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JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 3; Progress report on NUMO-JAEA collaborative research in FY2013 (Joint research)

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.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 2; Progress report on NUMO-JAEA collaborative research in FY2012 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Hayano, Akira; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.

JAEA-Research 2013-037, 455 Pages, 2013/12

JAEA-Research-2013-037.pdf:42.0MB

Following FY2011, JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, the tree diagram of methodology of groundwater travel time has been extended for crystalline rock, in addition, tree diagram for sedimentary rock newly has been organized. With regard to (2) study on scenario development, the existing approach has been improved in terms of a practical task, and applied and tested for near field focusing on the buffer. In addition, the uncertainty of some important processes and its impact on safety functions are discussed though analysis. With regard to (3) study on setting radionuclide migration parameters, the approaches for parameter setting have been developed for sorption for rocks and solubility, and applied and tested through parameter setting exercises for key radionuclides.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage; Progress report on NUMO-JAEA collaborative research in FY2011 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Hayano, Akira; Mitsui, Seiichiro; Taniguchi, Naoki; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.

JAEA-Research 2012-032, 298 Pages, 2012/09

JAEA-Research-2012-032.pdf:33.68MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation phase. The topics and the conducted research are follows; (1) Study on selection of host rock: in terms of hydraulic properties, items for assessing rock property, and assessment methodology of groundwater travel time has been organized with interaction from site investigation. (2) Study on development of scenario: the existing approach has been embodied, in addition, the phenomenological understanding regarding dissolution of and nuclide release from vitrified waste, corrosion of the overpack, long-term performance of the buffer are summarized. (3) Study on setting nuclide migration parameters: the approach for parameter setting has been improved for sorption and diffusion coefficient of buffer/rock, and applied and tested for parameter setting of key radionuclides. (4) Study on ensuring quality of knowledge: framework for ensuring quality of knowledge has been studied and examined aimed at the likely disposal facility condition.

Journal Articles

Numerical assessment of the influence of topographic and climatic perturbations on groundwater flow conditions

Saegusa, Hiromitsu; Yasue, Kenichi; Onoe, Hironori; Moriya, Toshifumi*; Nakano, Katsushi

Stability and Buffering Capacity of the Geosphere for Long-term Isolation of Radioactive Waste; Application to Crystalline Rock, p.257 - 267, 2009/03

In the study, simulations of landform development and groundwater flow have been carried out in the Tono area in order to provide a method to evaluate the effects of long term topographic and climatic changes on groundwater flow conditions. Results of the simulations show the influence of the topographic and climatic perturbations on hydraulic gradient and groundwater velocity. In particular, the influence on hydraulic gradient downstream of the faults normal to the major direction of groundwater flow is much smaller than in the area upstream of the faults. Through this study, it has been confirmed that the method of combining simulations of landform development with groundwater flow is useful for the evaluation of effects of topographic and climatic perturbations on groundwater flow conditions.

JAEA Reports

Annual report for research on long-term stability of geological environment in FY2005

Nohara, Tsuyoshi; Umeda, Koji; Sasao, Eiji; Asamori, Koichi; Hanamuro, Takahiro; Moriya, Toshifumi*; Nakatsuka, Noboru

JAEA-Research 2007-087, 102 Pages, 2008/02

JAEA-Research-2007-087.pdf:35.58MB

The Japanese islands are located in the tectonically active Circum-Pacific Mobile Belt. As a result, Japan has a high frequency of earthquakes and eruptions. Special consideration is given to the long-term stability of the geological environment, taking into account volcanism, faulting, uplift, denudation, climatic change and sea-level change in Japan. Development of research/prediction technologies for geotectonic events has been carried out to evaluate the long-term stability of the geological environment in Japan. Until fiscal year 2005, to confirm existence of phenomena that have a influence on geological disposal system (e.g. active fault or Quarternary volcanoes) and to confirm that there was not the trace that the phenomena occurred in the past and to predict/evaluate possibility of the phenomena, development of the research/prediction techniques for geotectonic events (e.g. Research techniques for earthquake source faults, Research techniques for detecting magmas and high-temperature fluids, Three-dimensional landform development simulator) were carried out. This report describes our efforts of these technologies based on its R&D program until fiscal year 2005.

Journal Articles

Study on Long-term stability for geological environment

Nakatsuka, Noboru; Nohara, Tsuyoshi; Umeda, Koji; Moriya, Toshifumi; Asamori, Koichi; Niwa, Masakazu

Hoshasei Haikibutsu Anzen Kenkyu Nenji Keikaku (Heisei-13-Nendo$$sim$$Heisei-17-Nendo) Kenkyu Seika Hokokushu, p.50 - 56, 2006/03

no abstracts in English

Journal Articles

Vegetation history since the middle Pleistocene in the middle-temperate zone of the Tokai district, Japan; A Palynological study of the small basin sediments

Morita, Yoshimune*; Kamiya, Chiho*; Sasaki, Toshinori*; Miyagi, Toyohiko*; Sugai, Toshihiko*; Yanagida, Makoto*; Furusawa, Akira*; Fujiwara, Osamu*; Moriya, Toshifumi*

Kikan Chirigaku, 58(3), p.123 - 139, 2006/00

A palynological study was carried out using the 25.3 m long sediment core taken from Okute basin, Mizunami city, central Japan. Sediments of this core were accumilated for more than ca. 300,000 years. From the results of pollen analysis, the sediments are devided into 15 pollen assemblages zones. These changes show a repetition of five warm and four cool stages. Each stage corresponds to MIS 9 to 1. Consequently, a temperature of MIS 5 was higher than those of MIS 7 and 9. A temperature of MIS 9 was not so high.

Oral presentation

Influence of topographic and climatic perturbations on groundwater flow conditions

Saegusa, Hiromitsu; Inaba, Kaoru*; Moriya, Toshifumi; Onoe, Hironori

no journal, , 

In the study, groundwater flow modeling has been performed in order to evaluate influence of topographic and climatic perturbations on groundwater flow conditions in the Tono area, Gifu, Japan. It was shown from the results of this study that the topographic and climatic perturbations influence hydraulic gradient, and groundwater flow path, path length and travel time. It is also found that these influences have spatial difference due to hydrogeological heterogeneity caused by faults with hydraulic contrast.

Oral presentation

Current status of the study on the long-term stability of the geological environment

Hanamuro, Takahiro; Nohara, Tsuyoshi; Umeda, Koji; Moriya, Toshifumi; Nakatsuka, Noboru

no journal, , 

Geoscientific research is performed as a basis of the research and development on the geological disposal technology of high-level radioactive waste in the Tono Geoscience Center, JAEA. In this seminar, we report on the current status of the research on long-term stability of the geological environment among research topics set by the geoscientific research.

Oral presentation

Study on faulting concerning long-term stability of geological environment; Spatial distribution and characteristics of fault crush zones

Ishimaru, Tsuneari; Niwa, Masakazu; Shimada, Koji; Kurosawa, Hideki; Moriya, Toshifumi*

no journal, , 

Fault activity causes deformation and mechanical damage, and subsequent change in the groundwater flow, to the surrounding rocks. For the site selection of underground repositories of high-level radioactive waste, describing the spatial distribution and characteristics of topographic lineaments, crush zones and fractures concerning fault activity is essential for the assessment of long-term stability of geological environment in the investigation area. As regarding fault crush zones, their spatial distribution is constrained by the heterogeneity of fault geometry such as stepover, and their characteristics is involved in their permeability structure. Here, we present the procedure and result of the geological survey in the western part of the Atotsugawa Fault, Gifu Prefecture, which is practiced a case study focused on the spatial distribution and characteristics of fault crush zones.

Oral presentation

Spatial distribution and features of fracture zones in and around the Atotsugawa Fault, northern Gifu Prefecture

Niwa, Masakazu; Ishimaru, Tsuneari; Kurosawa, Hideki; Shimada, Koji; Moriya, Toshifumi*; Takahashi, Kazuharu*

no journal, , 

It is suggested that fracture zones formed by fault activities have an effect on hydrologic feature of surrounding rocks. Spatial distribution and features of fracture zones in surveyed areas are informative for site selection and design of geological repositories. Here we show a case study in the Atotsugawa Fault, northern Gifu Prefecture. Field mapping in the study area indicates that the number of fracture zone is sharply reduced, and width of each fracture zones falls within 2 m, with distance of more than 500 m from the surface trace of the Atotsugawa Fault.

Oral presentation

A Tree diagram for compiling a methodology to evaluate suitability of host rock for geological disposal

Hayano, Akira; Sawada, Atsushi; Goto, Junichi*; Ishii, Eiichi*; Moriya, Toshifumi*; Inagaki, Manabu*; Kubota, Shigeru*; Ebashi, Takeshi*

no journal, , 

Detailed Investigation Areas have to be selected with focusing on suitability of the host rock in the siting process for high-level radioactive waste disposal in Japan. The suitability of the host rock is evaluated in terms of the preferable disposal condition such as thermal, hydraulic, mechanical and geochemical condition, and the feasibility of the geological disposal project relevant to volumetric capacity of host rock and economics, based on the site model. However, due to a limited number of surveys at relatively early stage of the investigation, the lack of understanding of geological environment at the site causes an uncertainty of the site model. It is essential to clarify an association the important factors relevant to safety assessment (SA) and a repository design (Design) with the information obtained by the site investigation through the site model. In this study, the methodology not only for defining evaluation factors relevant to SA in term of hydrogeology, but also for visualizing the methods to evaluate the factors through the site model is organized into a tree diagram. A method to evaluate groundwater travel time which is one of evaluation factors in granitic rock is organized into a first version of the tree diagram.

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