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Conceptual Modeling Coupled Thermal-Hydrological-Chemical Processes in Bentonite Buffer for High-Level Nuclear Waste Repository

고준위 방사성폐기물 처분장에서 벤토나이트 완충제에 대한 열-수리-화학 작용 개념 모델링

  • Received : 2015.10.28
  • Accepted : 2015.12.10
  • Published : 2016.03.30

Abstract

In this study, thermal-hydrological-chemical modeling for the alteration of a bentonite buffer is carried out using a simulation code TOUGHREACT. The modeling results show that the water saturation of bentonite steadily increases and finally the bentonite is fully saturated after 10 years. In addition, the temperature rapidly increases and stabilizes after 0.5 year, exhibiting a constant thermal gradient as a function of distance from the copper tube. The change of thermal-hydrological conditions mainly results in the alteration of anhydrite and calcite. Anhydrite and calcite are dissolved along with the inflow of groundwater. They then tend to precipitate in the vicinity of the copper tube due to its high temperature. This behavior induces a slight decrease in porosity and permeability of bentonite near the copper tube. Furthermore, this study finds that the diffusion coefficient can significantly affect the alteration of anhydrite and calcite, which causes changes in the hydrological properties of bentonite such as porosity and permeability. This study may facilitate the safety assessment of high-level radioactive waste repositories.

Keywords

Bentonite;TOUGHREACT;Thermal-hydrological-chemical;Porosity;High-level radioactive waste repository

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Acknowledgement

Grant : 지중 주입된 이산화탄소 거동 및 누출 모니터링 현장 적용 기술개발

Supported by : 한국지질자원연구원