It has been predicted that high level nuclear waste containers will be exposed to temperatures in the order of 250°C during the first 1000 years of emplacement. It is important to determine if a Ni-22Cr-13Mo-3W alloy (a proposed material for the containers) will maintain its mechanical and
chemical integrity under these conditions. Samples of several heats of this Ni-22Cr-13Mo-3W alloy were aged for times between 0.5 h to 40,000 h at temperatures ranging from 260°C to 800°C and their mechanical properties and corrosion resistance were evaluated as a function of aging temperature and aging time. Results show that the mechanical properties and corrosion resistance of the Ni-22Cr-13Mo-3W alloy (UNS N06022) decrease as the aging time increases for aging temperatures in
the order of 600°C and higher. For temperatures 427°C and below, the corrosion resistance and impact energy remain unchanged for aging times up to 40,000 h. Keywords: high level nuclear waste, nickel-based alloy, N06022, aging, microstructure, mechanical properties, corrosion resistance, electrochemical behavior, immersion tests, ASTM G 28 A, ASTM G 28 B, hydrochloric acid, ferric ions, caustic solution, J-13 water.