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Oda, Chie; Honda, Akira; Takase, Hiroyasu*; Ozone, Kenji*; Sasaki, Ryoichi*; Yamaguchi, Kohei*; Sato, Tsutomu*
Nendo Kagaku, 51(2), p.34 - 49, 2013/02
Proposed TRU repository designs for geological disposal envisage the use of a bentonite buffer to limit the migration of radionuclides by impeding groundwater flow. Under highly alkaline conditions due to cementitious materials could cause a complex series of coupled changes in the porewater chemistry, mineralogy and, ultimately, the mass transport properties of the bentonite buffer. To elucidate the consequences of these coupled changes, reactive-transport model analyses have been conducted for eight bentonite alteration test cases using different combinations of secondary minerals that could form in the bentonite buffer. It was found that after 100,000 years the amount of dissolved bentonite was at a maximum when metastable secondary minerals precipitated. It was also found that the diffusion and hydraulic coefficients after 100,000 years in all test cases were on the same order of magnitude as the initial values.
Savage, D.*; Soler, J. M.*; Yamaguchi, Kohei; Walker, C.; Honda, Akira; Inagaki, Manabu; Watson, C.*; Wilson, J.*; Benbow, S.*; Gaus, I.*; et al.
Applied Geochemistry, 26(7), p.1138 - 1152, 2011/07
Times Cited Count:19 Percentile:48.09(Geochemistry & Geophysics)The use of cement and concrete as fracture grouting or as tunnel seals in a geological disposal facility for rad wastes creates potential issues concerning chemical reactivity. From a long term safety perspective, it is desirable to be able model these interactions and changes quantitatively. As part of the LCS (Long-term Cement Studies) project programme, a modelling inter-comparison has been conducted, involving the modelling of two experiments describing cement hadration and cement-rock reaction, with teams representing the NDA (UK), Posiva (Finland), and JAEA. This modelling exercise showed that the dominant reaction pathways in the two experiments are fairly well understood and are consistent between the different modelling teams, although significant differences existed amongst the precise parameterisation. Future modelling exercises of this type should focus on a suitable natural or industrial analogue that might aid assessing mineral-fluid reactions at these longer timescales.
Kamei, Gento; Honda, Akira; Mihara, Morihiro; Oda, Chie; Ichige, Satoru; Kurimoto, Yoshitaka; Hoshino, Seiichi; Akagi, Yosuke; Sato, Nobuyuki; Murakami, Hiroshi*; et al.
JAEA-Research 2011-002, 82 Pages, 2011/03
Based on Japanese governmental policy and general scheme, research and development of geological disposal technology for TRU waste has been proceeding to improve reliability of the safety assessment of the co-locational disposal of TRU waste and of HLW, to expand the basement of generic safety assessment, and to develop the alternative technology to cope with the broad geologic environment of Japan. Japan Atomic Energy Agency is dealing with the assignments in the governmental generic scheme. We report here the progress of the studies at the end of H20 (2008) Japanese fiscal year, which are (1) evaluation of long-term mechanical stability in the near-field including development of a creep mode of rock and analyses of mechanical behavior of TRU waste repository, (2) performance assessment of the disposal system including data acquisition and preparation on radionuclides migration, cementitious material alteration, bentonite and hostrock alteration with alkaline solution and nitrate effect, and (3) alternative technology development including decomposition of nitrate.
Honda, Akira; Yamaguchi, Kohei*; Oda, Chie
JAEA-Research 2010-026, 19 Pages, 2010/08
More significant alteration of montmorillonite was estimated if the precipitation of meta-stable as opposed to stable secondary minerals was assumed in a chemical/mass-transport coupled analyses of cement/bentonite engineered barrier system for TRU-2. In general, this tendency is reversal. In order to understand the reason of this reversal tendency, geochemical calculations of batch system were conducted. The S.I. of montmorillonite is lower in the case of meta-stable secondary minerals, except for the very short initial period. Because the S.I. of montmorillonite is higher throughout most of the reaction period in the case of meta-stable secondary minerals, the alteration is more significant.
Honda, Akira; Yamaguchi, Kohei*; Inagaki, Manabu; Oda, Chie
JAEA-Research 2010-024, 44 Pages, 2010/08
An analysis method was attempted of the impact of hyper-alkaline pore water on the mass transport in a single fracture of a host rock. Initial mass transport fields were generated using the computer program "Mathematica", which were then used for the chemistry-mass transport coupling analyses by the computer program "PHREEQC-TRANS".
Honda, Akira; Inagaki, Manabu; Yamaguchi, Kohei; Walker, C.
Nagra NAB 10-07, p.66 - 116, 2010/03
This report was made as part of LCS (Long-term Cement Studies) that was an international project involving NAGRA, NDA, POSIVA and JAEA. A part of the in-situ experiment at Grimsel test site and the bench mark analysis in phase 1 is published in this report. In the bench mark analysis of the cement hydration reaction, there is a reasonable agreement between the measured and the predicted species in solution in terms of general trends being reproduced by the models produced by the three modelling groups. In the bench mark analysis of the chemical reaction of the granite in the environment with transportation and the high pH solution, the major trends in measured species concentrations could be reproduced by all models. The observed permeability profile could not be matched.
Ichige, Satoru; Yamaguchi, Kohei; Oda, Chie
JAEA-Technology 2009-065, 120 Pages, 2010/02
The focus of the present study was to examine the alteration of bentonite in high pH saline groundwaters. Two solutions were used in batch immersion experiments of bentonite. The first solution was prepared using a mixture of NaOH and NaCl (NN), and the second solution was prepared using synthetic Region 1 water (high K and Na content) and synthetic seawater (SR). Analysis showed that bentonite altered to analcime in the NN solution and to analcime and phillipsite-K in the SR solution. Moreover, the generation of calcium silicate hydrate and calcium aluminosilicate hydrate were extrapolated in the SR solution based on the concentrations of dissolved species. These alteration products were in accord with Oda et al. (2005), who summarized the possible relationships between the secondary mineral assemblage of bentonite under high pH conditions and the influence of solution composition.
Kamei, Gento; Honda, Akira; Mihara, Morihiro; Oda, Chie; Murakami, Hiroshi; Masuda, Kenta; Yamaguchi, Kohei; Matsuda, Setsuro; Ichige, Satoru; Takahashi, Kuniaki; et al.
JAEA-Research 2009-046, 80 Pages, 2010/01
Based on Japanese governmental policy and general scheme, research and development of geological disposal technology for TRU waste has been proceeding to improve reliability of the safety assessment of the co-locational disposal of TRU waste and of HLW, to expand the basement of generic safety assessment, and to develop the alternative technology to cope with the broad geologic environment of Japan. Japan Atomic Energy Agency is dealing with the assignments in the governmental generic scheme. We report here the progress of the studies at the end of H20 (2008) Japanese fiscal year.
Kamei, Gento; Honda, Akira; Mihara, Morihiro; Oda, Chie; Murakami, Hiroshi; Masuda, Kenta; Yamaguchi, Kohei; Matsuda, Setsuro; Ichige, Satoru; Takahashi, Kuniaki; et al.
JAEA-Research 2008-082, 84 Pages, 2008/11
Based on Japanese governmental policy and general scheme, research and development of geological disposal technology for TRU waste has been proceeding to improve reliability of the safety assessment of the co-locational disposal of TRU waste and of HLW, to expand the basement of generic safety assessment, and to develop the alternative technology to cope with the broad geologic environment of Japan. Japan Atomic Energy Agency is dealing with the assignments in the governmental generic scheme. We report here the progress of the studies at the end of H19 (2007) fiscal year, which are (1) treatment and packaging of TRU waste including applicability of calcination for unpacking and sorting of wastes, characterization and inspection methodology of TRU waste, (2) mechanical assessment for the near-field structure including model development and preparation, introduction of hostrock creep model and coupling analysis of deformation of hostrock and engineered barrier. (3) performance assessment of the disposal system including data acquisition and preparation on radionuclides migration, cementitious material alteration, bentonite and hostrock alteration with alkaline solution and nitrate effect, and (4) alternative technology development including decomposition of nitrate.
Kamei, Gento; Honda, Akira; Mihara, Morihiro; Oda, Chie; Murakami, Hiroshi; Masuda, Kenta; Yamaguchi, Kohei; Nakanishi, Hiroshi*; Sasaki, Ryoichi*; Ichige, Satoru*; et al.
JAEA-Research 2007-067, 130 Pages, 2007/09
After the publication of the 2nd progress report of geological disposal of TRU waste in Japan, policy and general scheme of future study for the waste disposal in Japan was published by ANRE and JAEA. This annual report summarized aim and progress of individual problem, which was assigned into JAEA in the published policy and general scheme. The problems are as follows; characteristics of TRU waste and its geologic disposal, treatment and waste production, quality control and inspection methodology for waste, mechanical analysis of near-field, data acquisition and preparation on radionuclides migration, cementitious material transition, bentonite and rock alteration in alkaline solution, nitrate effect, performance assessment of the disposal system and decomposition of nitrate as an alternative technology.
Ikeda, Norio*; Sasaki, Nobuyuki*; Oshima, Kazuo*; Yamaguchi, Kohei*; Saito, Shigeyuki*; Abe, Yoriyuki*; Katano, Takashi*; Ueda, Akira*
JNC TJ7440 2005-071, 122 Pages, 1998/03
no abstracts in English
Kitamura, Akira; Shibata, Masahiro; Yamaguchi, Tetsuji; Yui, Mikazu; Yamaguchi, Kohei*
no journal, ,
Solubility of radionuclides in geological disposal of HLW was determined using two activity coefficient models (Davies model and SIT model). The obtained values were compared and discussed.
Oda, Chie; Yamaguchi, Kohei; Savage, D.*; Benbow, S.*; Watson, C.*; Takase, Hiroyasu*
no journal, ,
Mudstones containing smectite have been altered under mildly alkaline conditions (9 pH 10) at Searles Lake. This natural alteration has been investigated using reaction-transport modelling. These data demonstrate that smectite alteration will be controlled by the kinetics of dissolution-precipitation reaction and the salinity of the pore fluid.
Yamaguchi, Kohei; Oda, Chie; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Takase, Toshio*
no journal, ,
High alkaline pore water runs out from a large amount of cementitious material used for the TRU waste disposal to the host rock, and there is a possibility that the migration characteristic of the nuclide. Here, the applicability of a chemical model in the environment with water flow was evaluated by the viewpoint of the solution composition and the precipitation composition by conducting the experiment that passed high alkaline solution to the column. As a result, a change with the lapse of time of the concentration was able to be reproduced almost for the solution composition. Moreover, the precipitation of Al was not able to be reproduced though Ca and Si were able to be wide in the column. The thermodynamics data of the secondary mineral including Al, the maintenance of the precipitation rate, and the applicability examination to the experiment result etc. are profitable as future tasks.
Shimoda, Satoko*; Yamaguchi, Kohei*; Akagi, Yosuke; Oda, Chie; Honda, Akira
no journal, ,
no abstracts in English
Yamaguchi, Kohei*; Shimoda, Satoko*; Akagi, Yosuke; Oda, Chie; Honda, Akira
no journal, ,
no abstracts in English
Tomiyama, Shingo*; Igarashi, Toshifumi*; Odashiro, Kana*; Yamaguchi, Kohei*; Fukushima, Shigeru; Ohara, Yoshiyuki
no journal, ,
no abstracts in English
Tobari, Hiroyuki; Hanada, Masaya; Watanabe, Kazuhiro; Kashiwagi, Mieko; Kojima, Atsushi; Dairaku, Masayuki; Seki, Norikatsu; Abe, Hiroyuki; Umeda, Naotaka; Yamanaka, Haruhiko; et al.
no journal, ,
Progress on technical development on ITER and JT-60SA neutral beam injector (NBI) were reported. In development of a 1 MV insulating transformer for ITER NB power supply, a bushing extracting 1 MV required a huge insulator that was impossible to manufacture. To solve this issue, a composite bushing with FRP tube and a small condenser bushing with insulation gas was newly developed. In development the HV bushing as an insulating feed through, voltage holding in large cylindrical electrodes inside the HV bushing was investigated. The scaling for vacuum insulation design of large cylindrical electrodes was obtained. Toward long pulse production and acceleration of negative ion beam, active control system of plasma grid temperature and a new extractor consisting of the extraction grid with high water cooling capability and aperture offset were developed. As a result, 15 negative ion beam has been achieved for 100 s. Also beam energy density has been increased two orders of magnitude.
Yamaguchi, Toshikazu*; Oda, Yasuhisa; Shimada, Yutaka*; Oda, Akinori*; Sawahara, Hironori*; Shimamura, Kohei*; Kajiwara, Ken; Takahashi, Koji; Sakamoto, Keishi; Komurasaki, Kimiya*
no journal, ,
no abstracts in English
Watanabe, Kazuhiro; Yamanaka, Haruhiko; Yamaguchi, Kohei*; Kadowaki, Makoto*; Ichimura, Satoshi*
no journal, ,
An insulation transformer for ITER Project is required to supply AC power source for ion source and extractor power supplies located on DC -1 MV insulated deck. A mockup model for the insulation transformer has been developed to verify the insulation capability of DC -1 MV and assembling procedure. It has been successfully demonstrated for sufficient insulation of higher than DC -1 MV through dielectric tests.