Effect of Hydrogen on Thermal Creep Behaviour of Zr–2.5Nb Pressure Tube

Zr–2.5Nb alloy, with its high yield strength and low hydrogen absorption, is used in Pressurized Heavy Water Reactor (PHWR) as pressure tube. Hydrogen in solid solution form and in hydride precipitate form may alter the mechanical properties of the Zr–2.5Nb pressure tube. In the present study, the effect of hydrogen on thermal creep behaviour of Zr–2.5Nb alloy pressure tube material is characterised in the temperature range of 350–450 °C and a stress ranging from 0.7 to 0.9 times of yield strength. The variation in rupture time, minimum creep rate, stress exponent and activation energy is determined for as-received, 150 and 200 wppm hydrogen charged samples. An attempt has been made to understand the role of hydrogen in solid solution form and as hydride precipitate form on thermal creep behaviour of Zr–2.5Nb pressure tube alloy.