Interaction of SO2 with Zircaloy-4 surfaces at various temperatures

Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) methods were used to study the interaction of SO with surfaces of Zircaloy-4 (Zry-4) over a wide temperature range under ultra-high vacuum (UHV) conditions. Experiments were performed under UHV conditions at a base pressure of about 3 × 10 -10 Torr. An ion getter pump was used in combination with a titanium sublimation pump while a turbomolecular pump was used for pumping of the gas handling system. DC heating was performed through tantalum wires that were spot welded to the sample while cooling was carried out using a copper braid connected to a liquid-nitrogen cold finger. The TPD data does not provide any evidence of molecular desorption following exposure of Zry-4 surfaces to SO2 regardless of adsorption temperature. The results show that the hydrogen desorption state not only depends on the presence of oxygen but also on adsorption temperature.