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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.
Yui, Mikazu; Ishikawa, Hirohisa; Watanabe, Atsuo*; Yoshino, Kyoji*; Umeki, Hiroyuki; Hioki, Kazumasa; Naito, Morimasa; Seo, Toshihiro; Makino, Hitoshi; Oda, Chie; et al.
JAEA-Research 2010-015, 106 Pages, 2010/05
JAEA-Research-2010-015.pdf:13.58MB
This report summarizes the activity of Phase I of Waste Management Working Group of the United States - Japan Joint Nuclear Energy Action Plan started in 2007. The working group focused on consolidation of the existing technical basis between the U.S. and Japan and the joint development of a plan for future collaborative activities. Firstly, the political/regulatory frameworks related to nuclear fuel cycles in both countries were reviewed. The various advanced fuel cycle scenarios in both countries were surveyed and summarized. Secondly, the waste management/disposal system optimization was discussed. Repository system concepts for the various classifications of nuclear waste were reviewed and summarized, then disposal system optimization processes and techniques were reviewed, and factors to consider in future repository design optimization activities were also discussed. Finally the potential collaboration areas and activities related to the optimization problem were extracted.
AgSeo, Hitoshi; Motome, Yukitoshi*
Physical Review Letters, 102(19), p.196403_1 - 196403_4, 2009/05
Times Cited Count：7 Percentile：45.41(Physics, Multidisciplinary)We theoretically study the effect of spiral-type charge frustration in a quasi-one-dimensional molecular conductor (DI-DCNQI)Ag. We clarify how the spiral frustration in the interchain Coulomb repulsion is relieved and leads to a self-organization of complex charge-lattice ordered chains, in agreement with the recent synchrotron X-ray study. Our results enlighten the relevance of the spiral frustration and provide a possible reconciliation among puzzling experimental data.
Otsuka, Yuichi*; Seo, Hitoshi; Motome, Yukitoshi*; Kato, Takeo*
Physica B; Condensed Matter, 404(3-4), p.479 - 481, 2009/03
Times Cited Count：5 Percentile：25.51(Physics, Condensed Matter)We investigate ground state properties of a quasi-one-dimensional electron-lattice coupled model for quarter-filled molecular conductors. The effective one-dimensional extended Hubbard model coupled to adiabatic lattice degree of freedom is derived by the inter-chain mean-field approximation and solved by Lanczos exact diagonalization method. We find that the critical behavior among lattice tetramerized states with different charge-lattice ordered patterns is sensitively affected by the inter-chain Coulomb interaction, lattice anharmonicity, and intrinsic dimerization.
Otsuka, Yuichi*; Seo, Hitoshi; Motome, Yukitoshi*; Kato, Takeo*
Journal of the Physical Society of Japan, 77(11), p.113705_1 - 113705_4, 2008/11
Times Cited Count：30 Percentile：77.39(Physics, Multidisciplinary)Finite-temperature phase transitions in quasi-one-dimensional quarter-filled systems are investigated using the extended Hubbard model with electron-lattice coupling. By a quantum Monte Carlo method combined with interchain mean-field approximation, we clarify competing and coexisting behaviors among charge ordering, dimer Mott, and spin-Peierls states. The results are compared with experimental data for quasi-one-dimensional molecular conductors such as DCNQI and TMTTF compounds.
Kawamura, Makoto; Oi, Takao; Niizato, Tadafumi; Yasue, Kenichi; Tokiwa, Tetsuya; Niwa, Masakazu; Shimada, Koji; Kurosawa, Hideki; Asamori, Koichi; Kawachi, Susumu; et al.
JAEA-Research 2008-018, 47 Pages, 2008/03
JAEA-Research-2008-018.pdf:24.18MB
In this report, we sophisticated the framework as a part of the total system performance assessment for two purposes: the first one is quantification of relationship of characteristic of natural phenomena between geological environmental conditions (THMCG), and the other one is quantification of relationship of THMCG condition between parameters of performance assessment. On the other hand, we applied the sophisticated framework to all natural phenomena. As a result, to apply the sophisticated framework, we could show that information integration could carry out efficiently. Moreover, we have checked that the framework was applicable to all phenomena. Furthermore, we could show that suitable scenarios might be chosen by information integration.
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systemsSeo, Hitoshi; Ishibashi, Shoji*; Okano, Yoshinori*; Kobayashi, Hayao*; Kobayashi, Akiko*; Fukuyama, Hidetoshi*; Terakura, Kiyoyuki*
Journal of the Physical Society of Japan, 77(2), p.023714_1 - 023714_4, 2008/02
Times Cited Count：34 Percentile：79.73(Physics, Multidisciplinary)Electronic states of single-component molecular metals M(tmdt) (M=Ni,Au) are studied theoretically. We construct an effective three-band Hubbard model for each material by numerical fitting to first-principles band calculations, while referring to molecular orbital calculations for the isolated molecules. The model consists of two kinds of base orbital for each molecule with hybridization between them, i.e., a -character orbital for each of the two tmdt ligands, and, a pd-orbital for M=Ni or a pd
-orbital for M=Au centered on the metal site; this indicates that these materials can be considered as novel multiband -d systems. We find that both orbitals contribute to realize the metallic character in Ni(tmdt). The origin of the antiferromagnetic transition observed in Au(tmdt) is also discussed based on this model.
Seo, Hitoshi; Yoshioka, Hideo*; Otsuka, Yuichi*
Journal of Physics; Conference Series, 132, p.012018_1 - 012018_6, 2008/00
We theoretically investigate the possibility of a Mott insulating state in a class of molecular conductors where the composition ratio between two molecular species is incommensurate to each other, i.e., incommensurate molecular conductors. Although the band-filling becomes irrational and then metallic behavior would be expected, the on-site Coulomb repulsion among the valence electrons together with the potential from the closed-shellions supplying the carriers can give rise to an "incommensurate Mott insulator", which is characterized by the carriers being localized with a period incommensurate to the underlying lattice.
Yoshioka, Hideo*; Tsuchiizu, Masahisa*; Seo, Hitoshi
Journal of the Physical Society of Japan, 76(10), p.103701_1 - 103701_4, 2007/10
Times Cited Count：25 Percentile：73.31(Physics, Multidisciplinary)We theoretically investigate the competition between charge-ordered state and Mott insulating state at finite temperatures in quarter-filled quasi-one-dimensional electron systems, by studying dimerized extended Hubbard chains with interchain Coulomb interactions. In order to take into account one-dimensional fluctuations properly, we apply the bosonization method to an effective model obtained by the interchain mean-field approximation. The results show that lattice dimerization, especially in the critical region, and frustration in the interchain Coulomb interactions reduce the charge-ordering phase transition temperature and enlarge the dimer-Mott insulating phase. We also derive a general formula of the Knight shift in the charge-ordered phase and its implication to experiments is discussed.
Maekawa, Keisuke; Sawada, Atsushi; Ota, Kunio; Kurikami, Hiroshi; Kunimaru, Takanori; Funaki, Hironori; Hama, Katsuhiro; Takeuchi, Shinji; Amano, Kenji; Saegusa, Hiromitsu; et al.
JAEA-Review 2007-011, 8 Pages, 2007/03
JAEA-Review-2007-011.pdf:0.66MB
In the current programme for research and development on the technical aspects of geological disposal, it is of significance to establish techniques for evaluating solute transport with a direct link to surface-based investigations through the processes of data interpretation, modelling and parameter designation within the immediate five years following the H17 Project. This report presents a basic approach to promoting multidisciplinary research activities involving field investigations and relevant solute transport analysis.
Fujita, Tomoo; Taniguchi, Naoki; Matsui, Hiroya; Tanai, Kenji; Nishimura, Mayuka; Kobayashi, Yasushi; Hiramoto, Masayuki; Maekawa, Keisuke; Sawada, Atsushi; Makino, Hitoshi; et al.
JAEA-Research 2007-045, 140 Pages, 2007/03
JAEA-Research-2007-045-1.pdf:38.33MBJAEA-Research-2007-045-2.pdf:44.62MB
This report summarizes the progress of research and development on geological disposal during the surface-based investigation phase (2001-2005) in the Horonobe Underground Research Laboratory project (HOR), of which aims are to apply the design methods of geological disposal and mass transport analysis to actual geological environments and derive future subjects based on the results. The design methods of geological disposal were reviewed based on the recent knowledge and the advertences were identified. Then the parameters for virtual design of engineered barrier system, backfill deposition hole and tunnel were set up based on actual geological conditions obtained from the surface-based investigations in HOR as an example of actual geological environment. The conceptual structure from site investigation and evaluation to mass transport analysis was represented as a work flow at first. Then following this work flow a series of procedures for mass transport analysis were carried out based on actual geological conditions obtained from the surface-based investigations in HOR to illustrate the functioning of the work flow and the applicability of this methodology. Consequently, knowledge that will help follow-up or future execution and planning activities was obtained.
Kawamura, Makoto; Oi, Takao; Makino, Hitoshi; Umeda, Koji; Niizato, Tadafumi; Yasue, Kenichi; Kawachi, Susumu; Ishimaru, Tsuneari; Seo, Toshihiro; Ebina, Takanori*; et al.
JAEA-Review 2006-039, 60 Pages, 2007/01
JAEA-Review-2006-039.pdf:7.39MB
This report is to outline a 5-year plan of research and development (R&D) for performance assessment of potential effect of natural phenomena on a geological disposal of high-level radioactive waste in JAEA. In each research plan, objectives based on the necessity and the significance of the research plan are clarified in the section of "Objectives and the past progresses", with summarizing the progresses of H12: Project to establish the scientific and technical basis for HLW disposal in Japan (Second Progress Report), and H17: Development and management of the technical knowledge base for the geological disposal of HLW (H17 report). In addition, next five year plan is described in the section.
Seo, Hitoshi; Motome, Yukitoshi*; Kato, Takeo*
Journal of the Physical Society of Japan, 76(1), p.013707_1 - 013707_4, 2007/01
Times Cited Count：18 Percentile：66.9(Physics, Multidisciplinary)Phase transitions in 1/4-filled quasi-one-dimensional molecular conductors are studied theoretically on the basis of extended Hubbard chains including electron-lattice interactions coupled by interchain Coulomb repulsion. We apply the numerical quantum transfer-matrix method to an effective one-dimensional model, treating the interchain term within mean-field approximation. Finite-temperature properties are investigated for the charge ordering, the "dimer Mott" transition (bond dimerization), and the spin-Peierls transition (bond tetramerization). A coexistent state of charge order and bond dimerization exhibiting dielectricity is predicted in a certain parameter range, even when intrinsic dimerization is absent.
Seo, Hitoshi; Tsutsui, Kenji*; Ogata, Masao*; Merino, J.*
Journal of the Physical Society of Japan, 75(11), p.114707_1 - 114707_8, 2006/11
Times Cited Count：18 Percentile：67.17(Physics, Multidisciplinary)Effects of geometrical frustration in low-dimensional charge ordering systems are theoretically studied, mainly focusing on dynamical properties. We treat extended Hubbard models at quarter-filling, where the frustration arises from competing charge ordered patterns favored by different intersite Coulomb interactions, which are effective models for various charge transfer-type molecular conductors and transition metal oxides. From previous studies, charge ordered insulating states are known to be unstable in the frustrated region, resulting in a robust metallic phase even when the interaction strenghs are strong. By applying the Lanczos exact diagonalization to finite-size clusters, we have found that fluctuations of different charge order patterns exist in the frustration-induced metallic phase, showing up as characteristic low energy modesin dynamical correlation functions.
Kawamura, Makoto; Oi, Takao; Makino, Hitoshi; Umeda, Koji; Niizato, Tadafumi; Ishimaru, Tsuneari; Seo, Toshihiro
Proceedings of 2006 East Asia Forum on Radwaste Management Conference (2006 EAFORM Conference), p.350 - 367, 2006/11
Evaluation for potential impact of natural phenomena ("earthquakes and fault movement", "volcanism", "uplift, subsidence and denudation", and "climatic and sea-level changes") on a High-Level radioactive Waste (HLW) disposal system is an important issue in safety assessment. In order to develop the perturbation scenario considering diverse and complex impact of natural phenomena comprehensively, it is important to identify the key factors to easily classify and organize these impacts and relate these factors with the system performance. In this method, a series of work to construct scenarios is divided into pieces to facilitate to elicit the features of potential impact of natural phenomena on a HLW disposal system and is organized to create reasonable scenarios with consistency, traceability and adequate conservativeness within realistic view.
Miyamoto, Yoichi; Umeki, Hiroyuki; Osawa, Hideaki; Naito, Morimasa; Nakano, Katsushi; Makino, Hitoshi; Shimizu, Kazuhiko; Seo, Toshihiro
Nuclear Engineering and Technology, 38(6), p.505 - 534, 2006/08
Ensuring sufficient supplies of clean, economic and acceptable energy is a critical global challenge for the 21st century. There seems little alternative to a greatly expanded role for nuclear power, but implementation of this option will depend on ensuring that all resulting wastes can be disposed of safely. Although there is a consensus on the fundamental feasibility of such disposal by experts in the field, concepts have to be developed to make them more practical to implement and, in particular, more acceptable to key stakeholders. By considering global trends and using illustrative examples from Japan, key areas for future R&D are identified and potential areas where the synergies of international collaboration would be beneficial are highlighted.
Makino, Hitoshi; Sawada, Atsushi; Maekawa, Keisuke; Shibata, Masahiro; Sasamoto, Hiroshi; Yoshikawa, Hideki; Wakasugi, Keiichiro; Koo, Shigeru*; Hama, Katsuhiro; Kurikami, Hiroshi; et al.
JNC TN1400 2005-021, 148 Pages, 2005/09
JNC-TN1400-2005-021.pdf:32.85MB
None
Kawamura, Makoto; Makino, Hitoshi; Umeda, Koji; Seo, Toshihiro; Ishimaru, Tsuneari; Osawa, Hideaki
Saikuru Kiko Giho, (28), p.53 - 64, 2005/09
Evaluation for potential effect of natural phenomena on a HLW disposal system is an important issue in safety assessment. A scenario construction method for the effects on a HLW disposal system condition and performance has been developed for two purposes, first one is effective elicitation and organization of information from investigators of natural phenomena and performance assessor, the other is maintenance of traceability of scenario construction processes with suitable records. In this method, a series of works to construct scenarios is divided into pieces to facilitate to elicit the features of potential effect of natural phenomena on a HLW disposal system and is organized to create reasonable scenarios with consistency, traceability and adequate conservativeness within realistic view.
Seo, Hitoshi; Kato, Takeo*; Motome, Yukitoshi*
no journal, ,
We have theoretically investigated finite-temperature properties ofIn this work, we aim at providing a unified view for such compounds by studying a quasi-one-dimensional model numerically, whose Hamiltonian iswritten as 
. The first term 
is the one-dimensional extended Hubbard model in the chain direction, the second term 
denotes the interchain interactions such as the Coulomb repulsion and the exchange coupling, and the third term 
represents the electron-lattice interaction. We use two methods to treat this model. One is the transfer matrix method applied to the effective one-dimensional model by treating within the "interchain mean-field" approximation. Another is the quantum Monte Carlo simulation with stochastic series expansionwhere the interchain interactionsas well as thermal fluctuations of lattice distortions can be taken into account in an unbiased way. We will compare the numerical results with the experimental dataso as to elucidate the origin of the various properties seen in the actual compounds.
Seo, Hitoshi; Kato, Takeo*; Motome, Yukitoshi*
no journal, ,
We have theoretically investigated finite-temperature properties of quarter-filled molecular conductors with quasi-one-dimensional structures. They exhibit a large variety of electronic and electron-lattice coupled phases, and since the systems have similar noninteracting electronic structures, such a variety in their physical properties implies the importance of strong correlation effects. In this work, we aim at providing a unified view for these compounds by studying a electron-lattice coupled quasi-one-dimensional model. We apply two numerical methods to this model, by treating the lattice degree of freedom as classical variables. One is the quantum transfer matrix method applied to an effective one-dimensional model. Another is the quantum Monte Carlo simulation with stochastic series expansion where the interchain interaction as well as the thermal fluctuation of the lattice can be taken into account in an unbiased way. We will compare numerical results with experimental data at a quantitative level so as to elucidate the origin of the various properties seen in the actual compounds.
