Parameter Study on Crystalline and Sedimentary Rock for High-Level Radioactive Waste Disposal Considering the Geological Characteristics of the Korean Peninsula

ABSTRACT: The selection of bedrock for deep geological disposal of high-level radioactive waste (HLW) typically depends on the geological characteristics of each country. In Korea, plutonic rock, gneiss, and sedimentary rock constitute 30%, 30%, and 25% of the geological composition, respectively, and the bed rock for deep geological repository has not yet been determined. In this study, 750 m deep drilling was conducted on several rock types. The drilling location was selected in consideration of the tectonic structure and the rock types. Several field tests were conducted using boreholes in granite and sedimentary rocks, as well as laboratory tests using cores. Among various evaluation parameters, uniaxial compressive strength, in-situ stress, hydraulic conductivity, fault development etc. were obtained and compared between granite and sedimentary rock. Through a series of analyses, it was found that in the case of crystalline rocks in Korea, granite from the Mesozoic Jurassic and in the case of sedimentary rocks, Jinju and Jindong formation from the Mesozoic Cretaceous period are likely candidate rock types. However, since it is the result of utilizing a small number of boreholes, it is expected that numerous in-depth investigations and mineralogical analyzes will be required. 1. INTRODUCTION Korea began site selection for nuclear power plants in 1964, and Gori Unit 1 began commercial operation for the first time in 1978. In 1978, the first year of nuclear power generation, it generated 2,324 GWh, accounting for 7.4% of Korea's total power generation, but in 2022, it generated 176,054 GWh, accounting for 29.6% of the total power generation, playing an important role in Korean industry. However, like any other country that uses nuclear power, the issue of disposal of spent nuclear fuel generated from nuclear power generation is an important task to resolve. Currently, Korea temporarily stores high-level radioactive waste within nuclear power plants. In December 2021, the government announced the second high-level radioactive waste management master plan and presented basic policies for high-level radioactive waste, facility plans such as site selection, technology development, and investment strategies. A step-by-step site selection procedure was presented to establish a deep disposal facility for high-level radioactive waste, and objectives and major activities for site suitability investigation were presented. According to the 2nd management master plan, site selection is scheduled to be carried out over a period of 13 years after the start of the project (Fig. 1)