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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

Variation of half-life and internal-conversion electron energy spectrum between $$^{235m}$$U oxide and fluoride

Shigekawa, Yudai*; Kasamatsu, Yoshitaka*; Yasuda, Yuki*; Kaneko, Masashi; Watanabe, Masayuki; Shinohara, Atsushi*

Physical Review C, 98(1), p.014306_1 - 014306_5, 2018/07

 Percentile:100(Physics, Nuclear)

The nuclear half-life of $$^{235m}$$U has been reported to vary depending on the chemical environment. In this study, both the half-life and the internal-conversion (IC) electron energy spectrum were measured for $$^{235m}$$U with identical chemical environments for the first time. $$^{235m}$$U oxide and fluoride samples were subjected to these measurements, and clear differences in the half-life and the energy spectrum between these samples were observed. The peaks in the energy spectra were identified with the relativistic density functional theory calculation, and the molecular orbital states of the $$^{235m}$$U oxide and fluoride estimated from the energy spectra and the calculation qualitatively explained the difference in the half-lives between the samples.

Journal Articles

Nihonium, and the next elements...

Sakurai, Hiroshi*; Shinohara, Atsushi*; Koura, Hiroyuki; Kamigaito, Osamu*; Morimoto, Koji*; Haba, Hiromitsu*; Enyo, Hideto*

Isotope News, (特別号2), p.2 - 14, 2018/01

no abstracts in English

Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

Journal Articles

Development of multi-colored neutron talbot-lau interferometer with absorption grating fabricated by imprinting method of metallic glass

Seki, Yoshichika; Shinohara, Takenao; Parker, J. D.*; Yashiro, Wataru*; Momose, Atsushi*; Kato, Kosuke*; Kato, Hidemi*; Sadeghilaridjani, M.*; Otake, Yoshie*; Kiyanagi, Yoshiaki*

Journal of the Physical Society of Japan, 86(4), p.044001_1 - 044001_5, 2017/03

 Times Cited Count:7 Percentile:18.97(Physics, Multidisciplinary)

For the effective phase imaging at pulsed neutron sources, we have designed and developed the multi-colored Talbot-Lau interferometer which works at several wavelengths. At the Energy Resolved Neutron Imaging System RADEN in J-PARC, we demonstrated its operation by observing the visibilities of moire fringes derived from different wavelengths (0.25, 0.50, and 0.75 nm). We also investigated the variation of moire fringes dependent on the wavelength resolution from 18% to 50% and showed the advantage of pulsed beams. At the central wavelength of 0.5 nm, we have succeeded in interferometric imaging for the samples of metal rods made of aluminum, lead, and copper. An absorption grating as an analyzer was fabricated by imprinting of metallic glass for the first time, and showed a clear moire fringe with the high visibility of 68% and a well-controlled shape in comparison with previous ones fabricated by oblique evaporation of gadolinium.

Journal Articles

Experimental evaluation of neutron absorption grating fabricated by oblique evaporation of gadolinium for phase imaging

Seki, Yoshichika; Shinohara, Takenao; Ueno, Wakana; Parker, J. D.*; Samoto, Tetsuo*; Yashiro, Wataru*; Momose, Atsushi*

Physics Procedia, 88, p.217 - 223, 2017/00

 Times Cited Count:4 Percentile:0.61

Journal Articles

Investigation of countermeasure against local temperature rise in vessel cooling system in loss of core cooling test without nuclear heating

Ono, Masato; Shimizu, Atsushi; Kondo, Makoto; Shimazaki, Yosuke; Shinohara, Masanori; Tochio, Daisuke; Iigaki, Kazuhiko; Nakagawa, Shigeaki; Takada, Shoji; Sawa, Kazuhiro

Journal of Nuclear Engineering and Radiation Science, 2(4), p.044502_1 - 044502_4, 2016/10

In the loss of forced core cooling test using High Temperature engineering Test Reactor (HTTR), the forced cooling of reactor core is stopped without inserting control rods into the core and cooling by Vessel Cooling System (VCS) to verify safety evaluation codes to investigate the inherent safety of HTGR be secured by natural phenomena to make it possible to design a severe accident free reactor. The VCS passively removes the retained residual heat and the decay heat from the core via the reactor pressure vessel by natural convection and thermal radiation. In the test, the local temperature was supposed to exceed the limit from the viewpoint of long-term use at the uncovered water cooling tube by thermal reflectors in the VCS, although the safety of reactor is kept. Through a cold test, which was carried out by non-nuclear heat input from gas circulators with stopping water flow in the VCS, the local higher temperature position was specified although the temperature was sufficiently lower than the maximum allowable working temperature, and natural circulation of water had insufficient cooling effect on the temperature of water cooling tube below 1$$^{circ}$$C. Then, a new safe and secured procedure for the loss of forced core cooling test was established, which will be carried out soon after the restart of HTTR.

Journal Articles

Preparation and evaluation of an astatine-211-labeled sigma receptor ligand for $$alpha$$ radionuclide therapy

Ogawa, Kazuma*; Mizuno, Yoshiaki*; Washiyama, Koshin*; Shiba, Kazuhiro*; Takahashi, Naruto*; Kozaka, Takashi*; Watanabe, Shigeki; Shinohara, Atsushi*; Odani, Akira*

Nuclear Medicine and Biology, 42(11), p.875 - 879, 2015/11

 Times Cited Count:9 Percentile:34.43(Radiology, Nuclear Medicine & Medical Imaging)

Journal Articles

Nondestructive elemental depth-profiling analysis by muonic X-ray measurement

Ninomiya, Kazuhiko*; Kubo, Kenya*; Nagatomo, Takashi*; Higemoto, Wataru; Ito, Takashi; Kawamura, Naritoshi*; Strasser, P.*; Shimomura, Koichiro*; Miyake, Yasuhiro*; Suzuki, Takao*; et al.

Analytical Chemistry, 87(9), p.4597 - 4600, 2015/05

 Times Cited Count:7 Percentile:58.47(Chemistry, Analytical)

Journal Articles

Production of $$^{88}$$Nb and $$^{170}$$Ta for chemical studies of element 105, Db, using the GARIS gas-jet system

Huang, M.*; Haba, Hiromitsu*; Murakami, Masashi*; Asai, Masato; Kaji, Daiya*; Kanaya, Jumpei*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Kikutani, Yuki*; Komori, Yukiko*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 304(2), p.845 - 849, 2015/05

 Times Cited Count:3 Percentile:66.76(Chemistry, Analytical)

A technique to utilize radioisotopes of Nb and Ta was developed for chemical studies of element 105, Db, by coupling a gas-jet transport system to the RIKEN gas-filled recoil ion separator (GARIS). The short-lived $$^{88}$$Nb and $$^{170}$$Ta were produced with nuclear reactions using a $$^{19}$$F beam whose energy was the same as that to produce $$^{262}$$Db. Then, they were separated with GARIS and extracted to a chemistry laboratory with the gas-jet transport system. By changing only magnetic field of GARIS and inserting an energy degrader and a shutter for recoil ions, we could deliver the $$^{88}$$Nb and $$^{170}$$Ta to a chemistry device for $$^{262}$$Db without changing other experimental conditions.

Journal Articles

Investigation of characteristics of natural circulation of water in vessel cooling system in loss of core cooling test without nuclear heating

Takada, Shoji; Shimizu, Atsushi; Kondo, Makoto; Shimazaki, Yosuke; Shinohara, Masanori; Seki, Tomokazu; Tochio, Daisuke; Iigaki, Kazuhiko; Nakagawa, Shigeaki; Sawa, Kazuhiro

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

In the loss of forced core cooling test using High Temperature engineering Test Reactor (HTTR), the forced cooling of reactor core is stopped without inserting control rods into the core and cooling by Vessel Cooling System (VCS) to demonstrate the inherent safety of HTGR be secured by natural phenomena to make it possible to design a severe accident free reactor. In the test, the local temperature was supposed to exceed the limit from the viewpoint of long-term use at the uncovered water cooling tube by thermal reflectors in the VCS, although the safety of reactor is kept. The local higher temperature position was specified although the temperature was sufficiently lower than the maximum allowable working temperature, and natural circulation of water had insufficient cooling effect on the temperature of water cooling tube below 1$$^{circ}$$C. Then, a new safe and secured procedure for the loss of forced core cooling test was established, which will be carried out soon after the restart of HTTR.

Journal Articles

Measurements of the neutron activation cross sections for Bi and Co at 386 MeV

Yashima, Hiroshi*; Sekimoto, Shun*; Ninomiya, Kazuhiko*; Kasamatsu, Yoshitaka*; Shima, Tatsushi*; Takahashi, Naruto*; Shinohara, Atsushi*; Matsumura, Hiroshi*; Satoh, Daiki; Iwamoto, Yosuke; et al.

Radiation Protection Dosimetry, 161(1-4), p.139 - 143, 2014/10

 Times Cited Count:2 Percentile:73.24(Environmental Sciences)

The neutron activation cross sections up to GeV are important for the neutron dosimetry of the radiation field in high-energy and high-intensity accelerator facilities for a project of intense spallation neutron source. But the evaluation of neutron activation cross section data is not enough above 20 MeV because experimental data are still scarce. This study aimed to measure the neutron activation cross sections of Bi and Co by using a quasi-monoenergetic neutron field. In this symposium, we will present obtained experimental cross section data with the other experimental data (neutron-induced and proton-induced), the calculated data by PHITS code and the evaluated nuclear data.

Journal Articles

Production of $$^{262}$$Db in the $$^{248}$$Cm($$^{19}$$F,5$$n$$)$$^{262}$$Db reaction and decay properties of $$^{262}$$Db and $$^{258}$$Lr

Haba, Hiromitsu*; Huang, M.*; Kaji, Daiya*; Kanaya, Jumpei*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Murakami, Masashi*; Ozeki, Kazutaka*; Sakai, Ryutaro*; et al.

Physical Review C, 89(2), p.024618_1 - 024618_11, 2014/02

 Times Cited Count:16 Percentile:17.81(Physics, Nuclear)

Journal Articles

Measurement of the Md$$^{3+}$$/Md$$^{2+}$$ reduction potential studied with flow electrolytic chromatography

Toyoshima, Atsushi; Li, Z.*; Asai, Masato; Sato, Nozomi; Sato, Tetsuya; Kikuchi, Takahiro; Kaneya, Yusuke; Kitatsuji, Yoshihiro; Tsukada, Kazuaki; Nagame, Yuichiro; et al.

Inorganic Chemistry, 52(21), p.12311 - 12313, 2013/11

 Times Cited Count:3 Percentile:78.65(Chemistry, Inorganic & Nuclear)

The reduction behavior of mendelevium (Md) was studied using a flow electrolytic chromatography apparatus. By applying appropriate potentials on the chromatography column, the more stable Md$$^{3+}$$ is reduced to Md$$^{2+}$$. The reduction potential of the Md$$^{3+}$$ + e$$^{-}$$ $$rightarrow$$ Md$$^{2+}$$ couple was determined to be -0.16$$pm$$0.05 V vs. a normal hydrogen electrode.

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

Development of nondestructive and quantitative elemental analysis method using calibration curve between muonic X-ray intensity and elemental composition in bronze

Ninomiya, Kazuhiko; Nagatomo, Takashi*; Kubo, Kenya*; Ito, Takashi; Higemoto, Wataru; Kita, Makoto*; Shinohara, Atsushi*; Strasser, P.*; Kawamura, Naritoshi*; Shimomura, Koichiro*; et al.

Bulletin of the Chemical Society of Japan, 85(2), p.228 - 230, 2012/02

 Times Cited Count:7 Percentile:66.74(Chemistry, Multidisciplinary)

Elemental analysis of bulk materials can be performed by detecting the high-energy X-rays emitted from muonic atoms. Muon irradiation of standard bronze samples was performed to determine the muon capture probabilities for the elemental components from muonic X-ray spectra. Nondestructive elemental analysis of an ancient Chinese coin was also performed.

Journal Articles

Production of $$^{265}$$Sg in the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$)$$^{265}$$Sg reaction and decay properties of two isomeric states in $$^{265}$$Sg

Haba, Hiromitsu*; Kaji, Daiya*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozeki, Kazutaka*; Sakai, Ryutaro*; Sumita, Takayuki*; Yoneda, Akira*; Kasamatsu, Yoshitaka*; et al.

Physical Review C, 85(2), p.024611_1 - 024611_11, 2012/02

 Times Cited Count:36 Percentile:8.68(Physics, Nuclear)

Two isomeric states in $$^{265}$$Sg, i.e, $$^{265}$$Sg$$^{a}$$ and $$^{265}$$Sg$$^{b}$$ were produced in the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$) reaction. Decay properties of $$^{265}$$Sg$$^{a,b}$$ were investigated with a rotating-wheel apparatus for $$alpha$$ and spontaneous fission (SF) spectrometry under low background condition attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated $$alpha$$-$$alpha$$ (-$$alpha$$) and $$alpha$$-SF decay chains, 18 and 24 events were assigned to $$^{265}$$Sg$$^{a}$$ and $$^{265}$$Sg$$^{b}$$, respectively. The half-life and $$alpha$$-particle energy of $$^{265}$$Sg$$^{a}$$ were measured to be $$8.5^{+2.6}_{-1.6}$$ s and $$8.84 pm 0.05$$ MeV, respectively, and those of $$^{265}$$Sg$$^{b}$$ were $$14.4^{+3.7}_{-2.5}$$ s and $$8.69 pm 0.05$$ MeV.

Journal Articles

Observation of energetic particle driven axisymmetric mode in the JT-60U tokamak

Matsunaga, Go; Kamiya, Kensaku; Shinohara, Koji; Miyato, Naoaki; Kojima, Atsushi; Bierwage, A.; JT-60 Team

Europhysics Conference Abstracts (Internet), 36F, p.P2.062_1 - P2.062_4, 2012/00

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

Measurement of neutron cross sections for yttrium and terbium at 287 MeV

Sekimoto, Shun*; Utsunomiya, Takashi*; Yashima, Hiroshi*; Ninomiya, Kazuhiko*; Omoto, Takashi*; Nakagaki, Reiko*; Shima, Tatsushi*; Takahashi, Naruto*; Shinohara, Atsushi*; Kinoshita, Norikazu*; et al.

Progress in Nuclear Science and Technology (Internet), 1, p.89 - 93, 2011/02

In this work, we tried to determine reaction cross sections for Y and Tb induced by neutrons at 300 MeV, which have never been reported. The irradiations were carried out using neutrons produced through $$^{7}$$Li(p, n) reaction at N0 beam line in the Research Center for Nuclear Physics (RCNP), Osaka University. To estimate quasi-monoenergetic neutron induced cross sections, the target stacks of Y and Tb were irradiated on the two angles of 0 degree and 30 degree for the axis of the primary proton beam. Neutron cross sections were estimated by subtracting the activities produced in the samples placed on 30 degree from those of 0 degree to correct the contribution of the low energy tail in the neutron spectrum.

133 (Records 1-20 displayed on this page)