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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
Times Cited Count：0 Percentile：0(Construction & Building Technology)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.
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：2 Percentile：26.57(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.
McKinley, I. G.*; Masuda, Sumio*; Hardie, S. M. L.*; Umeki, Hiroyuki*; Naito, Morimasa; Takase, Hiroyasu*
Journal of Energy, 2018, p.7546158_1 - 7546158_8, 2018/07
The Japanese geological disposal programme for radioactive waste is based on a volunteering approach to siting, which places particular emphasis on the need for public acceptance. This emphasises the development of a repository project as a partnership with local communities and involves stakeholders in important decisions associated with key milestones in the selection of repository sites and subsequent construction, operation and closure. To date, however, repository concept development has proceeded in a more traditional manner, focusing particularly on ease of developing a post-closure safety case. In the current project, we have attempted to go further by assessing what requirements stakeholders would place on a repository and assessing how these could be used to re-think repository designs so that they meet the desires of the public without compromising critical operational or long-term safety.
Nakayama, Shinichi; Okumura, Masahiko*; Nagasaki, Shinya*; Enokida, Yoichi*; Umeki, Hiroyuki*; Takase, Hiroyasu*; Kawasaki, Daisuke*; Hasegawa, Shuichi*; Furuta, Kazuo*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(2), p.131 - 148, 2016/12
A symposium "Science of nuclear fuel cycle and backend - Research and education -" was held at the Univer-sity of Tokyo in June 25, 2016. This aimed at developing the research on nuclear fuel cycle and backend. The time and the number of participants of the symposium were limited, but the active discussion was conducted, and the common perception for the future was shared among the experienced participants in those fields. This paper provides the discussions made in the symposium, and also, as a memory to Professor Ahn, the University of California, Berkeley, his prominent achievements in academic research and education.
-radiation on a direct disposal system for spent nuclear fuel, 1 Review of research into the effects of -radiation on the spent nuclear fuel, canisters and outside canistersKitamura, Akira; Takase, Hiroyasu*
Journal of Nuclear Science and Technology, 53(1), p.1 - 18, 2016/01
Times Cited Count：3 Percentile：12.5(Nuclear Science & Technology)Not only geological disposal of vitrified waste generated by spent fuel (SF) reprocessing, but also the possibility of disposing of SF itself in deep geological strata (hereinafter "direct disposal of SF") may be considered in the Japanese geological disposal program. In the case of direct disposal of SF, the radioactivity of the waste is higher and the potential effects of the radiation are greater. Specific examples of the possible effects of radiation include: increased amounts of canister corrosion; generation of oxidizing chemical species in conjunction with radiation degradation of groundwater and accompanying oxidation of reducing groundwater; and increase in the dissolution rate and the solubility of SF. Focusing especially on the effects of -radiation in safety assessment, this study has reviewed research into the effects of -radiation on the spent nuclear fuel, canisters and outside canisters.
-radiation on a direct disposal system for spent nuclear fuel, 2; Review of research into safety assessments of direct disposal of spent nuclear fuel in Europe and North AmericaKitamura, Akira; Takase, Hiroyasu*; Metcalfe, R.*; Penfold, J.*
Journal of Nuclear Science and Technology, 53(1), p.19 - 33, 2016/01
Times Cited Count：1 Percentile：6.25(Nuclear Science & Technology)Not only geological disposal of vitrified waste generated by spent fuel (SF) reprocessing, but also the possibility of disposing of SF itself in deep geological strata (hereinafter "direct disposal of SF") may be considered in the Japanese geological disposal program. In the case of direct disposal of SF, the radioactivity of the waste is higher and the potential effects of the radiation are greater. Specific examples of the possible effects of radiation include: increased amounts of canister corrosion; generation of oxidizing chemical species in conjunction with radiation degradation of groundwater and accompanying oxidation of reducing groundwater; and increase in the dissolution rate and the solubility of SF. Therefore, the influences of radiation, which are not expected to be significant in the case of geological disposal of vitrified waste, must be considered in safety assessments for direct disposal of SF. Focusing especially on the effects of -radiation in safety assessment, this study has reviewed safety assessments in countries other than Japan that are planning direct disposal of SF. The review has identified issues relevant to safety assessment for the direct disposal of SF in Japan.
Goto, Takahiro*; Mitsui, Seiichiro; Takase, Hiroyasu*; Kurosawa, Susumu*; Inagaki, Manabu*; Shibata, Masahiro; Ishiguro, Katsuhiko*
MRS Advances (Internet), 1(63-64), p.4239 - 4245, 2016/00
NUMO and JAEA have conducted a joint research since FY2011, which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage for deep geological disposal of radioactive waste. As a part of this joint research, we have been developing glass dissolution models which consider various processes in EBS, such as precipitation of Fe-silicates associated with iron overpack corrosion, and Si transport through corrosion products in the cracked overpack. The objectives of the modeling work are to evaluate relative importance of relevant processes and to identify further R&D issues towards development of a convincing safety case. Sensitivity analyses suggested that predicted glass dissolution time ranges from 1
10
to 110
years or more due to uncertainties in the current understanding of the key processes, namely precipitation of Fe-silicates and transport characteristics of the altered glass layer.
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.
Sasamoto, Hiroshi; Yui, Mikazu; Takase, Hiroyasu*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 11(3), p.233 - 246, 2012/09
Leachates from cementitious grouting materials used for reducing water-inflow are hyperalkaline and chemically reactive with the engineered barriers and host rock of deep repository of high level radioactive waste. Evaluation methods for long-term alteration of host rock have been developing since the extent of chemical modification may influence the transport and retardation properties of radionuclides in the far-field. Not only conventional Ordinary Portland Cement (OPC) but also low-pH (alkaline) cement (LoAC) has been considered as the grouting material in order to reduce the extent of alteration of host rock. Comparative simulations for long-term alteration of host rock considering both OPC and LoAC grouts are conducted to propose an idea for evaluation of applicability of cementitious grouting materials from view points of reducing uncertainty and conservatism of safety assessment.
Umeki, Hiroyuki; Takase, Hiroyasu*; McKinley, I. G.*
Knowledge Management Research & Practice, 9(3), p.236 - 244, 2011/09
Makino, Hitoshi; Umeki, Hiroyuki; Takase, Hiroyasu*; McKinley, I. G.*
Proceedings of 2011 International High-Level Radioactive Waste Management Conference (IHLRWMC 2011) (CD-ROM), p.25 - 31, 2011/04
In the Japanese deep geological disposal programme, the goals of applications of performance assessments (PA) have changed considerably from original generic feasibility demonstrations to site-specific comparison of options that may result from the current call for volunteer communities to host a repository. PA will play a key role to support highly sensitive decisions at main milestones, particular associated with ranking different site and design options. The paper will discuss requirements for next generation PA to play the role and associated R&D needs.
Osawa, Hideaki; Hioki, Kazumasa; Makino, Hitoshi; Semba, Takeshi; Umeki, Hiroyuki; Takase, Hiroyasu*
Kenkyu, Gijutsu Keikaku Gakkai Dai-25-Kai Nenji Gakujutsu Taikai Oyobi Sokai Koen Yoshishu (CD-ROM), p.55 - 60, 2010/10
This paper describes new concept of common platform for communication among stakeholders using argumentation model for safety on geological disposal.
Umeki, Hiroyuki; Takase, Hiroyasu*
Geological Repository systems for Safe Disposal of Spent Nuclear Fuels and Radioactive Waste, p.610 - 638, 2010/07
Savage, D.*; Benbow, S.*; Watson, C.*; Takase, Hiroyasu*; Ono, Kaori*; Oda, Chie; Honda, Akira
Applied Clay Science, 47(1-2), p.72 - 81, 2010/01
Times Cited Count：37 Percentile：70.43(Chemistry, Physical)Mudstones containing smectite have been altered under mildly alkaline conditions (9 
pH 10) at Searles Lake, California over a 3 million-year time period. This natural alteration has been simulated incorporating time-dependent boundary conditions of sedimentation and fluid composition, a Pitzer model for activities of aqueous species, and a coupled hydrogeological model for time-dependent flow in the sediment layers. Kinetic dissolution of detrital smectite under alkaline conditions was described using one of two models based on departure from thermodynamic equilibrium or by an empirical rate dependent upon aqueous Si concentrations. The zonal pattern of smectite dissolution observed at Searles Lake was reproduced reasonably well by the "Cama-TST" model of montmorillonite dissolution. This assessment provides a test of the accuracy and reliability of published data in the application of models of smectite dissolution in the long-term.
Osawa, Hideaki; Hioki, Kazumasa; Umeki, Hiroyuki; Takase, Hiroyasu*; McKinley, I. G.*
Proceedings of 12th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM '09/DECOM '09) (CD-ROM), 5 Pages, 2009/10
The paper will review progress to date in this work with illustrative examples of argumentation networks. An outline of future developments and challenges will also be provided, for example considering how confidence in arguments can be assessed, the weakest links in argumentation chains can be identified, arguments can be developed interactively at a level appropriate to all users, etc. Two companion papers demonstrate how these can be applied to critical areas of a repository programme, performance assessment and "geosynthesis". The link to the safety case forms a basis for decision making in the inevitable cases where conflicts between programme requirements arise. The long-term evolution of the safety case also forms a pathway for focusing the future challenges described in the final paper in this set.
Makino, Hitoshi; Hioki, Kazumasa; Umeki, Hiroyuki; Yang, H.*; Takase, Hiroyasu*; McKinley, I. G.*
Proceedings of 12th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM '09/DECOM '09) (CD-ROM), 8 Pages, 2009/10
This paper will outline the reformulation of PA as a Knowledge Management (KM) task, discuss application of knowledge management technologies to PA tasks, and illustrate how these can be handled electronically in a "Performance assessment All-In-one Report System (PAIRS)" utilising hyperlinks and embedded tools to minimise duplication of material, ease Quality Assurance (QA) and facilitate the regular updating required in the Japanese programme.
Makino, Hitoshi; Hioki, Kazumasa; Umeki, Hiroyuki; Tachibana, Shoko*; Takase, Hiroyasu*; McKinley, I. G.*
Proceedings of 12th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM '09/DECOM '09) (CD-ROM), 9 Pages, 2009/10
The JAEA Knowledge Management System (KMS) is being developed to be flexible and able to respond to potential changes of boundary conditions. On a shorter timescale, the KMS must encourage flexibility in the methodology used for carrying out and presenting performance assessments. This is closely linked to development of advanced repository concepts; considering the requirements for a safe and practical repository tailored to specific site conditions, which reflects evolving technology. These coupled development tasks were, in the past, carried out by expert teams in a rather informal manner. As the technical challenges increase - and the need for transparency is accepted - a more formal method of developing innovative design solutions is needed. A knowledge engineering approach (TRIZ) that is used in other financial and industrial applications has thus been tested for its usefulness for such tasks.
Semba, Takeshi; Osawa, Hideaki; Hioki, Kazumasa; Tachibana, Shoko*; Takase, Hiroyasu*; McKinley, I. G.*
Proceedings of 12th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM '09/DECOM '09) (CD-ROM), 8 Pages, 2009/10
To provide support for the Japanese implementer and also the regulator, a JAEA team is attempting to capture both Japanese and international geosynthesis experience within a KMS framework, which is termed ISIS. This is a hybrid system that combines "smart" software with human experts, although an aim is to capture tacit knowledge within expert systems to the maximum extent practicable. Initial tests, based mainly on field work carried out by JAEA at the sites of the Mizunami and Horonobe underground research laboratories.
Umeki, Hiroyuki; Hioki, Kazumasa; Takase, Hiroyasu*; McKinley, I. G.*
Proceedings of 12th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM '09/DECOM '09) (CD-ROM), 6 Pages, 2009/10
no abstracts in English
Osawa, Hideaki; Umeki, Hiroyuki; Ota, Kunio; Hama, Katsuhiro; Sawada, Atsushi; Takeuchi, Shinji; Semba, Takeshi; Takase, Hiroyasu*; McKinley, I. G.*
Proceedings of International Waste Management Symposium 2009 (WM '09) (CD-ROM), 11 Pages, 2009/03
The focus of this paper is development of advanced technology from the field of Knowledge engineering, termed the Information Synthesis and Interpretation System (ISIS), which incorporates past experience and know-how currently being obtained in complex URL projects within Expert System (ES) modules in 2009.
