Grants and Contributions:

Grant or Award spanning more than one fiscal year (2017-2018 to 2018-2019).

Zirconium alloy pressure tubes comprise the in-core portion of the primary pressure boundary of CANadianx000D
Uranium Deuterium (CANDU) reactors. These tubes are susceptible to degradation associated with thex000D
absorption of hydrogen from coolant. The absorption of even small amounts of hydrogen can causex000D
susceptibility to fracture or reduction in fracture toughness due to the precipitation of brittle hydride phases. Asx000D
pressure tubes age, engineers are required to continually develop more advanced evaluation procedures. Thesex000D
procedures are based upon improved understanding of the nature of these degradation mechanisms and arex000D
validated against experimental data.x000D
Microscopically, pressure tube material consists of crystals where atoms are stacked with specific orientations.x000D
Each crystal is also known as grain. It has been shown that pressure tubes with different manufacturingx000D
histories have different susceptibilities to hydride embrittlement. Although the macroscopic loads acting on thex000D
pressure tubes are well understood, there is a lack of data on the grain-level stresses, particularly close tox000D
hydrides. As hydrides and fracture are active on this level, it is likely that understanding this length scale couldx000D
help explain variability in hydride embrittlement.x000D
This project focuses on numerical modelling of grain-level stresses in pressure tubes. The modelling will bex000D
done by a Crystal plasticity finite element code that can simulate the effects of material microstructures. Thex000D
existence of possible relationship between microstructure and hydride embrittlement will be explored. Also, thex000D
feasibility of a modern diffraction technique for measuring such stresses will be explored. This project will bex000D
conducted in collaboration with Kinectrics Inc. The outputs will support industrial understanding of the naturex000D
of hydride phases, and can be used by industrial partners to develop more advanced engineering codes.