during metal fuel fabrication, their effectiveness as in-reactor diffusion barriers against aggressive fuel and fission products remains an open question.
This study addresses that challenge by evaluating both the limitations of standalone Y2O3 coatings and the potential of a multilayer design to enhance FCCI mitigation under simulated extreme reactor conditions. We present a novel multilayer metal–ceramic thin film (Y2O3/CrY) coating architecture, systematically developed through mechanical testing, radiation tolerance assessment, and high-temperature diffusion analysis.
The optimized architecture incorporates stoichiometric Y2O3 layers for their exceptional radiation stability, chemical inertness, and low fission product diffusivity (evaluated through this work). These oxide layers are alternated with ductile CrY interlayers that significantly improve fracture toughness and mechanical resilience. Design refinements, including increased ceramic thickness, optimized interlayer composition led to successful suppressed crack propagation and maintained coating integrity under extreme mechanical stress (>10x expected stress during reactor operations) and demonstrated radiation resistance (up to ~300 dpa).
This multilayer strategy marks a significant advance in FCCI barrier technology, offering a robust pathway toward safer, higher-performance fast reactors essential to the future of sustainable nuclear energy. |