Tensile properties and fracture toughness of Zr-2.5Nb alloy pressure tubes of IPHWR220

The pressure tubes of Indian Pressurized Heavy Water Reactor (IPHWR) of 220 MWe are made of Zr-2.5Nb alloy manufactured either from Double Melted (DM) or from Quadruple Melted (QM) ingots. These pressure tubes are manufactured by hot extrusion, two stages of cold pilgering with intermediate annealing and autoclaving. To achieve good in-reactor performance, it is required to have minimum variability in the mechanical properties of the pressure tube across its length and between tube to tube. In this work, tensile properties and fracture toughness parameters (Jmax, dJ/da and CCL determined as per ASTM E1820-11 standard) of unirradiated Zr-2.5Nb alloy pressure tubes manufactured from DM and QM ingots using samples obtained from front and back end of the tubes is presented. The mechanical properties were evaluated in temperature range of 25-450 °C and compared with the corresponding data reported in literature for CANDU pressure tubes.