A step-by-step approach is being adopted worldwide with respect to site selection for the geological disposal of high-level radioactive waste (HLW). Korea also adopted a three-step approach. In order to conduct systematic and efficient site investigation and site evaluation, a classification system for evaluation elements by stage has been proposed, and it is subdivided into aspects, items, and parameters. Among a total of 17 items and 103 parameters, rock engineering-related items are 3 items and 33 evaluation parameters. Uniaxial compressive strength, in-situ stress are selected as key evaluation parameters, taking into account domestic and foreign cases, the importance of rock engineering, and the existence of international standard testing methods. Their characteristics and the distribution range of the domestic parameters are investigated. In this study, two types of granite were selected and regional distribution characteristics were analyzed based on the data obtained through drilling up to 750 m.
According to the 1st (2016) and 2nd (2021) high-level radioactive waste management master plans announced by the government, site investigation and site selection for deep geological disposal of high-level radioactive waste follow a step-by-step procedure. The act related to deep geological disposal of high-level radioactive waste and site selection, which is currently being discussed in the National Assembly, also includes a step-by-step site survey procedure. A step-by-step site investigation procedure has been proposed by the International Atomic Energy Agency (IAEA, 1994). Similar to the IAEA and advanced countries, Korea's step-by-step site survey is planned for the third step, which is to conduct a nationwide survey, exclude unsuitable areas, and conduct basic and detailed surveys on the remaining candidate sites.
Based on domestic and foreign research cases, Kim et al., (2020a) proposed the geoenvironmental evaluation parameters necessary for site surveys at each step. The proposed classification system for investigation parameters was divided into evaluation aspects, items, and parameters, and a total of 17 items and 103 parameters were proposed, of which 33 were related to rock mechanics and engineering. The Korea Institute of Geoscience and Mineral Resources, which conducts research on geology and resources in Korea, is conducting deep drilling and multidisciplinary geoscientific surveys for the deep geological disposal of high-level radioactive waste on Korea's representative rock types, considering the geologic tectonic structures.
