Investigation of residual stress changes and formation of hydride phase in production stages of Zr-1%Nb alloy

Zr-1%Nb alloy is the most common alloy used as nuclear fuel cladding in Russian reactors. In producing a nuclear fuel cladding, the cold rolling (pilger) and the final straightening lead to the creation of residual stresses and a change in the distribution of these stresses within the fuel cladding. The residual stresses are known to be effective in increasing the hydride fraction in nuclear fuel pods formed under working conditions by hydrogen adsorption of water and have destructive effects. In this study, the residual stresses created in different stages of fuel cladding fabrication, including samples before annealing, post-annealing, and straightening, were measured using X-ray diffraction and splitting. In addition, the amount of hydride fraction in different samples was evaluated. The effect of annealing on the orientation of hydrides was performed in annealing at 500, 540, and 580 °C for 4 hours.