Study of the hardness and Young's modulus at the fuel-cladding interface of a high-burnup PWR fuel rod by nanoindentation measurements

• Published in: Journal of nuclear materials Vol. 560; p. 153511
• Main Authors: Schneider, C., Fayette, L., Zacharie-Aubrun, I., Blay, T., Sercombe, J., Favergeon, J., Chevalier, S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2022; Elsevier BV; Elsevier
• Subjects: Engineering Sciences; Fission products; Fuel-cladding interface; Grain size; Hardness; Interfaces characterization; Irradiation; Mechanical properties; Microstructure; Modulus of elasticity; Nanoindentation; Nuclear fuel elements; Nuclear fuels; Nuclear reactors; Nuclear spent fuel; Oxidation; Particle size; Porosity; Pressurized water reactors; Tetragonal zirconia polycrystals; Thickness; Uranium dioxide; Young's modulus; Yttria-stabilized zirconia; Zirconia; Zirconium; Zirconium dioxide; Nanoindentation; FP; PWR; Hardness; Interfaces characterization; FCI; Young's modulus; SE; Zy4; Fuel-cladding interface; HBS; HB; SEM; Nuclear spent fuel
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2022.153511

•Mechanical characterization of the fuel-cladding interface by nanoindentation.•Hardness and Young's modulus measurements in the fuel-cladding interface.•SEM characterization of grain size and shape in the fuel-cladding interface.•Correlation between microstructure, phases and mechanical properties. During irradiation in a nuclear reactor, the fuel swelling and the cladding creep are at the origin of the contact between the fuel and the cladding, which in turn leads to the initiation of Zr oxidation by the UO2 fuel. In high burnup fuels, the zirconia layer formed at the Fuel Cladding Interface (FCI) presents numerous circumvolutions and a heterogeneous microstructure within its thickness. In this paper, nanoindentation measurements are carried out in the fuel-cladding interface of a PWR fuel rod irradiated up to a high burnup of 61 GWd/tU. The measured hardnesses and Young's moduli of the internal zirconia layer are compared to reference measurements obtained on a non-irradiated sample of commercial Y-TZP. The study of the evolution of mechanical properties across the zirconia layer led to the identification of four distinct zones related to the zirconia microstructure (phase, grain size, porosity and fission product recoil). Close to the cladding, the zirconia hardness HZrO2tends toward the zirconium hardnessHZr. Then, the zirconia hardness increases significantly with the grain size, until reaching a plateau at the middle of the zirconia layer, where the maximum hardness is obtained. Following the same trend, the elastic modulus progressively increases in the zirconia layer and reaches a plateau near the fuel High Burnup Structure.