Journal of the Korean Geo-Environmental Society ISSN:1598-0820(Print) 2714-1233(Online) 한국지반환경공학회 논문집

A deep geological disposal facility for high-level radioactive waste (HLRW) must balance environmental impact, repository stability, constructability, and cost. The study evaluates key layout parameters - especially the center-to-center spacing of parallel disposal tunnels (CTC 25, 30, and 40 m) - using consistent assumptions and multiple indicators, including excavation volume, required underground footprint, construction period, blasting-vibration effects, and numerical tunnel stability. With a 97 °C canister surface-temperature limit, the minimum PWR SNF disposal-hole spacing is estimated as 9.0, 8.0, and 6.5 m for CTC 25, 30, and 40 m, respectively. Compared with the 25 m case, total excavation is reduced to about 92 % and 83 % for 30 m and 40 m spacing, while the footprint increases by about 6 % and 18 %. Larger spacing also improves constructability: tunneling duration decreases to 93 % and 71 %, and adjacent-tunnel blasting vibrations decrease to 75 % and 47 %. Numerical analyses confirm that at 40 m spacing, crown settlement, inner displacement, and shotcrete compressive stress drop to 67, 45, and 20 % relative to 25 m spacing, indicating meaningful stability gains. Overall, despite a modest increase in site area, a 40 m disposal-tunnel spacing with 6.5 m disposal-hole spacing is recommended as the most efficient conceptual arrangement for Korean HLRW disposal facilities. This paper proposes an optimal “Korean-style” conceptual layout reflecting the Korean Peninsula’s mountainous terrain, where portals and access/vertical disposal tunnels are typically located near mountain foothills to secure sufficient overburden while minimizing access-tunnel length and separating waste-handling areas from construction zones.