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Journal Articles

Experimental determination of the photooxidation of aqueous I$$^{-}$$ as a source of atmospheric I$$_{2}$$

Watanabe, Kosuke*; Matsuda, Shohei; Cuevas, C. A.*; Saiz-Lopez, A.*; Yabushita, Akihiro*; Nakano, Yukio*

ACS Earth and Space Chemistry (Internet), 3(4), p.669 - 679, 2019/04

 Times Cited Count:2 Percentile:62.6(Chemistry, Multidisciplinary)

The photooxidation of aqueous iodide ions (I$$^{-}$$$$_{(aq)}$$) at sea surface results in the emission of gaseous iodine molecules (I$$_{2}$$$$_{(g)}$$) into the atmosphere. It plays a certain role in the transport of iodine from ocean to the atmosphere in the natural cycle of iodine. In this study, we determined the photooxidation parameters, the molar absorption coefficient ($$varepsilon$$$$_{iodide}$$($$lambda$$)) and the photooxidative quantum yields ($$Phi$$$$_{iodide}$$($$lambda$$)) of I$$^{-}$$$$_{(aq)}$$, in the range of 290-500 nm. Through the investigation of the influence of pH and dissolved oxygen (DO) on $$Phi$$$$_{iodide}$$($$lambda$$), the subsequent emission rates of I$$_{2}$$$$_{(g)}$$ following the photooxidation of I$$^{-}$$$$_{(aq)}$$ in deionized water solution (pH 5.6, DO 7.8 mg L$$^{-1}$$) and artificial seawater solution (pH 8.0, DO 7.0 mg L$$^{-1}$$) were estimated. A global chemistry-climate model employed herein to assess the I$$_{2}$$$$_{(g)}$$ ocean emission on a global scale indicated that the photooxidation of I$$^{-}$$$$_{(aq)}$$ by solar light can enhance the atmospheric iodine budget by up to $$sim$$8% over some oceanic regions.

Journal Articles

Laser-induced breakdown spectroscopy and related resonance spectroscopy for nuclear fuel cycle management and for decommissioning of "Fukushima Daiichi Nuclear Power Station"

Wakaida, Ikuo; Oba, Hironori; Miyabe, Masabumi; Akaoka, Katsuaki; Oba, Masaki; Tamura, Koji; Saeki, Morihisa

Kogaku, 48(1), p.13 - 20, 2019/01

By Laser Induced Breakdown Spectroscopy and by related resonance spectroscopy, elemental and isotope analysis of Uranium and Plutonium for nuclear fuel materials and in-situ remote analysis under strong radiation condition for melt downed nuclear fuel debris at damaged core in "Fukushima Daiichi Nuclear Power Station", are introduced and performed as one of the application in atomic energy research field.

Journal Articles

Evaluation of effective dose coefficient with variation of absorption fraction in gastrointestinal system for ingestion of radiocesium

Pratama, M. A.; Takahara, Shogo; Hato, Shinji*

Hoken Butsuri, 52(3), p.200 - 209, 2017/09

The purpose of this study is to identify the significance of the change in the intestinal absorption rate values the ($$f_{1}$$ value) to the change of dose coefficient as well as to provide a list of dose coefficients which each of the value corresponds to a specific intestinal absorption rate and age groups. In the range of 0-1, 10 different values of $$f_{1}$$ for 1 year, 5 years old, and adult group were chosen and used in a separate calculation by using, a biokinetic compartment model, DCAL. It was found that the lower values of intestinal absorption rate lead to a significant decrease of the committed effective coefficient for adult. Oppositely for children, the decrease of committed effective coefficient was not as significant. This study also suggests that the significance of dose coefficient change due to the variation of $$f_{1}$$ substantially depends on the biological half-life of the radionuclide and the mass of organs and tissues in human body.

Journal Articles

Experimental observation of temperature and magnetic-field evolution of the 4${it f}$ states in CeFe$$_{2}$$ revealed by soft X-ray magnetic circular dichroism

Saito, Yuji; Yasui, Akira*; Fuchimoto, Hiroto*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Imada, Shin*; Narumi, Yasuo*; Kindo, Koichi*; Takahashi, Minoru*; Ebihara, Takao*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07


 Times Cited Count:1 Percentile:90.81(Materials Science, Multidisciplinary)

We revisit the delocalized character of the 4$$f$$ states of CeFe$$_2$$ in the ferromagnetically ordered phase by X-ray magnetic circular dichroism (XMCD) in X-ray absorption spectroscopy (XAS) with improved data quality using single crystals. Surprisingly, the Ce $$M_{4,5}$$ XMCD spectral shape changes significantly as a function of temperature and applied magnetic field, with no concomitant changes in the spectral shape of the Ce $$M_{4,5}$$ XAS as well as the Fe $$L_{2,3}$$ XAS and XMCD. This unusual behavior is characterized by the $$J=7/2$$ states in a 4$$f^1$$ configuration mixed into the $$J=5/2$$ ground state. Such extreme sensitivity of the Ce 4$$f$$ states to the external perturbations can be related to the magnetic instability toward an antiferromagnetic phase in CeFe$$_2$$. Our experimental data presented here provide valuable insights into the underlying physics in strongly-hybridized ferromagnetic Ce compounds.

Journal Articles

Hydrogen absorption behavior on zirconium under $$gamma$$-radiolysis of nitric acid solution

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

Nippon Genshiryoku Gakkai Wabun Rombunshi, 16(2), p.100 - 106, 2017/05

Zirconium (Zr) has been used as a structural material at the spent nuclear fuel reprocessing plant in Japan because of its excellent corrosion resistance against nitric acid solution. And the radiolytic hydrogen is known to be generated in the spent nuclear fuel solution. Zr is known to be highly susceptible to hydrogen embrittlement. Therefore, evaluating the radiolytic hydrogen absorption behavior of Zr in nitric acid solution (HNO$$_{3}$$) is essential. In this study, immersion tests were conducted on Zr in nitric acid solutions under $$gamma$$-ray irradiation to evaluate its radiolytic hydrogen absorption behavior. Results showed that hydrogen concentration on Zr increased both in 1-3 mol/L HNO$$_{3}$$ and pure water at 5 and 7 kGy/h after immersion. The amount of hydrogen absorption on Zr under $$gamma$$-ray irradiation had a direct correlation with the radiolytic hydrogen generation value in HNO$$_{3}$$. The results of glow discharge optical emission spectrometry, thermal desorption spectroscopy, and X-ray diffraction result shows that the absorbed radiolytic hydrogen generated a hydride on the surface of Zr.

Journal Articles

Investigation of absorption characteristics for thermal-load fluctuation using HTTR

Tochio, Daisuke; Honda, Yuki; Sato, Hiroyuki; Sekita, Kenji; Homma, Fumitaka; Sawahata, Hiroaki; Takada, Shoji; Nakagawa, Shigeaki

Journal of Nuclear Science and Technology, 54(1), p.13 - 21, 2017/01

 Times Cited Count:1 Percentile:82.62(Nuclear Science & Technology)

GTHTR300C is designed and developed in JAEA. The reactor system is required to continue a stable and safety operation as well as a stable power supply in the case that thermal-load is fluctuated by the occurrence of abnormal event in the heat utilization system. Then, it is necessary to demonstrate that the thermal-load fluctuation should be absorbed by the reactor system so as to continue the stable and safety operation could be continued. The thermal-load fluctuation absorption tests without nuclear heating were planned and conducted in JAEA to clarify the absorption characteristic of thermal-load fluctuation mainly by the reactor and by the IHX. As the result it was revealed that the reactor has the larger absorption capacity of thermal-load fluctuation than expected one, and the IHX can be contributed to the absorption of the thermal-load fluctuation generated in the heat utilization system in the reactor system. It was confirmed from there result that the reactor and the IHX has effective absorption capacity of the thermal-load fluctuation generated in the heat utilization system. Moreover it was confirmed that the safety estimation code based on RELAP5/MOD3 can represents the thermal-load fluctuation absorption behavior conservatively.

Journal Articles

Chemical states of trace-level strontium adsorbed on layered oxide by XPS and XANES under total reflection condition

Baba, Yuji; Shimoyama, Iwao

Photon Factory Activity Report 2016, 2 Pages, 2017/00

In order to elucidate the adsorption states of radioactive Sr-90 in soil, chemical bonding states of non-radioactive strontium adsorbed on layered oxide (mica) have been investigated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy. Since the number of atoms in radioactive Sr-90 is extremely small, the XPS and XANES were measured under total reflection condition of the incident X-rays. The detection limit in total reflection XPS was about 150 pg/cm$$^{2}$$, which corresponds to 300 Bq of Sr-90. The Sr 2p$$_{3/2}$$ core-level energy in XPS shifted to lower energy with the decrease in the thickness of Sr layer. Also, the Sr 2p$$_{3/2}$$ $$rightarrow$$ Sr 4d$$^{*}$$ resonance energy in XANES shifts to lower energy with the decrease in the thickness. On the basis of a simple point charge model, it was elucidated that the chemical bond between Sr and mica surface becomes ionic with the decrease in the adsorbed amount of strontium.

Journal Articles

Shapes of $$^{192,190}$$Pb ground states from $$beta$$-decay studies using the total-absorption technique

Est$'e$vez Aguado, M. E.*; Algora, A.*; Agramunt, J.*; Rubio, B.*; Tain, J. L.*; Jord$'a$n, D.*; Fraile, L. M.*; Gelletly, W.*; Frank, A.*; Csatl$'o$s, M.*; et al.

Physical Review C, 92(4), p.044321_1 - 044321_8, 2015/10

 Times Cited Count:12 Percentile:30.55(Physics, Nuclear)

Journal Articles

Infrared absorption and Raman scattering spectra of water under pressure via first principles molecular dynamics

Ikeda, Takashi

Journal of Chemical Physics, 141(4), p.044501_1 - 044501_8, 2014/07

 Times Cited Count:10 Percentile:54.64(Chemistry, Physical)

From both the polarized and depolarized Raman scattering spectra of supercritical water a peak located at around 1600 cm$$^{-1}$$, attributed normally to bending mode of water molecules, was experimentally observed to vanish, whereas the corresponding peak remains clearly visible in the measured infrared (IR) absorption spectrum. In this computational study a theoretical formulation for analyzing the IR and Raman spectra is developed via first principles molecular dynamics combined with the modern polarization theory. We demonstrate that the experimentally observed peculiar behavior of the IR and Raman spectra for water are well reproduced in our computational scheme. We discuss the origins of a feature observed at 1600 cm$$^{-1}$$ in Raman spectra of ambient water.

Journal Articles

Valence state in Ce-based heavy fermion compounds at high magnetic fields

Matsuda, Yasuhiro*; Her, J.-L.*; Michimura, Shinji*; Inami, Toshiya; Ebihara, Takao*; Amitsuka, Hiroshi*

JPS Conference Proceedings (Internet), 3, p.011044_1 - 011044_6, 2014/06

Synchrotron X-ray absorption spectroscopy of CeRh$$_2$$Si$$_2$$ has been performed in pulsed high magnetic fields of up to 32 T. The Ce valence is slightly larger than 3+ at 5 K and decreases with increasing magnetic above 20 T. The field-induced valence change seems to correspond to the metamagnetic transition in the magnetization process. This phenomena is similar to our previous result on CeRu$$_2$$Si$$_2$$ and seems to be common in Ce-based heavy fermion compounds.

Journal Articles

Characterization of F$$^{+}$$-irradiated graphite surfaces using photon-stimulated desorption spectroscopy

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Nath, K. G.

Surface and Interface Analysis, 38(4), p.352 - 356, 2006/04

 Times Cited Count:3 Percentile:92.02(Chemistry, Physical)

We investigated the orientation nature at the top-most layers of F$$^{+}$$-irradiated graphite using polarization dependent near-edge X-ray absorption fine structure (NEXAFS) spectroscopy which incorporates partial electron yield (PEY) detection and photon-stimulated ion desorption (PSID) techniques. The fluorine K-edge NEXAFS spectra conducted in PEY mode show no significant dependence on polarization angles. In contrast, NEXAFS spectra recorded in F$$^{+}$$ ion yield mode show enhanced yields at a feature of $$sim$$689.4 eV assigned as a $$sigma$$*(C-F) state relevant to =C-F sites, which depend on polarization angles. The C-F bonds prefer relatively tilting down the surface at the top-most layer, while the C-F bonds are randomly directed at deeper regions. We conclude that the difference in the orientation structures between the top surface and bulk is reflected in the NEXAFS recorded in the two different detection modes. It was also found that H$$^{+}$$- and F$$^{2+}$$- PSID NEXAFS spectra are helpful in understanding desorption mechanism, thus in analysing NEXAFS data.

Journal Articles

Study of radiation-induced primary process by ion pulse radiolysis

Yoshida, Yoichi*; Yang, J.*; Kondo, Takafumi*; Seki, Shuhei*; Kozawa, Takahiro*; Tagawa, Seiichi*; Shibata, Hiromi*; Taguchi, Mitsumasa; Kojima, Takuji; Namba, Hideki

JAEA-Review 2005-001, TIARA Annual Report 2004, p.183 - 185, 2006/01

A heavy-ion-pulse radiolysis technology was developed using a single-photon-counting system. In the system, the ion beam was injected a thin scintillator before irradiating the sample. The light emitted from the scintillator by the ion irradiation was used as analyzing source to detect the absorption of primary species in water. Measurement of time-dependent absorption of hydrated electrons in water was achieved using the system, which demonstrates the usefulness of this technique.

Journal Articles

Mechanism of state-specific enhancement in photon-stimulated desorption as studied using a polarization-dependent technique

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Wu, G.*; Kitajima, Yoshinori*

Surface Science, 593(1-3), p.310 - 317, 2005/11

 Times Cited Count:2 Percentile:87.55(Chemistry, Physical)

Using a newly developed rotatable time-of-flight mass spectrometer(R-TOF-MS) and polarized synchrotron radiation, orientation effect on fragmentation and desorption pathways occurring at the top-most layers of molecular solids have been investigated. Reported will be polarization-angle dependencies of TOF mass spectra, high-resolution electron- and ion-NEXAFS in condensed chlorobenzene.

Journal Articles

Direct and indirect processes in photon-stimulated ion desorption from condensed formamide

Ikeura, Hiromi*; Sekiguchi, Tetsuhiro; Baba, Yuji; Imamura, Motoyasu*; Matsubayashi, Nobuyuki*; Shimada, Hiromichi*

Surface Science, 593(1-3), p.303 - 309, 2005/11

 Times Cited Count:5 Percentile:72.37(Chemistry, Physical)

no abstracts in English

Journal Articles

Embrittlement and fracture behavior of pre-hydrided cladding under LOCA conditions

Nagase, Fumihisa; Fuketa, Toyoshi

Proceedings of 2005 Water Reactor Fuel Performance Meeting (CD-ROM), p.668 - 677, 2005/10

A systematic research program on high burnup fuel behavior under LOCA conditions is being conducted at JAERI. As a part of the program, integral thermal shock tests simulating the whole LOCA sequence were conducted with Zircaloy-4 fuel claddings, irradiated to 39 and 44 GWd/t at a PWR, to investigate behavior and condition of cladding fracture during quenching for safety evaluation. Differences were not clearly observed between irradiated and unirradiated claddings at similar hydrogen concentrations in terms of threshold of fracture during quenching, though the threshold is reduced as initial hydrogen concentration increases. Ductility of pre-hydrided, oxidized and quenched claddings was also evaluated by using ring-tensile and ring-compression tests. Embrittlement criteria (zero-ductility limits) from both the tests were lower than the fracture conditions in the integral thermal shock tests. This indicates that loading conditions should be well simulated to evaluate cladding performance under LOCA conditions.

Journal Articles

Viscosity and density measurements of melts and glasses at high pressure and temperature by using the multi-anvil apparatus and synchrotron X-ray radiation

Otani, Eiji*; Suzuki, Akio*; Ando, Ryota*; Urakawa, Satoru*; Funakoshi, Kenichi*; Katayama, Yoshinori

Advances in High-Pressure Technology for Geophysical Applications, p.195 - 209, 2005/09

This paper summarizes the techniques for the viscosity and density measurements of silicate melt and glasses at high pressure and temperature by using the X-ray radiography and absorption techniques in the third generation synchrotron radiation facility, SPring-8, Japan. The falling sphere method using in situ X-ray radiography makes it possible to measure the viscosity of silicate melts to the pressures above 6 GPa at high temperature. We summarize the details of the experimental technique of the viscosity measurement, and the results of the measurements of some silicate melts such as the albite and diopside-jadeite systems. X-ray absorption method is applied to measure the density of the silicate glasses such as the basaltic glass and iron sodium disilicate glass up to 5 GPa at high temperature. A diamond capsule, which is not reactive with the glass, is used for the density measurement of the glasses. The present density measurement of the glasses indicates that this method is useful for measurement of the density of silicate melts at high pressure and temperature.

Journal Articles

Substitution effect on orientation of organosilicon compounds (CH$$_{3}$$)$$_{3}$$SiX (X = F, Cl, Br, I, NCO) as studied using NEXAFS spectroscopy

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Nath, K. G.*; Uddin, M. N.*

Journal of Physics; Condensed Matter, 17(36), p.5453 - 5466, 2005/09

 Times Cited Count:1 Percentile:93.33(Physics, Condensed Matter)

The orientation nature of multilayer organosilicon compounds has been investigated by measuring the dependence of the Si K-shell near-edge X-ray absorption fine structures (NEXAFS) on the polarization angle. Two approaches helped to elucidate the orientation mechanism: the substitution effect and the deposition-rate dependence. The orientation angles of Si-X bond axes were obtained for trimethylsilyl halides, (CH$$_{3}$$)$$_{3}$$SiX (X =F Cl Br I NCO, condensed on Cu(111) at a low (82 K) temperature: the angles are 60, 73, 61, 55, and 55 degrees with respect to the surface normal, for X =F, Cl, Br, I, and NCO, respectively. Chloride (X =Cl) produces the most parallel tilt angle. The specific orientation nature of chloride is attributed to its strong dipole moment as well as the regular tetrahedron shape of the molecule. The molecular volumes calculated verify this view. Furthermore, deposition rates are found to greatly influence the growth manner: namely, high deposition rates led to a slightly perpendicular orientation of Si-X bond axis.

Journal Articles

X-ray absorption fine structure spectra of rust layers on Fe-based binary alloys exposed to Cl-rich environment

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Proceedings of 16th International Corrosion Congress (CD-ROM), 6 Pages, 2005/09

XANES measurements of rust layers formed on Fe, Fe-Cr alloys and Fe-Ni alloys exposed to a Cl-rich atmosphere have been performed using synchrotron radiation in order to clarify the relation between the structural properties of the rust layer on weathering steel and anticorrosive alloying elements and/or chloride ions. The XANES spectra around Cl K-edge revealed that the rust layer on the Fe-based binary alloys contains unidentified chloride in addition to akagan$'e$iteite. The Fe K-edge XANES results indicated that the rust layers are composed mainly of well-known iron oxides, goethite, akagan$'e$ite, lepidocrocite and magnetite. In particular, the mole ratio of akagan$'e$ite in the rust layers on the Fe-Ni alloys is relatively higher than that of the Fe-Cr alloys. The Cr K-edge XANES spectra of the rust layers on the Fe-Cr alloys depends on the Cr alloy content. Therefore, the local structure of Cr in the rust layer is variable with the Cr density. In contrast, the Ni K-edge XANES results show that the local structure of Ni in the rust layer are unique in a certain Ni content range.

Journal Articles

High-pressure induced structural changes in metastable Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ thin films; An X-ray absorption study

Fons, P.*; Kolobov, A.*; Tominaga, Junji*; Katayama, Yoshinori

Nuclear Instruments and Methods in Physics Research B, 238(1-4), p.160 - 162, 2005/08

 Times Cited Count:5 Percentile:57.42(Instruments & Instrumentation)

Super-resolution (SR) media offer up to a factor of ten increase in areal storage density over conventional DVD media. Although SR has been realized, there is a strong need for a deeper understanding of structural and electronic changes in Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ (GST), a principal optical memory component, with external perturbations. Recording of SR disks leads to the formation of gas-phase bubbles that in turn lead to the development of large stresses on the underlying GST layer. In this paper we report on XAFS of nominally hydrostatic (0-10 GPa) compressive stress-induced structural changes of the metastable crystalline phase of GST. An analysis showed that the initial splitting of Ge Te bond lengths of the room-temperature distorted rocksalt structure decreased to a small but finite splitting for $$p$$ $$_sim^{>}$$ 6 GPa. The implications of this upon the proposed ferroelectric catastrophe super-RENS readout mechanism are discussed.

Journal Articles

Synchrotron radiation photoabsorption and photoemission spectroscopy for thermal-induced reoriented Si polymer

Nath, K. G.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji

Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.323 - 326, 2005/06

 Times Cited Count:5 Percentile:71.16(Spectroscopy)

The effect of laser annealing on electronic atructures and molecular orientation for poly(dimethylsilane), {PDMS, [Si(CH$$_{3}$$)$$_{2}$$]$$_{n}$$} has been studied by synchrotron radiation photoemission and photoabsorption spectroscopy. Prior to annealing, PDMS powder was mounted on the basal plane of highly oriented pyrolytic graphite. Both Si 1s X-ray photoemission spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at Si 1s edge show that electronic structures have been modified due to annealing. Furthermore, the angle-dependent NEXAFS spectra clearly indicate that the annealed products maintain a specific orientation. Interestingly, no such kind of orientation is present in as-received PDMS powder as no angle-dependency is observed before annealing.

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