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Journal Articles

Current status of Geological disposal by "all-Japan" activities, 6; Post-closure safety assessment (2)

Tachi, Yukio; Saito, Takumi*; Kirishima, Akira*

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 64(5), p.290 - 295, 2022/05

no abstracts in English

Journal Articles

Development of dose evaluation method considering radionuclides migration on the surface of the site for confirmation of completion of decommissioning

Miwa, Kazuji; Namekawa, Masakazu*; Shimada, Taro; Takeda, Seiji

MRS Advances (Internet), 7(7-8), p.165 - 169, 2022/03

We have developed evaluation method of radiocesium (RCs) migration by surface runoff and soil erosion in considering vertical distribution of RCs in initial contaminated soil and concentration of RCs in different particle size. RCs migration on ground surface during single year has been evaluated in virtual site contaminated uniformly by Cs-137. As a result, RCs has concentrated in the impoundment, and 0.18% of total inventory in the site migrated into the sea. These results suggest that surface migration of RCs effects increasing of external exposure at impoundment and internal exposure from ingestion of marine product.

Journal Articles

A Scaling approach for retention properties of crystalline rock; Case study of the in-situ long-term sorption and diffusion experiment (LTDE-SD) at the $"A$sp$"o$ Hard Rock Laboratory in Sweden

Tachi, Yukio; Ito, Tsuyoshi*; Gylling, B.*

Water Resources Research, 57(11), 20 Pages, 2021/11

This paper focuses on the scaling approach for sorption and diffusion parameters from laboratory to in-situ conditions using the dataset of LTDE-SD experiment performed at the $"A$sp$"o$ HRL. The near-surface heterogeneities at both fracture surface and rock matrix could be evaluated by conceptual model with high porosity and diffusivity, and sorption capacity, and their gradual change at the near-surface zones. The modelling results for non-sorbing Cl-36 and weak-sorbing Na-22 could validate the model concept and the parameter estimation of porosity and diffusivity, by considering the disturbed zone of 5 mm thickness with gradual parameter changes. The De values of these cationic and anionic tracers showed typical cation excess and anion exclusion effects. The modelling results for high sorbing tracers (Cs-137, Ra-226, Ni-63 and Np-237) with different sorption mechanism could confirm the validity of the scaling approaches of Kd values as a function of particle size and their relation to the near-surface disturbances.

Journal Articles

General overview of the research project investigating the radionuclide solution behavior in mock mortar matrix modeled after conditions at the Fukushima-Daiichi Nuclear Power Station

Igarashi, Go*; Haga, Kazuko*; Yamada, Kazuo*; Aihara, Haruka; Shibata, Atsuhiro; Koma, Yoshikazu; Maruyama, Ippei*

Journal of Advanced Concrete Technology, 19(9), p.950 - 976, 2021/09

Journal Articles

A Systematic radionuclide migration parameter setting approach for potential siting environments in Japan

Hamamoto, Takafumi*; Ishida, Keisuke*; Shibutani, Sanae*; Fujisaki, Kiyoshi*; Tachi, Yukio; Ishiguro, Katsuhiko*; McKinley, I. G.*

Proceedings of 2019 International High-Level Radioactive Waste Management Conference (IHLRWM 2019) (USB Flash Drive), p.77 - 82, 2019/04

Journal Articles

Study on criticality in natural barrier for disposal of fuel debris from Fukushima Daiichi NPS

Shimada, Taro; Takubo, Kazuya*; Takeda, Seiji; Yamaguchi, Tetsuji

Progress in Nuclear Science and Technology (Internet), 5, p.183 - 187, 2018/11

After fuel debris is removed from the reactor containment vessel at Fukushima Daiichi NPS (1F) and collected in waste containers in the future, the waste containers will be disposed at a deep geological repository. The uranium inventory and uranium-235 ($$^{235}$$U) enrichment of the fuel debris are larger than those of high-level vitrified wastes which are produced from liquid waste during reprocessing of spent nuclear fuels. Therefore, there is a possibility not to be excluded that a criticality occurs in the geological media where the uranium precipitates at the far-field from the repository, after the uranium located in the repository is dissolved by groundwater. In this study, we calculated the quantity of uranium precipitated at the natural barrier, and studied dimension of uranium deposited in the natural barrier and carried out the criticality analysis.

Journal Articles

Effects of fine-scale surface alterations on tracer retention in a fractured crystalline rock from the Grimsel Test Site

Tachi, Yukio; Ito, Tsuyoshi*; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*

Water Resources Research, 54(11), p.9287 - 9305, 2018/11

 Times Cited Count:4 Percentile:37.78(Environmental Sciences)

Effects of fine-scale surface alterations on radionuclide migration in fractured crystalline rocks were investigated by a comprehensive approach coupling a series of laboratory tests, microscopic observations and modelling, using a single fractured granodiorite sample from the Grimsel Test Site, Switzerland. Laboratory tests including through-diffusion, batch sorption and flow-through tests using five tracers indicated that tracer retention was consistently in the sequence of HDO, Se, Cs, Ni, Eu, and as well as showing the existence of a diffusion-resistance layer near the fracture surface, cation excess and anion exclusion effects for diffusion. Microscale heterogeneities in structural properties around the fracture were clarified quantitatively by coupling X-ray CT and EPMA. A three layer model including weathered vermiculite, foliated mica and undisturbed matrix layers, and their properties such as porosity, sorption and diffusion parameters, could provide a reasonable interpretation for breakthrough curves and concentration distributions near fracture surface of all tracers, measured in flow-through tests.

Journal Articles

Assessment of sorption and diffusion in the rock matrix in the NUMO safety case

Hamamoto, Takafumi*; Shibutani, Sanae*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Yamada, Motoyuki*; Tachi, Yukio

Proceedings of 6th East Asia Forum on Radwaste Management Conference (EAFORM 2017) (Internet), 6 Pages, 2017/12

NUMO has developed a generic safety case to demonstrate the feasibility and safety of geological disposal of HLW and TRU in Japan and to provide a basic structure for the safety case which will be applicable to any potential site. In this safety case, the safety assessment was carried out for the repositories tailored to site descriptive models developed for three representative rock groups (plutonic, Neogene sedimentary and Pre-Neogene sedimentary rocks). Radionuclide migration parameters in rocks, i.e. distribution coefficients (Kds) and effective diffusion coefficients (Des), were derived to allow safety analysis for a range of scenarios. In this generic stage, the values of these parameter were given as the statistical values derived from laboratory data for certain rock types. The data were extracted from the latest database, with interpretation based on radionuclide speciation derived from relevant groundwater thermodynamic modelings.

Journal Articles

Diffusion model considering multiple pore structures in compacted bentonite

Yotsuji, Kenji; Tachi, Yukio; Okubo, Takahiro*

CMS Workshop Lectures, Vol.21, p.251 - 257, 2016/06

We have developed integrated sorption and diffusion model (ISD model) for assessment of diffusion parameters consistent with sorption processes in compacted bentonite. The ISD model gives consistent consideration to porewater chemistry, sorption and diffusion processes in compacted bentonite. The diffusion component based on the electric double layer theory and the homogeneous pore model in the ISD model accounts consistently for cation De overestimation and anion exclusion in narrow pores. The current ISD model can quantitatively account for diffusion of monovalent cations and anions, however, the model predictions disagree with diffusion data for multivalent cation and complex species. To improve the applicability of the model, it is necessary to consider the atomic level interactions between solute, solvent or clay mineral, and try that we apply the current ISD model to heterogeneous pore structure. In this study we try the application of the current ISD model to multiple pore structure. As results of numerical analysis of these models, the salinity dependence of effective diffusivity for the multi-pore model is comparatively smaller than that for the homogeneous pore model and the current diffusion model is improved.

Journal Articles

Development of a code MOGRA for predicting the migration of ground additions and its application to various land utilization areas

Amano, Hikaru; Takahashi, Tomoyuki*; Uchida, Shigeo*; Matsuoka, Shungo*; Ikeda, Hiroshi*; Hayashi, Hiroko*; Kurosawa, Naohiro*

Journal of Nuclear Science and Technology, 40(11), p.975 - 979, 2003/11

 Times Cited Count:2 Percentile:19.75(Nuclear Science & Technology)

MOGRA is a migration prediction code for toxic ground additions including radioactive materials in a terrestrial environment. MOGRA consists of computational codes that are applicable to various evaluation target systems, and can be used on personal computers. The computational code has the dynamic compartment analysis block, GUI for computation parameter settings and results displays, data bases. The compartments are obtained by classifying various natural environments into groups that exhibit similar properties. A hypothetical combination of land usage was supposed to check the function of MOGRA. The land usage was consisted from cultivated lands, forests, uncultivated lands, urban area, river, and lake. Each land usage has its own inside model which is basic module. Also supposed was homogeneous contamination of the surface land from atmospheric deposition of $$^{137}$$Cs (1.0 Bq/m$$^{2}$$). The system analyzed the dynamic changes of $$^{137}$$Cs concentrations in each compartment, fluxes from one compartment to another compartment.

Journal Articles

MOGRA-DB; Database system for migration prediction code MOGRA

Amano, Hikaru; Ikeda, Hiroshi*; Sasaki, Toshihisa*; Matsuoka, Shungo*; Kurosawa, Naohiro*; Takahashi, Tomoyuki*; Uchida, Shigeo*

KEK Proceedings 2003-11, p.239 - 244, 2003/11

A Code MOGRA (Migration Of GRound Additions) is a migration prediction code for toxic ground additions including radioactive materials in a terrestrial environment, which consists of computational codes that are applicable to various evaluation target systems, and can be used on personal computers. The computational code has the dynamic compartment analysis block at its core, the graphical user interface (GUI) for model formation, computation parameter settings, and results displays. The code MOGRA has varieties of databases, which is called MOGRA-DB. Another additional code MOGRA-MAP can take in graphic map and calculate the square measure about the target land.

JAEA Reports

Proceedings of the International Symposium: Transfer of Radionuclides in Biosphere, Prediction and Assessment; Mito, December 18-19, 2002

Amano, Hikaru; Uchida, Shigeo*

JAERI-Conf 2003-010, 394 Pages, 2003/09

JAERI-Conf-2003-010.pdf:25.13MB

The International Symposium : Transfer of Radionuclides in Biosphere, Prediction and Assessment was held at Mito on the 18th and 19th of Dec. 2002. This Symposium was organized by the Interchange Committee on Radionuclide Transfer in Soil Ecosphere. This project is the 3rd Phase Crossover Research, which is engaged in cooperation with five organizations:JAERI, MRI, NIRS, RIKEN and IES. The main objective of this symposium is to discuss and exchange recent findings and ideas in the area of the behavior and transfer of radionuclides in biosphere. One of the important topics in this symposium is to discuss a suitable transfer model and transfer parameters which may be adapted for Southeast Asian countries including Japan, as environmental conditions and foodstuffs in this region are significantly different from those in Europe and North America. The symposium consisted of 12 invited lectures and 44 poster presentations. The 120 participants attended the symposium, including 19 foreigners coming from 12 countries.

Journal Articles

Overview of the 3rd phase crossover research on migration of radionuclides in biosphere

Uchida, Shigeo*; Amano, Hikaru; Takahashi, Tomoyuki*; Chiba, Masaru*; Hisamatsu, Shunichi*; Enomoto, Shuichi*; Matsumoto, Shiro*

JAERI-Conf 2003-010, p.25 - 31, 2003/09

In the 3rd Stage Crossover Research (1998 to 2003), a project on Development of a dynamic transfer model of radionuclides in the soil ecosphere,is currently being promoted. The following five researches are carried out in this project. 1) Research into the forms of existence of nuclides and their change in the soil (NIRS and JAERI), 2) Research into the transition behavior of radionuclides in plants (IES, RIKEN and NIRS), 3) Research into the relation to the microorganism and on environmental remediation (RIKEN, JAERI and NIRS), 4) Research on the migration of radionuclides from atmosphere to soil and plant (MRI and JAERI), and 5) Database construction on transfer parameters (JAERI, NIRS and MRI). JAERI, MRI and NIRS are working on the development of a dynamic transfer model such as MOGRA for radionuclides on the basis of a gained knowledge about the environmental behavior through cooperation with universities, etc. This model is also capable of the predicting the behavior of materials that are harmful to the environment such as hazardous heavy metals discharged in the soil ecosphere. In this presentation, we will overview the ourcome of the 3rd stage research.

Journal Articles

Macroscopic simulation of radionuclide migration

Munakata, Masahiro; Kimura, Hideo

Shimyureshon, 21(1), p.3 - 8, 2002/03

no abstracts in English

JAEA Reports

Development of three dimensional ocean current model for coastal region

Kobayashi, Takuya

JAERI-Data/Code 99-049, p.47 - 0, 1999/12

JAERI-Data-Code-99-049.pdf:2.38MB

no abstracts in English

Journal Articles

A Study of actinide decay chains on the environmental effect of a geologic disposal of rock-like oxide fuels and uranium-plutonium oxide fuels

Kimura, Hideo; Takano, Hideki; Muromura, Tadasumi

Journal of Nuclear Materials, 274(1-2), p.197 - 205, 1999/00

 Times Cited Count:6 Percentile:46.57(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Environmental safety of the geologic disposal of ROX and MOX spent-fuels

Kimura, Hideo; Matsuzuru, Hideo; Takano, Hideki; Muromura, Tadasumi

JAERI-Research 97-049, 25 Pages, 1997/07

JAERI-Research-97-049.pdf:1.42MB

no abstracts in English

Journal Articles

Methodology of safety assessment and sensitivity analysis for geologic disposal of high-level radioactive waste

Kimura, Hideo; Takahashi, Tomoyuki; ; Matsuzuru, Hideo

Journal of Nuclear Science and Technology, 32(3), p.206 - 217, 1995/03

 Times Cited Count:4 Percentile:44.44(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Safety and sensitivity analyses of a generic geologic disposal system for high-level radioactive waste

Kimura, Hideo; Takahashi, Tomoyuki; ; Matsuzuru, Hideo

JAERI-Research 94-028, 50 Pages, 1994/11

JAERI-Research-94-028.pdf:2.3MB

no abstracts in English

Journal Articles

Interlaboratory modeling for performance assessment of engineered barriers in high-level radioactive waste disposal

; *; *; *; *; *; Kimura, Hideo; Munakata, Masahiro

Nihon Genshiryoku Gakkai-Shi, 34(4), p.342 - 364, 1992/04

 Times Cited Count:2 Percentile:28.1(Nuclear Science & Technology)

no abstracts in English

33 (Records 1-20 displayed on this page)