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Journal Articles

Atmospheric modeling of $$^{137}$$Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of Japan

Kitayama, 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

We compared seven atmospheric transport model results for $$^{137}$$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 $$^{137}$$Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for $$^{137}$$Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated $$^{137}$$Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated $$^{137}$$Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced $$^{137}$$Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.

Journal Articles

Application of multiple prompt $$gamma$$-ray analysis (MPGA) to geochemical and cosmochemical samples

Oura, Yasuji*; Watanabe, Ryo*; Ebihara, Mitsuru*; Murakami, Yukihiro*; Toh, Yosuke; Kimura, Atsushi; Koizumi, Mitsuo; Furutaka, Kazuyoshi; Oshima, Masumi; Hara, Kaoru; et al.

Journal of Radioanalytical and Nuclear Chemistry, 291(2), p.335 - 339, 2012/02

 Times Cited Count:3 Percentile:64.33(Chemistry, Analytical)

We applied multiple prompt $$gamma$$-ray analysis (MPGA) method to geochemical and cosmochemical samples to evaluate its analytical performance on signal to noise (S/N) ratio, sensitivity, and detection limit. The S/N ratio measured by MPGA system was larger than that by normal prompt $$gamma$$ ray activation analysis (PGAA) at JRR3. For some elements, the S/N ratio was improved more than ten times. Several elements that are not detected by PGAA were detected by MPGA. In the present experiment, concentrations of major elements and trace elements with high neutron capture cross section in geochemical and cosmochemical samples were determined accurately by the MPGA system. It is expected that it will determine a lot of trace elements after appropriate adjustments and modifications.

Journal Articles

Fluorido complex formation of element 104, rutherfordium (Rf)

Ishii, Yasuo; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Li, Z.*; Nagame, Yuichiro; Miyashita, Sunao*; Mori, Tomotaka*; Suganuma, Hideo*; Haba, Hiromitsu*; et al.

Bulletin of the Chemical Society of Japan, 84(9), p.903 - 911, 2011/09

 Times Cited Count:12 Percentile:50.96(Chemistry, Multidisciplinary)

The cation-exchange behavior of element 104, rutherfordium (Rf), was investigated together with its lighter group-4 homologues Zr and Hf, and the tetravalent pseudo-homologue Th in HF/HNO$$_{3}$$ mixed solution. The results demonstrate that distribution coefficients ($$K_{d}$$) of Rf in HF/0.10 M HNO$$_{3}$$ decrease with increasing concentration of the fluoride ion [F$$^{-}$$], indicating the consecutive formation of fluorido complexes of Rf. We also measured the $$K_{d}$$ values of Rf and the homologues as a function of the hydrogen ion concentration [H$$^{+}$$]. The log $$K_{d}$$ values decrease linearly with an increase of log [H$$^{+}$$] with slopes between -2.1 and -2.5. This indicates that these elements are likely to form the same chemical compounds: mixture of [MF]$$^{3+}$$ and [MF$$_{2}$$]$$^{2+}$$ (M = Rf, Zr, Hf and Th) in the studied solution. It is also ascertained that sequence in the fluoride complex formation is Zr $$sim$$ Hf $$>$$ Rf $$>$$ Th.

Journal Articles

Extraction of chromatographic behavior of Rf, Zr, and Hf in HCl solution with styrenedivinylbenzene copolymer resin modified by TOPO (trioctylphosphine oxide)

Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Tsukada, Kazuaki; Asai, Masato; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; Sch$"a$del, M.; et al.

Journal of Nuclear and Radiochemical Sciences, 11(1), p.7 - 11, 2010/06

The extraction behavior of rutherfordium (Rf) into trioctylphosphine oxide (TOPO) from 2.0 - 7.0 M HCl solution was studied together with that of the homologues Zr and Hf. The extracted yields of Rf, Zr, and Hf increased with an increase of HCl concentration, and the sequence of their extraction was Zr $$>$$ Hf $$geq$$ Rf. It is suggested that the stability of the RfCl$$_{4}$$$$cdot$$2(TOPO) complex is lower than that of the corresponding species of the homologues.

Journal Articles

Anionic fluoro complex of element 105, Db

Kasamatsu, Yoshitaka*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Li, Z.; Ishii, Yasuo; Tome, Hayato*; Sato, Tetsuya; Kikuchi, Takahiro; Nishinaka, Ichiro; et al.

Chemistry Letters, 38(11), p.1084 - 1085, 2009/10

 Times Cited Count:13 Percentile:48.46(Chemistry, Multidisciplinary)

We report on the characteristic anion-exchange behavior of the superheavy element dubnium (Db) with atomic number Z = 105 in HF/HNO$$_{3}$$ solution at the fluoride ion concentration [F$$^{-}$$] = 0.003 M. The result clearly demonstrates that the fluoro complex formation of Db is significantly different from that of the group-5 homologue Ta in the 6th period of the periodic table while the behavior of Db is similar to that of the lighter homologue Nb in the 5th period.

Journal Articles

Adsorption of Db and its homologues Nb and Ta, and the pseudo-homologue Pa on anion-exchange resin in HF solution

Tsukada, Kazuaki; Haba, Hiromitsu*; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko*; Kasamatsu, Yoshitaka; Nishinaka, Ichiro; Ichikawa, Shinichi; Yasuda, Kenichiro; Miyamoto, Yutaka; et al.

Radiochimica Acta, 97(2), p.83 - 89, 2009/02

 Times Cited Count:19 Percentile:15.82(Chemistry, Inorganic & Nuclear)

Anion-exchange chromatography of element 105, dubnium (Db), produced in the $$^{248}$$Cm($$^{19}$$F, 5n)$$^{262}$$Db reaction is investigated together with the homologues Nb and Ta, and the pseudo-homologue Pa in 13.9 M hydrofluoric acid (HF) solution. The distribution coefficient (K$$_{d}$$) of Db on an anion-exchange resin is successfully determined by running cycles of the 1702 chromatographic column separations. The result clearly indicates that the adsorption of Db on the resin is significantly different from that of the homologues and that the adsorption of anionic fluoro complexes of these elements decreases in the sequence of Ta $$approx$$ Nb $$>$$ Db $$geq$$ Pa.

Journal Articles

Fluoride complexation of element 104, rutherfordium (Rf), investigated by cation-exchange chromatography

Ishii, Yasuo; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Tome, Hayato; Nishinaka, Ichiro; Nagame, Yuichiro; Miyashita, Sunao*; Mori, Tomotaka*; Suganuma, Hideo*; et al.

Chemistry Letters, 37(3), p.288 - 289, 2008/03

 Times Cited Count:17 Percentile:43.4(Chemistry, Multidisciplinary)

We have investigated cation-exchange behavior of Rf together with the lighter homologues of the group-4 elements Zr and Hf, and the tetravalent pseudo-homologue Th, in HF/HNO$$_{3}$$ solution using Automated Ion exchange separation apparatus coupled with the Detection system for Alpha spectroscopy (AIDA). The ${it K}$ $$_{d}$$ values of Zr, Hf, Th and Rf in HF/0.1 M HNO$$_{3}$$ were decreased with increasing the concentration of the fluoride ion [F$$^{-}$$], indicating the formation of the fluoride complexes. The sequence of the fluoride complexation strength is Zr $$sim$$ Hf $$>$$ Rf $$>$$ Th.

Journal Articles

Hexafluoro complex of rutherfordium in mixed HF/HNO$$_{3}$$ solutions

Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko*; Goto, Shinichi*; Ishii, Yasuo; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; et al.

Radiochimica Acta, 96(3), p.125 - 134, 2008/03

 Times Cited Count:23 Percentile:13(Chemistry, Inorganic & Nuclear)

Formation of an anionic fluoride-complex of element 104, rutherfordium (Rf) produced in the $$^{248}$$Cm($$^{18}$$O,5n)$$^{261}$$Rf reaction was studied by an anion-exchange method based on an atom-at-a-time scale. It was found that the hexafluoro complex of Rf, [RfF$$_{6}$$]$$^{2-}$$, was formed in the studied fluoride ion concentrations of 0.0005 - 0.013 M. Formation of [RfF$$_{6}$$]$$^{2-}$$ was significantly different from that of the homologues Zr and Hf, [ZrF$$_{6}$$]$$^{2-}$$ and [HfF$$_{6}$$]$$^{2-}$$; the evaluated formation constant of [RfF$$_{6}$$]$$^{2-}$$ is at least one-order of magnitude smaller than those of [ZrF$$_{6}$$]$$^{2-}$$ and [HfF$$_{6}$$]$$^{2-}$$.

Journal Articles

An Attempt for determining $$^{235}$$U/$$^{238}$$U ratio for a trace amount of uranium: Search for an extinct radionuclide $$^{247}$$Cm in the early solar system

Chai, J.; Miyamoto, Yutaka; Kokubu, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu; Oura, Yasuji*; Ebihara, Mitsuru*

Journal of Radioanalytical and Nuclear Chemistry, 272(2), p.397 - 401, 2007/05

 Times Cited Count:2 Percentile:78.23(Chemistry, Analytical)

$$^{247}$$Cm is an important nuclide because it has the next-shortest half-life (1.6$$cdot$$10$$^{7}$$ yr) from $$^{244}$$Pu among the transuranic nuclides. The disintegration of $$^{247}$$Cm to $$^{235}$$U by three $$alpha$$ decays and two $$beta$$ decays and the chemical fractionation between Cm and U during the formation of solid materials in early solar system lead to changes in the ratios of $$^{235}$$U to $$^{238}$$U. This variation may provide strict constraints on the time interval between the last r-process nucleosynthetic event and the formation of the solar system. It is important to develop a practical analysis protocol to determine the isotope ratio of trace uranium in geochemical and environment samples. As uranium is the least abundant element in our solar system, analytical techniques with high sensitivity and precision are required. In this study, a double focusing inductively coupled plasma mass spectory was applied to measure isotopic ratio of uranium. By one set data obtained from the EDTA phase of the Jilin meteorite sample, the upper limit of $$^{247}$$Cm in the early solar system was calculated and $$^{247}$$Cm/$$^{235}$$U $$<$$ 0.003 was obtained.

Journal Articles

Multiple prompt $$gamma$$-ray analysis and construction of its beam line

Oshima, Masumi; Toh, Yosuke; Kimura, Atsushi; Ebihara, Mitsuru*; Oura, Yasuji*; Ito, Yasuo*; Sawahata, Hiroyuki*; Matsuo, Motoyuki*

Journal of Radioanalytical and Nuclear Chemistry, 271(2), p.317 - 321, 2007/02

 Times Cited Count:9 Percentile:38.44(Chemistry, Analytical)

By combining neutron activation analysis with multiple $$gamma$$-ray detection, we have proved better sensitivity and resolution for the trace element analysis than the ordinary single $$gamma$$-ray detection method. We now try to apply the multiple $$gamma$$-ray detection method to the prompt $$gamma$$-ray analysis (PGA). We have established a new cold neutron beam line for PGA in Japan Research Reactor, JRR-3M, at Tokai establishment of Japan Atomic Energy Research Institute(JAERI). It consists of a beam shutter, a beam attenuator, a $$gamma$$-ray detector array, a sample changer, and a beam stopper. We construct a high-efficiency $$gamma$$-ray detector array specially designed for this purpose. Its performance has been evaluated with the Monte Carlo simulation code, GEANT 4.5.0.

Journal Articles

Extraction behavior of rutherfordium into tributylphosphate from hydrochloric acid

Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Ishii, Yasuo; Tome, Hayato; Sato, Tetsuya; Nishinaka, Ichiro; Ichikawa, Takatoshi; Ichikawa, Shinichi; et al.

Radiochimica Acta, 95(1), p.1 - 6, 2007/01

 Times Cited Count:14 Percentile:24.72(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

$$alpha$$ decay of $$^{238}$$Cm and the new isotope $$^{237}$$Cm

Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Sakama, Minoru*; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

Physical Review C, 73(6), p.067301_1 - 067301_4, 2006/06

 Times Cited Count:18 Percentile:23.28(Physics, Nuclear)

no abstracts in English

Journal Articles

Experimental identification of spin-parities and single-particle configurations in $$^{257}$$No and its $$alpha$$-decay daughter $$^{253}$$Fm

Asai, Masato; Tsukada, Kazuaki; Sakama, Minoru*; Ichikawa, Shinichi; Ishii, Tetsuro; Nagame, Yuichiro; Nishinaka, Ichiro; Akiyama, Kazuhiko; Osa, Akihiko; Oura, Yasuji*; et al.

Physical Review Letters, 95(10), p.102502_1 - 102502_4, 2005/09

 Times Cited Count:56 Percentile:11.75(Physics, Multidisciplinary)

Excited states in $$^{253}$$Fm fed by the $$alpha$$ decay of $$^{257}$$No have been established through $$alpha$$-$$gamma$$ and $$alpha$$-electron coincidence spectroscopy using a gas-jet transport system and an on-line isotope separator. The spin-parity of the 124.1 keV level in $$^{253}$$Fm has been identified on the basis of the measured internal conversion coefficients. The $$nu 3/2^{+}[622]$$ configuration has been assigned to the ground state of $$^{257}$$No as well as to the 124.1 keV level. It was found that the ground state configuration of $$^{257}$$No is different from that of lighter $$N=155$$ isotones.

Journal Articles

Proton-neutron configurations in $$^{236g,m}$$Am and its EC-decay daughter $$^{236}$$Pu

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

European Physical Journal A, 23(3), p.395 - 400, 2005/02

 Times Cited Count:12 Percentile:32.22(Physics, Nuclear)

The EC decay of $$^{236}$$Am has been studied through $$gamma$$-ray spectroscopy. Two EC-decaying states have been found in $$^{236}$$Am with half-lives of 3.6 min and 2.9 min. In $$^{236}$$Pu, we have found the $$K^{pi}=0^{-}$$ octupole band and two-quasiparticle states one of which is a $$K$$ isomer with a 1.2 $$mu$$s half-life. The EC transitions from $$^{236g,m}$$Am to the two-quasiparticle states in $$^{236}$$Pu show small $$log ft$$ values of 4.8--5.3, which allowed us to assign proton-neutron configurations of $$^{236g,m}$$Am and the two-quasiparticle states.

Journal Articles

Chemical studies on rutherfordium (Rf) at JAERI

Nagame, Yuichiro; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko; Ishii, Yasuo; Sato, Tetsuya; Hirata, Masaru; Nishinaka, Ichiro; Ichikawa, Shinichi; et al.

Radiochimica Acta, 93(9-10), p.519 - 526, 2005/00

 Times Cited Count:27 Percentile:11.69(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

EC and $$alpha$$ decays of $$^{235}$$Am

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

European Physical Journal A, 22(3), p.411 - 416, 2004/12

 Times Cited Count:7 Percentile:51.8(Physics, Nuclear)

EC and $$alpha$$ decays of $$^{235}$$Am have been studied by means of $$gamma$$-ray spectroscopy. Excited states in $$^{235}$$Pu have been established for the first time, and tentative spin-parity and Nilsson assignments were given to these levels. The ground state of $$^{235}$$Am was evaluated to be the $$pi 5/2^{-}[523]$$ state from the experimental results. It was found that the $$pi 5/2^{-}[523]$$ state in $$^{231}$$Np is located at $$<$$15~keV, which allowed us to determine the $$Q_{alpha}$$ value of $$^{235}$$Am as 6569$$^{+27}_{-12}$$~keV, in combination with the measured $$alpha$$-particle energy.

Journal Articles

Fluoride complexation of element 104, rutherfordium

Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko; Nishinaka, Ichiro; Hirata, Masaru; Yaita, Tsuyoshi; Ichikawa, Shinichi; Nagame, Yuichiro; et al.

Journal of the American Chemical Society, 126(16), p.5219 - 5224, 2004/04

 Times Cited Count:38 Percentile:26.87(Chemistry, Multidisciplinary)

Fluoride complexation of element 104, rutherfordium (Rf), produced in the $$^{248}$$Cm($$^{18}$$O,5n)$$^{261}$$Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchangechromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the $$^{18}$$O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effect on the fluoride complexation of Rf.

Journal Articles

$$alpha$$-decays of neutron-deficient americium isotopes

Sakama, Minoru*; Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Nishinaka, Ichiro; Nagame, Yuichiro; Haba, Hiromitsu*; Goto, Shinichi*; Shibata, Michihiro*; Kawade, Kiyoshi*; et al.

Physical Review C, 69(1), p.014308_1 - 014308_11, 2004/01

 Times Cited Count:17 Percentile:27.81(Physics, Nuclear)

no abstracts in English

Journal Articles

Identification of the new isotope $$^{241}$$Bk

Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Sakama, Minoru*; Haba, Hiromitsu*; Nagame, Yuichiro; Nishinaka, Ichiro; Akiyama, Kazuhiko; Toyoshima, Atsushi; Kaneko, Tetsuya*; et al.

European Physical Journal A, 16(1), p.17 - 19, 2003/01

 Times Cited Count:8 Percentile:46.32(Physics, Nuclear)

The new isotope $$^{241}$$Bk has been identified for the first time using a gas-jet coupled on-line isotope separator at the JAERI tandem accelerator facility. Characteristic X rays and three $$gamma$$ transitions associated with the EC decay of $$^{241}$$Bk have been observed, and the half-life was determined to be 4.6 min. The half-life value and the observed $$gamma$$-ray energies and intensities can be consistently explained as a consequence of the allowed EC transition of $$pi 7/2^{+}[633]$$ $$rightarrow$$ $$nu 7/2^{+}[624]$$.

Journal Articles

Nuclear decay properties of the neutron-deficient actinides

Sakama, Minoru*; Tsukada, Kazuaki; Asai, Masato; Ichikawa, Shinichi; Haba, Hiromitsu; Goto, Shinichi*; Nishinaka, Ichiro; Nagame, Yuichiro; Oura, Yasuji*; Kojima, Yasuaki*; et al.

Journal of Nuclear Science and Technology, 39(Suppl.3), p.34 - 37, 2002/11

no abstracts in English

53 (Records 1-20 displayed on this page)