A thermochemical process known as sulfur-iodine (S-I) cycle has recently been identified as a route to generate hydrogen using nuclear power. The S-I cycle consists of several chemical reactions at temperatures ranging from 120 to 800^o C. Nickel-base austenitic Alloy 800H has been identified as a structural material for heat exchanger applications related to the nuclear hydrogen generation. Since Alloy 800H will be subjected to very hostile environmental conditions, the susceptibility of this material to stress-corrosion-cracking, hydrogen-embrittlement and localized corrosion has been determined by state-of-the-art experimental techniques. The tensile properties of Alloy 800H have also been determined at temperatures ranging from ambient to 600^o C. Metallographic and fractographic evaluations of the tested specimens have been performed by optical microscopy and scanning electron microscopy, respectively. The overall data will be presented in this paper.