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Journal Articles

Speciation of cesium in tree tissues and its implication for uptake and translocation of radiocesium in tree bodies

Tanaka, Kazuya; Kanasashi, Tsutomu*; Takenaka, Chisato*; Takahashi, Yoshio*

Science of the Total Environment, 755(Part 2), p.142598_1 - 142598_8, 2021/02

In this study, we investigated coordination structures of Cs in $$^{133}$$Cs-doped bark, sapwood, heartwood, needle, and branch samples of trees collected in Fukushima by extended X-ray absorption fine structure (EXAFS) spectroscopy. We examined four representative tree species in Fukushima, ${it Cryptomeria japonica}$, ${it Pinus densiflora}$, ${it Quercus serrata}$, and ${it Eleutherococcus sciadophylloides}$. EXAFS spectra suggested that Cs was adsorbed as an outer-sphere complex on all parts of the four species, with electrostatic binding to negatively charged functional groups in components of tree tissues. These results were supported by extraction experiments where most of the sorbed Cs was desorbed from all parts of each tree species using 1 M CH$$_{3}$$COONH$$_{4}$$.

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:86 Percentile:0.14(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Application of M$$_{V}$$-edge XANES to determination of U oxidation state in zircon

Tanaka, Kazuya; Takahashi, Yoshio*

Geochemical Journal, 53(5), p.329 - 331, 2019/00

 Times Cited Count:0 Percentile:100(Geochemistry & Geophysics)

We examined three natural zircon samples with different amounts of radiation doses using M$$_{V}$$-edge and L$$_{III}$$-edge U X-ray absorption near-edge structure (XANES). Analysis of XANES spectra at both M$$_{V}$$-edge and L$$_{III}$$-edge suggested that the oxidation state of U in the zircon sample with the highest radiation dose is tetravalent. The XANES spectra of the two other samples with lower radiation doses suggested a mixture of U(IV) and U(VI), while the possibility of U(V) was not excluded. This is the first work on the application of M$$_{V}$$-edge U XANES to the oxidation state of U in natural zircon.

Journal Articles

Mineralogical control of the size distribution of stable Cs and radiocesium in riverbed sediments

Tanaka, Kazuya; Watanabe, Naoko*; Yamasaki, Shinya*; Sakaguchi, Aya*; Fan, Q.*; Takahashi, Yoshio*

Geochemical Journal, 52(2), p.173 - 185, 2018/00

 Times Cited Count:4 Percentile:49.66(Geochemistry & Geophysics)

We analyzed riverbed sediments collected at two sites, Yamakiya and Kuroiwa, in Fukushima after the Fukushima accident. The size distributions of K, Rb, and $$^{133}$$Csreflected the mineralogy of sediments, where primary host minerals for these alkali elements would be biotite, K-feldspar, and clay minerals. Silt-size fractions contained high $$^{133}$$Cs and $$^{137}$$Cs concentrations possibly due to adsorption on clay minerals. Their concentrations decreased with particle size at the Yamakiya site. In contrast, coarse and very coarse sand fractions from the Kuroiwa site showed higher $$^{133}$$Cs and $$^{137}$$Cs concentrations in comparison to fine - medium sand fractions. The coarse sand fractions contained many weathered biotite grains. Overall, the size distributions of $$^{133}$$Cs and $$^{137}$$Cs were similar in the sediments, suggesting that the Fukushima-derived radiocesium was distributed into each particle size fraction in response to the distribution of the stable Cs that was controlled by mineralogical composition.

Journal Articles

Estimation of desorption ratios of radio/stable caesium from environmental samples (aerosols and soils) leached with seawater, diluted seawater and ultrapure water

Sakaguchi, Aya*; Chiga, Haruka*; Tanaka, Kazuya; Tsuruta, Haruo*; Takahashi, Yoshio*

Geochemical Journal, 52(2), p.187 - 199, 2018/00

 Times Cited Count:6 Percentile:34.53(Geochemistry & Geophysics)

An aerosol sample collected on the 15th of March 2011 at Kawasaki City (Kanagawa) was sequentially leached with seawater for 30 days. As a result, about 60% of the total $$^{137}$$Cs was extracted. In addition, a surface soil sample collected from Kawamata Town (Fukushima) two months after the Fukushima accident, was leached for 223 days with a natural seawater, a 1:1 mixture of ultrapure water and seawater, and ultrapure water. Eventually, more than 15% of the total $$^{137}$$Cs in the surface soil sample was efficiently desorbed by seawater leaching. In comparison, about 9% of the total $$^{137}$$Cs was leached with 1:1 diluted seawater and less than 1% of the total $$^{137}$$Cs was leached with ultrapure water over the 223 days. Overall, $$^{133}$$Cs and $$^{137}$$Cs showed similar leaching behaviour.

Journal Articles

Discovery of radiocesium-bearing microparticles in river water and their influence on the solid-water distribution coefficient ($$K_{rm d}$$) of radiocesium in the Kuchibuto River in Fukushima

Miura, Hikaru*; Kurihara, Yuichi*; Sakaguchi, Aya*; Tanaka, Kazuya; Yamaguchi, Noriko*; Higaki, Shogo*; Takahashi, Yoshio*

Geochemical Journal, 52(2), p.145 - 154, 2018/00

 Times Cited Count:20 Percentile:4.59(Geochemistry & Geophysics)

Solid-water distribution coefficient ($$K_{rm d}$$) of radiocesium in rivers is apparently increased due to the possible presence of highly radioactive radiocesium-bearing microparticles (CsMPs) in the solid phase. In this study, we evaluated the contribution of CsMPs to apparent Kd values. The ratio of the radioactivity of the separated CsMPs to the total radiocesium on fluvial suspended particles ranged from 0 to 46%. This means that the existence of CsMPs in fluvial suspended partcles did not change apparent Kd values in order magnitude.

Journal Articles

Discovery of ion-adsorption type deposits of rare earth elements (REE) in Southwest Japan with speciation of REE by extended X-ray absorption fine structure spectroscopy

Yamaguchi, Akiko*; Honda, Tasuku*; Tanaka, Masato*; Tanaka, Kazuya; Takahashi, Yoshio*

Geochemical Journal, 52(5), p.415 - 425, 2018/00

 Times Cited Count:3 Percentile:59.14(Geochemistry & Geophysics)

Ion-adsorption type REE deposits in weathered granite are main sources of REE essential for high-technology industries. However, these type deposits have not been searched in Japan. In this study, Bulk REE abundances (= REE$$_{TOT}$$), ion-exchangeable REE (= REE$$_{EX}$$) by ammonium chloride solution, and percentage of REE$$_{EX}$$ relative to REE$$_{TOT}$$ (= REE$$_{PER}$$) in fresh and weathered granite samples in Southwest Japan (i.e., Hiroshima and Shimane Prefectures) were determined. The REE$$_{TOT}$$ and REE$$_{PER}$$ were comparable to those of ion-adsorption type REE deposits in China. Extended X-ray adsorption fine structure (EXAFS) spectra of REE in original samples and samples after the extraction of ion-exchangeable REE showed that (i) REE in samples with high REE$$_{PER}$$ mainly forms outer-sphere complexes and (ii) the remaining REE in the rocks after the extraction forms inter-sphere complexes.

Journal Articles

Comparison of solid-water partitions of radiocesium in river waters in Fukushima and Chernobyl Areas

Takahashi, Yoshio*; Fan, Q.*; Suga, Hiroki*; Tanaka, Kazuya; Sakaguchi, Aya*; Takeichi, Yasuo*; Ono, Kanta*; Mase, Kazuhiko*; Kato, Kenji*; Kanivets, V. V.*

Scientific Reports (Internet), 7(1), p.12407_1 - 12407_11, 2017/09

 Times Cited Count:12 Percentile:33.26(Multidisciplinary Sciences)

We focused on factors controlling partition of radiocesium on particulate matters and sediments in rivers of Fukushima and Chernobyl. Radiocesium is more soluble in the Pripyat River (Chernobyl) due to weaker interaction of radiocesium with clay minerals caused by the inhibition effect of the adsorbed humic substances. In contrast, particulate matters and sediments in the Kuchibuto River (Fukushima) display high adsorption affinity with lesser inhibition effect of adsorbed humic substances. This difference is possibly governed by the geology and soil type of provenances surrounding both catchments.

Journal Articles

Ligand exchange adsorption and coordination structure of Pd on $$delta$$-MnO$$_{2}$$ in NaCl solution

Tanaka, Kazuya; Tanaka, Masato*; Watanabe, Naoko*; Tokunaga, Kohei*; Takahashi, Yoshio*

Chemical Geology, 460, p.130 - 137, 2017/06

 Times Cited Count:4 Percentile:63.01(Geochemistry & Geophysics)

Pd is highly accumulated in ferromanganese nodules and crusts relative to its concentration in seawater but the mechanism by which Pd(II) is incorporated remains poorly understood. We investigated the local coordination structure of Pd(II) adsorbed on $$delta$$-MnO$$_{2}$$, using X-ray absorption fine structure spectroscopy. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses indicated that Pd was adsorbed on $$delta$$-MnO$$_{2}$$ through ligand exchange, from Cl coordination to O coordination. Furthermore, curve fitting of EXAFS spectra demonstrated the formation of two different inner-sphere complexes, bidentate-mononuclear and bidentate-binuclear complexes, and this finding was supported by density functional theory calculations. The formation of inner-sphere complexes is reasonable given the relatively large distribution coefficients obtained from adsorption experiments.

Journal Articles

Development of methods for recovering uranium from sludge-like uranium generated in decontamination of metal wastes

Ohashi, Yusuke; Tanaka, Yoshio; Tsunashima, Yasumichi; Ikeda, Yasuhisa*

Journal of Nuclear Science and Technology, 54(3), p.382 - 390, 2017/03

 Times Cited Count:5 Percentile:31.96(Nuclear Science & Technology)

Sludge-like uranium wastes (SUWs) have been generated with neutralization of acidic aqueous solutions used for decontamination of metal wastes containing a large amount of iron. We have examined the method for recovering uranium from such SUWs using ${{it N-cyclohexyl}}$-2-pyrrolidone (NCP) as a precipitate. As a result, it was found that precipitation ratios (PRs) of uranium in the solutions prepared by dissolving SUWs in HNO$$_{3}$$ is 97.7% at [NCP]/[U(VI)] = 20, and that the PRs of iron, aluminum, fluorine, and sulfate species are less than 1%. This indicates that uranium species are precipitated selectively. The content ratios of U, Fe, Ca, F, and S in the materials after calcining precipitates obtained at [NCP]/[U(VI)] = 20 were in accordance with the conditions of uranium ore concentrate. From these results, it is expected that highly purified uranium can be efficiently recovered from SUWs by using NCP as the precipitant.

Journal Articles

Applicability of polyvinylpolypyrrolidone adsorbent to treatment process of wastes containing uranium

Ohashi, Yusuke; Harada, Masayuki*; Asanuma, Noriko*; Ando, Shion; Tanaka, Yoshio; Ikeda, Yasuhisa*

Journal of Radioanalytical and Nuclear Chemistry, 311(1), p.491 - 502, 2017/01

 Times Cited Count:1 Percentile:80.48(Chemistry, Analytical)

In order to assess the feasibility of method for recovering U from wastes containing uranium (scrap uranium) using polyvinylpolypyrrolidone (PVPP) adsorbent, we have examined the adsorption and desorption behavior of metal species in HCl aqueous solutions dissolving scrap uranium. It was found that the U(VI) species are selectively adsorbed onto PVPP regardless of the presence of a large amount of Na(I) and Al(III), that the adsorbed U(VI) species are desorbed from PVPP column selectively by water. Pure uranium was efficiently recovered from the eluates. From these results, the PVPP resin is expected to be used as the adsorbent in the treatment process of scrap uranium.

Journal Articles

Simultaneous recovery and separation of rare earth elements in ferromanganese nodules by using ${{it Shewanella putrefaciens}}$

Fujimoto, Jun*; Tanaka, Kazuya; Watanabe, Naoko*; Takahashi, Yoshio*

Hydrometallurgy, 166, p.80 - 86, 2016/12

 Times Cited Count:4 Percentile:63.57(Metallurgy & Metallurgical Engineering)

We examined recovery of REEs in Fe-Mn nodules by using ${{it Shewanella putrefaciens}}$ (Fe-reducing bacterium). In this method, Fe-Mn nodule decomposition and REE recovery were achieved simultaneously in a single solution system. Fe-Mn nodules were reductively decomposed in NaCl solution under anaerobic conditions with daily addition of sodium lactate as an electron donor. During the decomposition of Fe-Mn nodule, REEs released from the Fe-Mn nodule were adsorbed on bacterial cells. Of the conditions studied here, the best REE adsorption rates were obtained with 0.5M NaCl solution at pH7 with daily addition of 1 mmol sodium lactate.

Journal Articles

Studies on electrochemical behavior of uranium species in choline chloride-urea eutectic for developing electrolytically treating method of uranium-bearing wastes

Ohashi, Yusuke; Asanuma, Noriko*; Harada, Masayuki*; Tanaka, Yoshio; Ikeda, Yasuhisa*

Journal of Radioanalytical and Nuclear Chemistry, 309(2), p.627 - 636, 2016/08

 Times Cited Count:1 Percentile:83.2(Chemistry, Analytical)

As one of methods for recovering uranium from the uranium-bearing wastes, we have proposed the electrolytic deposition method using choline chloride-urea (CCU) which is known as an ambient temperature molten salt. More than 92% of uranium components in inactivated alumina and spent sodium fluoride adsorbent was dissolved into CCU solution. Cyclic voltammograms (CVs) of the solutions prepared by dissolving uranium-bearing wastes in CCU were measured in the potential range of -2.0 to 1.1 V (vs. Ag/AgCl). The one reduction peak was observed around -0.7 V for all solutions. Based on the results of CVs, bulk electrolyses of the solutions dissolving uranium-bearing wastes were also carried out at -1.5V at 80 $$^{circ}$$C. The deposits were formed on a carbon electrode as cathode. Consequently, we confirmed that CCU is effective media for recovering uranium selectively from uranium-bearing waste.

Journal Articles

Geochemistry for the Fukushima Dai-ichi Nuclear Power Plant accident; Production, dispersion and migration of radionuclides

Tanaka, Kazuya; Takahashi, Yoshio*; Fukushi, Keisuke*; Utsunomiya, Satoshi*

Chikyu Kagaku, 49(4), p.169 - 171, 2015/12

Many studies have been carried out since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. This paper introduces the special issue on the FDNPP accident which includes contributions from various fields covering aerosols, soil, forest, river, ocean and application of new analytical technique to samples collected in Fukushima.

Journal Articles

Cumulative history recorded in the depth distribution of radiocesium in sediments deposited on a sandbar

Tanaka, Kazuya; Kondo, Hiroaki*; Sakaguchi, Aya*; Takahashi, Yoshio*

Journal of Environmental Radioactivity, 150, p.213 - 219, 2015/12

 Times Cited Count:4 Percentile:79.81(Environmental Sciences)

We collected sediments deposited on a sandbar from the surface to 20 cm in depth in the Abukuma River to clarify the history of radiocesium derived from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. We analyzed the $$^{137}$$Cs concentration in the sediments from size-fractioned samples as well as bulk samples. The results of this study demonstrated that sediment layers deposited on a sandbar retained the cumulative history of the fluvial transport of radiocesium after the FDNPP accident.

Journal Articles

Application of support vector machine to rapid classification of uranium waste drums using low-resolution $$gamma$$-ray spectra

Hata, Haruhi; Yokoyama, Kaoru; Ishimori, Yuu; Ohara, Yoshiyuki; Tanaka, Yoshio; Sugitsue, Noritake

Applied Radiation and Isotopes, 104, p.143 - 146, 2015/10

 Times Cited Count:4 Percentile:54.36(Chemistry, Inorganic & Nuclear)

We investigated the feasibility of using support vector machine (SVM), a computer learning method, to classify uranium waste drums as natural uranium or reprocessed uranium based on their origins. The method was trained using 12 training datasets were used and tested on 955 datasets of $$gamma$$-ray spectra obtained with NaI(Tl) scintillation detectors. The results showed that only 4 out of 955 test datasets were different from the original labels-one of them was mislabeled and the other three were misclassified by SVM. These findings suggest that SVM is an effective method to classify a large quantity of data within a short period of time. Consequently, SVM is a feasible method for supporting the scaling factor method and as a supplemental tool to check original labels.

JAEA Reports

Evaluation formulas of manpower needs for dismantling of equipments in uranium refining and conversion plant

Izumo, Sari; Usui, Hideo; Kubota, Shintaro; Tachibana, Mitsuo; Kawagoshi, Hiroshi; Takahashi, Nobuo; Morimoto, Yasuyuki; Tokuyasu, Takashi; Tanaka, Yoshio; Sugitsue, Noritake

JAEA-Technology 2014-021, 79 Pages, 2014/07

JAEA-Technology-2014-021.pdf:22.8MB

Japan Atomic Energy Agency has developed PROject management data evaluation code for DIsmantling Activities (PRODIA) to make an efficient decommissioning for nuclear facilities. PRODIA is a source code which provides estimated value such as manpower needs, costs, etc., for dismantling by evaluation formulas according to the type of nuclear facility. Evaluation formulas of manpower needs for dismantling of equipments about reprocessed uranium conversion in Uranium Refining and Conversion Plant are developed in this report. In the result, 7 formulas for prepare process, 24 formulas for dismantling process and 8 formulas for clean-up process are derived. It is confirmed that an unified evaluation formula can be used instead of 8 formulas about dismantling process of steel equipment for uranium conversion process, and 3 types of simplified formula can be used for preparation process and clean-up process respectively.

Journal Articles

Technique for recovering uranium from sludge-like uranium-bearing wastes using hydrochloric acid

Ohashi, Yusuke; Nomura, Mitsuo; Tsunashima, Yasumichi; Ando, Shion; Sugitsue, Noritake; Ikeda, Yasuhisa*; Tanaka, Yoshio

Journal of Nuclear Science and Technology, 51(2), p.251 - 265, 2014/02

 Times Cited Count:4 Percentile:59.64(Nuclear Science & Technology)

Sludge-like uranium-bearing wastes generated from uranium refining and conversion R&D facilities are stored at the Ningyo-toge Environmental Engineering Center. We have proposed an aqueous process for recovering uranium from spent filter aid and CaF$${_2}$$ precipitate using hydrochloric acid. The distributions of the dissolved species in the sample solutions at different pH levels were calculated using the chemical equilibrium modeling system. Calculated results of fluorine contents of recovered uranium were compared with the experimental results. The fluorine content in the recovered uranium decreased as the aluminum concentration of the solution increased. On the other hand, uranium of spent filter aid was recovered selectively. The size of the particles of recovered uranium tends to decrease with increasing pH in the precipitation treatments. Also, the uranium concentration of the precipitate generated by the neutralization of the barren solution falls below 1 Bq/g.

Journal Articles

Existing status of uranium refining and conversion plant decommissioning project

Sugitsue, Noritake; Morimoto, Yasuyuki; Tokuyasu, Takashi; Tanaka, Yoshio

Nippon Genshiryoku Gakkai Wabun Rombunshi, 12(3), p.242 - 256, 2013/09

This technical report showed the situation of the dismantling of the main equipment in the radiation controlled area of a uranium refining and conversion plant. And, the dismantling which we did is the work of the beginning of a uranium refining and conversion plant decommissioning project. We started dismantling in April 2008, and finished dismantling of the main equipment in a radiation controlled area in 29 September 2011. The dismantling waste and equipment was stored in the 200 little drum. All the contamination equipment can be sealed and kept in this stage. The radioactivity inventory of a uranium refining and conversion plant does not change in this stage. However, the risk of contamination by aged deterioration of this facility became remarkable small. Moreover, we were able to get many information and experience about dismantling.

Journal Articles

Development of evaluation models of manpower needs for dismantling the dry conversion process-related equipment in Uranium Refining and Conversion Plant (URCP)

Izumo, Sari; Usui, Hideo; Tachibana, Mitsuo; Morimoto, Yasuyuki; Takahashi, Nobuo; Tokuyasu, Takashi; Tanaka, Yoshio; Sugitsue, Noritake

Proceedings of 15th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2013) (CD-ROM), 9 Pages, 2013/09

 Times Cited Count:0 Percentile:100

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