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Katsuta, Nagayoshi*; Umemura, Ayako*; Naito, Sayuri*; Masuki, Yuma*; Itayama, Yui*; Niwa, Masakazu; Shirono, Shinichi*; Yoshida, Hidekazu*; Kawakami, Shinichi*
Spectrochimica Acta, Part B, 210, p.106817_1 - 106817_11, 2023/12
Times Cited Count：0 Percentile：0.02(Spectroscopy)X-ray fluorescence (XRF) scanning of lacustrine sediments has been used to extend the approach to a wider range of elemental records in both ages and timescales of variations in past environments and climates. However, one of severe problems with effects of the XRF intensity by grain size and mineralogical composition known as "heterogeneity effects" have been pointed out. This study investigated the heterogeneity effect of Fe intensities on X-ray beam using several binary powder mixtures and lacustrine sediment cores.
Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of JapanKitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.
Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07
Times Cited Count：25 Percentile：69.93(Meteorology & Atmospheric Sciences)We compared seven atmospheric transport model results for Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.
impactsKitayama, Takumi*; Nakajima, Kaoru*; Suzuki, Motofumi*; Narumi, Kazumasa; Saito, Yuichi; Matsuda, Makoto; Sataka, Masao*; Tsujimoto, Masahiko*; Isoda, Shoji*; Kimura, Kenji*
Nuclear Instruments and Methods in Physics Research B, 354, p.183 - 186, 2015/07
Times Cited Count：2 Percentile：17.42(Instruments & Instrumentation)Oe, Kazuhiro*; Attallah, M. F.*; Asai, Masato; Goto, Naoya*; Gupta, N. S.*; Haba, Hiromitsu*; Huang, M.*; Kanaya, Jumpei*; Kaneya, Yusuke*; Kasamatsu, Yoshitaka*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1317 - 1320, 2015/02
Times Cited Count：10 Percentile：64.00(Chemistry, Analytical)A new technique for continuous dissolution of nuclear reaction products transported by a gas-jet system was developed for superheavy element (SHE) chemistry. In this technique, a hydrophobic membrane is utilized to separate an aqueous phase from the gas phase. With this technique, the dissolution efficiencies of short-lived radionuclides of 
Mo and 
W were measured. Yields of more than 80% were observed for short-lived radionuclides at aqueous-phase flow rates of 0.1-0.4 mL/s. The gas flow-rate had no influence on the dissolution efficiency within the studied flow range of 1.0-2.0 L/min. These results show that this technique is applicable for on-line chemical studies of SHEs in the liquid phase.
-orbital symmetry of the ground state in Yb compounds by linear dichroism in core-level photoemissionMori, Takeo*; Kitayama, Satoshi*; Kanai, Yuina*; Naimen, Sho*; Fujiwara, Hidenori*; Higashiya, Atsushi*; Tamasaku, Kenji*; Tanaka, Arata*; Terashima, Kensei*; Imada, Shin*; et al.
Journal of the Physical Society of Japan, 83(12), p.123702_1 - 123702_5, 2014/12
Times Cited Count：16 Percentile：68.25(Physics, Multidisciplinary)We show that the strongly correlated 4-orbital symmetry of the ground state is revealed by linear dichroism in core-level photoemission spectra, as we have discovered for YbRh
Si and YbCuSi. Theoretical analysis shows us that the linear dichroism reflects the anisotropic charge distributions resulting from a crystalline electric field. We have successfully determined the ground-state 4 symmetry for both compounds from the polarization-dependent angle resolved core-level spectra at a temperature well below the first excitation energy. The excited-state symmetry is also probed by temperature dependence of the linear dichroism where the high measurement temperatures are on the order of the crystal-field-splitting energies.
ions observed using high-resolution Rutherford backscattering spectroscopyNakajima, Kaoru*; Morita, Yosuke*; Kitayama, Takumi*; Suzuki, Motofumi*; Narumi, Kazumasa; Saito, Yuichi; Tsujimoto, Masahiko*; Isoda, Shoji*; Fujii, Yoshikazu*; Kimura, Kenji*
Nuclear Instruments and Methods in Physics Research B, 332, p.117 - 121, 2014/08
Times Cited Count：7 Percentile：48.01(Instruments & Instrumentation)Hirano, Fumio; Sato, Seichi*; Kozaki, Tamotsu*; Inagaki, Yaohiro*; Iwasaki, Tomohiko*; Oe, Toshiaki*; Kato, Kazuyuki*; Kitayama, Kazumi*; Nagasaki, Shinya*; Niibori, Yuichi*
Journal of Nuclear Science and Technology, 49(3), p.310 - 319, 2012/03
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)The thermal impacts of hull and end piece wastes from the reprocessing of MOX spent fuels burned in LWRs on repository performance were investigated. The heat generation rates in MOX spent fuels and the resulting heat generation rates in hull and end piece wastes change depending on the fuel histories including the burn-up of UO spent fuels, the cooling period before reprocessing, the storage period of fresh MOX fuels. The heat generation rates of hull and end piece wastes from the reprocessing of MOX spent fuels with any of those histories are significantly larger than those from UO spent fuels with burn-ups of 45 GWd/THM. If a temperature below 80
C is specified for cement-based materials used in waste packages after disposal, the allowable number of canisters containing compacted hull and end pieces in a package for 45 GWd-MOX needs to be limited to a value of 0.7 to 1.6, which is significantly lower than the value of 4.0 for 45 GWd-UO.
Sugita, Yutaka*; Takahashi, Yoshiaki*; Uragami, Manabu*; Kitayama, Kazumi*; Fujita, Tomoo; Yui, Mikazu
JAEA-Research 2007-023, 70 Pages, 2007/03
JAEA-Research-2007-023.pdf:26.16MB
The sealing performance of a repository is very important for the safety assessment of the geological disposal system for high-level radioactive waste. NUMO and JAEA set up a technical commission to investigate sealing technology in a repository in 2004 following a cooperation agreement between these two organisations. The objectives of this commission were to present a concept of sealing performance required in the disposal system and to direct future R&D for design requirements of closure components (backfilling material, clay plug, etc.). Hydraulic analyses on tunnel intersections were carried out during the first year in 2004. This was expanded into a hydraulic analysis of a complete disposal panel with all tunnels during the second year in 2005. Since the model structure in 2005 was more complicated than the one used in 2004, the concept of equivalent permeability was adopted in and around each tunnel in the hydraulic analyses. Parameters used in the hydraulic analyses were installation positions of clay plugs, permeability of the backfilling material, permeability of disposal tunnel and directions of hydraulic gradient to estimate influences to the analytical results preliminary. Analytical results showed that flow rate in a disposal tunnel was influenced by directions of hydraulic gradient, installation of the clay plug at the both ends of each disposal tunnel and permeability of the main tunnel.
Sugita, Yutaka; Fujita, Tomoo; Takahashi, Yoshiaki*; Kawakami, Susumu; Umeki, Hiroyuki; Yui, Mikazu; Uragami, Manabu*; Kitayama, Kazumi*
Physics and Chemistry of the Earth, 32(1-7), p.32 - 41, 2007/00
Times Cited Count：6 Percentile：20.62(Geosciences, Multidisciplinary)The H12 repository concept for vitrified high-level radioactive waste was developed based on a multi-barrier system with the emphasis on robust engineered barrier performance to ensure its feasibility for a wide range of geological conditions typically observed in Japan. The buffer is clay-based and plays a very important role in the engineered barrier system (EBS). The decision to use a volunteer siting process requires maximum flexibility of the repository concept to allow it to be adapted to potential sites and hence a wide range of variants of the basic H12 repository design has been developed. In order to evaluate the feasibility and the applicability of different repository options to specific siting environments, NUMO has established a set of "design factors" which classify the aspects that need to be considered when evaluating the pros and cons of different repository options. A Na-type bentonite from Japan is used as the reference material for all clay-based repository components (buffer, backfill, clay plug, etc.). The characteristics of this bentonite (thermal, mechanical, chemical, hydraulic) have been examined with consideration of various practical constraints (limitation on the repository footprint, the influence of saline water, the interaction of hyperalkaline leachates and practical working environment, etc.). Clay-based seals, which close off the tunnels after emplacement of the EBS, may also be key components for assessment of the repository. Full analyses considering all engineered barrier components (buffer, backfill, clay plug, concrete lining, tunnel, concrete plug, host rock) that may be used in a repository will be an essential future task. As a first step towards this goal, a numerical analysis focusing on hydraulic behaviour at the intersections of the disposal tunnels and the main tunnel is presented to illustrate how the design requirements of clay-based seals can be determined.
Kitayama, Kazumi*; Yui, Mikazu
Nihon Genshiryoku Gakkai-Shi, 45(12), p.787 - 797, 2003/00
Times Cited Count：1 Percentile：10.85(Nuclear Science & Technology)The report introduces the engineering technologies for geological disposal of high-level radioactive waste. The contents of the report are current status of the technologies on design and assessment of long-term behavior of the engineered barrier, and design, construction, operation and closure of a repository, based on the concept of geological disposal.
irradiationKitayama, Takumi*; Morita, Yosuke*; Nakajima, Kaoru*; Suzuki, Motofumi*; Narumi, Kazumasa; Saito, Yuichi; Matsuda, Makoto; Sataka, Masao*; Tsujimoto, Masahiko*; Isoda, Shoji*; et al.
no journal, ,
irradiationKitayama, Takumi*; Morita, Yosuke*; Nakajima, Kaoru*; Kimura, Kenji*; Narumi, Kazumasa; Saito, Yuichi; Matsuda, Makoto; Sataka, Masao*
no journal, ,
no abstracts in English
Hayashi, Hiroaki*; Kitayama, Takumi*; Morita, Yosuke*; Nakajima, Kaoru*; Narumi, Kazumasa; Saito, Yuichi; Matsuda, Makoto; Sataka, Masao*; Tsujimoto, Masahiko*; Isoda, Shoji*; et al.
no journal, ,
no abstracts in English
Toyoshima, Atsushi; Miyashita, Sunao*; Oe, Kazuhiro*; Kitayama, Yuta*; Lerum, H. V.*; Goto, Naoya*; Kaneya, Yusuke; Komori, Yukiko*; Mitsukai, Akina*; Vascon, A.; et al.
no journal, ,
no abstracts in English
ionsKitayama, Takumi*; Morita, Yosuke*; Nakajima, Kaoru*; Narumi, Kazumasa; Saito, Yuichi; Matsuda, Makoto; Sataka, Masao*; Kimura, Kenji*
no journal, ,
no abstracts in English
Toyoshima, Atsushi; Oe, Kazuhiro*; Asai, Masato; Attallah, M. F.*; Goto, Naoya*; Gupta, N. S.*; Haba, Hiromitsu*; Kaneko, Masashi*; Kaneya, Yusuke; Kasamatsu, Yoshitaka*; et al.
no journal, ,
Due to short half-lives less than 10 s and extremely low production rates, transactinide elements heavier than seaborgium (Sg) are produced on an atom per hour scale. Therefore, a continuous rapid chemistry assembly is required to study aqueous-phase chemistry of these heaviest elements. In the present study, we started developments of a continuous chemistry assembly. Our first attempt was made in on-line experiments with Mo and W, lighter homologs of Sg, to optimize a chemistry assembly consisting of a newly developed membrane degasser as an interface between gas-jet and aqueous phase, a flow electrolytic column apparatus utilized to control oxidation states of Mo and W ions, and the continuous liquid-liquid extraction apparatus of SISAK for separation. In the conference, present status of the developments will be presented.
Masuki, Yuma*; Itayama, Yui*; Minami, Masayo*; Niwa, Masakazu; Yoshimizu, Chikage*; Tayasu, Ichiro*; Katsuta, Nagayoshi*
no journal, ,
In this presentation, we report origin and depositional process of arsenic in lacustrine sediments of Ane River, inferred from the stable isotope ratios and organic elements compositions.
Itayama, Yui*; Masuki, Yuma*; Minami, Masayo*; Ochiai, Shinya*; Yoshimizu, Chikage*; Tayasu, Ichiro*; Niwa, Masakazu; Katsuta, Nagayoshi*
no journal, ,
In this presentation, we report the environmental changes using Buir lake sediments in eastern Mongolian Plateau.
Itayama, Yui*; Hayano, Asuka*; Kamegai, Yushi*; Yasuda, Shiori*; Murakami, Takuma*; Ochiai, Shinya*; Niwa, Masakazu; Katsuta, Nagayoshi*
no journal, ,
In this presentation, we report paleo-environmental changes in the southern region of Lake Baikal by chemical and grain-size analyses for the lake sediment cores.
Oe, Kazuhiro; Tsukada, Kazuaki; Asai, Masato; Sato, Tetsuya; Toyoshima, Atsushi; Miyashita, Sunao; Nagame, Yuichiro; Sch
del, M.; Kaneya, Yusuke*; Lerum, H. V.*; et al.
no journal, ,
We are planning to investigate the redox behavior of element 106, seaborgium (Sg). For the Sg study, we newly developed a continuous dissolution apparatus which dissolves the gas-jet transported nuclides produced in nuclear reactions into aqueous solution. The new apparatus has a hydrophobic membrane filter for separation of aqueous solution from the gas. We investigated the dissolution efficiencies with the apparatus for short-lived nuclides of molybdenum and tungsten which are lighter homologues of Sg. In the meeting, the dependence of the efficiencies on the aqueous- and gas-flow rates will be reported.
