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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：48.24(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
JAEA-Research-2011-002.pdf:5.64MB
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
JAEA-Research-2010-026.pdf:1.07MB
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
JAEA-Research-2010-024.pdf:13.43MB
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
JAEA-Technology-2009-065.pdf:10.65MB
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
JAEA-Research-2009-046.pdf:9.1MB
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
JAEA-Research-2008-082.pdf:2.52MBJAEA-Research-2008-082(errata).pdf:0.15MB
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
JAEA-Research-2007-067.pdf:28.78MB
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.
Yamaguchi, Kohei; Oda, Chie; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Takase, Toshio*
no journal, ,
In this research, the batch immersion experiment and the flow-through column experiment of granite and the artificial highperalkaline pore water were conducted, and the main geochemistry reaction was examined. A change with the lapse of time of the saturation index was calculated by the chemical equilibrium computation based on the batch immersion experiment result. The secondary mineral with the possibility of precipitation in the liquid phase based on the calculation result was extracted, and the combination was examined. In addition, the combination of these secondary minerals was applied to the flow-through column experiment result, and the liquid phase composition after the flow-through and the secondary mineral's spatial distribution were compared with geochemistry calculation (PHREEQC) result. As a result, it has been understood to have to understand the main geochemistry reaction paying attention at the precipitation rate of the secondary mineral in the future.
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.
Yamaguchi, Kohei; Honda, Akira; Inagaki, Manabu; Yui, Mikazu; Saito, Hironori*
no journal, ,
The bench mark analysis concerning the change in the material transportation characteristic according to the chemical reaction were done by using pass experiment result (Mader et al., 2006) of the high pH solution to the natural crack core in granite as part of international collaboration LCS (Long-term Cement Study). We were able to reproduce the observed blockage tendency as a result experimentally the material transportation model characteristic according to the chemical reaction.
Shimoda, Satoko*; Saito, Hironori*; Takase, Toshio*; Yamaguchi, Kohei; Oda, Chie; Honda, Akira
no journal, ,
The unstable primary mineral is dissolved and the precipitation of a steadier secondary mineral happens thermodynamically when a high alkaline groundwater of the cement system material origin is infiltrated from the radioactive waste geological disposal facilities to a peripheral bedrock. Therefore, the pore structure of the hostrock changes by the precipitation and dissolution, and the material transportation characteristic of the bedrock changes. It is necessary to decide the chemical reaction scheme for the analysis. However, the combination of the secondary minerals exists innumerably. Therefore, granite was assumed to be an example by summarizing the chemical reaction scheme in the mineral alteration scenario, and the mineral alteration scenario concerning the reaction with a high pH groundwater was presented. It dealt with the uncertainty concerning the mineral alteration by preparing two or more scenarios with a different alteration route.
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
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
