DLI-MOCVD CrxCy coating to prevent Zr-based cladding from inner oxidation and secondary hydriding upon LOCA conditions

Zirconium-based claddings with an outer chromium coating resistant to corrosion are studied and developed as evolutionary Enhanced Accident Tolerant Fuel (E-ATF) concept for light water reactors. However, in hypothetical LOss-of-Coolant-Accident (LOCA) conditions, following clad ballooning burst, the does not allow protect inner surface of cladding from High Temperature (HT) steam oxidation associated secondary hydriding due starvation occurring within gap between nuclear fuel pellets. To address this issue, DLI-MOCVD (Direct Liquid Injection Metal-Organic precursors - Chemical Vapor Deposition) CrxCy coatings have been successfully deposited onto Zr-based tube prototypes. Then, preliminary two-sided tests shown that such is able increase resistance at HT surface. The present study aimed performing new 1200 °C on Zircaloy-4 prototypes a 5–20µm-thick coating, conditions more representative LOCA, after first internal pressure-induced burst step. Additionally, complementary carried out up 1 h °C, short and/or outer-coated segments. Finally, Post-Quench (PQ) Ring Compression Tests (RCTs), fractographic analysis deep metallurgical investigations including neutron-tomography performed get insights into PQ behavior inner-coated clad. Among other results, it makes possible reduce significantly surface, burst. After least 600 s under reference uncoated fails upon final quenching while prototype keeps its integrity. RCTs showed higher strength material, related lower oxygen hydrogen uptakes substrate.