Development Of Gaseous Hydrogen Charging Of Zr Alloys Using A Coulometric Titration Technique

Abstract

The Coulometric titration technique is described and shown as a variant of the gaseous hydriding method. Zircaloy-4 samples were hydrided by exposure to ultrahigh purity argon gas containing up to 7500 ppm hydrogen in a quartz-tube furnace at 400°C. At known temperature and hydrogen partial pressure, the sample hydrogen uptake is controlled by the exposure time to the gas. This technique has been successfully used at Chalk River Laboratories to charge mechanical test specimens of Zircaloy-4 to high levels of hydrogen concentration, with adequate control of hydrogen uptake, with uniform distribution of the hydride phase and without extraneous changes to alloy microstructure.