Effect of Hydrogen Isotopes on Delayed Hydride Cracking Behavior of Zr-2.5Nb Pressure Tube Material

To study the effect of hydrogen isotopes on the delayed hydride cracking (DHC) behavior, Zr-2.5Nb pressure tube (PT) material was charged with about 100wppm hydrogen or deuterium and DHC tests were carried out between 202 and 283 degrees C. At 202 degrees C, DHC velocity ratio of hydrogen- and deuterium-charged Zr-2.5Nb PT material was less than the ideal value of root 2. The lower velocity ratio was explained on the basis of terminal solid solubility for dissolution (TSSD) and residual hydrogen (H-R) present in deuterium-charged PT material. Using TSSD and H-R, a mixture rule was developed to predict the DHC velocity of deuterium-charged material (V-DHC(D)) as well as DHC velocity ratio of hydrogen- and deuterium-charged material. The mixture rule was evaluated using present data and data reported in literature.