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Journal Articles

A Long-term THMC assessment on the geochemical behavior of the bentonite buffer

Suzuki, Hideaki; Nakama, Shigeo; Fujita, Tomo; Imai, Hisashi; Sazarashi, Masami

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 19(2), p.39 - 50, 2012/12

For the safety assessment of a geological disposal system for high-level radioactive waste, it is necessary to quantify coupled thermo-hydro-mechanical-chemical (THMC) processes in the near-field. The current study investigated the geochemical changes arising from the infiltration of groundwater into the bentonite buffer under a thermal regime of radiogenic heating arising from the vitrified waste with the computer simulated assistance of a developed THMC model. In the case of infiltration by a saline groundwater, sulfate precipitates as gypsum around the overpack in the bentonite buffer and the Na-type bentonite changes to Ca-type by exposure to Ca ions released from concrete supports. In addition, the temporal evolution of the bentonite buffer porewater composition can be obtained to assess its contribution to the corrosion of the overpack.

JAEA Reports

Development of numerical model on the coupled thermo-hydro-mechanical-chemical process for the assessment methodology of chemical effects in the buffer material

Kimura, Makoto*; Sazarashi, Masami; Fujita, Tomo; Nakama, Shigeo; Suzuki, Hideaki

JAEA-Research 2010-034, 131 Pages, 2010/10

JAEA-Research-2010-034.pdf:16.23MB

Numerical model which can quantify the complex evolution of the coupled thermo-hydro-mechanical-chemical processes in the near-field of a HLW repository has been developed and the outline of the model considering heat flow, fluid flow, mass transport and a variety of chemical reactions such as mineral dissolution/precipitation, gas dissolution/exsolution, ion-exchange and surface complexation are described. The applicability of the numerical model was shown by the following three efforts. (1) Intercomparison analysis against another coupled model, TOUGHREACT which has been developed in the Lawrence Berkeley National Laboratory. (2) Comparison with the measured data in the designed laboratory tests for the salt accumulation/precipitation. (3) Perspective simulation on chemical changes in the near-field involving the radioactive decay heat arising from the vitrified waste and infiltration of ground water into the buffer material.

JAEA Reports

Experimental study of alteration of bentonite coexisting iron material

Sasamoto, Hiroshi; Ishii, Tomoko*; Sato, Hisao*; Sazarashi, Masami

JAEA-Research 2010-030, 64 Pages, 2010/09

JAEA-Research-2010-030.pdf:15.41MB

It is necessary to evaluate the alteration behavior of buffer material by interactions of overpack (iron) and buffer (bentonite) materials for geological disposal of high level radioactive waste. In the present study, laboratory experiments were carried out for the better understanding of phenomena caused by iron-bentonite (smectite) interactions. Before conducting the experiments, literature survey was performed to summarize the existing knowledge about iron-bentonite interactions and to identify the dominant factors affecting the alteration behavior. As the results of experiment, experimental conditions caused remarkable alteration, secondary minerals suggested as alteration product, different behavior of alteration between batch and compacted systems etc. were revealed.

JAEA Reports

Study on simulation of salt accumulation (Joint research)

Fujita, Tomo; Yui, Mikazu; Suzuki, Hideaki*; Fujisaki, Kiyoshi; Sazarashi, Masami*

JAEA-Research 2007-017, 47 Pages, 2007/03

JAEA-Research-2007-017.pdf:9.27MB

This report describes the results of a joint research entitled "Study on Simulation of Salt Accumulation" which was conducted under the collaboration between the Institute of Research and Innovation and the Japan Atomic Energy Agency. In the experiments for salt accumulation, accumulation of ${it Na$_{2}$SO$_{4}$}$ and ${it CaSO$_{4}$}$ was observed near the heater surface. Based on the facts from experiments, we have made hypothesis for mechanism of salt accumulation, and developed the model for it. Then, we conducted numerical simulations for salt accumulation phenomena under the saturated condition using the geochemical code "PHREEQC". It became clear that salt accumulation behavior can be evaluated qualitatively from these simulations, but quantitative evaluation requires more realistic modeling. Moreover we evaluated salt accumulation phenomena by simulations using coupled thermo - hydro - mechanical and chemical model / code assuming the unsaturated and / or saturated condition. A series of simulations were conducted focusing on accumulation of gypsum, and the result showed that tendency of salt accumulation phenomena was in agreement with that of experiments, but the profile of distribution of accumulated gypsum was not in agreement. In conclusion, it became clear that more realistic boundary condition should be considered and problems on coupled model / code were identified for further study.

JAEA Reports

None

Sazarashi, Masami*; *; Ikeda, Yasuhisa*; Kumagai, Mikio*; *; *

PNC TJ1564 97-002, 20 Pages, 1997/03

PNC-TJ1564-97-002.pdf:0.67MB

None

JAEA Reports

None

Sazarashi, Masami*; Ikeda, Yasuhisa*; Kumagai, Mikio*; *; *

PNC TJ1564 96-002, 19 Pages, 1996/03

PNC-TJ1564-96-002.pdf:0.57MB

None

JAEA Reports

A Study on the Migration of Idins Species of Various Chemical Forms in Geological Media (V)

Sazarashi, Masami*; Ikeda, Yasuhisa*; Kumagai, Mikio*

PNC TJ1564 93-003, 17 Pages, 1993/02

PNC-TJ1564-93-003.pdf:0.37MB

The present study has been carrisd out to establish the final disposal methods for e wastes containing radioactive iodines. In the previous studies, cinnabar (spain) a montmorillonite containing Ag-thiourea complex were selected as the arificial barri materials. In the present report, the adsorption mechanisms of two adsorbents were udied in more detail. Furthermore, various synthetic inorganic ion exchangers were ao examined as the model materials of I$$^{-}$$ ion adsorbents. The results are summarized afollow : 1. Detail examination for I$$^{-}$$ ion adsorption behavior of cinnabar (1) In avaible cinnabars, only spain one has an adsorptivity to I$$^{-}$$ ion. (2) The cinnabar adsorde has the selective adsorptivity to I$$^{-}$$ ion. (3) It takes 40 days to reach the adsorpti equilibrium. (4) The amount of adsorbed I$$^{-}$$ ions decreases with the rise of pH, and t desorption of I$$^{-}$$ ions from cinnadar is not observed. These results suggest that thedsorption of I$$^{-}$$ ions on cinnabar is not due to the ion exchange but the compo

JAEA Reports

None

Sazarashi, Masami*; Ikeda, Yasuhisa*; Kumagai, Mikio*

PNC TJ1564 93-002, 23 Pages, 1993/02

PNC-TJ1564-93-002.pdf:0.53MB

None

JAEA Reports

A Study on the migration of iodine species of various chemical forms in geological media, III

Sazarashi, Masami*; Ikeda, Yasuhisa*; Kumagai, Mikio*

PNC TJ1262 91-001, 168 Pages, 1991/05

PNC-TJ1262-91-001.pdf:6.78MB

None

Oral presentation

Experimental studies of iron-bentonite interactions under high temperature condition

Sasamoto, Hiroshi; Sazarashi, Masami; Ishii, Tomoko*; Sato, Hisao*; Kato, Hiroyasu*

no journal, , 

To investigate bentonite-iron interaction under high temperature condition, alteration experiments considering several factors (smectite composition, solution chemistry, iron-bentonite ratio) which were believed to affect on bentonite alteration were conducted with different experimental conditions. As the results, it was suggested that the factors considered in this study could also significantly affect on bentonite alteration in addition to temperature condition.

Oral presentation

Effect of temperature on passivation and corrosion rate of carbon steel in HLW repository system environment

Sazarashi, Masami; Taniguchi, Naoki; Naito, Morimasa; Tateishi, Tsuyoshi*

no journal, , 

no abstracts in English

Oral presentation

Development of simulation technology for salt condensation and segregation in compacted bentonite

Nagatani, Mutsumi; Fujisaki, Kiyoshi*; Sazarashi, Masami; Fujita, Tomo; Chijimatsu, Masakazu*

no journal, , 

no abstracts in English

Oral presentation

Experimental investigation of iron-bentonite interactions under high temperature condition

Sasamoto, Hiroshi; Sazarashi, Masami; Ishii, Tomoko*; Sato, Hisao*; Kato, Hiroyasu*

no journal, , 

To investigate bentonite-iron interaction under high temperature condition, alteration experiments considering several factors (smectite composition, solution chemistry, iron-bentonite ratio) which were believed to affect on bentonite alteration were conducted with different experimental conditions. As the results, it was suggested that the factors considered in this study could also significantly affect on bentonite alteration in addition to temperature condition.

Oral presentation

Development of numerical simulation code for the salt accumulation/precipitation ocuur in the buffer material

Kimura, Makoto; Fujita, Tomo; Sazarashi, Masami

no journal, , 

For the purpose of developing of the coupled Thermo-Hydro-Mechanical-Chemical(THMC) simulation code which is available to the prediction of the salt accumulation/precipitation, a chemical reaction model paid attention to unsaturated buffer material is discussed. In the THMC simulation code, chemical reaction model such as ion-exchange and surface complexation which are based on water-retention form and infiltration history under the unsaturated condition is considered. Some results of THMC simulation against the laboratory test are shown and it is found that mass-transport under the unsaturated/saturated condition is suitable but necessary to consider the change of solid/liquid ratio for the chemical reaction.

Oral presentation

Studies on coupled behavior of the high-level radioactive waste repository, 1; Development of simulation technology for salt accumulation in compacted bentonite

Sazarashi, Masami; Nagatani, Mutsumi; Kimura, Makoto; Suzuki, Hideaki; Fujita, Tomo; Chijimatsu, Masakazu*

no journal, , 

no abstracts in English

Oral presentation

Studies on coupled behavior of the high-level radioactive waste repository

Sasamoto, Hiroshi; Sazarashi, Masami; Ishii, Tomoko*; Kato, Hiroyasu*; Sugiyama, Kazutoshi*

no journal, , 

Regarding to alteration of bentonite coexisting with iron material, laboratory experiments with different temperature and iron-bentonite (I/B) ratio and literature surveys for bentonite alteration in the natural system were conducted. As the results, the conditions which promote the alteration of smectite significantly were estimated approximately. Additionally, the important alteration products necessary for evaluation of smectite alteration were summarized by literature surveys. Such information will be useful for evaluation of smectite alteration considering the conditions of time and duration interested.

Oral presentation

Studies on coupled behavior of the high-level radioactive waste repository, 2; Influence of temperature on passivation behavior and corrosion rate of carbon steel

Tateishi, Tsuyoshi*; Taniguchi, Naoki; Sazarashi, Masami; Naito, Morimasa

no journal, , 

no abstracts in English

Oral presentation

Development of numerical simulation code for the salt accumulation/precipitation occur in the buffer material, 2

Kimura, Makoto; Fujita, Tomo; Sazarashi, Masami; Suzuki, Hideaki

no journal, , 

no abstracts in English

Oral presentation

Development of simulation technology for salt accumulation in compacted bentonite, 3

Sazarashi, Masami; Kimura, Makoto*; Suzuki, Hideaki; Fujita, Tomo; Chijimatsu, Masakazu*

no journal, , 

no abstracts in English

Oral presentation

Experimental and modeling studies on iron-bentonite interactions

Sasamoto, Hiroshi; Wilson, J.*; Sato, Hisao*; Sazarashi, Masami

no journal, , 

The proposed repository design for high-level radioactive waste in Japan includes iron containers surrounded by a bentonite buffer. Interactions of iron-bentonite (I/B) materials may lead to the adverse transformation of smectite to phases with a limited capacity to swell. Batch experiments that included native iron powder and bentonite and column experiments whereby compacted bentonites were reacted with embedded iron coupons were conducted in order to evaluate the effects of environmental parameters on I/B interactions. Additionally, several model simulations have been produced in order to evaluate the factors influencing the nature of bentonite alteration in the presence of iron. The dominant process of interest over performance assessment timescales was estimated as the results of variant simulations.

26 (Records 1-20 displayed on this page)