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Journal Articles

Simulation code for estimating external gamma-ray doses from a radioactive plume and contaminated ground using a local-scale atmospheric dispersion model

Satoh, Daiki; Nakayama, Hiromasa; Furuta, Takuya; Yoshihiro, Tamotsu*; Sakamoto, Kensaku

PLOS ONE (Internet), 16(1), p.e0245932_1 - e0245932_26, 2021/01

 Times Cited Count:2 Percentile:32.89(Multidisciplinary Sciences)

In this study, we developed a simulation code named SIBYL, which estimates external gamma-ray doses at ground level from radionuclides distributed nonuniformly in atmosphere and on ground. SIBYL can combine with the local-scale atmospheric dispersion model LOHDIM-LES, and calculate the dose distributions according to the map of the activity concentrations simulated by LOHDIM-LES. To apply the SIBYL code to emergency responses of nuclear accidents, the time-consuming three-dimensional radiation transport simulations were performed in advance using the general-purpose Monte Carlo code PHITS, and then the results were compiled to the database for the SIBYL's dose calculations. Moreover, SIBYL can consider the dose attenuation by obstacles and the changes of terrain elevations. To examine the accuracy of SIBYL, typical five cases including $$^{85}$$Kr emission from a ventilation shaft and $$^{137}$$Cs dispersion inside urban area were investigated. The results of SIBYL agreed within 10% with those of PHITS at the most of target locations. Furthermore, the calculation speed was approximately 100 times faster than that of PHITS.

Journal Articles

Proton-exchange mechanism of specific Cs$$^{+}$$ adsorption $$via$$ lattice defect sites of Prussian blue filled with coordination and crystallization water molecules

Ishizaki, Manabu*; Akiba, Sae*; Otani, Asako*; Hoshi, Yuji*; Ono, Kenta*; Matsuba, Mayu*; Togashi, Takanari*; Kanaizuka, Katsuhiko*; Sakamoto, Masatomi*; Takahashi, Akira*; et al.

Dalton Transactions, 42(45), p.16049 - 16055, 2013/12

 Times Cited Count:165 Percentile:99.56(Chemistry, Inorganic & Nuclear)

We have revealed the fundamental mechanism of specific Cs$$^{+}$$ adsorption into Prussian blue (PB) in order to develop high-performance PB-based Cs$$^{+}$$ adsorbents in the wake of the Fukushima nuclear accident. We compared two types of PB nanoparticles with formulae of Fe$$^{III}$$$$_{4}$$[Fe$$^{II}$$(CN)$$_{6}$$]3$$cdot$$xH$$_{2}$$O (x = 10-15) (PB-1) and (NH$$_{4}$$)0.70Fe$$^{III}$$1.10[Fe$$^{II}$$(CN)$$_{6}$$]$$cdot$$1.7H$$_{2}$$O (PB-2) with respect to the Cs$$^{+}$$ adsorption ability. The synthesised PB-1, by a common stoichiometric aqueous reaction between 4Fe$$^{3+}$$ and 3[Fe$$^{II}$$(CN)$$_{6}$$]$$^{4-}$$, showed much more efficient Cs$$^{+}$$ adsorption ability than did the commercially available PB-2.

Journal Articles

Yeast genes involved in uranium tolerance and uranium accumulation; A Functional screening using the nonessential gene deletion collection

Sakamoto, Fuminori; Nankawa, Takuya; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*

Geomicrobiology Journal, 29(5), p.470 - 476, 2012/05

 Times Cited Count:6 Percentile:17.47(Environmental Sciences)

We screened 4908 non-essential gene deletion mutant yeast strains for uranium sensitivity and low accumulation by growth in agar medium containing uranium. All mutant strains grew successfully on agar media containing 0 or 0.5 mM uranium for one week at 30 centigrade. Thirteen strains with single gene deletions showed reduced growth in the agar medium containing 0.5 mM uranium and were identified as uranium-sensitive mutant strains. The phosphate transporter genes of PHO86, PHO84, PHO2, and PHO87 were among the deleted genes in the uranium-sensitive mutant strains, suggesting that genes concerned with phosphate transport contribute to uranium tolerance. Seventeen single-deletion strains showed lower uranium accumulation than the wild-type after exposure to agar medium containing 0.5 mM uranium, and were identified as mutant strains with low uranium accumulation.

JAEA Reports

Evaluation of fundamental performance of JAEA's new supercomputer system

Sakamoto, Kensaku; Shimizu, Futoshi; Tsuruoka, Takuya*; Nemoto, Toshiyuki*; Ishikawa, Naota*

JAEA-Testing 2011-005, 88 Pages, 2011/11

JAEA-Testing-2011-005.pdf:5.16MB

A new supercomputer system was deployed at JAEA in March 2010. The system is mainly composed of a large scale Linux cluster system (PRIMERGY BX900: 200Tflops) and a lead off system of RIKEN's K computer (FX1: 12Tflops), whose purposes are to deliver a high-performance parallel computing environment and application code development environment for the K computer, respectively. In this report, we present results of the evaluation of fundamental performance of the system.

Journal Articles

Detection and activity of iodine-131 in brown algae collected in the Japanese coastal areas

Morita, Takami*; Niwa, Kentaro*; Fujimoto, Ken*; Kasai, Hiromi*; Yamada, Haruya*; Nishiuchi, Ko*; Sakamoto, Tatsuya*; Godo, Waichiro*; Taino, Seiya*; Hayashi, Yoshihiro*; et al.

Science of the Total Environment, 408(16), p.3443 - 3447, 2010/06

 Times Cited Count:13 Percentile:33.13(Environmental Sciences)

Iodine-131 ($$^{131}$$I) was detected in brown algae collected off the Japanese coast. The maximum measured specific activity of $$^{131}$$I in brown algae was 0.37$$pm$$0.010 Bq/kg-wet. Cesium-137 ($$^{137}$$Cs) was also detected in all brown algal samples used in this study. There was no correlation between specific activities of $$^{131}$$I and $$^{137}$$Cs in these seaweeds. Low specific activity and minimal variability of $$^{137}$$Cs in brown algae indicated that past nuclear weapon tests were the source of $$^{137}$$Cs. Although nuclear power facilities are known to be pollution sources of $$^{131}$$I, there was no relationship between the sites where $$^{131}$$I was detected and the locations of nuclear power facilities. Most of the sites where $$^{131}$$I was detected were near big cities with large populations. On the basis of the results, we suggest that the likely pollution source of $$^{131}$$I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures.

Journal Articles

Association of actinides with microorganisms and clay; Implications for radionuclide migration from waste-repository sites

Onuki, Toshihiko; Kozai, Naofumi; Sakamoto, Fuminori; Ozaki, Takuo; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.*

Geomicrobiology Journal, 27(3), p.225 - 230, 2010/04

 Times Cited Count:16 Percentile:21.61(Environmental Sciences)

The recent research results on the interation of heavy-elements and microorganisms are shown. (1) Adsorption of Pu(IV), Th(IV) and Eu(III)-DFO complexes on bacteria, (2) Biodegradation of Eu(III) in the presence of malic acids.

Journal Articles

Modeling of the interaction of Pu(VI) with the mixture of microorganism and clay

Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.*

Journal of Nuclear Science and Technology, 46(1), p.55 - 59, 2009/01

 Times Cited Count:8 Percentile:49.6(Nuclear Science & Technology)

Model analysis of the transformation of Pu(VI) in a mixture of a common soil bacterium, Bacillus subtilis, and kaolinite clay was carried out. When we assumed in the model analysis that reduction rate of Pu(V) to Pu(IV) was higher on B. subtilis than on kaolinite, the estimated fractions of Pu in the solution and in the mixture, oxidation states of Pu in the solution and in the mixture were in good agreement with the measured ones. On the contrary, assumption that reduction rate of Pu(V) to Pu(IV) was the same on kaolinite as on ${it B. subtilis}$ gave wrong prediction of Pu association with the mixture. These results strongly suggested the electron transfer from the bacteria to Pu(V) on the bacterial cell to be reduced to Pu(IV) during the accumulation of Pu(VI) to the mixture.

Journal Articles

Concurrent transformation of Ce(III) and formation of biogenic manganese oxides

Onuki, Toshihiko; Ozaki, Takuo; Kozai, Naofumi; Nankawa, Takuya; Sakamoto, Fuminori; Sakai, Takuro; Suzuki, Yoshinori; Francis, A. J.*

Chemical Geology, 253(1-2), p.23 - 29, 2008/07

 Times Cited Count:27 Percentile:54.22(Geochemistry & Geophysics)

We examined the changes in the chemical states of Ce(III) during the formation of manganese oxide occasioned by Mn(II)-oxidizing bacteria. The oxidation states of Ce and Mn then were measured by X-ray Absorption Near Edge Structure (XANES). We also determined the elemental distributions in the bacteria and precipitates by Scanning-Proton Induced X-ray Emission (S-PIXE). We found that the precipitation of Ce is preceded by its accumulation by the bacterium, followed by its oxidization to Ce(IV) by the Mn(III, IV)-containing precipitates that the bacteria generate.

Journal Articles

Protein expression of ${it Saccharomyces cerevisiae}$ in response to uranium exposure

Sakamoto, Fuminori; Nankawa, Takuya; Kozai, Naofumi; Fujii, Tsutomu*; Iefuji, Haruyuki*; Francis, A. J.; Onuki, Toshihiko

Journal of Nuclear and Radiochemical Sciences, 8(2), p.133 - 136, 2007/10

Protein expression of ${it Saccharomyces cerevisiae}$ grown in the medium containing $$^{238}$$U(VI) and $$^{233}$$U(VI) was examined by two-dimensional gel electrophoresis. ${it S. cerevisiae}$ of BY4743 was grown in medium containing $$^{238}$$U of 0, 2.0, and 5.0 $$times$$ 10$$^{-4}$$ M or $$^{233}$$U of 2.5 $$times$$ 10$$^{-6}$$ (radioactivity was higher by 350 times than 2.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U) and 5.0 $$times$$ 10$$^{-6}$$ M for 112 h at 30$$^{circ}$$C. The growths of the yeast grown in the above media were in the following order: control $$>$$ 2.5 $$times$$ 10$$^{-6}$$ M $$^{233}$$U $$>$$ 2.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U $$>$$ 5.0 $$times$$ 10$$^{-6}$$ M $$^{233}$$U $$>$$ 5.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U. This result indicated that not only radiological but also chemical effect of U reduced the growth of the yeast. The concentrations of U in the medium containing $$^{238}$$U or $$^{233}$$U decreased, suggesting U accumulation by the yeast cells. The 2-D gel electrophoresis analysis showed the appearance of several spots after exposure to $$^{238}$$U or to $$^{233}$$U but not in the control containing no uranium. These results show that the yeast cells exposed to U express several specific proteins.

Journal Articles

Chemical speciation and association of plutonium with bacteria, kaolinite clay, and their mixture

Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Suzuki, Yoshinori*; Francis, A. J.

Environmental Science & Technology, 41(9), p.3134 - 3139, 2007/05

 Times Cited Count:30 Percentile:57.2(Engineering, Environmental)

We investigated the interactions of Pu(VI) with Bacillus subtilis, kaolinite clay, and a mixture of the two to determine and delineate the role of the microbes in regulating the environmental mobility of Pu. The amount of Pu sorbed by B. subtilis increased with time, but had not reached equilibrium in 48 h, whereas equilibrium was attained in kaolinite within 8 h. After 48 h, the oxidation state of Pu in the solutions exposed to B. subtilis and the mixture had changed to Pu(V), whereas the oxidation state of Pu associated with B. subtilis and the mixture was Pu(IV). In contrast, there was no change in the oxidation state of Pu in the solution or on kaolinite after exposure to Pu(VI). SEM-EDS analysis indicated that most of the Pu in the mixture was associated with B. subtilis. These results suggest that Pu(IV) is preferably sorbed to bacterial cells in the mixture, and that Pu(VI) is reduced to Pu(V) and Pu(IV).

JAEA Reports

Development of module for TRU high temperature chemistry (Joint research)

Minato, Kazuo; Akabori, Mitsuo; Tsuboi, Takashi; Kurobane, Shiro; Hayashi, Hirokazu; Takano, Masahide; Otobe, Haruyoshi; Misumi, Masahiro*; Sakamoto, Takuya*; Kato, Isao*; et al.

JAERI-Tech 2005-059, 61 Pages, 2005/09

JAERI-Tech-2005-059.pdf:20.67MB

An experimental facility called the Module for TRU High Temperature Chemistry (TRU-HITEC) was installed in the Back-end Cycle Key Elements Research Facility (BECKY) of the Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF) for the basic studies of the behavior of the transuranium elements (TRU) in pyrochemical reprocessing and oxide fuels. TRU-HITEC consists of three alpha/gamma cells shielded by steel and polyethylene and a glove box shielded by leaded acrylic resin, where experimental apparatuses have been equipped and a high purity argon gas atmosphere is maintained. In the facility 10 g of $$^{241}$$Am as well as the other TRU of Np, Pu and Cm can be handled. This report summarizes the outline, structure, performance and interior apparatuses of the facility, and is the result of the joint research between the Japan Atomic Energy Research Institute and three electric power companies of Tokyo Electric Power Co., Tohoku Electric Power Co. and the Japan Atomic Power Co.

Journal Articles

A Continuous flow system for in-situ XANES measurements of change in oxidation state of Ce(III) to Ce(IV)

Onuki, Toshihiko; Yoshida, Takahiro*; Nankawa, Takuya; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Suzuki, Yoshinori*; Francis, A. J.*

Journal of Nuclear and Radiochemical Sciences, 6(1), p.65 - 67, 2005/07

no abstracts in English

Oral presentation

Mechanism of Pu(VI) association with a mixture of bacterium and kaolinite clay

Onuki, Toshihiko; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Yoshida, Takahiro*; Suzuki, Yoshinori*; Francis, A. J.*

no journal, , 

no abstracts in English

Oral presentation

Interactions of heavy elements with microorganisms

Yoshida, Takahiro*; Ozaki, Takuo; Sakamoto, Fuminori; Kozai, Naofumi; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.*; Onuki, Toshihiko

no journal, , 

no abstracts in English

Oral presentation

Microbial impacts on the environmental behavior of actinides

Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Sakamoto, Fuminori; Kozai, Naofumi; Nankawa, Takuya; Suzuki, Yoshinori*; Francis, A. J.*

no journal, , 

no abstracts in English

Oral presentation

Mechanism of U(VI) accumulation by yeast; Contribution of protein

Onuki, Toshihiko; Kozai, Naofumi; Sakamoto, Fuminori; Ozaki, Takuo; Nankawa, Takuya; Suzuki, Yoshinori; Iefuji, Haruyuki*; Francis, A. J.

no journal, , 

no abstracts in English

Oral presentation

Microbial impacts on the migration of actinides

Ozaki, Takuo; Nankawa, Takuya; Kozai, Naofumi; Sakamoto, Fuminori; Suzuki, Yoshinori; Francis, A. J.

no journal, , 

The interaction of actinides with microorganisms has been extensively studied to elucidate migration behavior of actinides in the environments. However, the mechanisms of interaction of microorganisms and actinides are poorly understood. We have been conducting basic on microbial accumulation of actinides in order to elucidate the environmental behavior of actinides under relevant conditions. Effect of desferrioxamine B (DFO) on the sorption of Pu(IV), Th(IV) and Eu(III) (analog for Am(III)) on Pseudomonas fluorescens was studied. In the presence of DFO the sorption of Pu(IV), Th(IV) and Eu(III) on the cells increased with a decrease in pH from 7 to 4. In contrast, without DFO most of Pu(IV), Th(IV) and Eu(III) were precipitated from solution. Adsorption of DFO on the cells was negligible in the solution with and without metals. Adsorption of Pu(IV), Th(IV) and Eu(III) on P. fluorescens cells decreased in the order Eu(III) $$>$$ Th(IV) $$>$$ Pu(IV), which corresponds to increasing stability constant of the DFO complexes. These results indicate that Th(IV), Pu(IV) and Eu(III) dissociate when in contact with cells, after which the metals are adsorbed. Mechanism of uranium(VI) mineralization by the yeast Saccharomyces cerevisia e was examined by batch experiment at pH 3.2. FESEM-EDS, TEM, and visible diffuse reflectance spectrometry revealed the formation of H-autunite, HUO$$_{2}$$PO$$_{4}$$ $$cdot$$ 4H$$_{2}$$O on the yeast cells. Thermodynamic calculations suggest that the chemical compositions of the solutions were undersaturated with respect to H-autunite, but were supersaturated with ten-times more U(VI) and P than were actually observed. Apparently, the sorbed U(VI) on the cell surfaces reacts with Preleased from the yeast to form H-autunite by local saturation. These findings indicate that the yeast's cell surfaces, rather than the bulk solution, offer the specific conditions for this geochemical process. We studied the effect of Eu(III) on the degradation o

Oral presentation

Microbial impacts on the migration of actinides; Effects of exudates on the migration

Onuki, Toshihiko; Ozaki, Takuo; Yoshida, Takahiro*; Nankawa, Takuya; Kozai, Naofumi; Sakamoto, Fuminori; Suzuki, Yoshinori*; Francis, A. J.

no journal, , 

We have been conducting basic studies on the microbial accumulation of actinides in order to understand the environmental behavior of actinides under relevant conditions. The effect of bacterial exudates on the sorption of Eu(III) and Cm(III) by Chlorella vulgaris was studied by a batch method. The pH dependence of log Kd of Eu(III) and Cm(III) for cellulose, major component of C. vulgaris cell, differed from that for C. vulgaris. However, thelog Kd of Eu(III) and Cm(III) for cellulose in the solution containing exudates from C. vulgaris cells in a 0.5% NaCl solution showed a similar pH dependence to that by C. vulgaris. These results suggests that exudates affect on the sorption of Eu(III) and Cm(III) on C. vulgaris.

Oral presentation

Adsorption of uranium(VI) on silica particles modified with protein

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$$_{2}$$, and -OPO$$_{3}$$H$$_{2}$$, 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.

Oral presentation

Modeling of the interaction of Pu(VI) with the mixture of microorganism and clay

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.

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