Study of hydrides precipitation on zirconium alloys for nuclear applications

Studies have been developed to improve the properties of zirconium alloys used in nuclear power reactors. The precipitation of hydrides is a limiting factor for the life of these materials. The understanding of the precipitation mechanisms for these hydrides and their relationship with the microstructural characteristics are still subject of study, particularly its characterization by TEM. This work aims to investigate the precipitation of hydrides in two commercial zirconium alloys - Zr-1Nb-1Sn-0,1Fe and Zr-1Nb – with very distinct microstructures, used as tubing which are parts of the fuel element in nuclear reactors. The characterization of these materials was performed, using optical microscopy, scanning electron microscopy and transmission electron microscopy, for hydrogen-free and hydrogenated conditions, including a sample modified by heat treatment. Hydrides presented acicular and plate morphologies. They were frequently associated to the β particles. In addition, the combined influence of microstructure and texture on hydrides precipitation was evaluated. The more intense texture was for the αZr basal poles (0001) , plus hydrides precipitated circumferentially in relation to the cross section of tubing, and were independent of the morphology of grain boundaries. (author)