A Review of Plug Design and Construction in Deep Geological Disposal System for a Spent Nuclear Fuel

Han-Byeol Kim; Kyung-Kyu Park; Seong-Jin Ahn; Seoung-Gyu Paik; Hyung-Mok Kim

doi:10.7474/TUS.2025.35.3.179

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2025 Vol.35, Issue 3 Next Page

Technical Note

A Review of Plug Design and Construction in Deep Geological Disposal System for a Spent Nuclear Fuel 사용후핵연료 심지층처분시스템의 플러그 설계 및 시공 사례 분석

30 June 2025. pp. 179-193

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Abstract

The purpose of a deep geological repository is to isolate radioactive isotopes of spent nuclear fuel from our biospheres. The isolation and shielding performance of a deep geological repository is ensured by engineered barriers, which are one of the components of a multi-barrier system. These engineered barriers are composed of disposal canister, buffer, and backfill that contain radioactive waste. Among these engineered barriers, plugs are designed to prevent the flow of water inflow during repository construction and gas flow during operation and after the closure of the facility, thereby preventing erosion of the bentonite buffer and sustaining a swelling pressure of the bentonite buffer. This paper reviews the results of a full-scale Domplu test conducted in Sweden to evaluate the sealing capacity and mechanical stability of plugs. The full-scale test results demonstrated that the concrete plug maintained its sealing and safety functions under groundwater pressure (4 MPa) and swelling pressure (2 MPa) conditions, which occur during the groundwater saturation process of the buffer and backfill materials at the disposal site depth. The study also introduces the potential improvements of field construction method of plug such as the prevention of void formation at the concrete plug's upper section due to the self-weight.

Keywords

Spent nuclear fuel

Deep geological disposal facility

Plug

Engineer barrier system

Sealing capacity

Mechanical stability

심지층처분시설의 목적은 인간 생활권으로부터 사용후핵연료의 방사성 핵종을 격리 및 차폐시키는 것이다. 심지층처분시설의 격리 및 차폐 성능은 다중방벽시스템(multi-barrier system)의 일부인 공학적방벽(engineered barrier)에 의해 담보되며 공학적방벽은 방사성 폐기물을 수용하는 처분용기, 완충재(buffer) 및 뒤채움재(backfill)로 구성된다. 공학적방벽의 하나인 플러그는 처분시설 건설 과정에서 있을 수 있는 유입 지하수 흐름과 처분 작업 과정 및 시설 폐쇄 후 발생할 수 있는 기체 이동을 막음으로써 벤토나이트 완충재의 침식을 막고 완충재의 팽윤압을 유지하는 역할을 수행한다. 본 고에서는 플러그의 수밀성과 역학적 안정성 평가를 목적으로 스웨덴에서 실행된 실규모 Domplu 시험 사례에 대한 결과를 검토하였다. 실규모 시험 결과, 콘크리트 플러그는 처분장 위치 심도 수준에 해당하는 지하수압(4 MPa) 및 완충재와 뒤채움재의 지하수 포화 과정에서 발생하는 팽윤압 조건(2 MPa)에서 수밀 및 안전기능이 유지됨을 확인할 수 있었으며 콘크리트 플러그의 상단의 자중에 의한 공극의 형성 방지책을 포함한 현장시공 개선 방안도 제시되었다.

키워드

사용후핵연료

심지층처분시설

플러그

공학적방벽

기밀성

역학적 안정성

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Information

Publisher :Korean Society for Rock Mechanics and Rock Engineering
Publisher(Ko) :한국암반공학회
Journal Title :Tunnel and Underground Space
Journal Title(Ko) :터널과 지하공간
Volume : 35
No :3
Pages :179-193
Received Date : 2025-04-18
Revised Date : 2025-04-29
Accepted Date : 2025-05-12
DOI :https://doi.org/10.7474/TUS.2025.35.3.179

Tunnel and Underground SpaceISSN:1225-1275(Print) 2287-1748(Online)한국암반공학회

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