Development of a method of safety assessment for geological disposal considering long-term evolution of geological and topographical environment by uplift and erosion

Wakasugi, Keiichiro; Yamaguchi, Masaaki; Koo, Shigeru*; Nagao, Fumiya; Kato, Tomoko; Suzuki, Yuji*; Ebashi, Takeshi; Umeki, Hiroyuki*; Niibori, Yuichi*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(1), p.15 - 33, 2017/03

https://doi.org/10.3327/taesj.J16.010

This study provides a method of safety assessment for the geological disposal of HLW to evaluate the effects of uplift and erosion which are widespread phenomena identified on regional and global scales, and are more or less difficult to avoid in Japan. This method enables to deal with different uplift rate and erosion rate, and to evaluate repository depth, the time required for a repository to reach the weathered zone and surface of the ground, and the number of waste packages eroded as a function of time by using a landform evolution model. Based on trial analysis, the result shows that the maximum dose in the Base Case (uplift rate: 0.3 mm/y) is less than the targeted criterion suggested by the international organization even if the repository reaches the ground surface. Furthermore, the diversifying effect on timing the waste packages to reach to weathered zone due to heterogeneity on altitude of bottom of weathered zone reduces one order magnitude of result of the existed dose assessment. The new method is applicable to evaluate safety of geological disposal based on realistic phenomena of uplift and erosion and to quantify a safety margin and robustness of the disposal system.

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.

Study on evaluation method of potentional geological environmenral changes of "uplift and erosion" for performance assessment on a high level radioactive waste geological disposal system

Kawamura, Makoto; Ebashi, Takeshi; Makino, Hitoshi; Niizato, Tadafumi; Yasue, Kenichi; Inagaki, Manabu; Oi, Takao

Oyo Chishitsu, 51(5), p.229 - 240, 2010/12

https://doi.org/10.5110/jjseg.51.229

Uplift, subsidence, denudation, and sedimentation are phenomena over long-term in a regional scale. It is difficult to ignore the impacts of those phenomena on a disposal system completely in long-term. Therefore, type and extent of the impacts on geological and disposal environmental conditions, and disposal systems need to be evaluated quantitatively in order to develop perturbation scenarios. We have been developing a systematic methodology to develop perturbation scenarios based on the appropriate understanding of those phenomena. The variety of the change of geological environment and evolution pattern of the environment, which are caused by the variation of the uplift, subsidence, denudation, sedimentation phenomena and those rates, are understood by arranging the information in the framework of the thermal-hydrological-mechanical-chemical-geometrical (T-H-M-C-G) system, and the impacts of those environmental change to the performance of the repository system are also examined by using the T-H-M-C-G system. In this study, firstly, the potential changes of the geological environment were identified by examination of possible combinations of the uplift/denudation and subsidence/ sedimentation. The effects of the initial environmental condition are also considered. Geohistorical information and View of Modern analogue theory should be used in this stage. This procedure is essential to set up the scenarios regarding uplift/denudation and subsidence/sedimentation, to clarify the trend and/or range of the change of the geological environmental conditions. Then, the phenomena which give the large impacts to a disposal system were extracted based on the T-H-M-C-G system. By applying the developed framework which deals with the impacts on the HLW disposal system realistic view and builds evaluation scenarios and models based on step wise manner, we acquired the prospect that realistic uplift and denudation scenario could be built to this examination procedure.

Development of biosphere assessment methodology in view of surface and near-surface environment

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.

Study on perturbation scenario for potential effect of uplift, denudation, subsidence and sedimentation on a HLW disposal system

Kawamura, Makoto; Ebashi, Takeshi; Makino, Hitoshi; Niizato, Tadafumi; Yasue, Kenichi; Oi, Takao

JAEA-Research 2008-119, 32 Pages, 2009/03

JAEA-Research-2008-119.pdf:8.06MB

Uplift, subsidence, denudation, and sedimentation are phenomena over long-term in a regional scale. It is difficult to ignore the impacts of those phenomena on a disposal system completely in long-term. Therefore, type and extent of the impacts on geological and disposal environmental conditions, and disposal systems need to be evaluated quantitatively in order to develop perturbation scenarios. JAEA has been developing a systematic methodology to develop perturbation scenarios based on the appropriate understanding of those phenomena. The variety of the change of geological environment and evolution pattern of the environment, which are caused by the variation of the uplift, subsidence, denudation, sedimentation phenomena and those rates, are understood by arranging the information in the framework of the thermal-hydrological-mechanical-chemical-geometrical (T-H-M-C-G) system, and the impacts of those environmental change to the performance of the repository system are also examined by using the T-H-M-C-G system. In this study, firstly, the potential changes of the geological environment were identified by examination of possible combinations of the uplift/denudation and subsidence/ sedimentation. The effects of the initial environmental condition are also considered. Geohistorical information and Modern analogue theory should be used in this stage. This procedure is essential to set up the scenarios regarding uplift/denudation and subsidence/sedimentation, to clarify the trend and/or range of the change of the geological environmental conditions. Then, the phenomena which give the large impacts to a disposal system were extracted based on the T-H-M-C-G system. By applying the developed framework which deals with the impacts on the HLW disposal system realistic view and builds evaluation scenarios and models based on step wise manner, we acquired the prospect that realistic uplift and denudation scenario could be built to this examination procedure.

A Demonstration of the usefulness of the systematic approach to evaluate the importance of concerns affecting the geological disposal of radioactive wastes

Oi, Takao; Inagaki, Manabu; Kawamura, Makoto; Ebashi, Takeshi

JAEA-Research 2008-111, 32 Pages, 2009/03

JAEA-Research-2008-111.pdf:3.95MB

A demonstration of the usefulness of the systematic approach to evaluate the importance of concerns affecting the geological disposal of radioactive wastes.

A Systematic approach to evaluate the importance of concerns affecting the geological disposal of radioactive wastes

Oi, Takao; Inagaki, Manabu; Kawamura, Makoto; Ebashi, Takeshi

Materials Research Society Symposium Proceedings, Vol.1124, p.407 - 412, 2009/00

In the safety assessment of geological disposal system of radioactive waste, diverse apprehensions have been extracted from the viewpoint of the impact on the safety and the researches relating to those have been carried out strenuously. However, systematical investigation for presenting the relative importance of those has so far scarcely been conducted. The demonstration of the importance is critical issue to contribute the improvement of reliability of safety assessment. In this study, the following investigations were carried out with the goal of developing the systematic approach which can present the relative importance of the apprehensions: (1) Establishment of Total Assessment Work Frame [TAWF], (2) Establishment of the organaization procedure for evaluating the relative importance.

Study on perturbation scenario for uplift and denudation in performance assessment of a HLW disposal system

Kawamura, Makoto; Yasue, Kenichi; Niizato, Tadafumi; Tokiwa, Tetsuya; Ebashi, Takeshi; Oi, Takao; Makino, Hitoshi; Ishimaru, Tsuneari; Umeda, Koji

Proceedings of 2008 East Asia Forum on Radwaste Management Conference (2008 EAFORM 2nd Conference) (USB Flash Drive), 6 Pages, 2008/10

Japan Atomic Energy Agency (JAEA) had developed a framework to assess the potential impact of natural phenomena (uplift and denudation/climatic and sea-level changes; earthquakes and faulting; volcanism) on a high level radioactive waste (HLW) disposal system as a part of the total system performance assessment. The framework is focused on identifying key T-H-M-C-G (Thermal-Hydrological-Mechanical-Chemical-Geometrical) process associated with potential changes of the geological environment caused by natural phenomena. By using the framework, we could grasp the relationship between characteristic of natural phenomena and geological environmental conditions (T-H-M-C-G) quantitatively, and grasp the relationship between T-H-M-C-G condition and parameters of performance assessment efficiently. In this paper, we tried to develop perturbation scenarios of uplift and denudation by using the framework. As a result, by applying this framework, we could not only grasp the impacts on the geological environmental conditions (T-H-M-C-G) quantitatively, but the excess and deficiency of information resulting from uplift and denudation.

Study on evaluation method of potential impact of natural phenomena on a HLW disposal system

Kawamura, Makoto; Oi, Takao; Niizato, Tadafumi; Yasue, Kenichi; Tokiwa, Tetsuya; Niwa, Masakazu; Shimada, Koji; Kurosawa, Hideki; Asamori, Koichi; Kawachi, Susumu; et al.

JAEA-Research 2008-018, 47 Pages, 2008/03

JAEA-Research-2008-018.pdf:24.18MB

In this report, we sophisticated the framework as a part of the total system performance assessment for two purposes: the first one is quantification of relationship of characteristic of natural phenomena between geological environmental conditions (THMCG), and the other one is quantification of relationship of THMCG condition between parameters of performance assessment. On the other hand, we applied the sophisticated framework to all natural phenomena. As a result, to apply the sophisticated framework, we could show that information integration could carry out efficiently. Moreover, we have checked that the framework was applicable to all phenomena. Furthermore, we could show that suitable scenarios might be chosen by information integration.

Study plan for performance assessment of HLW geological disposal, 5-year plan

Miyahara, Kaname; Yoshikawa, Hideki; Oi, Takao; Shibata, Masahiro; Sawada, Atsushi; Sasamoto, Hiroshi; Iijima, Kazuki; Maekawa, Keisuke; Kawamura, Makoto; Kato, Tomoko; et al.

JAEA-Review 2006-015, 29 Pages, 2006/03

JAEA-Review-2006-015.pdf:4.58MB

This report is to outline a 5-year plan of research and development (R&D) for performance assessment of geological disposal of high-level radioactive waste in JAEA. This 5-year plan is based on JAEA's mid-term plan which follows the R&D policy specified in "Framework for Nuclear Energy Policy" issued by Japan Atomic Energy Commission. Moreover, research plans for safety regulation issued by Nuclear Safety Commission of Japan should be taken into account. The contents of this 5-year plan follows a framework of R&D issues for performance assessment field established in "the R&D map", i.e. the mid and long term R&D plan for geological disposal of high-level radioactive waste, developed by JNC (predecessor of JAEA) and other relevant R&D organizations. In each research plan, objectives based on the necessity and the significance of the research plan are clarified in the section of "Objectives and the past progresses", with summarizing the progresses of H12: Project to establish the scientific and technical basis for HLW disposal in Japan (Second Progress Report), and H17: Development and management of the technical knowledge base for the geological disposal of HLW (H17 report). In addition, next five year plan is described in the section of "5-year plan (up to Fiscal year Heisei-22)".