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Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo; Ooka, Masao*; Kameya, Hiroshi*
no journal, ,
In the safety assessment for a geological disposal of radioactive waste, it is important to develop a methodology and uncertainties of long-term estimation of regional groundwater flow system. The authors discussed the uncertainties of hydraulic conductivity as a significant hydrological parameter for regional groundwater flow analysis model. This study demonstrated that confining pressure change cased by uplift and subsidence and change of hydraulic gradients under the long-term geological and hydrological environmental change could possibly produce variations more than one order of magnitude in hydraulic conductivity of rock mass. It also clarified that the effect of water quality change on hydraulic conductivity is not negligible and that the replacement of fresh water and saline water cased by sea level change could predict to reduce hydraulic conductivities in rock mass 0.6 times from its present data in case of Horonobe site.
Hiraga, Naoto; Ishii, Eiichi; Niinuma, Hiroaki
no journal, ,
no abstracts in English
Mukai, Masayuki; Shimada, Taro; Tanaka, Tadao; Sukegawa, Takenori; Nakayama, Shinichi
no journal, ,
Nuclear Safety Research Center in JAEA has been conducting R&D activities to support national safety regulatory systems. (1) Research on safety assessment for decommissioning of nuclear fuel cycle facilities: A prototype computer code for fuel cycle facilities was developed by improving the code previously developed for nuclear reactor facilities. (2) Research on dose evaluation during dismantling: Values on evaluation parameters were obtained through the cutting test using actual contaminated pipes. Observed values for dispersion ratio of Co-60 and filtration efficiency indicated that existing recommendation values were conservative for safety assessment. (3) Research on site release on termination of decommissioning: A computer code was developed to calculate remaining radionuclide concentrations as site release criteria, and improved by adding practical settings for external and internal exposed doses. Preliminary calculations were conducted on typical land reuse scenario.
Koo, Shigeru*; Ebashi, Takeshi; Inagaki, Manabu
no journal, ,
no abstracts in English
Itazu, Toru; Kato, Tomoko; Inagaki, Manabu; Suzuki, Yuji*
no journal, ,
The project of high-level radioactive waste disposal is in the stage of site selection in Japan, and the site-specific performance assessment using the methodology of site-generic study has been developed after the publication of the second progress report (H12). Japan Atomic Energy Agency (JAEA) has started the biosphere assessment using the behavior of radionuclides, which depends on the site-specific geological condition. In this presentation, we report the examination of biosphere assessment methodology in view of surface and near-surface environment.
Yamamoto, Yoichi; Maekawa, Keisuke; Yokota, Hideharu
no journal, ,
Horonobe Underground Research Center of Japan Atomic Energy Agency has carried out investigated surface hydrological investigation in and around the Horonobe Underground Research Laboratory (URL) area as a part of Horonobe URL project. We continue meteorological observation, observation of river flux and water quality, soil moisture observation and groundwater level observation in order to understand recharge rate and groundwater flow in the shallow part, which are required for the setting of boundary and initial condition of the groundwater flow analysis. Outline of the surface hydrological investigation and some study results of groundwater flow around surface are reported.
Sano, Michiaki; Sekiya, Yoshitomo
no journal, ,
no abstracts in English
Inagaki, Daisuke; Sano, Michiaki; Tsusaka, Kimikazu
no journal, ,
no abstracts in English
Miyahara, Shigenori
no journal, ,
no abstracts in English
Nakamura, Takahiro; Sugita, Yutaka; Sanada, Hiroyuki; Kato, Harumi*
no journal, ,
Horonobe Underground Research Laboratory (URL) project aims at improvement of the reliability of technologies for geological disposal of high level radioactive wastes. In investigation during construction of the underground facilities, the updating and check of the validity of initial stress estimations made during surface-based investigations is one of the main issues. Thus, three boreholes were made from the niche (GL-140 m) of ventilation and east shaft, and a three-dimensional evaluation of the initial stress in Koetoi Formation was done by the method called hydraulic fracturing technique and the analysis of the borehole breakout. Moreover, the direction of the maximum horizontal principal stress had been found to be east/west in general. However, the present test showed that the direction was 26 or 46 degrees counterclockwise from east/west.
Nakayasu, Akio; Yasue, Kenichi; Niizato, Tadafumi; Doke, Ryosuke; Shigehiro, Michiko*
no journal, ,
no abstracts in English
Sugita, Yutaka; Nakamura, Takahiro; Sanada, Hiroyuki; Kunimaru, Takanori
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no abstracts in English
Sato, Haruo
no journal, ,
Swelling pressure versus Na-montmorillonite partial density was estimated for solutions with various salinities (NaCl solutions, artificial saline water, Horonobe groundwater) based on the thermodynamic data of the interlayer water of Na-montmorillonite and of water in the solutions of various salinities coming in contact with the montmorillonite and compared to data measured under the same salinities for various kinds and different silica sand contents of bentonites. The calculated swelling pressures decreased with increasing salinity. This is in good agreement with the fact that the swelling pressure of bentonite generally decreases with increasing salinity. Since all measurements were carried out under the conditions that the soluble minerals remain being contained, all the measured data are considered to contain the effect of the increase of the ionic strength of porewater by dissolution of the soluble minerals, and the calculated values were within the range of the scattering in the measured data. By this model, swelling pressures for various Na-montmorillonite contents and silica sand contents of bentonites saturated with solutions of various salinities can be calculated as a function of dry density of the bentonites. Furthermore, analyses for THMC coupled processes can be also carried out by considering those enthalpy and entropy data.
Shimoda, Satoko*; Saito, Hironori*; Takase, Toshio*; Yamaguchi, Kohei; Oda, Chie; Honda, Akira
no journal, ,
The unstable primary mineral is dissolved and the precipitation of a steadier secondary mineral happens thermodynamically when a high alkaline groundwater of the cement system material origin is infiltrated from the radioactive waste geological disposal facilities to a peripheral bedrock. Therefore, the pore structure of the hostrock changes by the precipitation and dissolution, and the material transportation characteristic of the bedrock changes. It is necessary to decide the chemical reaction scheme for the analysis. However, the combination of the secondary minerals exists innumerably. Therefore, granite was assumed to be an example by summarizing the chemical reaction scheme in the mineral alteration scenario, and the mineral alteration scenario concerning the reaction with a high pH groundwater was presented. It dealt with the uncertainty concerning the mineral alteration by preparing two or more scenarios with a different alteration route.
Motoshima, Takayuki*; Ijiri, Yuji*; Saegusa, Hiromitsu
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no abstracts in English
Hatanaka, Koichiro
no journal, ,
Horonobe URL project is a research and development program with construction of underground facilities for sedimentary rock and saline groundwater distributing over the Horonobe Town area. The goal of the Horonobe URL project is to develop the basis for the technologies of investigation/analysis/evaluation, to develop the basis of engineering technology in the deep underground, and to confirm the applicability of disposal technologies in the actual geological environment. In addition, JAEA Horonobe has been observing the agreement concluded among Hokkaido prefecture, Horonobe Town and JNC (current JAEA) in November, 2000, in carrying out the research and development in the Horonobe Town area.
Tsusaka, Kimikazu; Yamasaki, Masanao*; Inagaki, Daisuke
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no abstracts in English
Maeda, Toshikatsu; Nakayama, Shinichi
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no abstracts in English
Ishikawa, Hirohisa
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no abstracts in English
Matsumoto, Kazuhiro; Saito, Yuya; Tanai, Kenji
no journal, ,
no abstracts in English