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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.
Inagaki, Manabu; Kato, Tomoko; Yoshida, Hideji*; Oyamada, Kiyoshi*; Fukaya, Yukiko*; Suzuki, Yuji*; Oi, Takao
JAEA-Research 2007-029, 81 Pages, 2007/03
JAEA-Research-2007-029.pdf:10.88MB
The project of high-level radioactive waste disposal is in activity for the site selection of HLW disposal facility and the performance assessment should be more site-specific rather than site-generic, where the applicability of the achievement of site-generic study such as second progress report (H12) to the site specific is to be clarified. In the same way, it is necessary for biosphere assessment to incorporate the site specific condition to the model. The exposure pathway or concentration of the radio nuclides should be determined according to the site specific geological condition, for example. In this paper, following topics have been selected to start the study to reflect specific geological condition to the biosphere modeling. (1) The literature survey of international and national approaches and issues relating to the treatment of GBIs within biosphere assessments, (2) To develop methodology to estimate the release point of the deep groundwater to the shallow accessible groundwater. (3) To prepare information to estimate water balance this is, in turn, necessary to assess the dilution and/or dispersion of the radionuclides in the shallow accessible groundwater body.
Oi, Takao; Takase, Hiroyasu*; Inagaki, Manabu; Oyamada, Kiyoshi*; Sone, Tomoyuki; Mihara, Morihiro; Ebashi, Takeshi; Nakajima, Kunihiko*
Materials Research Society Symposium Proceedings, Vol.985, p.129 - 134, 2007/00
A comprehensive sensitivity analysis method has been developed with the aim of providing quantitative information in an efficient manner. This methodology is composed of the following two components: (1) a statistical method with random sampling of independent parameters, which identifies important parameters and extracts threshold values of parameters and/or combinations yielding a "successful condition" where maximum dose does not exceed a target value, (2) A nuclide migration model that as far as possible incorporates a comprehensive set of phenomena occurring within the repository. This approach was applied as part of a safety assessment of the geological disposal of TRU waste in Japan (TRU-2). It was shown that the concept of TRU waste disposal is robust from the point of view of safety.
Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2004-007, 100 Pages, 2004/02
JNC-TJ8400-2004-007.pdf:3.89MB
This report presents results on trial study of methodology to identify Geosphere-Biosphere Interface (GBI), and examination in consideration of overseas trend of long-term biosphere assessment.
Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2004-006, 199 Pages, 2004/02
JNC-TJ8400-2004-006.pdf:8.87MB
This report presents results on trial study of methodology to identify Geosphere-biosphere Interface (GBI), and examination in consideration of overseas trend of long-term biosphere assessment.
Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2003-096, 53 Pages, 2004/02
JNC-TJ8400-2003-096.pdf:0.72MB
This study developed minute estimation by adopting comprehensive sensitivity analytical program for reliability of TRU waste repository concepts in a crystalline rock condition. We examined each components and groundwater scenario of geological repository and prepared systematic bases to examine the reliability from the point of comprehensiveness. Models and date are sophisticated to examine the reliability. Based on an existing TRU waste repository concepts, effects of parameters to nuclide migration were quantitatively classified. Those parameters, that will be decided quantitatively, are such as site character of natural barrier and design specification of engineered barriers. Considering the feasibility of those figures of specifications, reliability is re-examined on combinations of those parameters within a practical range. Future issues are ; (1)Comprehensive representation of hybrid geosphere model including the fractured medium and permeable matrix medium. (2)Sophistication of tools to develop the reliable combinations of parameters. It is significant to continue this study because the disposal concepts and specification of TRU nuclides containing waste on various sites shall be determined rationally and safely through these studies.
Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2003-095, 243 Pages, 2004/02
JNC-TJ8400-2003-095.pdf:4.06MB
This study developed minute estimation by adopting comprehensive sensitivity analytical program for reliability of TRU waste repository concepts in a crystalline rock condition. We examined each components and groundwater scenario of geological repository and prepared systematic bases to examine the reliability from the point of comprehensiveness. Models and date are sophisticated to examine the reliability. Based on an existing TRU waste repository concepts, effects of parameters to nuclide migration were quantitatively classified. Those parameters, that will be decided quantitatively, are such as site character of natural barrier and design specification of engineered barriers. Considering the feasibility of those figures of specifications, reliability is re-examined on combinations of those parameters within a practical range. Future issues are ; (1)Comprehensive representation of hybrid geosphere model including the fractured medium and permeable matrix medium. (2)Sophistication of tools to develop the reliable combinations of parameters. It is significant to continue this study because the disposal concepts and specification of TRU nuclides containing waste on various sites shall be determined rationally and safely through these studies.
Miki, Takahito*; Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2003-054, 45 Pages, 2003/02
JNC-TJ8400-2003-054.pdf:0.44MB
This study developed analytical programs and procedures based on a method of stochastic radionuclide migration to estimate the feasibility of disposal concepts and to define design specifications, considering the variety of scenarios and disposal concepts divided by depth of repository for TRU nuclides containing waste.
Miki, Takahito*; Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2003-053, 386 Pages, 2003/02
JNC-TJ8400-2003-053.pdf:10.69MB
This study developed analytical programs and procedures based on a method of stochastic radionuclide migration to estimate the feasibility of disposal concepts and to define design specifications, considering the variety of scenarios and disposal concepts divided by depth of repository for TRU nuclides containing waste.
Miki, Takahito*; Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2002-051, 40 Pages, 2002/02
JNC-TJ8400-2002-051.pdf:0.28MB
In this study, for the mid-depth disposal system for TRU wastes, asset of stochastic simulations covering uncertainties corresponding to variety of scenarios, models and parameter values were conducted to; (1)indicate measures to reduce potential exposure based on the knowledge of sensitivity structure (2)introduce new methodology for clarify the requirement of repository system (3)show guidelines of disposal system development by clarifying conditions in system specification for achieving a target which is well below the dose constraint for base scenarios (4)identify scenarios and conditions that could lead to a radiological impact greater than the dose constraint for alternative scenarios In the course of geological disposal for TRU waste, improvement of assessment methodology for the alternative scenarios was carried out.
Miki, Takahito*; Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2002-050, 217 Pages, 2002/02
JNC-TJ8400-2002-050.pdf:2.66MB
In this study, for the mid-depth disposal system for TRU wastes, asset of stochastic simulations covering uncertainties corresponding to variety of scenarios, models and parameter values were conducted to; (1)indicate measures to reduce potential exposure based on the knowledge of sensitivity structure (2)introduce new methodology for clarify the requirement of repository system (3)show guidelines of disposal system development by clarifying conditions in system specification for achieving a target which is well below the dose constraint for base scenarios (4)identify scenarios and conditions that could lead to a radiological impact greater than the dose constraint for alternative scenarios In the course of geological disposal for TRU waste, improvement of assessment methodology for the alternative scenarios was carried out.
Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2001-033, 71 Pages, 2001/02
JNC-TJ8400-2001-033.pdf:9.01MB
no abstracts in English
Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2001-032, 518 Pages, 2001/02
JNC-TJ8400-2001-032.pdf:20.16MB
Because of the time scale of concern, variety of the processes to be considered, and spatial heterogeneity of the natural barriers, performance assessment of geological disposal is subjected to considerable amount of uncertainty. This implies that it is very difficult, if not impossible, to prove long term safety of disposal in a rigorous scientific manner. Instead, it is more practical to define the goal of performance assessment as providing quantitative information to judgmental process concerning long term safety as a part of multiple lines of reasoning. Objectives of the scenario exploration is to extend and enhance the information available through conventional assessment methodology. In this study, the scenario exploration methodology, which has been developed primarily for HLW disposal, was extended and applied to TRU waste disposal. In the fiscal year 2000, asset of stochastic simulatiom covering uncertainties corresponding to variety of scenarios, models and parameter values were conducted to; (1)show guidelines of disposal system development by clarifying conditions in system specification for achieving a target which is well below the dose constraint, (2)identify scenarios and conditions that could lead to a radiological impact greater than the dose constraint, (3)indicate measures to reduce potential exposure based on the knowledge of sensitivity structure, In the courseofsccnarioexpk)ration for TRU waste disposal, (1)comparison of the transport code Tiger against Nestor, (2)improvement of the methodology aiming at its application to TRU waste disposal, were also carried out.
Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2000-026, 825 Pages, 2000/02
JNC-TJ8400-2000-026.pdf:26.86MB
Under the past Performance Assessment based on the scenario analysis, "conservatism" is employed to justify such simplifications. In order to underpin and defend tth definition of calculation cases and simplified PA models, we discuss a complementary approach which reverses the standard procedure of scenario development and case definition. A methodology which is prototypical to the Scenario Exploration Method is called the Environmental Simulation Method. An important feature of this methodology is in its capability of producing large number of quantitative realizations of the future system behaviour by varying the input parameter values in a stochastic manner. To overcome the constraint in the coverage due to use of specific mathematical models, we design a set of extremely flexible mathematical tools called 'Shadow Models' for the particular purpose of 'scanning' the whole parameter/model space which has not yet been rejected by the experts rather than scrutinizing it. In the current financial year, the objective of the study is: (1)To apply the Integrated Shadow Model to total system performance assessment and reveal sensitivity structure of the safety case treated in the second progress report of JNC. This, in turn, will be utilized to check comprehensiveness of the calculation cases defined and dealt with in the second progress report; (2)To extent methodology of the scenario exploration to safety assessment of TRU waste disposal and modify the tools accordingly; (3)To modify the nuclide transport solver, Tiger, so that its efficiency and robustness against nonlinear and time dependent nuclide migration problems.
Oyamada, Kiyoshi*; Ikeda, Takao*
JNC TJ8400 2000-025, 48 Pages, 2000/02
no abstracts in English