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Journal Articles

Matrix diffusion and sorption of Cs$$^{+}$$, Na$$^{+}$$, I$$^{-}$$ and HTO in granodiorite; Laboratory-scale results and their extrapolation to the in situ condition

Tachi, Yukio; Ebina, Takanori*; Takeda, Chizuko*; Saito, Toshihiko*; Takahashi, Hiroaki*; Ouchi, Yuji*; Martin, A. J.*

Journal of Contaminant Hydrology, 179, p.10 - 24, 2015/08

 Times Cited Count:23 Percentile:19.09(Environmental Sciences)

Matrix diffusion and sorption are important processes in the assessment of radionuclide transport in crystalline rocks. Diffusion and sorption parameters for Cs$$^{+}$$, Na$$^{+}$$, I$$^{-}$$ and HTO were determined by through-diffusion and batch sorption experiments using granodiorite samples from the Grimsel Test Site, Switzerland. The De values were in the order Cs$$^{+}$$, Na$$^{+}$$, HTO, I$$^{-}$$. The capacity factor and Kd values show the same trends. The dual depth profiles for Cs$$^{+}$$ and Na$$^{+}$$ can be interpreted by a near-surface Kd increment. The microscopic analysis indicated that this is caused by high porosity and sorption capacities in disturbed biotite minerals on the sample surface. The Kd values derived from the dual profiles are likely to correspond to Kd dependence on the grain sizes of crushed samples in the batch experiments. The results of the in situ LTD experiments were interpreted reasonably well by using transport parameters derived from laboratory data and extrapolating them to in situ conditions.

Journal Articles

Comparative modeling of an in situ diffusion experiment in granite at the Grimsel Test Site

Soler, J. M.*; Landa, J.*; Havlova, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Eikenberg, J.*; Martin, A. J.*

Journal of Contaminant Hydrology, 179, p.89 - 101, 2015/08

 Times Cited Count:30 Percentile:12.98(Environmental Sciences)

Matrix diffusion is a key process for radionuclide retention in crystalline rocks. An in-situ diffusion experiment in granite matrix was performed at the Grimsel Test Site (Switzerland). Several tracers (HTO, Na$$^{+}$$, Cs$$^{+}$$) were circulated through a borehole and the decrease in tracer concentrations was monitored for 2.5 years. Then, the borehole section was overcored and the tracer profiles in the rock were analyzed. Transport distances in the rock were 20 cm for HTO, 10 cm for Na$$^{+}$$ and 1 cm for Cs$$^{+}$$. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusivities (De) and rock capacity factors. There was a rather good agreement between the values from different teams, implied that De and capacity factors in the borehole damaged zone are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results.

Journal Articles

Modeling of an in-situ diffusion experiment in granite at the Grimsel Test Site

Soler, J. M.*; Landa, J.*; Havlova, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Martin, A. J.*

Materials Research Society Symposium Proceedings, Vol.1665, p.85 - 91, 2014/09

Matrix diffusion is a key process for radionuclide retention in crystalline rocks. An in-situ diffusion experiment in granite matrix was performed at the Grimsel Test Site (Switzerland). Several tracers (HTO, Na$$^{+}$$, Cs$$^{+}$$) were circulated through a borehole and the decrease in tracer concentrations was monitored for 2.5 years. Then, the borehole section was overcored and the tracer profiles in the rock were analyzed. Transport distances in the rock were 20 cm for HTO, 10 cm for Na$$^{+}$$ and 1 cm for Cs$$^{+}$$. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusivities ($$D$$e) and rock capacity factors. There was a rather good agreement between the values from different teams, implied that $$D$$e and capacity factors in the borehole damaged zone are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results, which have to be investigated in more detail.

Journal Articles

LTD experiment; Postmortem modelling of monopole I

Soler, J. M.*; Landa, J.*; Havlov$'a$, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Martin, A.*

Nagra NAB 12-53, 80 Pages, 2013/02

An in-situ long-term diffusion (LTD) experiment was performed at the Grimsel Test Site (Switzerland). Tracers, HTO, $$^{22}$$Na$$^{+}$$, $$^{134}$$Cs$$^{+}$$, were continuously circulated through a packed-off borehole and the tracer concentrations in the solution was monitored for 2.5 years. Subsequently, the borehole section was overcored and the tracer profiles in the rock analyzed. The drop in activity for Cs$$^{+}$$ in the solution was much pronounced. Transport distances were about 20 cm for HTO, 10 cm for Na$$^{+}$$ and 1 cm for Cs$$^{+}$$. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusion coefficients ($$D$$$$_{e}$$) and rock capacity ($$alpha$$) values. There was a rather good agreement between the values from different teams, implied that $$D$$$$_{e}$$ and $$alpha$$ values in the BDZ are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results, which have to be investigated in more detail.

JAEA Reports

Development of safety assessment model based on TRU-2 report using GoldSim

Ebina, Takanori*; Inagaki, Manabu*; Kato, Tomoko

JAEA-Data/Code 2010-029, 41 Pages, 2011/03

JAEA-Data-Code-2010-029.pdf:5.79MB

The safety assessment model at "Second Progress Report on Research and Development for TRU Waste Disposal in Japan" (TRU-2 report) was designed using the numerical code TIGER, that allows the physical and chemical properties within the system to vary with time. At the analysis using TIGER, the migration (i.e engineered barrier system, host rock and fault) have to be analysed independently at each region, consequently the huge number of complicated parameter setting have been required. On the other hand, by using numerical code GoldSim, all regions are analyzed synchronously and parameters can be defined at same model. In future, safety analyses of TRU waste package disposal will be carried out according as study of an optimization of nuclear fuel cycle. Therefor, safety assessment model for TRU waste disposal using GoldSim was designed, and calculation results were verified by comparing with the result of TRU-2 report.

Journal Articles

Consequence analysis of fluvial erosion scenarios for a HLW repository

Miyahara, Kaname; Kawamura, Makoto*; McKinley, I. G.*; Inagaki, Manabu*; Ebina, Takanori*

Journal of Nuclear Science and Technology, 48(7), p.1069 - 1076, 2011/00

 Times Cited Count:2 Percentile:78.83(Nuclear Science & Technology)

In Japan, uplift/erosion scenarios must be analysed even if they occur far in the future, as no assessment cut-off times have yet been defined. For this purpose, the geological record of river terrace formation and their long term evolution has been studied further, with the aim of constructing a more realistic fluvial erosion model compared with the original, rather simple cyclic fluvial erosion model developed in a previous study. The model allows the consequences of erosion of the repository to be assessed, as before using comparisons with natural radionuclide fluxes. This paper describes a conceptual model based on a generalization of field observations in relevant settings and discusses resultant analyses, which again illustrate the effectiveness and robustness of the reference HLW disposal system.

JAEA Reports

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.

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.

Journal Articles

Disruptive effects on a HLW repository due to uplift-erosion in the distant future

Miyahara, Kaname; Inagaki, Manabu; Kawamura, Makoto; Ebina, Takanori*; McKinley, I. G.*

Materials Research Society Symposium Proceedings, Vol.1193, p.177 - 184, 2009/05

Uplift and erosion cannot be generally precluded in Japan, therefore needs to be treated. In particular, uplift and erosion will cause major disruption of the engineered and natural barriers when the repository is exposed at the ground surface, although erosion of the repository should be excluded for very long times by careful siting and design. In Japan, uplift/erosion scenarios must be analysed, even if they occur far in the future as no assessment cut-off times have yet been defined. For this purpose, an argumentation method is being developed to allow sensible scenarios to be constructed. This paper discusses procedures to derive relevant conceptual models and resultant analyses in a credible manner which illustrates the effectiveness and robustness of the HLW disposal system, using relevant yardsticks based on natural radionuclide fluxes.

Journal Articles

Impact of silicon migration through buffer material on the lifetime of vitrified waste

Mitsui, Seiichiro; Makino, Hitoshi; Inagaki, Manabu; Ebina, Takanori*

Materials Research Society Symposium Proceedings, Vol.1193, p.397 - 404, 2009/05

The results of a sensitivity analysis for long-term glass dissolution taking into account Si release from the glass and its migration through the buffer material are presented to illustrate the impact of this near-field process on the lifetime of the vitrified waste. The lifetime of the glass estimated by the analysis showed a strong dependence on Si diffusion and distribution coefficients in the buffer material and groundwater flow rate in the EDZ. This indicates the significance of these parameters for the long-term evolution of vitrified waste. We also discuss the impact of glass hydration, which proceeds simultaneously with matrix dissolution considering Si release, on the lifetime of the vitrified waste. The results show that glass hydration is less important for the long-term evolution than matrix dissolution in an open system and it can be concluded that Si migration through the buffer material will be an important process for estimating the lifetime of the vitrified waste.

JAEA Reports

Construction of performance assessment method which correspond to disposal environment and optional designs, 2

Inagaki, Manabu; Ebina, Takanori*

JAEA-Research 2008-114, 36 Pages, 2009/03

JAEA-Research-2008-114.pdf:3.21MB

In arrangement of the premise of the total performance evaluation of the disposal system, it is important to build the "reference total performance evaluation concept" based on consideration of more realistic design situation, and consideration of the performance evaluation based on the safety function. Extract the scenario on changing some condition becomes easy with those "reference total performance evaluation concept". I can think the methodology which treats change in the disposal condition as perturbation to the condition put in order doesn't damage a existence concepts, and is also effective in step-by-step development of evaluation. Therefore I can think the method to put a flow of information on a system of existence in order by FepMatrix with the investigation/design-disposal condition-structure of the safety function is useful.

Journal Articles

"What-if?" calculations to illustrate fault-movement effects on a HLW repository

Miyahara, Kaname; Inagaki, Manabu; Kawamura, Makoto; Ebina, Takanori*

Proceedings of 2008 International High-Level Radioactive Waste Management Conference (IHLRWM 2008) (CD-ROM), p.593 - 599, 2008/09

This paper illustrated how to conduct "what if?" calculations in a transparent manner based on a developed formal procedure in order to treat perturbations of disruptive fault movement on a HLW disposal system. Calculation cases are defined due to stepwise combination of loss of key safety functions as what if? assumptions. The calculation results show effectiveness and robustness of the multibarrier system, even considering the most extreme combination of what if assumptions.

JAEA Reports

A Study of methodology and it's applications for the evaluation of total system performance which considered the site-information and the design-information

Inagaki, Manabu; Ebina, Takanori*

JAEA-Research 2008-022, 37 Pages, 2008/03

JAEA-Research-2008-022.pdf:2.26MB

The step-by-step progress for which a detailed investigation area(s) is chosen from the preliminary investigations area(s) in the volunteer sites is assumed on the high-level radioactive waste disposal in Japan. It's necessary to select an appropriate detailed investigation area from the preliminary investigation area, therefore, it's needed to combine the design options which have been assumed on the generic geological environment with the information of a limited investigation from the surface in the preliminary investigation area for evaluating the total performance of the investigation site. Requirements in the detailed investigation area are not only long term stability of geological environment but also stability of the engineered barrier system on influence by a flow of groundwater in major water conducting fracture, the correspondence by a site-design and the performance of the total system as a selection important matter in a detailed investigation area. I thought it was rational to build the scenario used by geological survey information, design situation and performance evaluations, the scenario which causes a model and data when combining geological information and design option as the early stage condition, and the frame able to make the model difference clear and feed this back to a design and a geological survey at the generic environment bottom considered up to now for it.

JAEA Reports

Development of advanced JGIS considering quality management and project management

Kawachi, Susumu; Oi, Takao; Kawamura, Makoto; Ishihara, Yoshinao*; Ebina, Takanori*

JAEA-Data/Code 2008-006, 55 Pages, 2008/03

JAEA-Data-Code-2008-006.pdf:4.17MB

The investigation and studies of site-specific geological conditions provide much information and data. A system for managing and integrating the technical information was developed (JGIS: JAEA Geological Disposal Information Integration System). In this study we built the conceptual design in order to implement the function of quality management and project management to JGIS. We considered that researchers could access the portal site of the research projects which were set as the WBS (Work Breakdown Structure) items and could confirm which WBS item the research project belonged to in the whole plan. We also considered that the research projects could be managed by using the conformity sheets which were adopted in the quality management system.

JAEA Reports

The Property investigation of the numerical code TIGER for the uncertain analysis

Ebina, Takanori*; Oi, Takao

JAEA-Data/Code 2008-002, 53 Pages, 2008/03

JAEA-Data-Code-2008-002.pdf:4.98MB

In order to obtain the information concerning the safety of the geological disposal, the sensitivity analysis considers the uncertainty of parameters resulting from the insufficiency of knowledge and information plays an important role. TIGER allows the physical and chemical properties within the system to vary with time and this function is useful for understanding the effect of the property change in sensitivity analysis. Therefore, at this study, some typical processing methods with the engineered barrier system and the host rock were developed, and through the comparison with the calculation time, the step of processing, the most suitable method was considered. After this, the interrelation between the calculation accuracy and the calculation time was examined for the purpose of using this method to the uncertain analysis. Through this consideration, the information of the best processing method, the calculation accuracy, and the analysis tool was arranged for an uncertain analysis used TIGER.

JAEA Reports

Study plan for performance assessment of potential effect of natural phenomena on a HLW disposal system, 5-year plan

Kawamura, Makoto; Oi, Takao; Makino, Hitoshi; Umeda, Koji; Niizato, Tadafumi; Yasue, Kenichi; Kawachi, Susumu; Ishimaru, Tsuneari; Seo, Toshihiro; Ebina, Takanori*; et al.

JAEA-Review 2006-039, 60 Pages, 2007/01

JAEA-Review-2006-039.pdf:7.39MB

This report is to outline a 5-year plan of research and development (R&D) for performance assessment of potential effect of natural phenomena on a geological disposal of high-level radioactive waste in JAEA. 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.

JAEA Reports

Study on Influence of Increase in Surface Area by Cracking on Glass Dissolution for HLW Performance Assessment

Ebina, Takanori*; Makino, Hitoshi

JNC-TN8400 2005-006, 37 Pages, 2005/03

JNC-TN8400-2005-006.pdf:1.12MB

Cracking of the glass that occurred during cooling in the vitrification process would cause increase in surface area of vitrified wastes and potential impact of the cracking on glass dissolution have been discussed.In the current performance assessments of HLW,increase in glass dissolution has been assumed to proportionate to increase in the surface area.On the other hand,leaching experiments on a full-scale simulated glass block with numerous cracks have shown that only a fraction of the crack surface contributed to glass dissolution. In this study,we developed a simple model and carried out sensitivity analysis for influence of increase in surface area on glass dissolution. Results show that increase in surface area in a fractured glass block does not impact on glass dissolution proportionately.Instead of surface area,ratio of the outside surface area and aperture of fractures that could control diffusion behavior through fracture have impact on glass dissolution.Under the condition of leaching experiments on a full-scale simulated glass block with numerous cracks,a few times increase in glass dissolution was estimated by the developed model,and that was consistent with the experimental results.

Oral presentation

What-if calculations to illustrate effects of fault movement on the safety functions of HLW disposal system

Miyahara, Kaname; Inagaki, Manabu; Ebina, Takanori*

no journal, , 

This study illustrates a transparent formal procedure for selecting what-if cases for fault movement scenario, discussing the relevance of assumptions and conducting what-if calculations to determine the consequences of fault movement on HLW repository safety.

Oral presentation

Study on total system performance analysis on a HLW disposal system, 1; A Study of extraction of scenarios which considered the realistic geological environment and site - design options

Inagaki, Manabu; Ebina, Takanori*; Oi, Takao; Kawamura, Makoto; Kawachi, Susumu; Miyahara, Kaname

no journal, , 

A study of extraction of scenarios which considered the realistic geological environment and site - design options.

Oral presentation

23 (Records 1-20 displayed on this page)