Manufacturing variability and deformation for Zr-2.5Nb pressure tubes

A research program (Task Group 3) aimed at determining the effect of microstructure variables on pressure tube performance was initiated over 30 years ago. Zr-2.5Nb pressure tubes were produced from the same ingot material by three variants on the standard CANDU reactor manufacturing process, designated by reference to routes 1, 2 and 3. Of the three Task Group 3 fabrication routes the route 1 tubes showed the largest difference compared to routes 2 and 3 and also compared with standard pressure tubes. They exhibited lower axial elongation and higher peak diametral strain. In addition, the deformation of tubes extruded by a single tube manufacturer using billets/ingots from three different producers has been studied. The results indicate that the Fe-content of the tubes has a significant effect on the final microstructure and this, in turn affects the axial elongation rates.