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Takubo, Yusaku*; Takayama, Yusuke; Idiart, A.*; Tanaka, Tatsuya*; Ishida, Keisuke*; Fujisaki, Kiyoshi*
Proceedings of 2022 International High Level Radioactive Waste Management Conference (IHLRWM 2022) (Internet), p.906 - 915, 2022/11
no abstracts in English
Hamamoto, Takafumi*; Ishida, Keisuke*; Shibutani, Sanae*; Fujisaki, Kiyoshi*; Tachi, Yukio; Ishiguro, Katsuhiko*; McKinley, I. G.*
Proceedings of 2019 International High-Level Radioactive Waste Management Conference (IHLRWM 2019) (USB Flash Drive), p.77 - 82, 2019/04
Hamamoto, Takafumi*; Shibutani, Sanae*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Yamada, Motoyuki*; Tachi, Yukio
Proceedings of 6th East Asia Forum on Radwaste Management Conference (EAFORM 2017) (Internet), 6 Pages, 2017/12
NUMO has developed a generic safety case to demonstrate the feasibility and safety of geological disposal of HLW and TRU in Japan and to provide a basic structure for the safety case which will be applicable to any potential site. In this safety case, the safety assessment was carried out for the repositories tailored to site descriptive models developed for three representative rock groups (plutonic, Neogene sedimentary and Pre-Neogene sedimentary rocks). Radionuclide migration parameters in rocks, i.e. distribution coefficients (Kds) and effective diffusion coefficients (Des), were derived to allow safety analysis for a range of scenarios. In this generic stage, the values of these parameter were given as the statistical values derived from laboratory data for certain rock types. The data were extracted from the latest database, with interpretation based on radionuclide speciation derived from relevant groundwater thermodynamic modelings.
Suzuki, Hideaki; Fujisaki, Kiyoshi*; Fujita, Tomoo
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 16(1), p.43 - 56, 2009/12
The numerical analysis model was developed that understand the coupled thermal - hydraulic - mechanical - chemical (THMC) processes in the near field of high-level radioactive waste (HLW) repository after emplacement of the engineered barrier system (EBS). This paper is focusing on measured data of the experiments and calculated results of the THC model which were carried out for the period of 830 days. It was found that the information about the geochemical reaction and the mass transfer in the buffer material was obtained; pH distribution of pore water, precipitation of the secondary mineral etc. It was also indicated that the temperature and water content in the buffer material and mineral dissolution/precipitation in a contact surface of buffer material and mortar could be represented by the developed numerical model.
Fujisaki, Kiyoshi; Suzuki, Hideaki; Fujita, Tomoo
JAEA-Research 2008-020, 62 Pages, 2008/03
JAEA-Research-2008-020.pdf:24.3MB
In evaluating the behavior of near-field after emplacement of engineered barriers, it is necessary to understand quantitative changes of near-field over time and space. However, the coupled phenomena in near-field are complicated because thermo-, hydro-, mechanical, chemical process will interact, so that no comparison with real behavior will make it possible to find out if the applied model will represent the coupled behavior adequately or not. Hence, it is necessary to validate the model, based on the result of coupled behavior experiment in laboratory or in site. In this report, authors evaluated the applicability of coupled T-H model under the condition of simulated near-field, based on the results of coupled experiment in room. As a result, it has shown that the model which improved the fit to the measured data, is reasonable under this condition.
Suzuki, Hideaki; Fujisaki, Kiyoshi; Fujita, Tomoo
JAEA-Research 2008-003, 48 Pages, 2008/03
JAEA-Research-2008-003.pdf:2.07MB
The development of excavation disturbed zone (EDZ) around the disposal tunnel affects such as the corrosive environment of the over-pack and environmental condition of the nuclear species migration on the geological disposal for the high-level radioactive waste (HLW). It is necessary to consider aftermath of EDZ in initial condition of the realistic numerical simulation of the long-term behavior of near-filed HLW repository after emplacement of engineered barrier system. This report presents the analysis assessment geochemical reaction with the development of the unsaturated zone around the disposal tunnel by developed the coupled Thermo-Hydro-Mechanical and Chemical (THMC) processes model / analysis code. As a result, the THMC processes analysis model apply a change of the solution composition by degasification of the carbon dioxide gas to the pore water and the change of the oxidation-reduction potential due to unsaturated zone around the disposal tunnel.
Fujita, Tomoo; 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 
and 
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.
Fujisaki, Kiyoshi; Suzuki, Hideaki*; Fujita, Tomoo; Ito, Akira*; Oda, Yoshihiro
Proceedings of 2nd International Conference on Coupled T-H-M-C Processes in Geo-systems; Fundamentals, Modeling, Experiments and Applications (GeoProc 2006), p.213 - 219, 2006/05
An important part of the safety assessments of near field in a geological disposal system of high-level radioactive waste consists an assessment of the coupled thermal-hydraulic-mechanical and chemical (THMC) phenomena. In order to validate the newly developed THMC model, the engineered scale experimental studies on the coupled THMC processes by COUPLE equipment have been carried out with a simulated engineered barrier surrounded by a mortar block. In this experiment, temperature at heater and side surface of mortar block was controlled at constant temperature, respectively. And high-pH water reacted with mortar infiltrates into the buffer material. This paper presents the results of measured data by various sensors during the experiment and sampling data of pH and leaching cations in buffer material after the experiment, in COUPLE equipment. And also the results of preliminary simulations on coupled T-H processes and chemical process in the experiment are described.
Aoyanagi, Shigeo; Oda, Yoshihiro; Sasamoto, Hiroshi; Shibata, Masahiro; Tanai, Kenji; Taniguchi, Naoki; Nishimura, Mayuka; Fujisaki, Kiyoshi; Kikuchi, Hirohito*; Matsumoto, Kazuhiro*
Hoshasei Haikibutsu Anzen Kenkyu Nenji Keikaku (Heisei-13-Nendo
Heisei-17-Nendo) Kenkyu Seika Hokokushu, p.179 - 203, 2006/03
no abstracts in English
Fujita, Tomoo; Fujisaki, Kiyoshi; Suzuki, Hideaki*; Kawakami, Susumu; Yui, Mikazu; Chijimatsu, Masakazu*; Neyama, Atsushi*; Ishihara, Yoshinao*; Hishiya, Tomoyuki*
Proceedings of 2nd International Conference on Coupled T-H-M-C Processes in Geo-systems; Fundamentals, Modeling, Experiments and Applications (GeoProc 2006), p.416 - 421, 2006/00
We have initiated a research on the coupled Thermo-Hydro-Mechanical-Chemical (THMC) processes and are trying to carry out numerical experiments on the coupled THMC processes in order to predict the near-field long-term evolution. This paper describes the modified THMC model to add on the function of de-gases and gases diffusion, accumulation and dilution phenomena for mass transport analysis, and of ionic exchange, surface reaction and kinetic reaction for geochemical analysis. And also the results of demonstration study with THMC code are shown.
Kawato, Takaya*; Ishida, Keisuke*; Yamamoto, Takeshi*; Minato, Daisuke*; Fujisaki, Kiyoshi*; Hamamoto, Takafumi*; Mihara, Morihiro
no journal, ,
no abstracts in English
Matsubara, Ryuta*; Fujisaki, Kiyoshi*; Ishida, Keisuke*; Ishiguro, Katsuhiko*; Inagaki, Yaohiro*; Okubo, Takahiro*; Mitsui, Seiichiro; Iwata, Hajime; Sekine, Nobuyuki*
no journal, ,
Since the performance of vitrified High-level Radioactive Waste depends on thermal, hydraulic, mechanical, and chemical (THMC) conditions, NUMO, as the implementer of geological disposal, has been promoting R&D of operational model the long-term performance of vitrified High-level Radioactive Waste in consideration of THMC conditions. NUMO has identified R&D issues regarding the glass dissolution and planed the R&D program through FEP (Features, Events, and Processes) analysis and parametric study with numerical model to evaluate relative importance of relevant processes. At present, three R&D programs are ongoing as joint researches with JAEA and two universities: long term glass dissolution experiment to understand evolution of glass dissolution kinetics, glass dissolution experiment at various environmental conditions to assess the performance under several potential repository conditions with the time evolution, and molecular dynamics simulation to understand elemental migration at the interface between glass surface and groundwater. The current status of R&D programs will be introduced in this presentation.
Matsubara, Ryuta*; Fujisaki, Kiyoshi*; Ishida, Keisuke*; Ishiguro, Katsuhiko*; Inagaki, Yaohiro*; Okubo, Takahiro*; Mitsui, Seiichiro; Iwata, Hajime; Sekine, Nobuyuki*
no journal, ,
Restriction of radionuclide release by low dissolution rate is expected for the vitrified waste as a one of safety functions of the geological disposal system. In order to assess the performance of vitrified waste, it is important to understand how its safety function works under the environmental condition of a deep geological repository. This presentation provides the recent progress on the R&D to improve the current understanding of the key processes affecting glass dissolution rate and the predictive modeling of long-term behavior of the vitrified waste.
Matsubara, Ryuta*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Ishiguro, Katsuhiko*; Inagaki, Yaohiro*; Okubo, Takahiro*; Iwata, Hajime
no journal, ,
In order to improve reliability of performance assessment of vitrified waste for geological disposal, we have been developing a model to predict the long-term glass dissolution under disposal conditions. This presentation provides our R&D plan and the recent progress.
Onoe, Hironori*; Saegusa, Hiromitsu*; Tanaka, Tatsuya*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Sawada, Atsushi
no journal, ,
no abstracts in English
Hane, Koji*; Onoe, Hironori*; Ishibashi, Masayuki*; Tabei, Kazuto*; Namikawa, Tadashi*; Tagawa, Yoichi*; Saegusa, Hiromitsu*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Sawada, Atsushi
no journal, ,
no abstracts in English
Ichikawa, Nozomi*; Hamamoto, Takafumi*; Sasamoto, Hiroshi; Ichige, Satoru*; Kawakita, Ryohei; Fujisaki, Kiyoshi*
no journal, ,
For model validation of bentonite behavior under high alkaline condition, a batch type reaction experiment and modeling were performed. In the batch type reaction experiment, simulated solutions for the leachate from cement material (Region I solution of pH13 simulated by mixture of both 0.2M NaOH and KOH solutions, Region II solution of pH12.5 simulated by 0.016M CaOH
solution) and bentonite (Kunigel V1 and Kunipia F) were reacted under L/S ratio of 50 mL/g and temperature for either 25 or 50 degrees, and for 2 years as the maximum duration. As the results, for example of the experiment for reactions between Region I solution and Kunipia F at 50 degrees, the peak intensity for montmorillonite slightly decreased with time and the new formed secondary mineral suggested as phillipsite occur. Geochemical modeling for this experimental case was performed. Regarding the amount of montmorillonite dissolution, the modeling considering the reactions of both montmorillonite dissolution and ion exchange approximated the experimental result well, however, the addition of the secondary mineral precipitation reaction was less effective. Sensitivity analyses considering the parameter uncertainties of secondary mineral precipitation reaction stimulated that the inconsistency was not dependent on the parameter uncertainties.
Esaki, Taichi*; Ishibashi, Masayuki*; Tagawa, Yoichi*; Namikawa, Tadashi*; Hane, Koji*; Masumoto, Kazuhiko*; Onoe, Hironori*; Saegusa, Hiromitsu*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; et al.
no journal, ,
no abstracts in English
Namikawa, Tadashi*; Ishibashi, Masayuki*; Esaki, Taichi*; Tagawa, Yoichi*; Hane, Koji*; Masumoto, Kazuhiko*; Onoe, Hironori*; Saegusa, Hiromitsu*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; et al.
no journal, ,
no abstracts in English
Takubo, Yusaku*; Takayama, Yusuke; Idiart, A.*; Toya, Naruhisa*; Ishida, Keisuke*; Fujisaki, Kiyoshi*
no journal, ,
Coupled THC analysis below 100 degrees was performed for existing studies (laboratory tests and Full-scale Engineered Barriers Experiment (FEBEX) in-situ tests) using PFLOTRAN, which has been applied as a TH/THC coupled analysis code. By comparing the results of each test measurement and analysis, input parameters that are considered to have a significant impact on the analysis result of the chemical field were investigated.
