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Ohashi, Hiroshi*; Sato, Seichi*; Kozaki, Tamotsu*
JAERI-Tech 2002-021, 52 Pages, 2002/03
JAERI-Tech-2002-021.pdf:2.95MB
no abstracts in English
Kozai, Naofumi; Adachi, Yoshifusa*; Kawamura, Sachi*; Inada, Koichi*; Kozaki, Tamotsu*; Sato, Seichi*; Ohashi, Hiroshi*; Onuki, Toshihiko; Bamba, Tsunetaka
Journal of Nuclear Science and Technology, 38(12), p.1141 - 1143, 2001/12
This study briefly reports characteristics of Fe-montmorillonite. Fe-montmorillonite was used as a simulant of buffer material in which corrosion products of carbon steel overpack, Fe
, were diffused. We have found that this clay retains Se(VI) for which natural montmorillonite, such as Na+-type and Ca-type, has little retentivity.
*; *; *
JNC TJ8400 2001-005, 42 Pages, 2001/03
JNC-TJ8400-2001-005.pdf:2.08MB
Diffusion behavior of radionuclides in compacted bentonite plays an important role in the performance assessment of bentonite buffer material in geological disposal of high-level radioactive waste. Microstructure of bentonite is considered to be one of the key parameters to affect on the diffusion behavior. In this study, therefore, two kinds of montmorillonite (major clay mineral of bentonite) with different particle sizes were prepared, and characterized with several methods. In addition, the apparent and effective diffusion coefficients of HTO, Cl
, and Cs
were determined using the montmorillonite samples with different particle sizes and dry densities. In the sample characterization, the specific surface areas of montmorillonite samples with different particle sizes were determined by the BET and the EGME methods, and the particle size distributions of each sample were analyzed by laser diffraction/scatterring particle size analysis. Microstructure of the samples was also observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The BET method gave a higher specific surface area of the fine grained sample than of the coarse sample, while the EGME method gave same values for both samples. The laser diffraction/scattering particle size analysis using ethanol as a dispersion medium gave different particle size distributions, but when the samples were dispersed in water with Na
(PO
), the particle size distributions were similar. These findings indicate that the montmorillonite layers, which compose the montmorillonite particles, have the same size, even if the particle sizes of the samples are different. In the diffusion experiments, it was found that the apparent diffusion coefficients of HTO and Cl for the fine grained sample were higher than for the coarse grained sample at two dry densities, 1.0 and 1.8 Mg m
, while the opposite particle size effect was observed for Cs ions. These ...
Kozai, Naofumi; Inada, Koichi*; Kozaki, Tamotsu*; Sato, Seichi*; Ohashi, Hiroshi*; Bamba, Tsunetaka
Journal of Contaminant Hydrology, 47(2-4), p.149 - 158, 2001/02
Times Cited Count：15 Percentile：41.9(Environmental Sciences)no abstracts in English
Suzuki, Satoru; Sato, Seichi*; *; Kozai, Naofumi*
Journal of Nuclear Science and Technology, 38(8), p.697 - 699, 2001/00
Times Cited Count：23 Percentile：82.31(Nuclear Science & Technology)None
*; *; *
JNC TJ8400 2000-018, 79 Pages, 2000/02
JNC-TJ8400-2000-018.pdf:2.09MB
As a basic research for geological disposal of high-level radioactive wastes, diffusion behavior of radionuclides and corrosion behavior of overpack materials in clay buffer materials (bentonite) were studied. In the study on the diffusion behavior of radionuclides, basal spacing and water content were determined for water saturated, compacted Na-montmorillonite that is major clay mineral of bentonite. The apparent diffusion coefficients of Na, Sr, Cs and Cl ions and their activation energies were also determined at different dry densities of montmorillonite. For all kinds of ions, the activation energies were found to increase as the dry density increased. These findings suggest that the diffusion mechanism of ions in compacted montmorillonite changed with increasing dry density. As a reasonable explanation for the changes in the activation energy, we proposed a multiprocess diffusion model, in which predominant diffusion process is considered to change from pore water diffusion to interlayer diffusion via surface diffusion when the dry density increases. The Na-montmorillonite is expected to alter by the ion exchange with Ca ions, which could be introduced from groundwater and/or cementitious materials in a repository. The apparent diffusion coefficients of Na and Cs ions and their activation energies were studied for Na/Ca montmorillonite mixtures in order to know the effect of this kind of alteration on the diffusion behavior of ions. It was found that the alteration of montmorillonite affected diffusion coefficients and the activation energies for both kinds of cations. These effects cannot be explained only by the pore water diffusion. The multiprocess diffusion model proposed in this study is suggested as the most reasonable explanation for the effects. The oxidation behavior of pyrite in bentonite during drying process was studied for understanding corrosion behavior of overpack materials in bentonite. There ...
Takano, Masahide; Minato, Kazuo; Fukuda, Kosaku; Sato, Seichi*; Ohashi, Hiroshi*
Journal of Nuclear Science and Technology, 35(7), p.485 - 493, 1998/07
Times Cited Count：4 Percentile：38.63(Nuclear Science & Technology)no abstracts in English
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Takano, Masahide; Minato, Kazuo; Fukuda, Kosaku; Sato, Seichi*; Ohashi, Hiroshi*
Journal of Alloys and Compounds, 278, p.277 - 282, 1998/00
Times Cited Count：1 Percentile：19.61(Chemistry, Physical)no abstracts in English
Takano, Masahide; Minato, Kazuo; Fukuda, Kosaku; Sato, Seichi*; Ohashi, Hiroshi*
JAERI-Research 97-021, 19 Pages, 1997/03
JAERI-Research-97-021.pdf:0.74MB
no abstracts in English
Minato, Kazuo; Takano, Masahide; Fukuda, Kosaku; Sato, Seichi*; Ohashi, Hiroshi*
Journal of Alloys and Compounds, 255, p.18 - 23, 1997/00
Times Cited Count：14 Percentile：66.89(Chemistry, Physical)no abstracts in English
*; Sato, Seichi*; Ohashi, Hiroshi*; Ogawa, Toru; Ito, Akinori; Fukuda, Kosaku
Journal of Nuclear Materials, 247, p.50 - 58, 1997/00
Times Cited Count：3 Percentile：30.34(Materials Science, Multidisciplinary)no abstracts in English
*; Sato, Seichi*; Ohashi, Hiroshi*; Sakamoto, Yoshiaki; Onuki, Toshihiko; Nagao, Seiya; Muraoka, Susumu
Journal of Nuclear Materials, 248, p.328 - 332, 1997/00
Times Cited Count：37 Percentile：91.4(Materials Science, Multidisciplinary)no abstracts in English
Minato, Kazuo; Takano, Masahide*; Sato, Seichi*; Ohashi, Hiroshi*; Fukuda, Kosaku
Transactions of the American Nuclear Society, 74, p.95 - 96, 1996/00
no abstracts in English
Sakamoto, Yoshiaki; Nagao, Seiya; Onuki, Toshihiko; ; *; Sato, Seichi*; Ohashi, Hiroshi*
Materials Research Society Symposium Proceedings, Vol.353, 0, p.997 - 1004, 1995/00
no abstracts in English
, III*; Sato, Seichi*; Ohashi, Hiroshi*; Ogawa, Toru; Ito, Akinori; Fukuda, Kosaku
JAERI-M 92-118, 49 Pages, 1992/08
no abstracts in English
*; Ohashi, Hiroshi*; Morozumi, Takashi *; Ogawa, Toru; Fukuda, Kosaku
JAERI-M 90-113, 46 Pages, 1990/07
no abstracts in English
, 1; Sample fabrication and characterization*; Ogawa, Toru; Fukuda, Kosaku; Ohashi, Hiroshi*; *; Morozumi, Takashi *
JAERI-M 89-092, 12 Pages, 1989/07
no abstracts in English
