The delayed hydride cracking avoidance manoeuvre for Zr-2.5 Nb pressure tube alloy

Abstract In this work, the effectiveness of using a temperature manoeuvre to reduce the susceptibility of Zr-2.5 wt% Nb pressure tube alloy to delayed hydride cracking (DHC) is studied. The temperature manoeuvre consists of lowering the temperature by at least 30°C to a subcooling temperature when the specimen is under load, and heating up to the original temperature. The DHC suppressed by this temperature manoeuvre can usually be restored by a subsequent temperature decrease, which can be used as a measurement of the effectiveness of the temperature manoeuvre. Factors that affect the effectiveness of the temperature manoeuvre are studied. It is found that stress intensity factor has the strongest effect, and that the tensile and yield strengths of the pressure tube alloy also have a significant effect. Some experiments were carried out simultaneously in two laboratories, and reasonably consistent results were obtained.