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Journal Articles

Modelling concrete degradation by coupled non-linear processes

Oda, Chie; Kawama, Daisuke*; Shimizu, Hiroyuki*; Benbow, S. J.*; Hirano, Fumio; Takayama, Yusuke; Takase, Hiroyasu*; Mihara, Morihiro; Honda, Akira

Journal of Advanced Concrete Technology, 19(10), p.1075 - 1087, 2021/10

Concrete in a transuranic (TRU) waste repository is considered a suitable material to ensure safety, provide structural integrity and retard radionuclide migration after the waste containers fail. In the current study, coupling between chemical, mass-transport and mechanical, so-called non-linear processes that control concrete degradation and crack development were investigated by coupled numerical models. Application of such coupled numerical models allows identification of the dominant non-linear processes that will control long-term concrete degradation and crack development in a TRU waste repository.

Journal Articles

Using natural systems evidence to test models of transformation of montmorillonite

Savage, D.*; Wilson, J.*; Benbow, S.*; Sasamoto, Hiroshi; Oda, Chie; Walker, C.*; Kawama, Daisuke*; Tachi, Yukio

Applied Clay Science, 195, p.105741_1 - 105741_11, 2020/09

 Times Cited Count:1 Percentile:0.02(Chemistry, Physical)

Safety functions for the clay buffer in a repository for high-level radioactive waste (HLW) are fulfilled if the presence of montmorillonite with high swelling capacity and low permeability is maintained in the long-term. The transformation of montmorillonite to the non-swelling mineral likely illite is addressed in most safety assessments by using simple semi-empirical kinetic models, but this approach contrasts with more complex reactive-transport simulations. In the present study, reactive-transport simulations are compared with simple semi-empirical kinetic models. Results suggest that reactive-transport simulations err on the side of conservatism, but may produce unrealistic estimates of illitization. This comparison demonstrates that reactive-transport models may be carefully applied to simulate the long-term evolution of near field environment for HLW disposal.

Journal Articles

A Coupled modeling simulator for near-field processes in cement engineered barrier systems for radioactive waste disposal

Benbow, S. J.*; Kawama, Daisuke*; Takase, Hiroyasu*; Shimizu, Hiroyuki*; Oda, Chie; Hirano, Fumio; Takayama, Yusuke; Mihara, Morihiro; Honda, Akira

Crystals (Internet), 10(9), p.767_1 - 767_33, 2020/09

 Times Cited Count:1 Percentile:37.3(Crystallography)

Details are presented of the development of a coupled modeling simulator for assessing the evolution in the near-field of a geological repository for radioactive waste disposal where concrete is used as a backfill. The simulator uses OpenMI, a standard for exchanging data between simulation software programs at run-time, to form a coupled chemical-mechanical-hydrogeological model of the system. The approach combines a tunnel scale stress analysis finite element model, a discrete element model for accurately modeling the patterns of emerging cracks in the concrete, and a finite element and finite volume model of the chemical processes and alteration in the porous matrix and cracks in the concrete, to produce a fully coupled model of the system. Combining existing detailed simulation software in this way with OpenMI has the benefit of not relying on simplifications that might be necessary to combine all of the modeled processes in a single piece of software.

Journal Articles

Structural, magnetic, transport, and thermoelectric properties of the pseudobrookite AlTi$$_{2}$$O$$_{5}$$-Ti$$_{3}$$O$$_{5}$$ system

Takahama, Ryusei*; Ishii, Toi*; Indo, Daigo*; Arizono, Mitsutoshi*; Terakura, Chieko*; Tokura, Yoshinori*; Takeshita, Nao*; Noda, Masaaki*; Kuwahara, Hideki*; Saiki, Takuo*; et al.

Physical Review Materials (Internet), 4(7), p.074401_1 - 074401_11, 2020/07

 Times Cited Count:1 Percentile:20.84(Materials Science, Multidisciplinary)

Journal Articles

Natural systems evidence for the effects of temperature and the activity of aqueous silica upon montmorillonite stability in clay barriers for the disposal of radioactive wastes

Savage, D.*; Wilson, J.*; Benbow, S.*; Sasamoto, Hiroshi; Oda, Chie; Walker, C.*; Kawama, Daisuke*; Tachi, Yukio

Applied Clay Science, 179, p.105146_1 - 105146_10, 2019/10

 Times Cited Count:5 Percentile:57.36(Chemistry, Physical)

Natural systems evidence for the effects of temperature and the activity of aqueous silica upon montmorillonite stability was evaluated. Thermodynamic modeling using three different TDBs shows that stability fields for montmorillonite exist from 0 to 140$$^{circ}$$C, but at low values of silica activity, a stability field for illite replaces that for montmorillonite. Pore fluid chemical and mineralogical data for sediments from ODP sites from offshore Japan show a trend from montmorillonite + amorphous silica stability at temperatures up to 60$$^{circ}$$C to that for illite + quartz at higher temperatures. However, even over very long timescales ($$gg$$ 1 Ma), smectite does not transform to illite under thermodynamically-favourable conditions at temperatures less than 80$$^{circ}$$C.

Journal Articles

Hydration and degradation of High content Fly ash Silica fume Cement (HFSC)

Anraku, Sohtaro; Walker, C.*; Oda, Chie; Mihara, Morihiro; Honda, Akira

Proceedings of 15th International Congress on the Chemistry of Cement (ICCC 2019) (Internet), 11 Pages, 2019/09

Journal Articles

Formation of metal ion complexes in cementitious porewaters and leachates

Walker, C.*; Anraku, Sohtaro; Oda, Chie; Mihara, Morihiro; Honda, Akira

Proceedings of 15th International Congress on the Chemistry of Cement (ICCC 2019) (Internet), 11 Pages, 2019/09

JAEA Reports

Biosphere assessment methodology commonly applicable to various disposal concepts

Kato, Tomoko; Fukaya, Yukiko*; Sugiyama, Takeshi*; Nakai, Kunihiro*; Oda, Chie; Oi, Takao

JAEA-Data/Code 2019-002, 162 Pages, 2019/03

JAEA-Data-Code-2019-002.pdf:2.78MB

The radioactive waste generated from Fukushima Daiichi nuclear power station (FDNPS) accident have features such as wide range of radioactivity level (from low to high) and huge amount etc. It would be necessary for the waste from the FDNPS accident to develop suitable disposal concept and to be disposed safely and reasonably. When considering such appropriate disposal concepts in site-generic phase, it is necessary to appropriately develop models and parameters depending on the disposal concepts, such as disposal depth and specification of engineered barrier. In addition, it is desirable to evaluate the safety of repository with common models and parameters independent on the disposal concepts. In the safety assessment of disposal, it is useful to show the difference in performance of repository with "dose" as an indicator of safety assessment. Biosphere model and parameter set and flux-to-dose conversion factors calculated using them are originally dependent on the disposal concepts. However, the biosphere models and the parameter set in safety assessment of near-surface disposal, sub-surface disposal and geological disposal are prepared in each case, and are different according to the age and purpose of the discussion. In this study, an example of biosphere model and parameter-set of groundwater sceinario commonly applicable to various disposal concepts were shown, to calculate flux-to-dose conversion factors, as common indicators independent to disposal concept. And, a set of flux-to-dose conversion factors was also calculated by using the commonly available biosphere model and parameter set. By applying the flux-to-dose conversion factors, it is possible to compare the performance of disposal concepts to the waste generated from FDNPS accident, focusing on the parts depending on the disposal concepts.

Journal Articles

Evaluation of the intake of radon through skin from thermal water

Sakoda, Akihiro; Ishimori, Yuu; Tschiersch, J.*

Journal of Radiation Research, 57(4), p.336 - 342, 2016/07

 Times Cited Count:6 Percentile:40.54(Biology)

In general, the deposition of inhaled radon progeny on lung gives the largest dose when the dose evaluation is made for the so-called radon exposure. In this case, the dose from inhalation of radon itself is much lower than that from its progeny. Also, very little studies of the absorption of radon via skin have not been done so far. However, specific environments such as radon hot springs have the characteristics that radon concentration in water is significantly higher by a few orders than that in air. In the present study, a biokinetic model of radon into which its skin-absorption process was incorporated was developed to discuss the change in radon concentrations in tissues during and after bathing in thermal water. This derived dose was compared with other exposure routes from radon and its progeny.

Journal Articles

An Approach to discriminatively determine thoron and radon emanation rates for a granular material with a scintillation cell

Sakoda, Akihiro; Meisenberg, O.*; Tschiersch, J.*

Radiation Measurements, 89, p.8 - 13, 2016/06

 Times Cited Count:2 Percentile:14.27(Nuclear Science & Technology)

In the present study, the methodology for the discriminative determination of thoron and radon emanation rates from a granular material has been examined using a flow-through scintillation cell and so-called sandwich sample. The mathematical model was developed to differentiate total alpha counts into thoron- and radon-associated counts. This method was experimentally validated, and then the detection limits and uncertainties were evaluated to characterize this method. It was concluded that the present method is advantageous to a sample that has much higher $$^{226}$$Ra activity than $$^{224}$$Ra if the emanation fractions are similar between thoron and radon.

Journal Articles

Calcium silicate hydrate (C-S-H) gel solubility data and a discrete solid phase model at 25$$^{circ}$$C based on two binary non-ideal solid solutions

Walker, C.; Suto, Shunkichi; Oda, Chie; Mihara, Morihiro; Honda, Akira

Cement and Concrete Research, 79, p.1 - 30, 2016/01

 Times Cited Count:40 Percentile:89.36(Construction & Building Technology)

Modeling the solubility behavior of calcium silicate hydrate (C-S-H) gel is important to make quantitative predictions of the degradation of hydrated ordinary Portland cement (OPC) based materials. Experimental C-S-H gel solubility data have been compiled from the literature, critically evaluated and supplemented with new data from the current study for molar Ca/Si ratios = 0.2-0.83. All these data have been used to derive a discrete solid phase (DSP) type C-S-H gel solubility model based on two binary non-ideal solid solutions in aqueous solution(SSAS). Features of the DSP type C-S-H gel solubility model include satisfactory predictions of pH values and Ca and Si concentrations for all molar Ca/Si ratios = 2.7 $$rightarrow$$ 0 in the C-S-H system, portlandite (CH) for Ca/Si ratios $$>$$ 1.65, congruent dissolution at Ca/Si ratios = 0.85, and amorphous silica (SiO$$_{2 (rm am)}$$) for Ca/Si ratios $$<$$ 0.55 as identified in the current study by IR spectroscopy.

Journal Articles

Behavior of radon progeny produced in a scintillation cell in the flow-through condition

Sakoda, Akihiro; Meisenberg, O.*; Tschiersch, J.*

Radiation Measurements, 77, p.41 - 45, 2015/06

 Times Cited Count:6 Percentile:48.17(Nuclear Science & Technology)

When a scintillation cell is used for radon measurement, detection efficiencies for individual alpha emitters ($$^{222}$$Rn, $$^{218}$$Po and $$^{214}$$Po) are required depending on the methods of data analysis. The present study describes an attempt to obtain an empirical parameter which is necessary to calculate their individual detection efficiencies in the flow-through cell: the fraction of the progeny generated in the cell which is deposited onto the wall. As a result, an empirical formula was acquired to estimate the deposition fraction of $$^{218}$$Po as a function of flow rate. This result is helpful in understanding the characteristics of the scintillation cell. The empirical formula derived in this study can also be applied to predicting the behavior of thoron progeny ($$^{212}$$Pb and its progeny) in continuous thoron measurements with the flow-through scintillation cell.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 3; Progress report on NUMO-JAEA collaborative research in FY2013 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Kitamura, Akira; Yoshikawa, Hideki; Oda, Chie; Ishidera, Takamitsu; et al.

JAEA-Research 2014-030, 457 Pages, 2015/03

JAEA-Research-2014-030.pdf:199.23MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and post-closure performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, based on some examples of developing method of hydro-geological structure model, acquired knowledge are arranged using the tree diagram, and model uncertainty and its influence on the evaluation items were discussed. With regard to (2) study on scenario development, the developed approach for "defining conditions" has been reevaluated and improved from practical viewpoints. In addition, the uncertainty evaluation for the effect of use of cementitious material, as well as glass dissolution model, was conducted with analytical evaluation. With regard to (3) study on setting radionuclide migration parameters, based on survey of precedent procedures, multiple-approach for distribution coefficient of rocks was established, and the adequacy of the approach was confirmed though its application to sedimentary rock and granitic rock. Besides, an approach for solubility setting was developed including the procedure of selection of solubility limiting solid phase. The adequacy of the approach was confirmed though its application to key radionuclides.

Journal Articles

Na-montmorillonite dissolution rate determined by varying the Gibbs free energy of reaction in a dispersed system and its application to a coagulated system in 0.3M NaOH solution at 70$$^{circ}$$C

Oda, Chie; Walker, C.; Chino, Daisuke*; Ichige, Satoru; Honda, Akira; Sato, Tsutomu*; Yoneda, Tetsuro*

Applied Clay Science, 93-94, p.62 - 71, 2014/05

 Times Cited Count:6 Percentile:21.77(Chemistry, Physical)

Na-montmorillonite dissolution in a 0.3M NaOH solution has been investigated at pH12 and 70$$^{circ}$$C. The flow-through dissolution experiments were conducted in a dispersed system with varying concentrations of Si and Al to derive a Na-montmorillonite dissolution rate, as a non-linear function of the Gibbs free energy of reaction, dGr. This rate equation was used to simulate the batch-type Na-montmorillonite reaction experiments conducted in a coagulated system. The model simulation of the batch-type experiment adopting the empirical rate equations of Na-montmorillonite dissolution and secondary mineral analcime precipitation were able to reproduce the measured changes in the amount of dissolved Na-montmorillonite and concentrations of Si and Al in solution. The results showed that the empirical rate equation of Na-montmorillonite dissolution determined in the dispersed system was applicable to the coagulated system over a higher dGr range and that the concentrations of Si and Al in the batch experiment were controlled by the precipitation of analcime.

Journal Articles

Molecular orbital analysis on dissolution of smectite under strong alkaline condition with high Ca concentration

Matsue, Naoto*; Abidin, Z.*; Fujii, Naoki*; Oda, Chie; Honda, Akira

Nendo Kagaku, 52(2), p.62 - 70, 2014/00

Bentonite is expected to be used along with cement as engineered barrier components of TRU waste geological disposal system. There is a concern that the bentonite dissolved or altered owing to the contact with strong alkaline and high Ca concentration water derived from the reaction of the cement and groundwater. The first-principles quantum chemical calculations using the cluster model of montmorillonite, the main component of bentonite, were performed, and it was indicated that octahedral Al has higher solubility than octahedral Mg under strong alkaline condition and unsaturated Si-O-Al bond connecting tetrahedral and octahedral sheets at the edge of 110 and 010 planes cleaves easily. The adsorption of OH$$^{-}$$ on tetrahedral Si atom caused dissolution of adjacent Si and Al atoms in addition to the Si atom. While, the dissociation of Si-OH and Al-OH$$_{2}$$ groups and the difference in exchangeable cation species were shown to be less likely to affect the dissolution behavior of montmorillonite.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 2; Progress report on NUMO-JAEA collaborative research in FY2012 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Hayano, Akira; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.

JAEA-Research 2013-037, 455 Pages, 2013/12

JAEA-Research-2013-037.pdf:42.0MB

Following FY2011, JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, the tree diagram of methodology of groundwater travel time has been extended for crystalline rock, in addition, tree diagram for sedimentary rock newly has been organized. With regard to (2) study on scenario development, the existing approach has been improved in terms of a practical task, and applied and tested for near field focusing on the buffer. In addition, the uncertainty of some important processes and its impact on safety functions are discussed though analysis. With regard to (3) study on setting radionuclide migration parameters, the approaches for parameter setting have been developed for sorption for rocks and solubility, and applied and tested through parameter setting exercises for key radionuclides.

Journal Articles

Reactive-transport model analyses of bentonite alteration behavior at alkaline condition generated by cement-water interaction in a TRU wastes repository

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.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage; Progress report on NUMO-JAEA collaborative research in FY2011 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Hayano, Akira; Mitsui, Seiichiro; Taniguchi, Naoki; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.

JAEA-Research 2012-032, 298 Pages, 2012/09

JAEA-Research-2012-032.pdf:33.68MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation phase. The topics and the conducted research are follows; (1) Study on selection of host rock: in terms of hydraulic properties, items for assessing rock property, and assessment methodology of groundwater travel time has been organized with interaction from site investigation. (2) Study on development of scenario: the existing approach has been embodied, in addition, the phenomenological understanding regarding dissolution of and nuclide release from vitrified waste, corrosion of the overpack, long-term performance of the buffer are summarized. (3) Study on setting nuclide migration parameters: the approach for parameter setting has been improved for sorption and diffusion coefficient of buffer/rock, and applied and tested for parameter setting of key radionuclides. (4) Study on ensuring quality of knowledge: framework for ensuring quality of knowledge has been studied and examined aimed at the likely disposal facility condition.

JAEA Reports

Research and development for treatment and disposal technologies of TRU waste; JFY 2010 annual report

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.

JAEA Reports

Research and development for treatment and disposal technologies of TRU waste; JFY 2009 annual report

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.

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