Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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An Evaluation of Soil-Water Characteristic Curve Model for Compacted Bentonite Considering Temperature Variation

온도 변화를 고려한 압축 벤토나이트 완충재의 함수특성곡선 모델 평가

  • Yoon, Seok (Radioactive Waste Disposal Research Division, KAERI) ;
  • Jeon, Jun-Seo (Building Safety Research Center & Seismic Safety Research Center, KICT) ;
  • Go, Gyu-Hyun (Dept. of Civil Engrg., Kumoh National Institute of Technology) ;
  • Kim, Geon-Young (Radioactive Waste Disposal Research Division, KAERI)
  • 윤석 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 전준서 (한국건설기술연구원 건축안전연구센터&지진안전연구센터) ;
  • 고규현 (금오공과대학교 토목공학과) ;
  • 김건영 (한국원자력연구원 방사성폐기물처분연구부)
  • Received : 2020.09.11
  • Accepted : 2020.09.22
  • Published : 2020.10.31
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Abstract

A geological repository has been considered as an option for the disposal of high-level radioactive waste (HLW). The HLW is disposed in a host rock at a depth of 500~1,000 meters below the ground surface based on the concept of engineered barrier system (EBS). The EBS is composed of a disposal canister, buffer material, backfill material, and gap-filling material. The compacted bentonite buffer is very important since it can restrain the release of radionuclide and protect the canister from the inflow of ground water. The saturation of the buffer decreases because high temperature in a disposal canister is released into the surrounding buffer material, but saturation of the buffer increases because of the inflow of ground water. The unsaturated properties of the buffer are critical input parameters for the entire safety assessment of the engineered barrier system. In Korea, Gyeongju bentonite can be considered as a candidate buffer material, but there are few test results of the unsaturated properties considering temperature variation. Therefore, this paper conducted experiment of soil-water characteristic curve for the Gyeongju compacted bentonite considering temperature variation under a constant water content condition. The relative error showed approximately 2% between test results and modified van-Genuchten model values.

심층 처분 방식은 고준위폐기물을 처분하기 위한 가장 적합한 대안으로 고려되어지고 있다. 고준위폐기물은 공학적방벽시스템에 의해 지하 500~1,000m 깊이의 암반층에 처분된다. 공학적방벽시스템의 구성 요소로는 처분용기, 완충재, 뒷채움재 및 갭채움재가 있다. 이 중 벤토나이트 완충재는 지하수 유입으로부터 처분용기를 보호하고, 방사성 핵종 유출을 저지하는 역할을 하기에 심층 처분시스템에 있어 매우 중요하다고 할 수 있다. 초기에는 처분용기로부터 발생하는 고온의 열량으로 인해 완충재의 포화도는 감소하지만, 그 후 주변 암반으로부터 유입되는 지하수로 인해 완충재의 포화도는 증가한다. 이렇듯 완충재의 불포화 거동 특성은 공학적방벽의 전체 안전성을 좌우할 수 있는 중요한 입력자료이다. 국내의 경우 경주에서 생산되는 벤토나이트가 완충재의 주요 후보물질로 고려될 수 있는데 국내 벤토나이트 완충재의 온도를 고려한 불포화 거동 특성에 대한 연구는 매우 미진한 상황이다. 따라서 본 연구에서는 국내 압축 벤토나이트 완충재의 온도 증가에 따라 함수비가 일정한 조건에서의 함수특성곡선을 도출하였으며, 시험 값과 온도가 고려된 수정 van-Genuchten 모델 값과의 상대오차는 약 2%를 나타냈다.

Keywords

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