Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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Introduction to Researches on the Characteristics of Gas Migration Behavior in Bentonite Buffer

벤토나이트 완충재 내 기체 이동의 거동 특성 관련 연구 동향 소개

  • Received : 2021.09.10
  • Accepted : 2021.10.01
  • Published : 2021.10.31
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Abstract

Gases such as hydrogen and radon can be generated around the canister in high-level radioactive waste disposal systems due to several reasons including the corrosion of metal materials. When the gas generation rate exceeds the gas diffusion rate in the low-permeability bentonite buffer, the gas phase will form and accumulate in the engineered barrier system. If the gas pressure exceeds the gas entry pressure, gas can migrate into the bentonite buffer, resulting in pathway dilation flow and advective flow. Because a sudden occurrence of dilation flow can cause radionuclide leakage out of the engineered barrier of the radioactive waste disposal system, it is necessary to understand the gas migration behavior in the bentonite buffer to quantitatively evaluate the long-term safety of the engineered barrier. Experimental research investigating the characteristics of gas migration in saturated bentonite and research developing numerical models capable of simulating such behaviors are being actively conducted worldwide. In this technical note, previous gas injection experiments and the numerical models proposed to verify such behaviors are introduced, and the future challenges necessary for the investigation of gas migration are summarized.

고준위방사성폐기물 처분시스템에서는 처분용기 인근에서 용기 금속 물질의 부식 등 여러 이유로 인해 수소, 라돈 등의 기체가 발생할 수 있다. 기체 발생 속도가 투수계수가 낮은 벤토나이트 완충재 공극에서의 기체 확산 속도보다 커질 경우, 형성된 기체가 축적된다. 기체 압력이 증가하여 유입 압력에 도달하면 완충재 내부로 기체의 팽창 흐름 및 이류가 발생하게 된다. 기체의 급격한 팽창 흐름 발생 시 방사성 핵종이 완충재 외부로 유출될 가능성이 있으므로, 처분시설의 설계 과정에서 점토 기반 물질에서의 기체 유동의 영향성 및 공학적방벽의 건전성을 평가하기 위해 기체 이동 현상에 대한 거동 특성을 명확하게 규명할 필요가 있다. 전세계적으로 벤토나이트 완충재 내 기체 이동 현상 규명을 위한 실험적 연구와 이를 모사할 수 있는 전산 수치 모델 개발 연구가 활발히 진행되고 있다. 본 기술보고에서는 현재까지 수행된 기체 주입 시험 및 전산 수치모델 관련 주요연구를 소개하고 향후 기체 이동 현상 규명을 위한 연구 수행 방향에 대해 정리하였다.

Keywords

Acknowledgement

이 논문은 2021년도 정부(과학기술정보통신부)의 재원으로 사용후핵연료관리핵심기술개발사업단 및 한국연구재단의 지원(2021M2E1A1085193)과 고준위폐기물관리차세대혁신기술개발사업의 지원(2021M2E3A2041312)을 받아 수행된 연구사업입니다.

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