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Journal Articles

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

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.

Journal Articles

"Relative rates method" for evaluating the effect of potential geological environmental change due to uplift/erosion to radionuclide migration of high-level radioactive waste

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.

JAEA Reports

Study on relationship between multiple safety functions in the engineered barrier system

Wakasugi, Keiichiro; Koo, Shigeru*; Shibata, Masahiro

JAEA-Research 2011-006, 31 Pages, 2011/06

JAEA-Research-2011-006.pdf:2.37MB

Although confirmation of the long-term safety of the constructed geological disposal system has been conducted by using scenario, model and data according to the internationally agreed methodology, there were a few researches that focused on individual safety functions and their relationships. This is because multiple safety functions are a fundamental concept for ensuring the safety of the geological disposal, and the long-term safety is accomplished by the whole system. Therefore, we developed a methodology to identify performance of the individual safety functions and their relationships considering the characteristic of the multiple safety functions, and examined the safety functions in the engineered barrier system based on this methodology. The results from this study are useful for constructing design requirements for the system components of the geological disposal as well as developing repository concept.

JAEA Reports

Study on potential impacts of natural phenomena on a HLW geological disposal system

Kawamura, Makoto; Makino, Hitoshi; Sasao, Eiji; Niizato, Tadafumi; Yasue, Kenichi; Asamori, Koichi; Umeda, Koji; Ishimaru, Tsuneari; Osawa, Hideaki; Ebashi, Takeshi; et al.

JAEA-Research 2010-027, 85 Pages, 2010/09

JAEA-Research-2010-027.pdf:9.37MB

Japan Atomic Energy Agency (JAEA) have developed a formal evaluation method to assess the potential impacts of natural phenomena (earthquakes and faulting; volcanism; uplift, subsidence, denudation and sedimentation; climatic and sea-level changes) on a high level radioactive waste (HLW) disposal system for the purpose of maintenance of evaluation method for potential impacts of natural phenomena within more realistic view. In this report, we developed a 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 (T-H-M-C-G), and the other one is quantification of relationship of T-H-M-C-G condition between parameters of performance assessment. We tried to apply the framework to all natural phenomena to confirm the effectiveness of the framework. On the other hand, we applied an argument-diagram that was developed one of the methods of the knowledge management to elicit future tasks. As a result, to apply the framework, we could show that information integration could carry out efficiently, and information integration was attained by the common framework by combining information on geohistory and existing information of natural phenomena and geological environmental conditions as modern-analogue. We could show that suitable scenarios might be chosen by information integration. Furthermore, we were able to elicit future tasks to this study by applying the argument-diagram.

JAEA Reports

Development of computation model on the GoldSim platform for the radionuclide transport in the geosphere with the time-dependent parameters

Koo, Shigeru*; Inagaki, Manabu

JAEA-Data/Code 2010-006, 41 Pages, 2010/06

JAEA-Data-Code-2010-006.pdf:1.39MB

In the HLW disposal system, numerical evaluation for radionuclide transport with the time-dependent parameters is necessary to evaluate various scenarios. In H12 report, numerical code MESHNOTE and TIGER were used for the evaluation of some natural phenomena scenarios that had to handle the time-dependent parameters. In the future, the necessity of handling the time-dependent parameters will be expected to increase, and more efficient calculation and improvement of quality control of input/output parameters will be required. Therefore, for the purpose of corresponding this requirement, a radionuclide transport model has been developed on the Goldsmith GoldSim is a general simulation software, that was used for the computation modeling of Yucca Mountain Project. The conceptual model, the mathematical model and the verification of the GoldSim Model are described in this report. In the future, application resources on this report will be able to upgrade for perturbation scenarios analysis model.

JAEA Reports

Study and design of safety assessment model based on H12 reference case using GoldSim

Nakajima, Kunihiko*; Koo, Shigeru*; Ebina, Takanori*; Ebashi, Takeshi; Inagaki, Manabu

JAEA-Data/Code 2009-009, 62 Pages, 2009/07

JAEA-Data-Code-2009-009.pdf:19.19MB

Reference case of safety assessment analysis at the H12 report was calculated using the numerical code MESHNOTE and MATRICS mainly. On the other hand, recently general simulation software witch has a character of object-oriented is globally used and the numerical code GoldSim is typical software. After the H12 report, probability theory analysis and sensitivity analysis using GoldSim have carried out by statistical method for the purpose of following up safety assessment analysis at the H12 report. On this report, details of the method for the model design using GoldSim are summarized, and to confirm calculation reproducibility, verification between the H12 report and GoldSim results were carried out. And the guide book of calculation method using GoldSim is maintained for other investigators at JAEA who want to calculate reference case on the H12 report. In the future, application resources on this report will be able to upgrade probability theory analysis and other conceptual models.

JAEA Reports

Illustration of an approach to evaluate the effect of the uplift and denudation for a groundwater scenario of a geological disposal concept in a hypothetical sedimentary rock

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.

Journal Articles

Assessment approach for a safety margin of parameters on the high-level radioactive waste disposal

Ebashi, Takeshi; Koo, Shigeru*; Oi, Takao

Genshiryoku Bakkuendo Kenkyu, 15(2), p.99 - 115, 2009/03

In order to demonstrate the robustness of the design of a high-level waste (HLW) disposal system, an important measure is to preliminarily set parameter values, which take into account safety margins for an acceptable dose. In evaluating the safety margin, it is necessary to estimate a range of parameters for an acceptable dose by a sensitivity analysis based on the appropriate conditions for each scenario. In this study, the comprehensive sensitivity analysis method was applied to performance assessment of a HLW disposal system. This paper presents the approach to assess a safety margin for parameters. As a result, safety margins for the parameters of the engineered barrier system (glass dissolution rate, overpack failure time, buffer thickness) were illustrated under conservative conditions of the natural barrier. Such an approach will provide useful information for scenario analysis and offer insights into the design and construction of a robust system for HLW disposal concept.

Journal Articles

Application of the comprehensive sensitivity analysis method to a Korean geological disposal concept

Ebashi, Takeshi; Hwang, Y.-S.*; Lee, Y.-M.*; Oi, Takao; Koo, Shigeru*

Journal of Nuclear Science and Technology, 45(11), p.1138 - 1149, 2008/11

 Times Cited Count:10 Percentile:59.54(Nuclear Science & Technology)

In this study, as a part of the joint research between JAEA and KAERI, the comprehensive sensitivity analysis method developed by JAEA was applied to a Korean HLW disposal concept that spent fuel will be directly disposed in a rock. The purpose of this study was to confirm whether the threshold values of near-filed parameters yielding a "successful condition" where maximum dose does not exceed a target value can be extracted with regard to direct disposal concept of spent fuel. As a result, the successful conditions composed of near-field parameters were illustrated under different conservative conditions of the natural barrier. In conclusion, the comprehensive sensitivity analysis method can be applied to extraction of a successful condition composed of near-field parameters for direct disposal concept of spent fuel. Such an approach will provide useful information for scenario analysis and offer insights into construction of a robust system for direct disposal concept of spent fuel.

JAEA Reports

Sensitivity analysis of parameters for engineered barrier and natural barrier; Application of the comprehensive sensitivity analysis method to HLW geological disposal concept

Ebashi, Takeshi; Koo, Shigeru*; Oi, Takao

JAEA-Research 2008-019, 142 Pages, 2008/03

JAEA-Research-2008-019.pdf:22.97MB

In this study, comprehensive sensitivity analysis method was applied to HLW geological disposal concept. In this application, level of importance and successful condition for intended parameters on one barrier were extracted under conservative conditions of parameters on the other barrier, taking into account diverse uncertainties on initial stage of stepwise approach. We achieved analysis results with level of importance and successful condition for intended parameters. In conclusion, the comprehensive sensitivity analysis method can be applied to extraction of sensitivity characteristics on each barrier, under conservative conditions. Such study on the applicability of method and the extracted sensitivity characteristics will contribute to construction of a robust barrier and a scenario analysis for initial stage of stepwise approach.

JAEA Reports

None

Makino, Hitoshi; Sawada, Atsushi; Maekawa, Keisuke; Shibata, Masahiro; Sasamoto, Hiroshi; Yoshikawa, Hideki; Wakasugi, Keiichiro; Koo, Shigeru*; Hama, Katsuhiro; Kurikami, Hiroshi; et al.

JNC TN1400 2005-021, 148 Pages, 2005/09

JNC-TN1400-2005-021.pdf:22.58MB

None

Journal Articles

Study on model variation of the excavation disturbed zone for the nuclides migration analysis

Wakasugi, Keiichiro; Makino, Hitoshi; Koo, Shigeru*

Genshiryoku Bakkuendo Kenkyu, 10(1), p.21 - 30, 2004/00

None

Journal Articles

Study on Retardation Effects in the Excavated Disturbed Zone Using a Two-Dimensional Radionuclide Migration Model

Wakasugi, Keiichiro; Makino, Hitoshi; Koo, Shigeru*

GoldSim International User Conference 2004, 0 Pages, 2004/00

A Method of thermal neutron capture cross section measurement by unfolding prompt $$gamma$$ ray spectra were developed. Response function for unfolding spectra was constructed by using EGS-4 code. To check the reliability of the response function, prompt $$gamma$$ rays emitted from 15N produced in thermal neutron capture reaction were reproduced.

JAEA Reports

Irradiation effects on plasma diagnostic components, 2

Nishitani, Takeo; Shikama, Tatsuo*; Sugie, Tatsuo; Kasai, Satoshi; Ishitsuka, Etsuo; Kawamura, Hiroshi; Kakuta, Tsunemi; Yagi, Toshiaki; Tanaka, Shigeru; Narui, Makoto*; et al.

JAERI-Research 2002-007, 149 Pages, 2002/03

JAERI-Research-2002-007.pdf:8.08MB

no abstracts in English

JAEA Reports

Assessment on the mechanical stability of underground excavations

; Taniguchi, Wataru; Koo, Shigeru*; Hasegawa, Hiroshi; ; Kubota, Shigeru*; *

JNC TN8400 99-037, 281 Pages, 1999/11

JNC-TN8400-99-037.pdf:15.51MB

It is planned to construct the tunnels and emplace waste packages at several hundred meters to 1,000 meters under the ground for the repository of high-level radioactive waste based on a policy to assure the safe life environment. It is required to be mechanically stable for the tunnels to assure the work safety throughout the construction, operation and closure phase. In this report, the mechanical stability of tunnels, that is a factor of design requisites, was evaluated by the analyses to present an outline of the technical reliability of geological disposal. To put it concretely, the tunnel sections were determined to have the required areas and shapes, and the analyses on the mechanical stability at tunnel excavations and earthquake, at tunnel intersections were conducted by the theoretical analysis and finite element method. The results obtained by these investigations are shown below: (1)It will be able to construct the tunnels with present techniques. The mechanical stability of tunnels will be assured if proper supports are given, and adequate tunnel spacing and disposal-pit pitches are set. (2)The mechanical stability will be assured at the tunnels intersections if proper reinforcement measures are taken. The reinforcement will be required for the intersection areas over the distance of 1D (D: diameter of tunnels) on the obtuse angle side, and 4D on the acute angle side, when intersection angle is set at 30 degrees. (3)The investigations were conducted on the assumption that the experienced big earthquake occurred. The results show that the effect of earthquake on the mechanical stability of tunnels is small, and tunnels are stable at the earthquake when the mechanical stability at tunnel excavations is assured.

Oral presentation

Study on identification of important R&D issues on HLW geological disposal using a comprehensive sensitivity analysis method

Ebashi, Takeshi; Oi, Takao; Koo, Shigeru*

no journal, , 

no abstracts in English

Oral presentation

Illustration of an approach to assess the effect of uplift/denudation for groundwater scenarios of a geological disposal concept in a hypothetical sedimentary rock

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.

Oral presentation

Development of tool for radionuclide migration analysis on the basis of time change of parameters

Koo, Shigeru*; Ebashi, Takeshi; Inagaki, Manabu

no journal, , 

no abstracts in English

Oral presentation

Development of the technology basis for holistic waste management taking into consideration whole fuel cycle system, 3; Electronic-performance analysis report to support nuclide migration analysis and report writing

Koo, Shigeru; Makino, Hitoshi; Umeki, Hiroyuki; Hioki, Kazumasa; Kawasaki, Daisuke*; Tachibana, Shoko*

no journal, , 

no abstracts in English

Oral presentation

Study on uplift and erosion scenario for HLW on the base of long-term geomorphic change

Yamaguchi, Masaaki; Wakasugi, Keiichiro; Koo, Shigeru; Shimemoto, Hidenori; Shibata, Masahiro

no journal, , 

Since its tectonically active and humid setting, uplift and erosion scenarios must be covered in safety assessment of HLW in Japan. This study suggests a new methodology for scenario and parameter setting for uplift and erosion scenario assessment, on the bases of long-term geomorphic change by using previous equations based on correlative relationship between relief, altitude, and erosion.

22 (Records 1-20 displayed on this page)