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3상 거동 상대투수율 선정에 따른 불포화대 및 포화대 내NAPL 거동 특성 연구
김태훈,한원식,전현정,양우종,윤원우 한국지하수토양환경학회 2022 지하수토양환경 Vol.27 No.S
Differences in subsurface migration of LNAPL/DNAPL contaminants caused by a selection of 3-phase (aqueous, NAPL,and gas) relative permeability function (RPF) models in numerical modeling were investigated. Several types of RPFmodels developed from both experimental and theoretical backgrounds were introduced prior to conducting numericalmodeling. Among the RPF models, two representative models (Stone I and Parker model) were employed to simulatesubsurface LNAPLs/DNAPLs migration through numerical calculation. For each model, the spatiotemporal distribution ofindividual phases and the mole fractions of 6 NAPL components (4 LNAPL and 2 DNAPL components) were calculatedthrough a multi-phase and multi-component numerical simulator. The simulation results indicated that both spilledLNAPLs and DNAPLs in the unsaturated zone migrated faster and reached the groundwater table sooner for Stone Imodel than Parker model while LNAPLs migrated faster on the groundwater table under Parker model. This resultssignified the crucial effect of 3-phase relative permeability on the prediction of NAPL contamination and suggested thatRPF models should be carefully selected based on adequate verification processes for proper implementation of numericalmodels.
벤토나이트의 일라이트화에 의한 세슘 수착 특성 변화 연구
황정환,정성욱,한원식,윤원우,Hwang, Jeonghwan,Choung, Sungwook,Han, Weon Shik,Yoon, Wonwoo 한국지하수토양환경학회 2021 지하수토양환경 Vol.26 No.5
This study investigated the mineralogical properties of bentonite and illite and evaluated the Cs sorption at various concentrations (C<sub>w</sub>≈1-10<sup>5</sup> ㎍/L). Bentonite samples, collected from South Korea and USA, majorly consisted of Ca- and Na-montmorillonite, showed large cation exchange capacity (CEC, 91.4 and 47.3 meq/100 g) and specific surface area (SSA, 46.1 and 39.7 m<sup>2</sup>/g). In contrast, illite sample (USA) had relatively low values for 14.4 meq/100g of CEC and 29.3 m<sup>2</sup>/g of SSA, respectively. Bentonite and illite had different non-linear sorption for Cs along with C<sub>w</sub>. At low C<sub>w</sub><10 ㎍/L, illite showed higher sorption capacity than bentonite despite low CEC because of the existence of specific sorption sites at the weathered mineral edge. However, as C<sub>w</sub> increased, bentonite represented high sorption capacity because the cation exchange between Cs and interlayer cations was effective at high C<sub>w</sub> conditions. These results implicated that the Cs concentration is important to evaluate the sorption performance of bentonite and illite. Finally, the Cuadros' kinetic model for illitization using various K concentrations (2×10<sup>-5</sup> and 1.7×10<sup>-3</sup> mol/L) and temperature (100-200℃) showed that up to 50% of the montmorillonite in bentonite could be converted to illite, suggesting that the illitization should be considered to evaluate the sorption performance of the bentonite in deep geological disposal repository.
황정환,김정우,한원식,윤원우,이지용,최승규 대한자원환경지질학회 2023 자원환경지질 Vol.56 No.5
벤토나이트는 고준위 방사성폐기물 처분을 위한 심층처분 시스템에서 처분용기와 암반 사이를 메우는 완충재로 고려되는 팽창성 점토이다. 벤토나이트는 높은 양이온교환능과 비표면적을 가지고 있기 때문에, 처분용기로부터 핵종이 누출될 경우, 수착하여 암반으로의 유출을 지연시키는 역할을 한다. 본 연구에서는 여러 선행연구에서 8종류의 벤토나이트를 사용하여 수행된 U, Am, Se, Eu 핵종의 수착실험 및 모델 자료를 취합하고, 각 연구에서 설정된 실험 조건들을 기반으로 열역학적 수착모델의 특성을 평가하였다. 핵종과 벤토나이트 간의 수착 거동 해석에 중요한 역할을 하는 열역학적 수착모델은 벤토나이트의 광물학적 특성뿐만 아니라 핵종 농도, 용액의 이온강도, 주 양이온, 온도, 고액비, 용존 탄산 농도 등 세부적인 실험 조건과 밀접하게 연관되어 있는 것으로 확인되었다. 이러한 결과는 특정 실험 조건에서 수행된 수착실험 및 모델의 최적화로 제안되는 수착 반응식과 반응상수가 다양한 환경 조건에 적용하기에 불확실성이 크다는 것을 의미한다. 따라서, 심층처분 시스템에 적용가능한 열역학적 수착모델을 구축하기 위해서는 현장 조사 및 실험이 함께 수행되어야 한다. Bentonite, predominantly consists of expandable clay minerals, is considered to be the suitable buffering material in high-level radioactive waste disposal repository due to its large swelling property and low permeability. Additionally, the bentonite has large cation exchange capacity and specific surface area, and thus, it effectively retards the transport of leaked radionuclides to surrounding environments. This study aims to review the thermodynamic sorption models for four radionuclides (U, Am, Se, and Eu) and eight bentonites. Then, the thermodynamic sorption models and optimized sorption parameters were precisely analyzed by considering the experimental conditions in previous study. Here, the optimized sorption parameters showed that thermodynamic sorption models were related to experimental conditions such as types and concentrations of radionuclides, ionic strength, major competing cation, temperature, solid-to-liquid ratio, carbonate species, and mineralogical properties of bentonite. These results implied that the thermodynamic sorption models suggested by the optimization at specific experimental conditions had large uncertainty for application to various environmental conditions.