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Nagao, Fumiya; Kato, Tomoko; Suzuki, Yuji*; Itazu, Toru*
JAEA-Research 2016-003, 80 Pages, 2016/05
JAEA-Research-2016-003.pdf:14.15MB
In the performance assessment study in the geological disposal of the high-level radioactive waste in Japan, the assessment technique that can treat local characteristics is examined, and establishing the method for the biosphere modeling using specific local information is aimed. In this report, the basic matrices were compiled which contain transport and exposure processes in the surface environment from a generic point of view. And the method was shown to construct the steady-state biosphere model in the actual surface environments by the combination of the basic matrices. To confirm applicability of the method, the biosphere modeling for the hypothetical site was tried. In addition, the important issues to describe the surface environmental condition and human lifestyle were identified to extract future problems and viewpoints by referring to the earlier study of the biosphere assessment at the actual repository site in Sweden.
Ebashi, Takeshi; Kawamura, Makoto*; Inagaki, Manabu*; Koo, Shigeru*; Shibata, Masahiro; Itazu, Toru; Nakajima, Kunihiko*; Miyahara, Kaname; Apted, M. J.*
Materials Research Society Symposium Proceedings, Vol.1665, p.39 - 45, 2014/07
In Japan, the likelihood of uplift/erosion on repository performance and waste isolation can be typically greatly reduced or excluded by careful siting, however, the inability to completely exclude the uplift/erosion scenario may require an analysis of the consequences of such a scenario. For this purpose, an assessment approach has been developed to more realistically treat the effect of uplift/erosion for a hypothetical repository located in sedimentary host rock. A key advantage to this approach is the extrapolation of the geohistory of modern analogue sites to develop credible initial inputs for future volunteer sites that may be poorly characterized at the initial stages of site investigation. In addition, the approach provides a systematic basis for bounding the range of possible evolution in thermal-hydrological-mechanical-chemical conditions of a repository experiencing different uplift/ erosion rates.
Itazu, Toru; Kato, Tomoko; Maekawa, Keisuke
Nihon Chikasui Gakkai 2011-Nen Shunki Koenkai Koen Yoshi, p.34 - 39, 2011/05
Biosphere assessment, which is a part of safety assessment for geological disposal of radioactive waste, addresses the migration of radionuclide from underground to near the ground surface. Advection-dispersion calculation for this purpose must take into the consideration the following factors: long-distance migration of solute, a requirement to calculate the inflow of solute into the rivers or sea bed supposed to be the final position, demand to control numerical dispersion in heterogeneous field. In this study, we adopt the Random-Walk Method having functions required to biosphere assessment and developed a program available to groundwater analysis by using MODFLOW. The program is verified by comparison with the analytical solution and studied about application method to biosphere assessment.
Kato, Tomoko; Itazu, Toru; Suzuki, Yuji*
JAEA-Review 2010-075, 42 Pages, 2011/02
JAEA-Review-2010-075.pdf:4.11MB
As the biosphere assessment of geological disposal covers an extremely long time period, it is difficult to predict the future human environment and lifestyles. IAEA-TECDOC addresses that a stylized approach is proposed for selecting critical groups and biospheres in future situations where human behaviour or biosphere conditions cannot be known with any certainty, although it is possible to construct biosphere models based on the characteristics and evolution of the surface environment at the actual site in shorter time period. BIOMASS methodology is especially effective for treating uncertainty of biosphere in these situations. To address the approaches of biosphere modelling, time period after closure of repository was divided; period 0 to 100 years, 100 years to 10,000 years and beyond them. Critical issues of biosphere modelling were specified through summarising the past progresses in domestic and foreign institutes. Based on the critical issues specified, 5-year research plan on biosphere assessment were identified.
Itazu, Toru; Inagaki, Manabu; Kato, Tomoko; Suzuki, Yuji*; Oyamada, Kiyoshi*; Ebashi, Takeshi; Kawamura, Makoto; Ebina, Takanori*; Miyahara, Kaname
JAEA-Review 2009-015, 59 Pages, 2009/07
JAEA-Review-2009-015.pdf:10.84MB
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). In the same way, biosphere assessment using the behavior of radionuclides, which depends on the site-specific condition, has been started. In this paper, the following issues have been addressed. (1) Survey of the foreign literature relating to the surface and near- surface hydrology for biosphere assessments. (2) Survey of the domestic literature of flow and transport in subsurface systems valuable for biosphere assessments. (3) Trial of transport analysis in surface and near-surface environment of the model site. (4) The setting and boundary conditions of model used for the surface and near-surface hydrological analysis. About the fist issue, from literature of Sweden, we studied the calculation of the dose with account to radionuclides migration in the Quaternary. Concerning the second item, collecting and compiling the useful information for the surface and near-surface hydrological analysis from literature related to groundwater flow and pollution survey in Japan, we learned about the environmental tracer method and so on. Concerning the third point, transport analysis in surface and near-surface environment using site-specific data for sensitivity analysis after this has been carried out to check out the influence of some parameters on transport phenomena, and the relative high sensitivity of the difference of the source positions were shown. Concerning the fourth item, we examined the setting and the boundary conditions of model whose outputs include groundwater flow and transport rate into river, lake, sea. These outputs are used as inputs of biosphere assessment model.
Ebashi, Takeshi; Kawamura, Makoto; Inagaki, Manabu; Koo, Shigeru*; Shibata, Masahiro; Itazu, Toru; Nakajima, Kunihiko*; Miyahara, Kaname
JAEA-Research 2008-117, 36 Pages, 2009/03
JAEA-Research-2008-117.pdf:3.18MB
It is considered that it is possible to avoid the effect of the uplift and denudation process on geological disposal system by siting and a repository design. However, since the uplift/denudation continues far into the future, it is important to enhance the confidence of the methodology to evaluate such an effect, based on the understanding of geohistorical information and potential impact on the disposal system. This paper presents an evolution pattern of the geological environment and the influence analysis in terms of system performance affected by the uplift and denudation process based on the relevant conceptual models for groundwater scenarios of the disposal system for a hypothetical sedimentary rock. As a result, it is indicated that the conceptual model is capable to identify a specific combination of patterns of system evolution of the geological environment in terms of features on the uplift and denudation process, and also provides technical basis for setting up parameters of nuclide migration model and the subsequent influence analysis. Consequently, it is also indicated that the evaluation methodology applied in this study is valuable to evaluate the uplift/denudation phenomena with specific geological environment, and the results obtained by the analysis could be valuable information for site investigation and/or the prediction of a future change trend for the uplift/denudation.
Ebashi, Takeshi; Kawamura, Makoto; Inagaki, Manabu; Koo, Shigeru*; Shibata, Masahiro; Itazu, Toru; Nakajima, Kunihiko*
no journal, ,
It is considered that it is possible to avoid the effect of the uplift and denudation process on geological disposal system by siting and a repository design. However, since the uplift/denudation continues far into the future, it is important to enhance the confidence of the methodology to evaluate such an effect, based on the understanding of geohistorical information and potential impact on the disposal system. This paper presents an evolution pattern of the geological environment and the influence analysis in terms of system performance affected by the uplift and denudation process based on the relevant conceptual models for groundwater scenarios of the disposal system for a hypothetical sedimentary rock.
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.
Itazu, Toru; Kato, Tomoko; Inagaki, Manabu; Maekawa, Keisuke; Suzuki, Yuji*; Oyamada, Kiyoshi*
no journal, ,
On the performance assessment of HLW Geological Disposal, we must evaluate the human impact of radionuclides delivered to the ground surface by groundwater flow, which evaluation requires the setting of pathways of the radionuclides and the estimation of dilution effect. In this presentation, for development of methodology for biosphere assessment modeling including the dilution effect with the site-specific information in the stage of site selection, we show the examination of the methodology through trial of groundwater flow analysis in surface and near-surface environment of Horonobe by using existing literature.
Kato, Tomoko; Makino, Hitoshi; Takeuchi, Shinji; Miyahara, Kaname; Maekawa, Keisuke; Yamaguchi, Masaaki; Iijima, Kazuki; Amano, Kenji; Saegusa, Hiromitsu; Sawada, Atsushi; et al.
no journal, ,
no abstracts in English
Nagao, Fumiya; Kato, Tomoko; Suzuki, Yuji*; Itazu, Toru*
no journal, ,
The basic matrices were compiled structurally which contain transport and exposure processes in the surface environment. And the method was shown to construct the steady-state biosphere model by combination of the basic matrices. To confirm applicability of the method, a dry run of the biosphere modeling for the hypothetical site was conducted.
