Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 103

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

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:42.94(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

Comparison of field data and numerical simulation of nitrate evolution in groundwater using the model of nitrate evolution

Abe, Toru*; Hirano, Fumio; Mihara, Morihiro; Honda, Akira

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(1), p.3 - 11, 2020/06

Degradation of TRU waste in a geological disposal facility may cause the formation of a nitrate plume. A Nitrate Evolution model due to mineral reactions, microbial activity, and metal corrosiON (NEON) has therefore been developed to evaluate the safety case for geological disposal of TRU waste. Small scale laboratory experiments can be reproduced satisfactorily, however, it is necessary to demonstrate the applicability of the NEON model on scales relevant to the geological disposal of TRU waste. In the current study, an industrial analogue of a nitrate plume from the pollution of groundwater from nitrate fertilizers used on Ikuchi Island, Japan was selected to test the applicability of the NEON model. Concentration profiles of nitrate ions in the groundwater were successfully reproduced over the hundreds of meters scale demonstrating the applicability of the NEON model in evaluating the chemical behavior of a nitrate plume derived from the geological disposal of TRU waste.

JAEA Reports

Data acquisition for radionuclide sorption on barrier materials for performance assessment of geological disposal of TRU wastes

Tachi, Yukio; Suyama, Tadahiro*; Mihara, Morihiro

JAEA-Data/Code 2019-021, 101 Pages, 2020/03

JAEA-Data-Code-2019-021.pdf:4.05MB

Sorption of radionuclides in cement and bentonite as engineered barrier materials, and rocks as natural barrier is the one of key processes in the performance assessment of geological disposal of TRU and high-level waste. The magnitude of sorption, expressed normally by a distribution coefficient (K$$_{rm d}$$), needs to be measured and determined taking into account the properties of barrier materials and geochemical conditions and associated uncertainty in the performance assessment. The basic concept for TRU waste disposal contains cementitious materials as an engineered barrier materials, in addition to bentonite and rock. It is therefore needed to consider the effects of the cement degradation and co-existing substances such as nitrates on radionuclide sorption. This report focused on data acquisition of distribution coefficient (K$$_{rm d}$$) by batch sorption experiments for the systems coupling barrier material-chemical condition-radionuclides that are needed to consider for the performance assessment of geological disposal of TRU waste. The barrier materials considered are ordinary Portland cement (OPC), degraded OPC and tuff rock. The chemical conditions are distilled water and synthetic seawater equilibrated with OPC and those containing nitrates and ammonium salts, etc. The radionuclides considered are organic carbon, inorganic carbon, Cl, I, Cs, Ni, Se, Sr, Sn, Nb, Am and Th. Although K$$_{rm d}$$ values have been partly reported previously as RAMDA (Radionuclide Migration Datasets) for the performance assessment in the TRU-2 report, these results and addition K$$_{rm d}$$ data are reported with the details of experimental methods and conditions.

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

Journal Articles

Apparent diffusion coefficients of Cs and I in hardened cement paste using mineral admixtures

Mihara, Morihiro; Harasawa, Shuichi*; Torii, Kazuyuki*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 26(1), p.15 - 23, 2019/06

Hardened cement pastes (HCPs) of water/cement ratio (W/C) 50% and 30% using fly ash (FA), blast furnace slag (BFS) and silica fume (SF) for 28 days were prepared. Apparent diffusion coefficients (D$$_{a}$$) of Cs and I in HCPs were obtained using electron probe microanalysis. For Cs, BFS and SF contributed to a reduction of D$$_{a}$$ for W/C=50% and 30%, respectively. For I, BFS reduced D$$_{a}$$ for W/C=50%, however a significant reduction in D$$_{a}$$ for W/C=30% was not observed. Using SF enhanced sorption of Cs on HCP, and using BFS slightly improved sorption of Cs on HCP. It was also confirmed that the pore structures of HCP using SF and BFS were connected by fine pores. It was therefore considered that using SF and BFS contributes to the reduction of D$$_{a}$$ in HCP.

Journal Articles

Long-term mechanical analysis code considering chemical alteration for a TRU waste geological repository

Mihara, Morihiro; Hirano, Fumio; Takayama, Yusuke; Kyokawa, Hiroyuki*; Ono, Shintaro*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(1), p.15 - 25, 2017/06

A computer program MACBECE has been developed to provide rigorous calculations of the long-term mechanical behavior of a TRU waste geological repository. Consideration is given to the expected chemical alteration of repository components, including cementitious materials and bentonite, and the mechanical interactions between repository and host rock. The long-term mechanical behavior of a TRU waste repository was evaluated in a deep soft rock site, where creep deformation is likely to occur from the initial construction phase to 10$$^{5}$$ years after repository closure. It was found that the stress didn't fall into a singularity of yield surface of the EC model applied to the mechanical behavior model of bentonite. The calculated displacement of the inner diameter of the repository, considering mechanical interaction between repository and host rock, was about half that of a result in 2nd progress report on R&D for TRU waste disposal in Japan.

Journal Articles

Crack formation in cementitious materials used for an engineering barrier system and their impact on hydraulic conductivity from the viewpoint of performance assessment of a TRU Waste disposal system

Hirano, Fumio; Otani, Yoshiteru*; Kyokawa, Hiroyuki*; Mihara, Morihiro; Shimizu, Hiroyuki*; Honda, Akira

Nippon Genshiryoku Gakkai Wabun Rombunshi, 15(2), p.97 - 114, 2016/06

A mechanical analysis code MACBECE2014 has been developed at the Japan Atomic Energy Agency to make realistic simulations of the physical integrity of the near-field for performance assessment of geological disposal of TRU waste in Japan. The MACBECE2014 code can be used to evaluate long-term changes in the mechanical behavior and any subsequent changes in the permeability of engineering barrier components, including crack formation in cementitious materials caused by expansion due to metal corrosion. Simulated results of the TRU waste disposal system with a bentonite buffer using the MACBECE2014 code demonstrated that the low permeability of the engineering barrier system could be maintained for long time periods after disposal because the physical integrity of the bentonite buffer remained intact. Simulated results of the disposal system with a concrete backfill, showed that crack formation leads to a significant increase in permeability of the system.

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:35 Percentile:9.44(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

Thorium and americium solubilities in cement pore water containing superplasticiser compared with thermodynamic calculations

Kitamura, Akira; Fujiwara, Kenso; Mihara, Morihiro; Cowper, M.*; Kamei, Gento

Journal of Radioanalytical and Nuclear Chemistry, 298(1), p.485 - 493, 2013/10

 Times Cited Count:9 Percentile:34.16(Chemistry, Analytical)

Solubility of thorium and americium in pore water squeezed from a cement paste was investigated by a batch method from oversaturation. The ordinary Portland cement was mixed with deionised water to prepare a cement paste from which the pore water was squeezed following solidification. Another batch of pore water was collected by the same method except that a superplasticiser was added to the deionised water used to prepare the cement paste. The aim was to investigate an effect of superplasticiser on solubility of thorium and americium in the squeezed cement porewaters. The obtained solubility values in the two squeezed pore waters (with and without superplasticiser present) were similar. Thermodynamic calculations were performed with the JAEA-TDB thermodynamic database and compared with the experimental data to verify their applicability. This result showed that superplasticisers after mixing with the cement paste did not have a significant effect on solubility of thorium and americium, and the thermodynamic calculations were applicable in the present system. Size distribution of colloidal species of thorium and americium was also investigated.

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.

JAEA Reports

A Study for the safety evaluation of geological disposal of TRU waste and influence on disposal site design by change of amount of TRU waste (Joint research)

Hasegawa, Makoto; Kondo, Hitoshi; Kamei, Gento; Hirano, Fumio; Mihara, Morihiro; Takahashi, Kuniaki; Funabashi, Hideyuki; Kawatsuma, Shinji; Ueda, Hiroyoshi*; Oi, Takao*; et al.

JAEA-Research 2011-003, 47 Pages, 2011/02

JAEA-Research-2011-003.pdf:3.99MB

In 2009, NUMO and JAEA set up a technical commission to investigate the reasonable TRU waste disposal following a cooperation agreement between these two organizations. In this report, the calculation result of radionuclide transport for a TRU waste geological disposal system was described, by using the TIGER code and the GoldSim code at identical terms. Comparing the calculation result, a big difference was not seen. Therefore, the reliability of both codes was able to be confirmed. Moreover, the influence on the disposal site design (Disposal capacity: 19,000 m$$^{3}$$) was examined when 10% of the amount of TRU waste increased. As a result, it was confirmed that the influence of the site design was very little based on the concept of the Second Progress Report on Research and Development for TRU Waste Disposal in Japan.

JAEA Reports

Thermodynamic data of compounds and complexes of metal elements with organic ligands for JAEA-TDB

Mihara, Morihiro

JAEA-Review 2009-060, 27 Pages, 2010/03

JAEA-Review-2009-060.pdf:2.14MB

It is planned that JAEA-TDB has been developed modifying JNC-TDB released in 1999 by the end of FYJ 2009. The JAEA-TDB is planned to include thermodynamic data of compounds and complexes of metal elements with organic ligands which were not included in JNC-TDB. This report shows the selected thermodynamic data of compounds and complexes of metal elements with organic ligands which might be included in TRU waste in JAEA-TDB. Selected organics are oxalic acid, citric acid, ethylenediaminetetraacetic acid (EDTA) and iso-saccharinic acid (ISA) which were of interest in the OECD/NEA. The thermodynamic data evaluated by OECD/NEA were selected for JAEA-TDB. However, selected values by OECD/NEA are limited to evaluate the solubility calculation. Therefore, other published values and estimated values by LFER are also selected as tentative values for JAEA-TDB.

JAEA Reports

Development of mechanical analysis code (MACBECE) for TRU waste disposal

Mihara, Morihiro; Sato, Nobuyuki; Ono, Shintaro*; Morikawa, Seiji*

JAEA-Data/Code 2009-026, 114 Pages, 2010/03

JAEA-Data-Code-2009-026.pdf:15.21MB

This report shows the capability, incorporated mechanical model and sample calculation of MACBECE. MACBECE incorporated the non-liner elastic model for cement-based material, the elasto- viscoplastic model considering swelling of bentonite-based material and the visco-elastic model reported by Okubo for host-rock. Furthermore, MACBECE can consider chemical transition of bentonite-based and cement-based materials.

JAEA Reports

JAEA thermodynamic database for performance assessment of geological disposal of high-level radioactive and TRU wastes

Kitamura, Akira; Fujiwara, Kenso; Doi, Reisuke; Yoshida, Yasushi*; Mihara, Morihiro; Terashima, Motoki; Yui, Mikazu

JAEA-Data/Code 2009-024, 84 Pages, 2010/03

JAEA-Data-Code-2009-024.pdf:2.84MB

A thermodynamic database was established to develop a thermodynamic database for performance assessment of geological disposal of high-level and TRU wastes. Twenty-four elements (actinides, fission products and their daughters) which are of importance for the performance assessment of geological disposal have been selected. The fundamental plan was in principle based on the guidelines established by the Nuclear Energy Agency in the Organisation for Economic Co-operation and Development (OECD/NEA). Additional unique guidelines were established due to a requirement from the performance assessment to select tentative thermodynamic values obtained from chemical analogues and/or models for elements with insufficient thermodynamic values. Selected thermodynamic data were compiled for geochemical calculation programs.

JAEA Reports

Research and development for treatment and disposal technologies of TRU waste; JFY 2008 annual report

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.

JAEA Reports

Study on pore structure and diffusion coefficient of chloride ion in hardened low-alkaline cement

Mihara, Morihiro; Torii, Kazuyuki*

JAEA-Research 2008-109, 46 Pages, 2009/03

JAEA-Research-2008-109.pdf:8.04MB

Low-alkaline cement using pozzolans is under consideration as a possible filling and structural material in geological disposal for long-lived radioactive waste. Silica fume and high-volume fly ash are used to develop the low-alkaline cement which is named as HFSC, High-volume Fly ash Cement. In this study, pore structure and diffusivity of chloride ion in HFSC pastes were investigated in order to understand the fundamental transport properties of ions.

JAEA Reports

Research and development for treatment and disposal technologies of TRU waste; JFY 2007 annual report

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:2.52MB
JAEA-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.

Journal Articles

Development of low-alkaline cement using pozzolans for geological disposal of long-lived radioactive waste

Mihara, Morihiro; Iriya, Keishiro*; Torii, Kazuyuki*

Doboku Gakkai Rombunshu, F, 64(1), p.92 - 103, 2008/02

To reduce uncertainties in the safety assessment of a disposal system for long-lived radioactive waste, cement was developed which generates leachates with a lower pH than that of ordinary cement paste. This cement was termed "low-alkaline cement". Large amounts of pozzolans were used to produce the low-alkaline cement from ordinary Portland cement. To reduce the pH values, silica fume was found to be efficient, however large amounts of silica fume reduced the workability of fresh concrete. Therefore, we also used fly ash with silica fume, high-volume fly ash silica fume cement (HFSC). The low pH value and self-compacting HFSC was developed. Two types of HFSC showed high compressive strength, smaller drying shrinkage and lower temperature rise than those of ordinary cement concrete. They can therefore be applied to the structure and filling concrete in the disposal system.

Journal Articles

Evaluation of diffusion coefficients of chloride ion in hardened high-volume fly ash silica fume cement pastes

Mihara, Morihiro; Torii, Kazuyuki*

Semento, Konkurito Rombunshu, (61), p.331 - 337, 2008/02

In order to evaluate a long-term behavior of hardened high-volume fly ash silica fume cement paste, HFSC, which is considered to be used as filling and structural materials in a repository for the radioactive waste disposal, apparent diffusion coefficients of chloride ion were obtained which might diffused from the surrounded groundwater into the cementitous material. The profiles of chloride concentration in hardened cement paste after the immersion of sodium chloride and calcium chloride solution were measured by electron probe microscopy analysis and apparent diffusion coefficients were calculated fitting these profiles. And, effects of mixture proportion of fly ash content, 40%, 30% and 20%, in HFSC and period of diffusion experiment, 28days and 91days, on the apparent diffusion coefficient were studied from the view point of the pore structure and immobilization ability of chloride ions in HFSC. It was found that the diffusion coefficient of HFSC using 40% of fly ash, HFSC424, was the smallest value in the cement pastes used and the apparent diffusion coefficient degreased as the experimental period. Although HFSC424 had a larger porosity and lower immobilization ability of chloride ion than ordinary Portland cement, it was concluded that the smallest diffusion coefficient was caused by the fine and discontinuous pore structure of HFSC424.

103 (Records 1-20 displayed on this page)