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Yotsuji, Kenji; Tachi, Yukio; Nishimaki, Yuichiro*
Materials Research Society Symposium Proceedings, Vol.1665, p.123 - 129, 2014/07
The integrated sorption and diffusion (ISD) model has been developed to quantify these processes in compacted bentonite. The ISD model assuming averaged narrow porespace and the electric double layer (EDL) theory could give quantitative agreement with diffusion data of monovalent cations and anions under wide range of conditions. However, the systematic disagreements were observed for multivalent cations, anions and complex species. In this study, the excluded volume effect and the dielectric saturation effect were introduced into the current ISD model and the modified Poisson-Boltzmann equations were numerically solved. The ionic distributions were influenced at the near surface, however, these changes were canceled by averaging for the porespace. As a result, these modified models had little effect on the effective diffusivity. On the other hand, the modified model considering hydrated ions with the effective electric charge could give good reproducibility of diffusion data.
Yotsuji, Kenji; Tachi, Yukio; Nishimaki, Yuichiro*
Proceedings of 5th International Meeting on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement (USB Flash Drive), p.427 - 428, 2012/10
We have developed integrated sorption and diffusion model (ISD model) for assessment of diffusion parameters consistent with sorption processes in compacted bentonite. Conventional ISD model is unsatisfactory because for multivalent cation/anion and complex ion model predictions disagree with experimental data, and because the model contains additional non-physical fitting parameter. Accordingly we extract the factors influencing the assessment from fundamental assumptions of the conventional ISD model. In this study we incorporated the excluded volume effect and the dielectric saturation effect into ISD model. As results of numerical analysis of these models the considering factors influence hardly the effective diffusivity. Therefore it does not mean that the disagreement with experimental data are caused by considering factors in this report.
Yotsuji, Kenji; Tachi, Yukio; Nishimaki, Yuichiro*
JAEA-Research 2011-047, 105 Pages, 2012/02
JAEA-Research-2011-047.pdf:4.34MB
We have developed integrated sorption and diffusion model (ISD model) for assessment of diffusion parameters consistent with sorption processes in compacted bentonite. Conventional ISD model is unsatisfactory because for multivalent cation/anion and complex ion model predictions disagree with experimental data, and because the model contains additional non-physical fitting parameter. Accordingly we extract the factors influencing the assessment from fundamental assumptions of the conventional ISD model. In this report we incorporated the excluded volume effect, the dielectric saturation effect and the fluctuation potential effect caused by ion-ion electrostatic interaction into ISD model. As results of numerical analysis of these models the considering factors influence hardly the effective diffusivity. Therefore it does not mean that the disagreement with experimental data are caused by considering factors in this report.
Liu, Q.; Homma, Toshimitsu; Nishimaki, Yuichiro*; Hayashi, Hiroko*; Terakado, Masato*; Tamura, Satoshi*
JAEA-Data/Code 2010-001, 57 Pages, 2010/03
JAEA-Data-Code-2010-001.pdf:16.81MB
For a risk assessment model of an engineering system, the uncertainties in the model inputs propagate through the model and lead to the uncertainty in the model output. In order to evaluate the model output uncertainty and the contribution of each model input to the output uncertainty, the computer code GSALab, which is based on Monte Carlo simulations, has been developed. It is composed of three parts, namely, random samples generation, uncertainty analysis and sensitivity analysis. In the part of sensitivity analysis, several global sensitivity indicators, including the popularly used variance-based indicators, are implemented. In addition, the GUI (Graphical User Interface) of GSALab has been developed for the user's convenience. In addition to risk assessment models, it is also possible to use GSALab for uncertainty and sensitivity analysis of a wide class of mathematical models.
Ohara, Takashi; Kusaka, Katsuhiro*; Hosoya, Takaaki; Kurihara, Kazuo; Tomoyori, Katsuaki*; Niimura, Nobuo*; Tanaka, Ichiro*; Suzuki, Jiro*; Nakatani, Takeshi; Otomo, Toshiya*; et al.
no journal, ,
For a single crystal diffractometer, a data reduction software which extracts a HKLF list from the raw data is one of the most important components. We are now developing a new data reduction software for a new single crystal neutron diffractometer, "IBARAKI Biological Crystal Diffractometer (iBIX)", which is now constructing at the MLF of J-PARC.
Ohara, Takashi; Kusaka, Katsuhiro*; Hosoya, Takaaki*; Kurihara, Kazuo; Tomoyori, Katsuaki*; Niimura, Nobuo*; Tanaka, Ichiro*; Suzuki, Jiro*; Nakatani, Takeshi; Otomo, Toshiya*; et al.
no journal, ,
no abstracts in English
Yotsuji, Kenji; Tachi, Yukio; Nishimaki, Yuichiro*
no journal, ,
To evaluate diffusivity of nuclides in compacted bentonite, the modified Poisson-Boltzmann equation taking account of molecular pictures of solutions was solved numerically for the ion distributions in single pore homogeneous medium based on the electrical double layer theory. Especially the effects of volume exclusion and dielectric saturation were investigated by comparison with the base model.
