None

Onoe, Hironori*; Saegusa, Hiromitsu*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Sawada, Atsushi

NUMO-TR-22-02, p.78 - 80, 2023/03

https://www.numo.or.jp/technology/technical_report/NUMO-TR-22-02.pdf

no abstracts in English

Model development of coupled THMC processes for a geological repository at higher temperature region

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

Assessment of sorption and diffusion in the rock matrix in the NUMO safety case

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

http://eaform2017.aesj.or.jp/file/PapersList/Session4/(4A-2)_%20T.Hamamoto(NUMO).pdf

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.

Developing confidence in a coupled TH model based on the results of experiment by using engineering scale test facility, "COUPLE"

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.

Study on simulation of salt accumulation (Joint research)

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.

Study of long-term behavior of engineered and geological barrier system

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-NendoHeisei-17-Nendo) Kenkyu Seika Hokokushu, p.179 - 203, 2006/03

no abstracts in English

Development of methodologies for validation of groundwater flow and mass transport model, 2; A Case study using investigation data obtained at the Mizunami Underground Research Laboratory

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

Fracture conditioning examination of DFN model by in-situ investigation data, 2

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

Coupled hydro-transport analysis study on geochemical environmental change caused by tunnel excavation using geological data obtained from the Horonobe URL project

Suzuki, Hideaki; Fujita, Tomoo; Fujisaki, Kiyoshi*

no journal, , 

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 affect of EDZ in the realistic numerical simulation of the long-term behavior of near-filed HLW repository after emplacement of engineered barrier system. This study presents the results on the analysis assessment on geochemical reaction with the evolution of the unsaturated zone around the tunnel with consideration of Horonobe area geological environment, using the developed coupled Thermo-Hydro-Mechanical and Chemical (THMC) processes analysis model. As a result, this model is applied 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 tunnel.

Progress of R&D for geological disposal of vitrified waste

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.