Mechanical properties on δ-zirconium hydride grown on Zr2.5%Nb

In the zirconium components of the CANDU reactor, a secondary phase of zirconium hydride can precipitate if the hydrogen concentration reaches the terminal solid solubility (TSS) for precipitation. The amount of hydrogen in components increases during the lifetime as a consequence of hydrogen pick-up from corrosion reactions with coolant. Due to the very small size of the hydrides within the zirconium matrix, it is challenging to make direct measurements of the mechanical properties of the hydride phase; knowledge of these properties is beneficial when predicting the performance of hydrided zirconium components. Measurements of the mechanical properties of δ-zirconium hydrides were made possible using a novel approach combining a numerical model with results from atomic force microscopy (AFM) and nanoindentation. We have been able to extract the hardness and effective yield stress of δ-zirconium hydrides. Data is reported for hydride grown on a Zr2.5Nb pressure tube. The combination of experimental data and a numerical model showed a reliable way to measure the local mechanical properties of δ-zirconium hydrides. (author)