JOPSS - Search Results

Journal Articles

Radiocesium interaction with clay minerals; Theory and simulation advances Post-Fukushima

Okumura, Masahiko; Kerisit, S.*; Bourg, I. C.*; Lammers, L. N.*; Ikeda, Takashi*; Sassi, M.*; Rosso, K. M.*; Machida, Masahiko

Journal of Environmental Radioactivity, 189, p.135 - 145, 2018/09

https://doi.org/10.1016/j.jenvrad.2018.03.011

Times Cited Count：61 Percentile：87.51(Environmental Sciences)

no abstracts in English

Journal Articles

A Thermodynamic model for ZrO $_{2}$ (am) solubility at 25 $^{circ}$ C in the Ca $^{2+}$ -Na $^{+}$ -H $^{+}$ -Cl $^{-}$ -OH $^{-}$ -H $_{2}$ O system; A Critical review

Rai, D.*; Kitamura, Akira; Altmaier, M.*; Rosso, K. M.*; Sasaki, Takayuki*; Kobayashi, Taishi*

Journal of Solution Chemistry, 47(5), p.855 - 891, 2018/05

https://doi.org/10.1007/s10953-018-0766-4

Times Cited Count：11 Percentile：10.26(Chemistry, Physical)

We have critically reviewed experimental data for Zr hydrolysis constant values for formation of several mononuclear and polynuclear species and a solubility product value for ZrO $_{2}$ (am). We have determined new/revised values for the formation constants of Zr(OH) $_{2}$ $^{2+}$ , Zr(OH) $_{4}$ (aq), Zr(OH) $_{5}$ $^{-}$ , Zr(OH) $_{6}$ $^{2-}$ and Ca $_{3}$ Zr(OH) $_{6}$ $^{4+}$ , and the solubility product for ZrO $_{2}$ (am) after the critical review.

Journal Articles

Reply to "Comments on radiation-damage resistance in phyllosilicate minerals from first principles and implications for radiocesium and strontium retention in soils"

Sassi, M.*; Rosso, K. M.*; Okumura, Masahiko; Machida, Masahiko

Clays and Clay Minerals, 65(5), p.371 - 375, 2017/11

https://doi.org/10.1346/CCMN.2017.064078

Times Cited Count：2 Percentile：77.31(Chemistry, Physical)

no abstracts in English

Journal Articles

Transmutation effects on long-term Cs retention in phyllosilicate minerals from first principles

Sassi, M.*; Okumura, Masahiko; Machida, Masahiko; Rosso, K. M.*

Physical Chemistry Chemical Physics, 19(39), p.27007 - 27014, 2017/10

https://doi.org/10.1039/C7CP04496H

Times Cited Count：4 Percentile：15.21(Chemistry, Physical)

no abstracts in English

Journal Articles

A Thermodynamic model for the solubility of HfO $_{2}$ (am) in the aqueous K $^{+}$ - HCO $_{3}$ $^{-}$ - CO $_{3}$ $^{2-}$ - OH $^{-}$ - H $_{2}$ O system

Rai, D.*; Kitamura, Akira; Rosso, K.*

Radiochimica Acta, 105(8), p.637 - 647, 2017/08

https://doi.org/10.1515/ract-2016-2623

Times Cited Count：4 Percentile：33.39(Chemistry, Inorganic & Nuclear)

Solubility of HfO $_{2}$ (am) was determined as a function of KHCO $_{3}$ concentrations ranging from 0.001 mol.kg $^{-1}$ to 0.1 mol.kg $^{-1}$ . The solubility of HfO $_{2}$ (am) increased dramatically with the increase in KHCO $_{3}$ concentrations, indicating that Hf(IV) makes strong complexes with carbonate. Thermodynamic equilibrium constants for the formation of Hf-carbonate complexes were determined using both the Pitzer and SIT models. The dramatic increase in Hf concentrations with the increase in KHCO $_{3}$ concentrations can best be described by the formation of Hf(OH-) $_{2}$ (CO $_{3}$ ) $_{2}$ $^{2-}$ and Hf(CO $_{3}$ ) $_{5}$ $^{6-}$ . The log $_{10}$ K $^{0}$ values for the reactions [Hf $^{4+}$ + 2 CO $_{3}$ $^{2-}$ +2 OH $^{-}$ Hf(OH) $_{2}$ (CO $_{3}$ ) $_{2}$ $^{2-}$ ] and [Hf $^{4+}$ + 5 CO $_{3}$ $^{2-}$ Hf(CO $_{3}$ ) $_{5}$ $^{6-}$ ], based on the SIT model, were determined to be 44.53 0.46 and 41.53 0.46, respectively.

Journal Articles

Origin of 6-fold coordinated aluminum at (010)-type pyrophyllite edges

Okumura, Masahiko; Sassi, M.*; Rosso, K. M.*; Machida, Masahiko

AIP Advances (Internet), 7(5), p.055211_1 - 055211_9, 2017/05

https://doi.org/10.1063/1.4983213

Times Cited Count：6 Percentile：26.75(Nanoscience & Nanotechnology)

no abstracts in English

Journal Articles

Molecular simulation of cesium adsorption at the basal surface of phyllosilicate minerals

Kerisit, S.*; Okumura, Masahiko; Rosso, K. M.*; Machida, Masahiko

Clays and Clay Minerals, 64(4), p.389 - 400, 2016/08

https://doi.org/10.1346/CCMN.2016.0640405

Times Cited Count：32 Percentile：72.32(Chemistry, Physical)

no abstracts in English

Journal Articles

Issues concerning the determination of solubility products of sparingly soluble crystalline solids; Solubility of HfO $_{2}$ (cr)

Rai, D.*; Kitamura, Akira; Rosso, K. M.*; Sasaki, Takayuki*; Kobayashi, Taishi*

Radiochimica Acta, 104(8), p.583 - 592, 2016/08

https://doi.org/10.1515/ract-2015-2540

Times Cited Count：6 Percentile：45.92(Chemistry, Inorganic & Nuclear)

Solubility studies were conducted with HfO $_{2}$ (cr) solid as a function of acid concentrations. These studies involved (1) using two different amounts of the solid phase, (2) acid washing the bulk solid phase, (3) preheating the solid phase to 1400 $^{circ}$ C, and (4) heating amorphous HfO $_{2}$ (am) suspensions to 90 $^{circ}$ C to ascertain whether the HfO $_{2}$ (am) converts to HfO $_{2}$ (cr) and to determine the solubility from the oversaturation direction. Based on the results of these treatments it is concluded that the HfO $_{2}$ (cr) contains a small fraction of less crystalline, but not amorphous, material [HfO $_{2}$ (lcr)] and this, rather than the HfO $_{2}$ (cr), is the solubility-controlling phase in the range of experimental variables investigated in this study. The solubility data are interpreted using both the Pitzer and SIT models. The log $_{10}$ of the solubility product of HfO $_{2}$ (cr) is estimated. The observation of a small fraction of less crystalline higher solubility material is consistent with the general picture that mineral surfaces are often structurally and/or imperfect leading to a higher solubility than the bulk crystalline solid. This study stresses the urgent need, during interpretation of solubility data, of taking precautions to make certain that the observed solubility behavior for sparingly-soluble solids is assigned to the proper solid phase.

Journal Articles

Radiation-damage resistance in phyllosilicate minerals from first principles and implications for radiocesium and strontium retention in soils

Sassi, M.*; Rosso, K. M.*; Okumura, Masahiko; Machida, Masahiko

Clays and Clay Minerals, 64(2), p.108 - 114, 2016/04

https://doi.org/10.1346/CCMN.2016.0640203

Times Cited Count：6 Percentile：18.82(Chemistry, Physical)

no abstracts in English

Journal Articles

Shell evolution beyond =40; $^{69,71,73}$ Cu

Sahin, E.*; Doncel, M.*; Sieja, K.*; De Angelis, G.*; Gadea, A.*; Quintana, B.*; Grgen, A.*; Modamio, V.*; Mengoni, D.*; Valiente-Dobn, J. J.*; et al.

Physical Review C, 91(3), p.034302_1 - 034302_9, 2015/03

https://doi.org/10.1103/PhysRevC.91.034302

Times Cited Count：26 Percentile：82.48(Physics, Nuclear)

Oral presentation

Free energy landscapes of cesium adsorption from mesopore to the interlayer of montmorillonite; Classical molecular dynamics simulation studies

Hiraguchi, Atsuki; Zheng, X.*; Underwood, T. R.*; Kobayashi, Keita; Yamaguchi, Akiko; Itakura, Mitsuhiro; Machida, Masahiko; Rosso, K. M.*; Bourg, I. C.*; Okumura, Masahiko

no journal, ,

The migration behavior of radionuclides in clay minerals used as buffer material must be clarified for the long-term safety of geological disposal of high-level radioactive waste. The recent development of supercomputers enables us to perform large-scale classical molecular dynamics (MD) simulations to evaluate the adsorption properties of cation to clay minerals. We evaluated the free-energy profiles of cesium adsorption from mesopore to the interlayer of Na-montmorillonite by classical MD on a supercomputer. We found that the free-energy profiles of cesium adsorption depend on the interlayer distance of the Na-montmorillonite and mesopore salinity in the water system. In the presentation, we also discuss the distribution and diffusion coefficients of cesium ions.

Oral presentation

Large-scale molecular dynamics simulations of cesium diffusion in systems with clay particles and water molecules

Hiraguchi, Atsuki; Zheng, X.*; Underwood, T. R.*; Kobayashi, Keita; Yamaguchi, Akiko; Itakura, Mitsuhiro; Machida, Masahiko; Rosso, K. M.*; Bourg, I. C.*; Okumura, Masahiko

no journal, ,

Understanding the radionuclide diffusion phenomena is crucial for the safe geological disposal of high-level radioactive waste. The diffusion in clay-water systems is particularly important for the performance of the artificial barrier made of bentonite. Numerical simulation is one of the best research methods for understanding the phenomenon at the microscopic level. Recently, large-scale molecular dynamics (MD) simulations of the systems with clay particles and water molecules were realized. In this presentation, we will show numerical simulation results of diffusion of cesium in the large system with MD. Our recent results suggest that cesium is less diffuse than sodium.

Oral presentation

Difference in the diffusion behavior of cesium and sodium ions in the interlayer space of montmorillonite using classical molecular dynamics simulations

Hiraguchi, Atsuki; Zheng, X.*; Underwood, T. R.*; Kobayashi, Keita; Yamaguchi, Akiko; Itakura, Mitsuhiro; Machida, Masahiko; Rosso, K. M.*; Bourg, I. C.*; Okumura, Masahiko

no journal, ,

In order to evaluate the long-term safety of geological disposal of high-level radioactive waste, it is necessary to understand the migration behavior of radionuclides in clay minerals used as buffer materials. In this study, the difference in the diffusion behavior of cesium and sodium ions in Na-montmorillonite is analyzed by evaluating the free energy using classical molecular dynamics simulations.

Oral presentation

Estimation of free energy landscapes of cesium adsorption/diffusion in clay minerals-water systems using classical molecular dynamics simulation

Hiraguchi, Atsuki; Zheng, X.*; Underwood, T. R.*; Kobayashi, Keita; Yamaguchi, Akiko; Itakura, Mitsuhiro; Machida, Masahiko; Rosso, K. M.*; Bourg, I. C.*; Okumura, Masahiko

no journal, ,

In order to evaluate the long-term safety of geological disposal of high-level radioactive waste, it is necessary to clarify and model the migration behavior of radionuclides in clay minerals used as buffer material on a molecular scale. In this study, we perform classical molecular dynamics simulations in clay minerals-water systems and evaluate free-energy profiles of clay minerals to clarify and model the diffusion behavior of cesium on a molecular scale.

Oral presentation

Adsorption properties of cesium to micaceous clay minerals; Molecular modeling using density functional theory calculations

Okumura, Masahiko; Nakamura, Hiroki; Machida, Masahiko; Sassi, M.*; Rosso, K.*

no journal, ,

no abstracts in English

Oral presentation

Addressing radiocesium contamination in Fukushima waste soil through the lens of systematic numerical simulations

Okumura, Masahiko; Kerisit, S.*; Bourg, I.*; Lammers, L.*; Ikeda, Takashi*; Sassi, M.*; Rosso, K.*; Machida, Masahiko

no journal, ,

no abstracts in English

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Radiocesium interaction with clay minerals; Theory and simulation advances Post-Fukushima

A Thermodynamic model for ZrO $_{2}$ (am) solubility at 25 $^{circ}$ C in the Ca $^{2+}$ -Na $^{+}$ -H $^{+}$ -Cl $^{-}$ -OH $^{-}$ -H $_{2}$ O system; A Critical review

Reply to "Comments on radiation-damage resistance in phyllosilicate minerals from first principles and implications for radiocesium and strontium retention in soils"

Transmutation effects on long-term Cs retention in phyllosilicate minerals from first principles

A Thermodynamic model for the solubility of HfO $_{2}$ (am) in the aqueous K $^{+}$ - HCO $_{3}$ $^{-}$ - CO $_{3}$ $^{2-}$ - OH $^{-}$ - H $_{2}$ O system

Origin of 6-fold coordinated aluminum at (010)-type pyrophyllite edges

Molecular simulation of cesium adsorption at the basal surface of phyllosilicate minerals

Issues concerning the determination of solubility products of sparingly soluble crystalline solids; Solubility of HfO $_{2}$ (cr)

Radiation-damage resistance in phyllosilicate minerals from first principles and implications for radiocesium and strontium retention in soils

Shell evolution beyond =40; $^{69,71,73}$ Cu

Free energy landscapes of cesium adsorption from mesopore to the interlayer of montmorillonite; Classical molecular dynamics simulation studies

Large-scale molecular dynamics simulations of cesium diffusion in systems with clay particles and water molecules

Difference in the diffusion behavior of cesium and sodium ions in the interlayer space of montmorillonite using classical molecular dynamics simulations

Estimation of free energy landscapes of cesium adsorption/diffusion in clay minerals-water systems using classical molecular dynamics simulation

Adsorption properties of cesium to micaceous clay minerals; Molecular modeling using density functional theory calculations

Addressing radiocesium contamination in Fukushima waste soil through the lens of systematic numerical simulations