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Yamaguchi, Tetsuji; Sawaguchi, Takuma; Tsukada, Manabu; Hoshino, Seiichi*; Tanaka, Tadao
Clay Minerals, 51(2), p.279 - 287, 2016/02
Times Cited Count：7 Percentile：24.47(Chemistry, Physical)Alteration of bentonite-cement interfaces and accompanying changes in diffusivity of tritiated water was experimentally investigated using intact hardened cement specimens. The alteration by carbonate solution was accompanied by mineralogical changes at the interface and a decrease in the diffusivity to 70% of the initial value after 180-day period. Another alteration under silicate system contacting hardened cement and compacted bentonite was accompanied by mineralogical changes at the interface and a decrease in the diffusivity to 71% of the initial value after 600-day period. The changes in the diffusivity were much less than those observed for mixed specimens of granulated hardened cement and bentonite where the diffusivity decreased down to 20% of the initial value over 180 days. The results were extrapolated to 15 years under simple assumptions and showed good agreement with those observed in the cement-argillite interface at Tournemire URL. Such an explanation enhances our confidence in our assessment of alteration of cement-bentonite systems and can be a base for using our data and models in long term assessment of radioactive waste disposal.
Hoshino, Seiichi; Negishi, Kumi*; Honda, Akira
Konkurito Kogaku Rombunshu, 25, p.97 - 107, 2014/05
A pH lowering mechanism of highly flyash contained silicafume cement (HFSC) in Region I and the chemical equilibrium model of HFSC incorporating the mechanism were studied. As a result, it is suggested that the dissolution and precipitation behavior of SO
partially contributes to the pH lowering of HFSC in Region I. A chemical equilibrium model of HFSC incorporating alkali (Na, K) adsorption, which was supposed as another contributing factor of pH lowering effect, was also developed, and immersion experiment of HFSC was analyzed using the model. The calculated results by the developed model were in agreement with the experiment results. From the above results, it was concluded that the pH lowering of HFSC in Region I was attributed to both of the dissolution and precipitation behavior of SO and the alkali adsorption.
concrete/clay interactions at the Tournemire URLYamaguchi, Tetsuji; Kataoka, Masaharu; Sawaguchi, Takuma; Mukai, Masayuki; Hoshino, Seiichi; Tanaka, Tadao; Marsal, F.*; Pellegrini, D.*
Clay Minerals, 48(2), p.185 - 197, 2013/05
Times Cited Count：3 Percentile：9.54(Chemistry, Physical)Highly alkaline environments induced by cement based materials are likely to deteriorate the physical and/or chemical properties of the bentonite buffer materials in radioactive waste repositories. Predicting long-term alteration of concrete/clay systems requires physico-chemical models and a number of input parameters. In order to provide reliability to the long-term prediction of bentonite buffer performance under disposal conditions, it is necessary to develop and verify reactive transport codes for concrete/clay systems. In this study, a PHREEQC-based, reactive transport analysis code (MC-CEMENT ver.2) was developed and was verified by comparing results of the calculations with 
observations of the mineralogical evolution at the concrete/argillite interface. The calculation reproduced the observations such as the mineralogical changes limited within one cm in thickness, formation of CaCO
and CSH, dissolution of quartz, decrease of porosity in argillite and increase in concrete. These agreements indicate possibility that the models based on lab-scale (
1 y) experiments can be applied to longer time scale. The fact that the calculation did not reproduce the dissolution of clays and the formation of gypsum indicates that there is still room for improvement in our model.
Kamei, Gento; Honda, Akira; Oda, Chie; Hirano, Fumio; Ichige, Satoru; Kurimoto, Yoshitaka; Hoshino, Seiichi; Akagi, Yosuke; Sato, Nobuyuki; Takahashi, Kuniaki; et al.
JAEA-Research 2012-010, 80 Pages, 2012/06
JAEA-Research-2012-010.pdf:7.45MB
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 H22 (2010) Japanese fiscal year and their products during the last 5 years. These include (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 cementitious material alteration, bentonite and hostrock alteration with alkaline solution and nitrate effect, and (3) alternative technology development including decomposition of nitrate.
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.
Yamaguchi, Tetsuji; Negishi, Kumi*; Hoshino, Seiichi; Tanaka, Tadao
Cement and Concrete Research, 39(12), p.1149 - 1155, 2009/12
Times Cited Count：29 Percentile：65.2(Construction & Building Technology)In order to predict long-term leaching behavior of cement constituents in safety assessments of radioactive waste disposal, we modeled diffusive mass transport in micropores cement based materials. Based on available knowledge on the pore structure, we developed a transport porosity model that enables us to estimate effective porosity available for diffusion (transport porosity) in cement based materials. We microscopically examined the pore structure of hardened cement pastes to partially verify the model. Effective diffusivities of tritiated water in hardened cement pastes were also obtained experimentally, and were shown to be proportional to the estimated transport porosity. We successfully modeled the effective diffusivity in cement based materials consistent with previously acknowledged pore diffusion model.
Yamaguchi, Tetsuji; Yamada, Fumika; Negishi, Kumi*; Hoshino, Seiichi; Mukai, Masayuki; Tanaka, Tadao; Nakayama, Shinichi
Physics and Chemistry of the Earth, 33(Suppl.1), p.S285 - S294, 2008/00
It is important to assess long-term alteration of engineered barrier composed of bentonite and cement for the safety assessment of radioactive waste disposal. In order to promote our development of the assessment methodologies, we developed a secondary mineral formation model for cement based materials and a hydraulic conductivity model for bentonite buffer materials. These models were verified by comparing with experimental observations. We also calculated changes in mineralogy of bentonite buffer materials and accompanying changes in the hydraulic conductivity over 10,000 y. We identified the temperature as an important factor dominating the alteration of the buffer. We also identified that the alteration is limited by slow kinetics of the dissolution of montmorillonite and by the diffusive mass transfer. Our calculation showed that the mineralogical change proceeds rather fast during the initial 1,000 y and slows down afterwards, and that salinity of the groundwater has both positive and negative effects on the hydraulic conductivity.
Shimizu, Nobuaki*; Oue, Atsushi*; Otsuki, Takahiro*; Mori, Takahisa*; Yamaguchi, Kayo*; Nakamura, Takako*; Wada, Seiichi*; Kobayashi, Yasuhiko; Hoshino, Hiroo*
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 105, 2007/02
Tanaka, Tadao; Yamaguchi, Tetsuji; Iida, Yoshihisa; Kimura, Yuichiro; Taki, Hiroshi; Fujiwara, Takeshi; Ueda, Masato*; Mukai, Masayuki; Yamada, Fumika; Mizuno, Tsuyoshi; et al.
no journal, ,
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Hoshino, Hiroo*; Shimizu, Nobuaki*; Oue, Atsushi*; Tanaka, Atsushi*; Saha, M. N.*; Shinagawa, Masahiko*; Otsuki, Takahiro*; Hoque, A.*; Mori, Takahisa*; Wada, Seiichi*; et al.
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C ion-beam in a glioma cell line latently infected with HTLV-ITanaka, Atsushi*; Oue, Atsushi*; Shimizu, Nobuaki*; Wada, Seiichi*; Kobayashi, Yasuhiko; Hoshino, Hiroo*
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Shimizu, Nobuaki*; Oue, Atsushi*; Otsuki, Takahiro*; Mori, Takahisa*; Yamaguchi, Kayo*; Nakamura, Takako*; Wada, Seiichi*; Kobayashi, Yasuhiko; Hoshino, Hiroo*
no journal, ,
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Hoshino, Seiichi; Yamaguchi, Tetsuji; Mukai, Masayuki; Yamada, Fumika; Negishi, Kumi*; Tanaka, Tadao; Nakayama, Shinichi
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Hoshino, Seiichi; Yamada, Fumika; Negishi, Kumi*; Mukai, Masayuki; Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Nakayama, Shinichi
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Kimura, Yuichiro; Yamaguchi, Tetsuji; Iida, Yoshihisa; Otsuka, Ichiro; Taki, Hiroshi*; Mukai, Masayuki; Yamada, Fumika; Hoshino, Seiichi; Kadowaki, Mitsushi; Tanaka, Tadao; et al.
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Oue, Atsushi*; Shimizu, Nobuaki*; Tanaka, Atsushi*; Otsuki, Takahiro*; Shinagawa, Masahiko*; Mori, Takahisa*; Saha, M. N.*; Ariful, H. S.*; Islam, S.*; Nakamura, Takako*; et al.
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Hoshino, Hiroo*; Shimizu, Nobuaki*; Oue, Atsushi*; Tanaka, Atsushi*; Saha, M. N.*; Shinagawa, Masahiko*; Otsuki, Takahiro*; Mori, Takahisa*; Ariful, H. S.*; Salequl, I. S.*; et al.
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Otsuki, Takahiro*; Oue, Atsushi*; Tanaka, Atsushi*; Salequl, I. S.*; Shimizu, Nobuaki*; Wada, Seiichi*; Hamada, Nobuyuki*; Funayama, Tomoo; Kobayashi, Yasuhiko; Hoshino, Hiroo*
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Hoshino, Seiichi; Yamada, Fumika*; Mukai, Masayuki; Yamaguchi, Tetsuji; Tanaka, Tadao
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Iida, Yoshihisa; Usui, Hideo; Mitsumoto, Yoshibumi; Hoshino, Seiichi; Kadowaki, Mitsushi; Mukai, Masayuki; Yamaguchi, Tetsuji; Tanaka, Tadao
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