HYDROGEN PICKUP DURING CORROSION OF ZIRCONIUM ALLOYS

Several factors such as alloy composition, hydrogen content of the alloy, surface hydrides, and hydrogen content of the water have been investigated for their effect upon the amount of hydrogen picked up by zirconium alloys during corrosion in 680 deg F water. Metallic additions of nickel increase hydrogen pickup, antimony, chromium, and iron appear to decrease the hydrogen pickup, while the addition of tin has little or no effect. The hydrogen content of the metal (50 to 400 ppm) or of the water (0 in 2 atm of hydrogen pressure) does not appreciably change the amount of hydrogen picked up by the alloys studied. It is proposed that certain intermetallic compounds provide cathodic areas which aid in the concentration of hydrogen at the compound. The amount of corrosion-produced hydrogen entering the metal is controlled by the reaction of hydrogen with the particular compound. The hydriding of Zircaloy-2 by gaseous hydrogen is stopped when small quantities of water vapor are added to the hydrogen. (auth)