Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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Numerical Modelling of One Dimensional Gas Injection Experiment using Mechanical Damage Model: DECOVALEX-2019 Task A Stage 1A

역학손상모델을 이용한 1차원 기체 주입 시험 모델링: 국제공동연구 DECOVALEX-2019 Task A Stage 1A

  • Lee, Jaewon (Radioactive Waste Disposal Research Division, Korea Atomic Energy Research Institute) ;
  • Lee, Changsoo (Radioactive Waste Disposal Research Division, Korea Atomic Energy Research Institute) ;
  • Kim, Geon Young (Radioactive Waste Disposal Research Division, Korea Atomic Energy Research Institute)
  • 이재원 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 이창수 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 김건영 (한국원자력연구원 방사성폐기물처분연구부)
  • Received : 2019.08.21
  • Accepted : 2019.08.28
  • Published : 2019.08.31
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Abstract

In the engineering barriers of high-level radioactive waste disposal, gases could be generated through a number of processes. If the gas production rate exceeds the gas diffusion rate, the pressure of the gas increases and gases could migrate through the bentonite buffer. Because people and the environment can be exposed to radioactivity, it is very important to clarify gas migration in terms of long-term integrity of the engineered barrier system. In particular, it is necessary to identify the hydro-mechanical mechanism for the dilation flow, which is a very important gas flow phenomenon only in medium containing large amounts of clay materials such as bentonite buffer, and to develop and validate new numerical approach for the quantitative evaluation of the gas migration phenomenon. Therefore, in this study, we developed a two-phase flow model considering the mechanical damage model in order to simulate the gas migration in the engineered barrier system, and validated with 1D gas flow modelling through saturated bentonite under constant volume boundary conditions. As a result of numerical analysis, the rapid increase in pore water pressure, stress, and gas outflow could be simulated when the dilation flow was occurred.

고준위방사성폐기물처분장의 공학적 방벽에서는 다양한 원인으로 인해 기체가 발생한다. 만약 기체 생성 속도가 기체 확산 속도보다 빠를 경우 기체의 압력이 증가하게 되고, 기체 유입 압력(gas entry pressure)을 넘어서게 되면 기체가 급격히 벤토나이트 완충재를 통과하는 기체 이동 현상(gas migration)이 발생하게 되며 이는 사람과 주변 환경을 방사능에 노출시킬 수 있기 때문에, 공학적 방벽의 장기 건전성 확보 측면에서 기체 이동 현상을 명확히 규명하는 것이 매우 중요하다. 특히 벤토나이트 완충재와 같이 점토 물질을 다량 함유한 매질에서만 나타나는 매우 중요한 기체 흐름 현상인 팽창 흐름에 대한 수리-역학적 메커니즘을 규명하고, 기체 이동 현상의 정량적 평가를 위한 새로운 수치 해석 기법 개발 및 검증이 필수적이다. 따라서 본 연구에서는 공학적 방벽에서의 기체 이동 현상을 모사하고자 역학 손상 모델 및 손상도를 고려한 2상 유동 모델을 개발하였으며, 일정 체적 경계 조건 하에서의 1차원 기체 주입 시험 모사를 통해 개발된 모델의 적용성을 검토하였다. 수치 해석 결과 공극 수압 및 응력, 기체 유출량이 팽창 흐름 발생 시 급격히 증가하는 현상을 모사할 수 있었다.

Keywords

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