[en] The Korea Radioactive Waste Agency (KORAD) has developed a dual-purpose metal cask for the dry storage of spent nuclear fuel that has been generated by domestic light-water reactors. The metal cask has been designed in compliance with international and domestic technology standards, and safety was the most important consideration in developing its design. It has been designed to maintain its integrity for 50 years in terms of major safety factors. The metal cask ensures the minimization of waste generated by maintenance activities during the storage period as well as the safe management of waste. An activation evaluation of the main body including internal and external components of metal casks whose design lifetime has expired provides quantitative data on their radioactive inventory. The radioactive inventory of the main body and the components of the metal cask was calculated by applying the MCNP5·ORIGEN-2 evaluation system and by considering each component’s chemical composition, neutron flux distribution, and reaction rate, as well as the duration of neutron irradiation during the storage period. From the evaluation results, it was found that 10 years after the end of the cask’s design life, ⁶⁰Co had greater radioactivity than other nuclides among the metal materials. In the case of the neutron shield, nuclides that emit high-energy gamma rays such as ²⁸Al and ²⁴Na immediately after the design lifetime had greater radioactivity. However, their radioactivity level became ignorable after 6 months due to their short half-life. Based on the evaluations of this study it is believed that the nuclide inventory of a spent nuclear fuel metal cask can be utilized as basic data when the decommissioning of a metal cask is planned, for example, for the development of a decommissioning plan, the determination of a decommissioning method, the estimation of radiation exposure of workers engaged in decommissioning operations, the management of radioactive wastes, etc. (author)