A Study on Nationwide Maps with Geoenvironmental Information and Geological Characteristics of Bedrock for HLW Disposal

Abstract

High-level radioactive waste (HLW) disposal in the nuclear generation industry is a critical issue that must be solved not only in South Korea, but also worldwide. In South Korea, temporary storage facilities for spent fuels of each power plant are nearly saturated. Thus, discussions on the interim storage and permanent disposal of HLW are inevitable. For the geological disposal of HLW, determining a suitable disposal system that considers the geological environment of each country is essential. Since a disposal system wholly depends on the characteristics of the disposing host rock, selecting a suitable host rock is vital. However, a host rock for the geological disposal of HLW in South Korea has not yet been determined because the geological environments of South Korea are tectonically diverse and complicated. Moreover, information available on the deep geological environment is insufficient for selecting a suitable host rock. Therefore, in this paper, we introduced production processes of geoenvironmental information maps for nationwide geological characteristics that can be used to exclude unsuitable areas for HLW geological disposal, which constitutes the first step in the process of site selection. The geoenvironmental information maps were prepared for 8 items, including rock type, mine distribution, lineament, faults, seismotectonics, uplift rate, hydraulic conductivity, and geothermal gradient. Based on the geoenvironment information map of the rock type and the geological structures in South Korea, an ongoing multidisciplinary study on the characteristics of bedrock was introduced. The southern part of the Korean peninsula was divided into four tectonic structures and four representative rock types, and methods for obtaining their geological, hydrogeological, geochemical, geophysical, and rock mechanical characteristics using a 750-m deep borehole drilled in the relevant area were presented. Additionally, the results were analyzed with focus on the uniaxial compressive strength and in-situ stress characteristics, which are key parameters in the field of rock mechanics. This information could be useful for investigating reliable basement characteristics through multidisciplinary analysis linked to fields other than rock mechanics.