High-Resolution Characterization of Corrosion of Nuclear Fuel Cladding Alloys

• 作 者: Jing Hu Alistair Garner Na Ni Ali Gholinia Rebecca Nicholls Sergio Lozano-Perez Philipp Frankel Michae Preuss Chris Grovenor
• 机 构: Department of Materials, Oxford University, Parks Road, Oxford, UK
• 出 处: The 4th International Symposium on Materials and Reliability
• 发表日期: 2015年8期

　　As part of the MUZIC2 project, several high resolution analysis techniques have been used to study the microstructure of a range of commercial and developmental Zr alloys under autoclave simulated PWR conditions1.Here we report a methodology combining Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), Transmission-EBSD (t-EBSD) and Electron Energy Loss Spectroscopy(EELS) to analyse the structural and chemical properties of the metal-oxide interface of a WestinghouseTM developmental Zr-1.0Nb alloy in unprecedented detail.The sample was oxidized in an autoclave at EDF Energy under simulated Pressurized Water Reactor (PWR) water conditions at 360℃ for 360 days, and shows no sign of transition, suggesting its excellent corrosion resistance1.TEM and STEM results reveal the complexity of the distribution of suboxidegrainsat the metal-oxide interface.Convergent beam electron diffraction (CBED) patterns were acquired from a region close to the metal/oxide interface which matches with the [3 2-4]zone axis of the hexagonal ZrO phase with P-62m symmetry and lattice parameters a=5.31 (A) and c=3.20 (A) predicted by Nicholls et al2.EELS provided accurate quantitative analysis of the oxygen concentration across the interface, identifying the existence of local regions of stoichiometric ZrO and Zr3O2, with significant local variations in thicknesses from 20 nm to 326nm, much thicker than observed previously in otheroxidised zirconium alloys3.Transmission-EBSD confirmed that the suboxide grains can be indexed with the hexagonal ZrO structure.The t-EBSD analysis has also allowed us to map a relatively large region (~7μm) of the metal-oxide interface,revealing the location and size distribution of the suboxide grains4.These observations will be compared to previous reports of less corrosion-resistant alloys studied by the same techniques.