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Journal Articles

Dispersive XAFS Study on the Laser-Induced Reduction of a Rh$$^{3+}$$ ion complex; Presence of a Rh$$^{+}$$ Intermediate in Direct Photoreduction

Saeki, Morihisa*; Matsumura, Daiju; Nakanishi, Ryuzo*; Yomogida, Takumi; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

Journal of Physical Chemistry C, 126(12), p.5607 - 5616, 2022/03

https://doi.org/10.1021/acs.jpcc.1c10160
 Times Cited Count：1 Percentile：14.66(Chemistry, Physical)

The reaction mechanism of the direct photoreduction of a Rh$$^{3+}$$ ion complex to a Rh$$^{0}$$ species induced by pulsed ultraviolet laser irradiation was studied using dispersive X-ray absorption fine structure (DXAFS) spectroscopy. The time-resolved X-ray absorption near edge structure (XANES) showed the absence of isosbestic points and suggested that more than two Rh$$^{n+}$$ species contribute toward the direct photoreduction of Rh$$^{3+}$$. Analysis of the time-resolved XANES data by singular value deposition showed that the direct photoreduction involves three Rh$$^{n+}$$ species. Multivariate curve resolution by alternating least-squares analysis (MCR-ALS) of the time-resolved XANES data gave pure spectra and concentration profiles of the three Rh$$^{n+}$$ species. The Rh$$^{n+}$$ species were assigned to Rh$$^{3+}$$, Rh$$^{+}$$, and Rh$$^{0}$$ species based on the features of the pure XANES spectra. The concentration profiles suggested that the direct photoreduction proceeds in the order of Rh$$^{3+}$$ $$rightarrow$$ Rh$$^{+}$$ $$rightarrow$$ Rh$$^{0}$$. A reaction mechanism, which was proposed involving photoreductions of Rh$$^{3+}$$ and Rh$$^{+}$$, photoinduced autocatalytic reductions of Rh$$^{3+}$$ and Rh$$^{+}$$, and photooxidation of Rh$$^{+}$$, well reproduced the concentration profiles of three Rh$$^{n+}$$ species.

Journal Articles

Application of an augmentation method to MCR-ALS analysis for XAFS and Raman data matrices in the structural change of isopolymolybdates

Saeki, Morihisa*; Yomogida, Takumi; Matsumura, Daiju; Saito, Takumi*; Nakanishi, Ryuzo*; Tsuji, Takuya; Oba, Hironori*

Analytical Sciences, 36(11), p.1371 - 1378, 2020/11

https://doi.org/10.2116/analsci.20P147
 Times Cited Count：2 Percentile：10(Chemistry, Analytical)

We measured X-ray absorption fine structure (XAFS) and Raman spectra of isopolymolybdates(VI) in HNO$$_{3}$$ solution (0.15- 4.0 M), which change their geometries depending on acid concentration, and performed simultaneous resolution of the XAFS and Raman data using a multivariate curve resolution by alternating least-squares (MCR-ALS) analysis. In iterative ALS optimization, initial data matrices were prepared by two different methods. The MCR-ALS result of single XAFS data matrix shows large dependence on the preparation method of the initial data matrices. The MCR-ALS result of an augmented matrix of Raman and XAFS data has little dependence on the initial data matrices. It indicates that the augmentation method effectively improves the rotation ambiguities in the MCR-ALS analysis of the XAFS data. Based on the model fitting of the pure EXAFS oscillations, we revealed the change of [Mo$$_{36}$$O$$_{112}$$(H$$_{2}$$O)$$_{16}$$]$$^{2+}$$ $$rightarrow $$ [Mo$$_{2}$$O$$_{5}$$(H$$_{2}$$O)$$_{6}$$]$$^{2+}$$ $$rightarrow $$ [HMoO$$_{3}$$(H$$_{2}$$O)$$_{3}$$]$$^{+}$$ in the highly concentrated HNO$$_{3}$$ solution.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018) (Translated document)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2020-007, 249 Pages, 2020/10

JAEA-Research-2020-007.pdf:15.83MB

The accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, Japan Atomic Energy Agency (JAEA) has been conducting "Long-term Assessment of Transport of Radioactive Contaminants in the Environment of Fukushima" concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2019-002, 235 Pages, 2019/08

JAEA-Research-2019-002.pdf:21.04MB

The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Journal Articles

In Situ Time-Resolved XAFS Studies on Laser-induced Particle Formation of Palladium Metal in an Aqueous/EtOH solution

Saeki, Morihisa*; Matsumura, Daiju; Yomogida, Takumi; Taguchi, Tomitsugu*; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

Journal of Physical Chemistry C, 123(1), p.817 - 824, 2019/01

https://doi.org/10.1021/acs.jpcc.8b09532
 Times Cited Count：14 Percentile：53.94(Chemistry, Physical)

Reaction kinetics of laser-induced particle formation in an aqueous solution of PdCl$$_{4}$$$$^{2-}$$ was investigated by transmission electron microscope (TEM) and dispersive X-ray absorption fine structure (DXAFS). The Pd particle was generated by irradiation of nanosecond pulsed 266-nm laser. The TEM observation showed dependence of the particle size on the laser fluence and promotion of the particle growth by irradiation of high-fluence laser. The DXAFS data give us the Pd$$^{2+}$$ concentration. Temporal changes of the Pd$$^{2+}$$ concentration analyzed based on Finke-Watzky two step mechanism. The analysis elucidates that the laser photon contributes to the reduction of the PdCl$$_{4}$$$$^{2-}$$ ion by the one-photon process and to the autocatalytic growth of the Pd particles by the multi-photon process.

Journal Articles

Estimation of mitigation effects of sodium nanofluid for SGTR accidents in SFR

Ichikawa, Kenta*; Kanda, Hironori; Yoshioka, Naoki*; Ara, Kuniaki; Saito, Junichi; Nagai, Keiichi

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 6 Pages, 2018/07

Studies on the suppression of the reactivity of sodium itself have been performed on the basis of the concept of suspended nanoparticles in liquid sodium (sodium nanofluid). According to the experimental and theoretical results of studies for sodium nanofluid, velocity and heat of sodium nanofluid-water reaction are lower than those of the pure sodium-water reaction. The analytical model for the peak temperature of a sodium nanofluid-water reaction jet has been developed in consideration of these suppression effects by the authors. In this paper, the prediction method for mitigation effects for a damage of adjacent tubes in a steam generator tube rupture (SGTR) accidents is arranged by applying this analytical model for the peak temperature of the reaction jet. On the assumption that the sodium nanofluid is used for the secondary coolant of sodium-cooled fast reactor (SFR), mitigation effects under the design-base accident (DBA) condition and the design-extension condition (DEC) of SGTR are estimated by using this method. As a result, there is a possibility to reduce the number of damaged tubes and to suppress the pressure generated by SGTR accidents by using sodium nanofluid in the secondary coolant.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima; As a part of dissemination of evidence-based information

Tsuruta, Tadahiko; Niizato, Tadafumi; Nakanishi, Takahiro; Dohi, Terumi; Nakama, Shigeo; Funaki, Hironori; Misono, Toshiharu; Oyama, Takuya; Kurikami, Hiroshi; Hayashi, Seiji*; et al.

JAEA-Review 2017-018, 86 Pages, 2017/10

JAEA-Review-2017-018.pdf:17.58MB

Since the accidents at Fukushima Daiichi Nuclear Power Plant following the Tohoku Region Pacific Coast Earthquake on March 11th, 2011, Fukushima Environmental Safety Center has carried out research on natural mobilization of radionuclide (especially radiocesium) and future forecast from forest to water system and surrounding residential areas. The report summarizes the latest results that have been accumulated from each study field, of our agency together with the other related research organizations. The contents of the report is to be used as evidence-based information for the QA-styled pages in the website of JAEA Sector of Fukushima Research and Development at the time of next renewal.

Journal Articles

Indirect contribution of transition metal towards oxygen reduction reaction activity in iron phthalocyanine-based carbon catalysts for polymer electrolyte fuel cells

Kobayashi, Masaki*; Niwa, Hideharu*; Saito, Makoto*; Harada, Yoshihisa*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.

Electrochimica Acta, 74, p.254 - 259, 2012/07

https://doi.org/10.1016/j.electacta.2012.04.075
 Times Cited Count：52 Percentile：80.98(Electrochemistry)

The electronic structure of the residual metal atoms in FePc-based carbon catalysts, prepared by pyrolyzing a mixture of FePc and phenolic resin polymer at 800$$^{circ}$$C, before and after acid washing have been investigated using XAFS spectroscopy to clarify the role of Fe in the ORR activity. The decomposition analyses for the XAFS spectra reveal that the composition ratio of each Fe component is unaltered by the acid washing, indicating that the residual Fe components were removed by the acid washing irrespective of their chemical states. Because the oxygen reduction potential was approximately unchanged by the acid washing, the residual Fe itself does not seem to contribute directly to the ORR activity. The residual Fe can act as a catalyst to accelerate the growth of the sp$$^{2}$$ carbon network during pyrolysis. The results imply that light elements are components of the ORR active sites in the FePc-based carbon catalysts.

Journal Articles

NMR determination of noncollinear antiferromagnetic structure in TbCoGa$$_5$$

Tokunaga, Yo; Saito, Yo*; Sakai, Hironori; Kambe, Shinsaku; Sanada, Naoyuki*; Watanuki, Ryuta*; Suzuki, Kazuya*; Kawasaki, Yu*; Kishimoto, Yutaka*

Physical Review B, 84(21), p.214403_1 - 214403_7, 2011/12

https://doi.org/10.1103/PhysRevB.84.214403
 Times Cited Count：8 Percentile：36.17(Materials Science, Multidisciplinary)

We report NMR studies of TbCoGa$$_5$$, which has the tetragonal HoCoGa$$_5$$ structure and exhibits two antiferromagnetic (AF) transitions at $$T_{rm N1}$$=36.2 K and $$T_{rm N2}$$=5.4 K. From a symmetry analysis of internal magnetic fields at orthorhombic Ga sites, we have successfully determined the magnetic structures in the AF-I ($$T_{rm N2}<T<T_{rm N1}$$) and AF-II ($$T<T_{rm N2}$$) phases. The AF-I phase is a collinear AF order with a propagation vector $$q=[1/2, 0, 1/2]$$ and ordered moments parallel to the [001] direction. In the AF-II phase, on the other hand, we found a non-collinear AF structure described by double propagation vectors $$q_1=[1/2, 0, 1/2]$$ and $$q_{2}=[0, 1/2, 1/2]$$, where the moments tilt away from the [001] direction toward [100], keeping a constant value along the [001] direction. In the context of these results we discuss the possible presence of magnetic frustration in this system.

JAEA Reports

Study on uncertainty of soil-to-plant transfer factor for the safety assessment (Contract research)

Saito, Hironori*; Takeda, Seiji; Kimura, Hideo

JAEA-Research 2011-032, 92 Pages, 2011/11

JAEA-Research-2011-032.pdf:2.11MB

The objective of this study is to estimate the parameter uncertainty of soil-to-plant transfer factor used in the safety assessment. The database on the soil-to-plant factors was improved to clarify the factors associated with the uncertainty of soil-to-plant transfer factor. The factors were specified based on investigating the relation between published data of soil-to-plant transfer factor and some kinds of experimental conditions. Under the assumption of stylization by both general habits of ingestion of farm products and soil conditions in Japan, we proposed the procedure to estimate the parameter uncertainty of soil-to-plant transfer factor according to the investigation results of the factors. Based on the procedure, the variation of soil-to-plant transfer factors for main radionuclides of high level radioactive waste and TRU waste were estimated in this report.

Journal Articles

Growth and characterization of bismuth magnesium titanate Bi(Mg$$_{1/2}$$Ti$$_{1/2}$$)0$$_3$$

Yoneda, Yasuhiro; Saito, Hiroyuki; Yoshii, Kenji; Nishida, Takashi*; Hayakawa, Hironori*; Ikeda, Naoshi*

Key Engineering Materials, 421-422, p.30 - 33, 2010/00

Polycrystalline Bi(Mg$$_{1/2}$$Ti$$_{1/2}$$)O$$_3$$ samples were prepared under high pressure. A mixed powder of Bi$$_2$$O$$_3$$, Ti$$_2$$O$$_3$$ and MgO with a prescribed ratio was packed into platinum cell and was heated a cubic anvil-type apparatus at 6.5 GPa and 1000 $$^circ$$C. The obtained samples were characterized by powder X-ray diffraction measurements. Although some impurity peaks existed, the main peaks were perovskite peaks. The structure of Bi(Mg$$_{1/2}$$Ti$$_{1/2}$$)O$$_3$$ is rhombohedral, as well as BiFeO$$_3$$. The D-E hysteresis loop was not saturated due to the impurities, but the possibility as ferroelectric can be expected enough.

Oral presentation

Study of electronic states of uranium mixed chalcogenides

Takeda, Yukiharu; Okane, Tetsuo; Okochi, Takuo; Kobayashi, Masaki*; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Ikeda, Shugo; Sakai, Hironori; et al.

no journal, , 

no abstracts in English

Oral presentation

Study of the electronic structure of uranium mixed chalcogenides by soft X-ray spectroscopy

Takeda, Yukiharu; Okane, Tetsuo; Okochi, Takuo; Kobayashi, Masaki*; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Ikeda, Shugo*; Sakai, Hironori; et al.

no journal, , 

no abstracts in English

Oral presentation

Benchmark analysis of the flow through experiment of high pH solution to natural fracture

Yamaguchi, Kohei; Honda, Akira; Inagaki, Manabu; Yui, Mikazu; Saito, Hironori*

no journal, , 

The bench mark analysis concerning the change in the material transportation characteristic according to the chemical reaction were done by using pass experiment result (Mader et al., 2006) of the high pH solution to the natural crack core in granite as part of international collaboration LCS (Long-term Cement Study). We were able to reproduce the observed blockage tendency as a result experimentally the material transportation model characteristic according to the chemical reaction.

Oral presentation

Scenario development for mineral alternations in granite by high pH solution

Shimoda, Satoko*; Saito, Hironori*; Takase, Toshio*; Yamaguchi, Kohei; Oda, Chie; Honda, Akira

no journal, , 

The unstable primary mineral is dissolved and the precipitation of a steadier secondary mineral happens thermodynamically when a high alkaline groundwater of the cement system material origin is infiltrated from the radioactive waste geological disposal facilities to a peripheral bedrock. Therefore, the pore structure of the hostrock changes by the precipitation and dissolution, and the material transportation characteristic of the bedrock changes. It is necessary to decide the chemical reaction scheme for the analysis. However, the combination of the secondary minerals exists innumerably. Therefore, granite was assumed to be an example by summarizing the chemical reaction scheme in the mineral alteration scenario, and the mineral alteration scenario concerning the reaction with a high pH groundwater was presented. It dealt with the uncertainty concerning the mineral alteration by preparing two or more scenarios with a different alteration route.

Oral presentation

Study of electronic states of uranium chalcogenides using soft X-ray photoemission spectroscopy and magnetic circular dichroism

Takeda, Yukiharu; Okane, Tetsuo; Okochi, Takuo*; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi*; Ikeda, Shugo*; Sakai, Hironori; Haga, Yoshinori; et al.

no journal, , 

no abstracts in English

Oral presentation

The Approach to the small animal experiment by new technique in JRR-4

Endo, Kiyoshi*; Nakai, Kei*; Yoshida, Fumiyo*; Shirakawa, Shin*; Yamamoto, Tetsuya*; Matsumura, Akira*; Sawahata, Hiroyuki*; Kawate, Minoru*; Saito, Kimiaki; Kumada, Hiroaki; et al.

no journal, , 

no abstracts in English

Oral presentation

Study on uncertainty of soil-to-plant transfer factor for the safety assessment

Saito, Hironori; Takeda, Seiji; Kimura, Hideo

no journal, , 

no abstracts in English

Oral presentation

NMR study of PrTi$$_2$$Al$$_{20}$$

Tokunaga, Yo; Sakai, Hironori; Saito, Yo; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

NMR/NQR studies of TbCoGa$$_{5}$$

Saito, Yo; Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku

no journal, , 

TbCoGa$$_{5}$$ composed of the tetragonal HoCoGa$$_{5}$$type structure(D$$_{4h}$$-P4/mmm) was reported that it has below the upper critical temperature T$$_{N1}$$ and above the lower critical temperature T$$_{N2}$$, and shows unusual successive phase transitions. Generally, systems caused successive phase transitions are origin of the geometrical frustration of exchange interactions between spins of magnetic ions. (Ex. triangular lattice antiferro magnets CsNiCl$$_{3}$$) But, the tetragonal compound TbCoGa$$_{5}$$ was thought that it's not caused the geometrical frustration. Therefore, TbCoGa$$_{5}$$ is considered to be a new mechanism different from the geometrical frustration of triangular lattice antiferro magnets. For example, there is competition of magnetic interactions and quadrupolar interactions in f-Electron systems.

30 (Records 1-20 displayed on this page)