Rai, D.*; Yui, Mikazu; Kitamura, Akira
Progress in Nuclear Science and Technology (Internet), 5, p.19 - 26, 2018/11
The objectives of this presentation are (1) to describe the solubility method, (2) to list desirable criteria of the solubility method so that the reader can recognize which studies have been done in a way that yields quality information, (3) to present an example of how to use the evaluation criteria, and (4) to provide a few examples of future research needs where the solubility method is ideally suited and the other methods are unsuitable for these investigations.
Kitamura, Akihiro; Kurikami, Hiroshi; Yamaguchi, Masaaki; Oda, Yoshihiro; Saito, Tatsuo; Kato, Tomoko; Niizato, Tadafumi; Iijima, Kazuki; Sato, Haruo; Yui, Mikazu; et al.
Nuclear Science and Engineering, 179(1), p.104 - 118, 2015/01
The prediction of the distribution and fate of radioactive materials eventually deposited at surface in the Fukushima area is one of the main objectives and expected to be achieved in an efficient manner. In order to make such prediction, a number of mathematical models of radioactive contaminants, with particular attention on cesium, on the land and in rivers, lakes, and estuaries in the Fukushima area are developed. Simulation results are examined with the field investigations simultaneously implemented. The basic studies of the adsorption/absorption mechanism of cesium and soils have been performed to shed light on estimating distribution coefficient between dissolved contaminant and particulate contaminant.
Kitamura, Akihiro; Imaizumi, Yoshitaka*; Yamaguchi, Masaaki; Yui, Mikazu; Suzuki, Noriyuki*; Hayashi, Seiji*
Kankyo Hoshano Josen Gakkai-Shi, 2(3), p.185 - 192, 2014/09
Annual discharge rates of radioactive cesium through selected rivers due to the Fukushima Dai-ichi Nuclear Power Plant accident were simulated by two different watershed models. One is the Soil and Cesium Transport, SACT, model which was developed by Japan Atomic Energy Agency and the other one is the Grid-Catchment Integrated Modeling System, G-CIEMS, which was developed by National Institute of Environmental Studies. We choose the Abukuma, the Ukedo, and the Niida rivers for the present study. Comparative results showed that while components and assumptions adopted in two models differ, both methods predicted the same order of magnitude estimates.
Kitamura, Akihiro; Yamaguchi, Masaaki; Kurikami, Hiroshi; Yui, Mikazu; Onishi, Yasuo*
Anthropocene, 5, p.22 - 31, 2014/03
Amount of soil and cesium losses in Eastern Fukushima Prefecture is evaluated by a simple and fast simulation model which we developed utilizing the universal soil loss equation and the geographical information system. We focused on the land use factor of the universal soil loss equation in this study. It was estimated that the forest occupies 64% of the total land surface of the study area, but only accounts for 24% of total soil runoff and 33% of total cesium dispersion. The most contributing component comes from the crop field, while the forest becomes the second. Also, calculation was performed for each river basins and results were compared with field monitoring data.
Kitamura, Akihiro; Machida, Masahiko; Sato, Haruo; Nakayama, Shinichi; Yui, Mikazu
Transactions of the American Nuclear Society, 109(1), p.156 - 157, 2013/11
Computational modeling and simulating team of Fukushima Environmental Safety Center, Japan Atomic Energy Agency has been started to develop a number of mathematical models of radioactive contaminants on the land and rivers, lakes, and estuaries in Fukushima, as well as the basic studies of adsorption/absorption mechanism of Cs and soils. These predictions will be utilized for the dose assessment from the environmental contamination and the proposal of countermeasures to dispersion of contaminant. In this presentation we describe the outline of our current activities.
Yoshikawa, Hideki; Iijima, Kazuki; Sasamoto, Hiroshi; Fujiwara, Kenso; Mitsui, Seiichiro; Kitamura, Akira; Kurikami, Hiroshi; Tokizawa, Takayuki; Yui, Mikazu; Nakayama, Shinichi
Materials Research Society Symposium Proceedings, Vol.1518, p.269 - 275, 2013/10
Following the release of radionuclides into the environment as a result of the accident at Fukushima Daiichi Nuclear Power Plant, Japan Atomic Energy Agency (JAEA) had to develop an immediate and effective method of reducing the dose rate received by students in school facilities. A demonstration of a reducing method was carried out by JAEA at a junior high school ground and kindergarten yard in the center of Fukushima-city. Dose rates of the released radionuclides are largely controlled by the ground level contamination and accumulation of mainly cesium-137 (Cs) and cesium-134 (Cs) in populated areas. An effective means of reducing dose rate was to remove the surface soil and to bury it on-site under fresh uncontaminated soil or soil collected under deep depth at the site for shielding. The dose rate at1 m above ground level was reduced from 2.5 Sv/h to 0.15 Sv/h.
Rai, D.*; Yui, Mikazu
JAEA-Technology 2013-002, 35 Pages, 2013/05
The solubility method is one of the most powerful tools to obtain reliable thermodynamic data for (1) solubility products of discrete solids and double salts, (2) complexation constants for various ligands, (3) development of data in a wide range of pH values, (4) evaluation of data for metals that form very insoluble solids (e.g. tetravalent actinides), (5) determining solubility-controlling solids in defferent types of wastes and (6) elevated temperature for redox sensitive systems. This document is focused on describing various aspects of obtaining thermodynamic data using the solubility method. This manuscript deals with various aspects of conducting solubility studies, including selecting the study topic, modeling to define important variables, selecting the range of variables and experimental parameters, anticipating results, general equipment requirements, conducting experiments, and interpreting experimental data.
Tsuda, Hidenori; Walker, C.; Shinkai, Fumiaki*; Kishi, Hirokazu*; Yui, Mikazu
Journal of Nuclear Science and Technology, 49(11), p.1110 - 1113, 2012/11
Fujita, Tomoo; Kawaguchi, Masanao; Walker, C.; Sasamoto, Hiroshi; Yui, Mikazu; Onishi, Yuzo*
Proceedings of 7th Asian Rock Mechanics Symposium (ARMS-7) (USB Flash Drive), p.675 - 681, 2012/10
The Japan Atomic Energy Agency started new grout project for geological disposal of high-level radioactive waste in 2007. This study presented the overall JAEA grout project program and an example of how to apply key engineering technologies to the construction and operation of an underground facility for the geological disposal of HLW.
Sasamoto, Hiroshi; Yui, Mikazu; Takase, Hiroyasu*
Nippon Genshiryoku Gakkai Wabun Rombunshi, 11(3), p.233 - 246, 2012/09
Leachates from cementitious grouting materials used for reducing water-inflow are hyperalkaline and chemically reactive with the engineered barriers and host rock of deep repository of high level radioactive waste. Evaluation methods for long-term alteration of host rock have been developing since the extent of chemical modification may influence the transport and retardation properties of radionuclides in the far-field. Not only conventional Ordinary Portland Cement (OPC) but also low-pH (alkaline) cement (LoAC) has been considered as the grouting material in order to reduce the extent of alteration of host rock. Comparative simulations for long-term alteration of host rock considering both OPC and LoAC grouts are conducted to propose an idea for evaluation of applicability of cementitious grouting materials from view points of reducing uncertainty and conservatism of safety assessment.
Walker, C.; Yui, Mikazu
NEA/RWM/R(2012)3/REV, p.159 - 163, 2012/03
no abstracts in English
Matsui, Hiroya; Mizuno, Takashi; Sasamoto, Hiroshi; Sugihara, Kozo; Yui, Mikazu
Dai-41-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.179 - 184, 2012/01
Japan Atomic Energy Agency has been conducted a contract study with METI (Ministry of Economy, Trade and Industry) called "The project for Grouting Technology Development" since 2008. As a part of the study, the monitoring of groundwater chemistry in a pre-grouted area has been carried out for three and half years after pre-grouting in Mizunami URL. The results suggested that the chemical compositions in groundwater affected by pre-grouting was recovered and the period to recover is evaluated about two years around an underground opening.
Arthur, R. C.*; Sasamoto, Hiroshi; Walker, C.; Yui, Mikazu
Clays and Clay Minerals, 59(6), p.626 - 639, 2011/11
Regarding to geological disposal of high level radioactive waste, long-term evolution of chemical condition in the rock mass by interactions of cementitious grout and rock would be predicted, if the grout is used for reducing the groundwater inflow during construction of drifts. Evolution of chemical condition is important because it could affect the evaluation of radionuclides migration for performance assessment. Zeolite is one of important alteration minerals by interactions of cementitious grout and rock. For evaluation of long-term evolution of chemical condition, it is necessary to develop thermodynamic data for alteration minerals like zeolite. The present paper proposes a revised model to derive more reliable thermodynamic data for zeolite. Additionally, a possibility to apply this revised model on other important alteration minerals is suggested.
Tachi, Yukio; Yotsuji, Kenji; Seida, Yoshimi*; Yui, Mikazu
Geochimica et Cosmochimica Acta, 75(22), p.6742 - 6759, 2011/11
Diffusion and sorption behaviors of Cs, I and HTO in samples of the Wakkanai Formation from Horonobe URL were investigated as a function of ionic strength (IS) of synthetic groundwater by through-diffusion and batch sorption experiments. The values showed cation excess and anion exclusion effects, which were strongly dependent on IS; for Cs decreased as IS increased, for I showed the opposite dependency and for HTO showed no dependence. The Kd values for Cs determined by through-diffusion and batch experiments were in good agreement and decreased with IS as a result of competitive ion exchange. Diffusion and sorption behaviors were interpreted based on the clay-based modeling approach in assuming the clay components of illite and smectite control diffusion and sorption mechanisms. The model predicted the and Kd trends obtained by the series of experiments reasonably well, implying the key contribution of the clay particle and nano-size pore for ionic migration.
Fujita, Tomoo; Taniguchi, Naoki; Matsui, Hiroya; Tanai, Kenji; Maekawa, Keisuke; Sawada, Atsushi; Makino, Hitoshi; Sasamoto, Hiroshi; Yoshikawa, Hideki; Shibata, Masahiro; et al.
JAEA-Research 2011-001, 193 Pages, 2011/03
This report summarizes the progress of research and development on geological disposal during the surface-based investigation phase (2001-2005) in the Horonobe Underground Research Laboratory project, of which aims are to apply the design methods of geological disposal and mass transport analysis to actual geological conditions obtained from the surface-based investigations in the Horonobe Underground Research Laboratory project as an example of actual geological environment.
Ochs, M.*; Tachi, Yukio; Ganter, C.*; Suyama, Tadahiro; Yui, Mikazu
JAEA-Research 2010-052, 59 Pages, 2011/02
For reliable parameter setting in performance assessment of geological disposal, JAEA has developed the integrated sorption and diffusion (ISD) model/database in bentonite systems. The main goal of the mechanistic model/database development is to provide a tool for a consistent explanation, prediction, and uncertainty assessment. This report focuses on developing the thermodynamic sorption model (TSM) including selection of model design and surface species, and on the quantification and handling of model uncertainties, based on illustrating by example of Ni sorption on montmorillonite/bentonite. Two fundamentally different approaches are presented and compared for representing TSM uncertainties: (1) TSM parameter uncertainties based on optimization routines and statistical procedure, (2) overall error estimated by direct comparison of modeled and experimental Kd values. The overall error in Kd is viewed as the best representation of model uncertainty in ISD model/database development.
Tachi, Yukio; Nakazawa, Toshiyuki*; Ochs, M.*; Yotsuji, Kenji; Suyama, Tadahiro; Seida, Yoshimi; Yamada, Norikazu*; Yui, Mikazu
Radiochimica Acta, 98(9-11), p.711 - 718, 2010/11
Diffusion and sorption of radionuclides in compacted bentonite are the key processes in the safe geological disposal. The effects of carbonate and salinity on Np(V) diffusion and sorption in compacted montmorillonite were investigated by experimental and modeling approaches. Effective diffusion coefficients () and distribution coefficients () of Np in montmorillonite compacted to dry density of 800 kg/m were measured under four conditions with different salinities (0.05/0.5 M NaCl) and carbonate concentrations (0/0.01 M NaHCO). The for carbonate-free conditions decreased as salinity increased, and those for carbonate conditions showed the opposite dependency. The decreased by one order of magnitude under high carbonate condition. Diffusion and sorption behaviors were interpreted by coupling the thermodynamic aqueous speciation, the thermodynamic sorption model based on ion exchange and surface complexation, and the diffusion model based on electrical double layer theory in narrow pores. The mechanistic model could be useful in predicting the sorption and diffusion behavior of complex species in compacted systems.
Seida, Yoshimi; Terashima, Motoki; Tachi, Yukio; Iijima, Kazuki; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Yui, Mikazu
Radiochimica Acta, 98(9-11), p.703 - 709, 2010/11
Diffusion and sorption behaviors of Eu in sedimentary rock were investigated in the presence of humic substance in the present study. Sedimentary rock obtained from Horonobe URL test site in Hokkaido, Japan, (accessible pore diameter is around several to several ten nanometer) was used. The Diffusion behaviors of Eu were examined based on reservoir depletion method coupled with analysis of inner distribution of the radioactive elements in the rock. Time sequence of concentration of each radioactive element as well as the humic substance in the reservoir was obtained as a function of concentration and molecular size of humic substance. Coexistence of humic substance reduced the depletion of Eu in the reservoir, indicating complexation between the radioactive elements and the humic substance. On the contrary, obvious decrease of humic substance in the reservoir was not observed in the system. This observation suggests that the radioactive elements became hard to diffuse into the sedimentary rock due to an increase of their size through complexation with the humic substance. The sorption of Eu was reduced with increase of the humic substance although the sorption of the humic substance was not influenced by the existence of Th or Eu. The diffusion and sorption of Eu were found to be reduced in the presence of humic substance.
Kitamura, Akira; Yui, Mikazu
Journal of Nuclear Science and Technology, 47(8), p.760 - 770, 2010/08
Thermodynamic data for palladium(II) in Pd-OH-ClO system were obtained through critical reviews and reinterpretations of literature data using the Bro nsted-Guggenheim-Scatchard Model. The solubility product of palladium(II) hydroxide, the hydrolysis constants of palladium(II), and ion interaction coefficients between palladium(II) species and electrolyte ions were determined with 95% confidence interval. The thermodynamic data thus obtained help accurately predict the solubility limiting concentrations of palladium(II) as a function of hydrogen ion concentration in dilute to relatively concentrated solutions.
Yui, Mikazu; Ishikawa, Hirohisa; Watanabe, Atsuo*; Yoshino, Kyoji*; Umeki, Hiroyuki; Hioki, Kazumasa; Naito, Morimasa; Seo, Toshihiro; Makino, Hitoshi; Oda, Chie; et al.
JAEA-Research 2010-015, 106 Pages, 2010/05
This report summarizes the activity of Phase I of Waste Management Working Group of the United States - Japan Joint Nuclear Energy Action Plan started in 2007. The working group focused on consolidation of the existing technical basis between the U.S. and Japan and the joint development of a plan for future collaborative activities. Firstly, the political/regulatory frameworks related to nuclear fuel cycles in both countries were reviewed. The various advanced fuel cycle scenarios in both countries were surveyed and summarized. Secondly, the waste management/disposal system optimization was discussed. Repository system concepts for the various classifications of nuclear waste were reviewed and summarized, then disposal system optimization processes and techniques were reviewed, and factors to consider in future repository design optimization activities were also discussed. Finally the potential collaboration areas and activities related to the optimization problem were extracted.