HYDRIDING OF ZIRCONIUM ALLOYS IN HYDROGEN GAS

Zirconium alloys were hydrided by exposure to hydrogen gas at pressures up to 13.6 MPa in an autoclave maintained at 350-degrees-C for 10 h. Hydrogen uptake was found to increase with applied hydrogen pressure. Surface oxide was found to inhibit hydrogen uptake; hydrogen uptake measurements and hydride morphologies of the specimens confirm that the rate of hydrogen uptake is controlled by die oxide. Under test conditions, at known temperature and pressure, the 10 h exposure was sometimes insufficient for uniformly distributed hydride formation. A layer of relatively high hydride concentration near the specimen surface was produced. A method for charging mechanical testing specimens, which exploits the uptake rate control by the oxide film, is proposed.