Kenji Yotsuji

Diffusion and sorption of Cs in the mudstone matrix at the Horonobe URL: comparative experimental and modeling analysis between in situ and laboratory conditions

Masaki Takeda, Hirokazu Ohno, Tsuyoshi Ito, Kenji Yotsuji et autres

Diffusion and sorption of radionuclides in potential host rocks are key processes controlling the safe geological disposal of radioactive waste. To set reliable parameters of diffusion and sorption relevant to safety assessment, it is necessary to understand these processes under laboratory and …

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Effect of different interlayer counter-ions on montmorillonite swelling:

Kenji Yotsuji, Yukio Tachi, Hiroshi Sakuma, Katsuyuki Kawamura

放射性廃棄物の処分システムにおいて，粘土鉱物を主体とするベントナイトの物理的・化学的挙動を予測するうえで，モンモリロナイトの膨潤現象を理解することは重要である．本論文では，モンモリロナイト層間の結晶膨潤挙動を支配する層間対イオンの特性因子について，分子動力学（molecular dynamics, MD）シミュレーションによって調査した．5種類の単一イオン型モンモリロナイト（Na型，K型，Cs型，Ca型，Sr型）の膨潤現象に関する分析試験の結果にMD計算で得られた情報を統合することにより，モンモリロナイト層間への水分子吸着量は，層間対イオンの水和数に強く依存していることが確認された．また，層間における対イオンの水和数は，対イオンの水和自由エネルギー，体積および対イオンの分布状態により決まることが示された．さらに，層間対イオンの特性パラメータを仮想的に変動させたMD計算の結果から，層間対イオンの水和自由エネルギーと電荷とが影響因子として競合することにより，対イオンの分布状態が制御されることが明らかになった．これらの結果から得られた影響因子を含む経験式によって，層間対イオンの異なるモンモリロナイト層間の膨潤挙動を定量的に予測することが可能となる．

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Diffusion of tritiated water, 137Cs+, and 125I− in compacted Ca-montmorillonite: Experimental and modeling approaches

Yuta Fukatsu, Kenji Yotsuji, Takahiro Ohkubo, Yukio Tachi

Mechanistic understanding and predictive modeling of radionuclide diffusion in Na- and Ca-montmorillonite are essential to evaluate the long-term evolution of the bentonite barrier and their impact on radionuclide migration during geological disposal of radioactive wastes . Thus, the diffusion behavior of 137 …

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Effect of interlayer cations on montmorillonite swelling: Comparison between molecular dynamic simulations and experiments

Kenji Yotsuji, Yukio Tachi, Hiroshi Sakuma, Katsuyuki Kawamura

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Viscosity of Interlayer Water in Montmorillonite from Molecular Dynamics Method

Kenji Yotsuji

Stability of Montmorillonite Edge Faces Studied Using First-Principles Calculations

Hiroshi Sakuma, Yukio Tachi, Kenji Yotsuji, Shigeru Suehara et autres

Abstract The reactivity and stability of the edge faces of swelling clay minerals can be altered by layer charge and the stacking structure; however, these effects are poorly understood due to experimental limitations. The structure and stability of the montmorillonite {110}, {010}, …

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Swelling Properties of Montmorillonite Clay Minerals from Molecular Dynamics Method

Kenji Yotsuji

Diffusion and adsorption of uranyl ion in clays: Molecular dynamics study

Tatsumi Arima, Kazuya Idemitsu, Yaohiro Inagaki, Katsuyuki Kawamura et autres

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Clay-based modeling approach to diffusion and sorption in the argillaceous rock from the Horonobe URL: Application to Ni(II), Am(III), and Se(IV)

Yukio Tachi, Tadahiro Suyama, Kenji Yotsuji, Yasuo Ishii et autres

Diffusion model considering multiple pore structures in compacted bentonite

Kenji Yotsuji, Yukio Tachi, Takahiro Ohkubo

Diffusion Model Considering Multiple Pore Structures in Compacted Bentonite

Kenji Yotsuji, Yukio Tachi, Takahiro Ohkubo

Abstract Sorption and diffusion of radionuclides in compacted clays and argillaceous rocks are key processes in the safe geological disposal of radioactive waste. The integrated sorption and diffusion (ISD) model was developed to quantify radionuclide transport in compacted bentonite. The current ISD …

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Clay-Based Modeling Approach to Diffusion and Sorption in the Argillaceous Rock from the Horonobe URL

Yukio Tachi, Tadahiro Suyama, Kenji Yotsuji, Yasuo Ishíi et autres

Abstract Sorption and diffusion of radionuclides (RNs) in argillaceous rocks are key processes in the safe geological disposal of radioactive waste. Sorption and diffusion of Ni(II), Am(III), and Se(IV) in mudstone from the Horonobe Underground Research Laboratory were investigated using experimental and …

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