|
Role of Microchemistry and Microstructure on Variability in Corrosion and Deuterium Uptake of Zr-2.5Nb Pressure Tube Material Pages: 26 Published: Jan 2002
Download this paper for $25
PDF (1.1M)
View License Agreement Source: STP1423-EB Abstract Understanding the reasons for variability in D uptake in Canadian Deuterium Uranium (CANDU) reactor Zr-2.5Nb pressure tubes (PT)s will lead to improved surveillance and predictive strategies. Results from out-reactor aqueous exposures that suggest PT performance should be predictable based on offcut characteristics and may lead to the development of techniques to identify PTs with highest D uptake rates. The range of out-reactor corrosion and D uptake rates in Zr-2.5Nb coupons from different PT offcuts is similar to that found in test/power reactors. Out-reactor post-transition corrosion and D uptake rates at 310 and 360°C are found to be strongly correlated and decrease with increasing concentrations of Fe and Cr in the alloy. In the Bruce 3 reactor, PTs with higher D uptake show curly - microstructures with a large number of basal planes (in the -Zr grains), and -Zr grains, oriented towards the radial direction of the tube. Since oxidized -Zr regions are found to be associated with lateral cracking, the presence of a higher frequency of -Zr grains aligned normal to the surface in these curly microstructures may result in increased routes for D uptake in this material. Oxide structure is also found to be dependent on the -Zr orientation that results in different relative proportions of [001] growth versus general columnar oxide grains. Improved corrosion and D uptake performance is also found in Zr-2.5Nb material that is prefilmed (400°C for 24 h), -quenched in the billet stage and in material from the back of the extrusion.
| ||
