Threshold stress intensity factor for delayed hydride cracking in Zr–2.5%Nb pressure tube alloy

Influence of hydrogen content on fracture toughness of CWSR Zr–2.5Nb pressure tube alloy

“…Though the Zr-2.5Nb alloy pressure tubes manufactured for CANDU reactors are extensively investigated [3,5,7,8,16,17,20,22,24,25], no information is available in open literature on the fracture toughness of CWSR Zr-2.5Nb alloy pressure tube used in IPHWRs. The flow behavior [26], impact toughness [27] and delayed hydride cracking (DHC) behavior (DHC crack growth velocity -V DHC and threshold stress intensity factor associated with DHC -K IH ) [21,28,29] of CWSR Zr-2.5Nb alloy used in Indian PHWR was reported earlier. The objective of the present investigation is to estimate the influence of hydrides on the fracture initiation and fracture propagation toughness of unirradiated, double melted CWSR Zr-2.5Nb pressure tube alloy in the temperature range of ambient (30°C) to the reactor operating temperature of 300°C.…”

“…The tubes for the Indian PHWRs are manufactured at Nuclear Fuel Complex (NFC), Hyderabad [21], following a fabrication route similar to but not same as the modified route II developed for the pressure tubes of CANDU reactors [22]. The modified route II [22] consists of two cold working steps (instead of one cold working step for the conventional route) and an intermediate annealing step [21].…”

“…The modified route II [22] consists of two cold working steps (instead of one cold working step for the conventional route) and an intermediate annealing step [21]. However, there are two differences between modified route II developed for CANDU reactors and that being practiced at NFC.…”

“…The microstructure of CWSR Zr-2.5Nb pressure tube comprises of heavily elongated and textured a-Zr grains surrounded by thin grain-boundary network of b-Zr phase [21,22]. The texture of CWSR Zr-2.5Nb alloy is such that crystallographically, only two hydride platelet orientations are permissible, viz., along the circumferential-axial and the radial-axial planes [10,23], which are respectively called circumferential and radial hydrides, as illustrated schematically in Fig.…”

Simulation studies for optimisation of phased array parameters for examination of roll-joints in pressurised heavy water reactor coolant channels

“…This is due to the diffusion of hydrogen up the stress gradient. The hydrogen build-up ultimately leads to initiation and growth of delayed hydride cracking (DHC) [5][6][7][8] . The roll-joint area is therefore monitored periodically during in-service inspection to look for any DHC.…”