Numerical Assessment of Repository Stability Based on Preliminary Disposal Concept for High-Level Radioactive Waste in Korea

Summary

Abstract

The operation of nuclear power plants inevitably generates spent nuclear fuel, and its disposal is principally managed within national borders. Disposal concepts vary depending on the geological characteristics of each country. In Korea, the High-Level Radioactive Waste Management Act took effect in 2025, under which the Korea Radioactive Waste Agency (KORAD) leads the development and implementation of disposal strategies. As part of this effort, KORAD has proposed a preliminary disposal concept tailored to domestic conditions, which will be further refined through successive research and project phases. This study presents a numerical stability assessment of the proposed high-level radioactive waste repository concept, incorporating in-situ stress data and uniaxial compressive strength measurements compiled by the Korea Institute of Geoscience and Mineral Resources (KIGAM). The evaluation explores three key scenarios: vertical vs. horizontal disposal, mechanical vs. thermo-mechanical analysis, and short-term vs. long-term performance. The dimensions and layout of disposal holes and tunnels used in the simulations are based on repository designs developed by the Korea Atomic Energy Research Institute (KAERI), while geotechnical properties reflect both field measurements and standard input values commonly used in Korean rock engineering. Numerical results indicate that the horizontal disposal configuration offers superior stability over the vertical design. Even when thermal effects are considered, the system remains mechanically stable. Long-term analyses also suggest that stability can be maintained under typical geological conditions, provided the site is not in an extremely unfavorable environment. As this study is based on generalized geological settings rather than a specific site, future efforts should focus on site selection, characterization, and detailed repository design to enable more accurate safety assessments.