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Iijima, Kazuki; Shoji, Yoshiyuki*; Tomura, Tsutomu*
Radiochimica Acta, 96(9-11), p.721 - 730, 2008/00
Times Cited Count：10 Percentile：55.82(Chemistry, Inorganic & Nuclear)Distribution coefficients of Am onto bentonite colloid were evaluated under weak basic and low ionic strength conditions, in taking the influence of Am colloid into account. The obtained values are larger than those obtained for larger montmorillonite particles in literatures. It is attributed to one order of magnitude higher reactive site density of the bentonite colloid. Applicability of a relatively simple and generalized mechanistic sorption model to the bentonite colloid is also discussed.
Mihara, Morihiro; Sasaki, Ryoichi; Kamei, Gento
no journal, ,
Japan Atomic Energy Agency and The Federation of Electric Power Companies of Japan have published the second progress report on research and development for TRU (long-lived) waste disposal in Japan. This report is important to promote the establishment of a regulatory framework and an implementation body for TRU waste disposal in Japan. A deep geological underground disposal with cementitious filler and bentonite buffer for a part of this waste was considered to isolate the waste from the biosphere over the long-term. In this safety assessment of the repository, radionuclides migration datasets were needed. The solubilities, diffusion coefficients and sorption coefficients of radionuclides for cementitious filler and compacted bentonite buffer are some of the important parameters. These datasets were developed considering the long-term chemical evolutions of engineered barriers and variation of ground water type under the reducing condition.
Mizuno, Takashi; Milodowski, A. E.*; Iwatsuki, Teruki
no journal, ,
no abstracts in English
Ota, Kunio
no journal, ,
no abstracts in English
Iijima, Kazuki; Shoji, Yoshiyuki; Tomura, Tsutomu*
no journal, ,
Sorption behavior of Am onto bentonite colloid was investigated. Distribution coefficient of Am was evaluated taking account for the existence of Am colloid. Obtained values were larger than those obtained with larger bentonite particles included in the JNC-SDB. In the acid-base titration, bentonite colloid shows larger edge site density than larger bentonite particles. In the calculation by sorption model assuming ion exchange and surface complexation, similar distribution coefficient was obtained at pH 8 with this edge site density. Based on these results, it is considered that larger distribution coefficient of bentonite colloid is due to the higher edge site density, which is dominant for the Am sorption.
Ochs, M.*; Kunze, S.*; Yui, Mikazu; Sasamoto, Hiroshi
no journal, ,
JAEA has been developing generic methodologies using the generic type of underground research laboratory (URL). In order to develop a practical method for mass transport analysis, it is important to evaluate the application of method to an actual geological environment. Kd is the one of important parameter for mass transport analysis, thus the present study discusses the practical method to derive the Kd for some important radionuclides at the environment of Horonobe URL using the sorption database. As a first step, the present study has been conducted (1) to design the experimental program to be conducted in the Horonobe URL, and to (2) test the usefulness of and identify important gaps in the existing database. The sorption database was applied to an initial prediction of the sorption of Cs, Np, Th, and Se under expected URL-conditions. Kd-derivation was done using the estimation methods discussed in Ochs et al, (2006). This preliminary exercise in Kd-setting allowed to estimate the magnitude of sorption under the expected in-situ conditions. More importantly, it also allowed to identify critical gaps in the existing database and process understanding.
Kozai, Naofumi; Suzuki, Yoshinori; Nankawa, Takuya; Sakamoto, Fuminori; Onuki, Toshihiko; Francis, A. J.
no journal, ,
One of the biomolecules at the cell surface of bacteria to bind uranium is protein. To clarify adsorption mechanism of uranium on protein, this study investigated the adsorption of uranium (VI) on protein by use of silica particles modified with a cell surface protein, protein A. Unmodified silica particles (Si-OH) and the silica particles on which one kind of the following functional groups, -COOH, -NH
, and -OPO
H, was fixed were also used as reference. The adsorption pf uranyl ions on the silica particles modified with amino group and phosphoric group are the greatest. The sorption behavior of uranyl ions on silica particles modified with protein A was similar to those on the silica particles modified with amino group and phosphoric group. However, because the content of phosphoric group in protein A is low, amino group is thought to be the major adsorption site of uranyl ions on the protein A-modified particles.
Onuki, Toshihiko; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.
no journal, ,
In this study, we carried out experiments and model analysis of the transformation of Pu(VI) in a mixture of a common soil bacterium, Bacillus subtilis, and clay (kaolinite). A simplified kinetic model was proposed to describe the association of Pu with the mixture. In the model Pu(VI) and Pu(V) are assumed to be adsorbed on B. subtilis and kaoloinite. Pu(VI) is reduced to Pu(V) only in the solution because of simplification of the model, even though the reduction of Pu(VI) is actually occurred in solution, on B. subtilis and kaoloinite. Comparison of model estimation with experimental results suggest that kinetic simple model described the association of Pu(VI) with the mixture, and suggested that reduction of Pu(V) to Pu(IV) was mainly proceeded on the surface of B. subtilis in the mixture.
Suzuki, Yoshinori; Nankawa, Takuya; Francis, A. J.; Onuki, Toshihiko
no journal, ,
We investigated the redox behavior of Ce(IV)/Ce(III) in the presence of organic acids by cyclic voltammetry and column electrolysis. In the presence of malic, citric acid, NTA, or DFO, the redox potentials of Ce(IV)/Ce(III) were much lower than the standard redox potential of that, indicating that Ce(IV) was stabilies by complexation with these organic acids comparing to Ce(III). We determined the redox reaction of Ce-NTA and Ce-DFO complexes from the pH and the concentration of organic acid dependences of the redox potential.
exposed by uranium(VI)Sakamoto, Fuminori; Nankawa, Takuya; Onuki, Toshihiko; Francis, A. J.
no journal, ,
Yeast is known to accumulate U(VI). This suggests that yeast may be utilized as bisorbents for removing U from U mine tailings wastewater. It is reported that cell surface sorption, extracellular accumulation and intracellular accumulation are predominant processes in the biosorption by yeast. It is suggested that some proteins function important role for biosorption. In the present study, we explored the proteins expressed by exposure of yeast to U(VI) solutions of different concentrations. As the concentration of U increase, some proteins are gradually expressed. These proteins are TPI1 and SOD1 proteins. TPI1 protein is related to glycolytic pathway and catalyzes the reversible interconversion of glyceraldehyde 3-phosphate and dihydroxyacetone phospate. SOD1 protein catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide. These results indicate that SOD protein and some enzymes in the system of glycolytic pathway are related with U accumulation by S. cerevisiae.
