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Journal Articles

Activity of $$^{90}$$Sr in fallout particles collected in the difficult-to-return zone around the Fukushima Daiichi Nuclear Power Plant

Zhang, Z.*; Igarashi, Junya*; Satou, Yukihiko; Ninomiya, Kazuhiko*; Sueki, Keisuke*; Shinohara, Atsushi*

Environmental Science & Technology, 53(10), p.5868 - 5876, 2019/05

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released abundant radioactive particles into the surrounding environment. Herein, we analyzed the activity of $$^{90}$$Sr in these particles to estimate the contribution of this radionuclide to the overall radiation exposure and shed light on the processes that occurred during the accident. Seven radioactive particles were isolated from the dust and soil samples collected from areas surrounding the FDNPP, and the minimum/maximum $$^{137}$$Cs activities were determined as 224/4,100 Bq. Based on the size, specific activity, and $$^{134}$$Cs/$$^{137}$$Cs activity ratios, we concluded that six of the seven radioactive particles were released from the Unit 1 reactor, while one particle was released from the Unit 3 reactor by a hydrogen explosion. Strontium-90 was detected in all radioactive particles, and the minimal/maximal $$^{90}$$Sr activities were determined as 0.046/1.4 Bq. $$^{137}$$Cs/$$^{90}$$Sr activity ratios above 1000 were observed for all seven particles, that is, compared to $$^{137}$$Cs, $$^{90}$$Sr had negligible contribution to the overall radiation exposure. The $$^{137}$$Cs/$$^{90}$$Sr activity ratios of the radioactive particles were similar to those of terrestrial environmental samples and were higher for particles released from the Unit 1 reactor than for samples collected from the Unit 1 reactor building, which indicates possibility of additional $$^{90}$$Sr -rich contamination after release of the particles.

Journal Articles

Depth profile and inventory of $$^{36}$$Cl in soil near the Fukushima Dai-ichi Nuclear Power Plant

Ota, Yuki*; Sueki, Keisuke*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Matsunaka, Tetsuya*; Matsumura, Masumi*; Tosaki, Yuki*; Honda, Maki*; Hosoya, Seiji*; Takano, Kenta*; et al.

JAEA-Conf 2018-002, p.99 - 102, 2019/02

no abstracts in English

Journal Articles

Radiocarbon variations in tree rings since 1960 near the Tokai nuclear facility, Japan

Matsunaka, Tetsuya*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Hosoya, Seiji*; Matsumura, Masumi*; Satou, Yukihiko; Shen, H.*; Sueki, Keisuke*

Nuclear Instruments and Methods in Physics Research B, 439, p.64 - 69, 2019/01

 Percentile:100(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Analysis of two forms of radioactive particles emitted during the early stages of the Fukushima Dai-ichi Nuclear Power Station accident

Satou, Yukihiko; Sueki, Keisuke*; Sasa, Kimikazu*; Yoshikawa, Hideki; Nakama, Shigeo; Minowa, Haruka*; Abe, Yoshinari*; Nakai, Izumi*; Ono, Takahiro*; Adachi, Koji*; et al.

Geochemical Journal, 52(2), p.137 - 143, 2018/00

 Times Cited Count:10 Percentile:1.74(Geochemistry & Geophysics)

Journal Articles

Journal Articles

Radiocarbon variations since 1960 in tree rings around the nuclear facilities of the eastern Japan

Matsunaka, Tetsuya*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Hosoya, Seiji*; Matsumura, Masumi*; Sueki, Keisuke*; Satou, Yukihiko

Dai-19-Kai AMS Shimpojiumu, 2016-Nendo "Jumoku Nenrin" Kenkyukai Kyodo Kaisai Shimpojiumu Hokokushu, p.76 - 79, 2017/06

To evaluate the radiological impact of the atmospheric $$^{14}$$C discharge from the Tokai nuclear facilities, a 80-year-old Japanese pine tree from Tokai, 1.8 km south-southwest of the Tokai Nuclear Power Plants (Tokai NPP and Tokai-2 NPP) and 1.4 km North-Northwest of the Tokai Reprocessing Plant (Tokai RP), was cored and each annual ring was measured for $$^{14}$$C. The $$^{14}$$C specific activities varied from 232.8 Bq kg$$^{-1}$$ C to 403.3Bq kg$$^{-1}$$ C in the tree rings formed during the periods 1954-2013. The specific activities in 1967-2010 are significantly elevated compared with the ambient background values, clearly indicating $$^{14}$$C discharges from the nuclear facilities during their normal operation. The excess $$^{14}$$C activities of 0.5-70.0 Bq kg$$^{-1}$$ C in 1970-2011 are positively correlated with the estimated annual $$^{14}$$C discharges of 0.1-1.2 TBq from Tokai NPP and Tokai-2 NPP with R$$^{2}$$ of 0.66 (n = 38). These activity values of $$<$$ 70.0 Bq kg$$^{-1}$$ C were corresponding to an additional annual effective dose of $$<$$ 3.9 uSv via the food ingestion pathway in the study location.

Journal Articles

Investigation of the chemical characteristics of individual radioactive microparticles emitted from reactor 1 by the Fukushima Daiichi Nuclear Power Plant accident by using multiple synchrotron radiation X-ray analyses

Ono, Takahiro*; Iizawa, Yushin*; Abe, Yoshinari*; Nakai, Izumi*; Terada, Yasuko*; Satou, Yukihiko; Sueki, Keisuke*; Adachi, Koji*; Igarashi, Yasuhito*

Bunseki Kagaku, 66(4), p.251 - 261, 2017/04

 Times Cited Count:6 Percentile:32.86(Chemistry, Analytical)

no abstracts in English

Journal Articles

Radioactive Cs in the estuary sediments near Fukushima Daiichi Nuclear Power Plant

Yamasaki, Shinya*; Imoto, Jumpei*; Furuki, Genki*; Ochiai, Asumi*; Onuki, Toshihiko; Sueki, Keisuke*; Namba, Kenji*; Ewing, R. C.*; Utsunomiya, Satoshi*

Science of the Total Environment, 551-552, p.155 - 162, 2016/05

 Times Cited Count:15 Percentile:17(Environmental Sciences)

Cesium-137 ($$^{137}$$Cs) of estuary sediment impacted by the FDNPP was measured. Increasing radioactivity was observed from surface to bottom. 90% of the $$^{137}$$Cs was strongly bound to clay minerals in the estuary sediments. These results suggest that $$^{137}$$Cs is being transported from contaminated paddy fields to the estuary.

Journal Articles

New result in the production and decay of an isotope, $$^{278}$$113 of the 113th element

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sumita, Takayuki*; Wakabayashi, Yasuo*; Yoneda, Akira*; Tanaka, Kengo*; et al.

Journal of the Physical Society of Japan, 81(10), p.103201_1 - 103201_4, 2012/10

 Times Cited Count:111 Percentile:2.38(Physics, Multidisciplinary)

An isotope of the 113th element, $$^{278}$$113, was produced in a nuclear reaction with a $$^{70}$$Zn beam on a $$^{209}$$Bi target. We observed six consecutive $$alpha$$ decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector, in extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of $$^{262}$$Db and $$^{258}$$Lr both in decay energies and decay times. This indicates that the present decay chain consisted of $$^{278}$$113, $$^{274}$$Rg (Z = 111), $$^{270}$$Mt (Z = 109), $$^{266}$$Bh (Z = 107), $$^{262}$$Db (Z = 105), and $$^{258}$$Lr (Z = 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads the unambiguous production and identification of the isotope $$^{278}$$113, of the 113th element.

Journal Articles

Sulfate complexation of element 104, Rf, in H$$_{2}$$SO$$_{4}$$/HNO$$_{3}$$ mixed solution

Li, Z.*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Sato, Nozomi; Kikuchi, Takahiro; Nagame, Yuichiro; Sch$"a$del, M.; Pershina, V.*; et al.

Radiochimica Acta, 100(3), p.157 - 164, 2012/03

 Times Cited Count:8 Percentile:32.85(Chemistry, Inorganic & Nuclear)

Journal Articles

Neutron one-quasiparticle states in $$^{251}$$Fm$$_{151}$$ populated via the $$alpha$$ decay of $$^{255}$$No

Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Ishii, Yasuo; Ichikawa, Takatoshi*; Toyoshima, Atsushi; Ishii, Tetsuro; Nagame, Yuichiro; Nishinaka, Ichiro; Kojima, Yasuaki*; et al.

Physical Review C, 83(1), p.014315_1 - 014315_12, 2011/01

 Times Cited Count:19 Percentile:19.41(Physics, Nuclear)

Excited states in $$^{251}$$Fm populated via the $$alpha$$ decay of $$^{255}$$No are studied in detail through $$alpha$$-$$gamma$$ coincidence and $$alpha$$ fine structure measurements. Spin-parities and neutron configurations of the excited states in $$^{251}$$Fm as well as the ground state of $$^{255}$$No are definitely identified on the basis of deduced internal conversion coefficients, lifetimes of $$gamma$$ transitions, rotational-band energies built on one-quasiparticle states, and hindrance factors of $$alpha$$ transitions. It is found that the excitation energy of the 1/2$$^{+}$$[620] state in $$N$$=151 isotones increases with the atomic number, especially at $$Z$$$$ge$$100, while that of the 1/2$$^{+}$$[631] state decreases at $$Z$$=100. Energy systematics of the one-quasiparticle states in the $$N$$=151 isotones are discussed in terms of the evolution of nuclear deformation involving the hexadecapole and hexacontatetrapole deformations.

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

$$^{225}$$Ac metallofullerene; Toward $$^{225}$$Ac nanogenerator in fullerene

Akiyama, Kazuhiko*; Haba, Hiromitsu*; Sueki, Keisuke*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Nagame, Yuichiro; Katada, Motomi*

Chemistry Letters, 38(10), p.978 - 979, 2009/09

 Times Cited Count:7 Percentile:62.27(Chemistry, Multidisciplinary)

We report on the successful production of a metallofullerene encapsulating the radioactive tracer $$^{225}$$Ac and on its electronic properties studied by radiochromatography. Considering the number of $$pi$$-electrons on the fullerene cage estimated from an HPLC retention time on the 5PBB column and the general oxidation state of Ac (+3), a chemical species of the dominant chromatographic peak is suggested to be Ac@C$$_{82}$$.

Journal Articles

Chloride complexation of Zr and Hf in HCl investigated by extended X-ray absorption fine structure spectroscopy; Toward characterization of chloride complexation of element 104, rutherfordium (Rf)

Haba, Hiromitsu*; Akiyama, Kazuhiko*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Yaita, Tsuyoshi; Hirata, Masaru; Sueki, Keisuke*; Nagame, Yuichiro

Bulletin of the Chemical Society of Japan, 82(6), p.698 - 703, 2009/06

 Times Cited Count:9 Percentile:56.91(Chemistry, Multidisciplinary)

Chloride complexation of the group-4 elements Zr and Hf in 8.0-11.9 M HCl is investigated by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy to characterize chloro complexes of the transactinide element, rutherfordium (Rf). The complexes of Zr and Hf successively vary with the concentration of HCl from a hydrated complex [M(H$$_{2}$$O) $$_{8}$$]$$^{4+}$$ at 8.0 M to a hexachloro complex [MCl$$_{6}$$]$$^{2-}$$ at 11.9 M (M = Zr and Hf). The present structural changes of the Zr and Hf complexes well reflect the previously studied anion-exchange behavior of Zr and Hf in HCl. From both the EXAFS and anion-exchange results, we suggest that Rf forms the same complexes as those of Zr and Hf in HCl, and that the complexation strength of the hexachloro complexes of the group-4 elements, [MCl$$_{6}$$] $$^{2-}$$ (M = Zr, Hf, and Rf), is in the sequence of Rf $$>$$ Zr $$>$$ Hf.

Journal Articles

A Metallofullerene that encapsulates $$^{225}$$Ac

Akiyama, Kazuhiko*; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Sueki, Keisuke*; Nagame, Yuichiro; Katada, Motomi*

Journal of Radioanalytical and Nuclear Chemistry, 280(2), p.329 - 331, 2009/05

 Times Cited Count:7 Percentile:45.86(Chemistry, Analytical)

The properties of a metallofullerene that encapsulates $$^{225}$$Ac were studied by radio-chromatographic methods. The results of chromatography on a Buckyclutcher column suggest that there are some metallofullerene isomers of AcC$$_{82}$$. The identical HPLC retention time of the major AcC$$_{82}$$ peak with that of La@C$$_{82}$$ indicates that the structure of one of the AcC$$_{82}$$ isomers is the same as La@C$$_{82}$$.

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

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

Experiment on synthesis of an isotope $$^{277}$$112 by $$^{208}$$Pb + $$^{70}$$Zn reaction

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Katori, Kenji*; Koura, Hiroyuki; Kudo, Hisaaki*; et al.

Journal of the Physical Society of Japan, 76(4), p.043201_1 - 043201_5, 2007/04

 Times Cited Count:116 Percentile:4(Physics, Multidisciplinary)

The production and decay of $$^{277}$$112 has been investigated using a gas-filled recoil ion separator in irradiations of $$^{208}$$Pb targets with $$^{70}$$Zn beam at 349.5 MeV. We have observed two $$alpha$$-decay chains that can be assigned to subsequent decays from $$^{277}$$112 produced in the 208 Pb($$^{70}$$Zn,n) reaction. After emitting four consecutive $$alpha$$-particles, the both chains ended by spontaneous fission decays of $$^{261}$$Rf and decay energies and decay times of the both chains obtained in the present work agree well with those reported by a group at Gesellschaft f$"u$r Schwerionenforschung (GSI), Germany. The present result gives the first clear confirmation of the discovery of $$^{277}$$112 and its $$alpha$$-decay products $$^{273}$$Ds reported previously.

Journal Articles

Observation of second decay chain from $$^{278}$$113

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Katori, Kenji*; Koura, Hiroyuki; Kikunaga, Hidetoshi*; et al.

Journal of the Physical Society of Japan, 76(4), p.045001_1 - 045001_2, 2007/04

 Times Cited Count:153 Percentile:2.68(Physics, Multidisciplinary)

The production and decay of $$^{278}$$113 has been investigated using a gas-filled recoil ion separator in irradiations of $$^{209}$$Bi targets with $$^{70}$$Zn beam at 353 MeV. We have observed one $$alpha$$-decay chain that can be assigned to subsequent decays from $$^{278}$$113 produced in the $$^{209}$$Bi($$^{70}$$Zn,n) reaction. After emitting four consecutive $$alpha$$-particles, the both chains ended by spontaneous fission decays of $$^{262}$$Db and decay energies and decay times of the both chains obtained in the present work agree well with those reported by our group in 2004. The present result gives the first clear confirmation of the discovery of $$^{278}$$113 and its $$alpha$$-decay products $$^{274}$$Rg reported previously.

Journal Articles

Experiments on synthesis of the heaviest element at RIKEN

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Kanungo, R.*; Katori, Kenji*; Kikunaga, Hidetoshi*; et al.

AIP Conference Proceedings 891, p.3 - 9, 2007/03

A series of experiments studying the productions and their decays of the heaviest elements have been performed by using a gas-filled recoil separator GARIS at RIKEN. Results on the isotope of the 112th element, $$^{277}$$112, and on that of the 113th element, $$^{278}$$113, are reviewed. Two decay chains which are assigned to be ones originating from the isotope $$^{277}$$112 were observed in the $$^{208}$$Pb($$^{70}$$Zn, n) reaction. The results provide a confirmation of the production and decay of the isotope $$^{277}$$112 reported by a research group at GSI, Germany, produced via the same reaction by using a velocity filter. Two decay chains, both consisted of four consecutive alpha decays followed by a spontaneous fission, were observed also in the reaction $$^{209}$$Bi($$^{70}$$Zn, n). Those are assigned to be the convincing candidate events of the isotope of the 113th element, $$^{278}$$113, and its daughter nuclei. $$^{274}$$Rg, $$^{270}$$Mt, $$^{266}$$Bh, and $$^{262}$$Db.

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