Effect of deuterium content on fracture toughness of Zr-2.5Nb pressure tube material in the temperature range of ambient to 300 °C

Axial fracture toughness of cold worked and stress relieved Zr-2.5Nb pressure tube material containing deuterium between 5 and 200wppm was determined as per ASTM E−1820-15 between 25 and 300 °C using 17 mm wide Curved Compact Tension samples. For deuterium charged materials, the variation of the fracture toughness with test temperature showed typical S curve behavior. At 25 °C, the fracture toughness dropped drastically between 5 and 30wppm of deuterium concentration and afterwards it was constant between 30 and 200wppm. Samples having similar axial split density had similar fracture toughness. The lower-shelf and upper-shelf temperature was attributed to a critical axial split density and disappearance of axial split on fracture surface, respectively. •Fracture toughness of Zr-2.5Nb pressure tube was evaluated.•Fracture toughness was dropped drastically between 5 and 30wppm of deuterium concentration.•Variation of fracture toughness of deuterium charged pressure tube material showed typical S curve behavior with upper shelf temperature of about 200 °C.•The lower-shelf temperature shown by deuterium charged material was attributed to a critical axial split density.•The upper-shelf temperature shown by deuterium charged material was attributed to disappearance of axial split.