Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Ito, Keita*; Yasutomi, Yoko*; Zhu, S.*; Nurmamat, M.*; Tahara, Masaki*; Toko, Kaoru*; Akiyama, Ryota*; Takeda, Yukiharu; Saito, Yuji; Oguchi, Tamio*; et al.
Physical Review B, 101(10), p.104401_1 - 104401_8, 2020/03
Times Cited Count:17 Percentile:75.65(Materials Science, Multidisciplinary)Horie, Hiroki*; Yukumatsu, Kazuki*; Mishima, Fumihito*; Akiyama, Yoko*; Nishijima, Shigehiro*; Sekiyama, Tomio*; Mitsui, Seiichiro; Kato, Mitsugu
Journal of Physics; Conference Series, 871, p.012102_1 - 012102_7, 2017/07
Times Cited Count:1 Percentile:49.36(Physics, Applied)Li, Z.*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Sato, Nozomi; Kikuchi, Takahiro; Nagame, Yuichiro; Schdel, M.; Pershina, V.*; et al.
Radiochimica Acta, 100(3), p.157 - 164, 2012/03
Times Cited Count:14 Percentile:68.93(Chemistry, Inorganic & Nuclear)Koarashi, Jun; Mikami, Satoshi; Miyauchi, Toru; Kozawa, Tomoyasu*; Yokota, Tomokazu*; Nakada, Akira; Akiyama, Kiyomitsu; Momose, Takumaro
JAEA-Technology 2010-039, 34 Pages, 2010/12
The current methodology for monitoring airborne radioiodine at the Tokai reprocessing plant (TRP) was reviewed, and some investigations were made to re-evaluate collection and measurement techniques in the methodology. The investigations focused particularly on: (1) in situ collection efficiency of an iodine sampler for I and its dependence on sampling flow rate; (2) evaluation of I and I activities collected in an activated charcoal cartridge; (3) I collection capacity of an activated charcoal cartridge under reprocessing off-gas conditions; and (4) real-time monitoring system for I in airborne effluent. The results obtained gave not only the validity of the TRP's monitoring method, but also technical aspects required for establishing a more reliable and effective monitoring method for radioiodine isotopes.
Tanaka, Kenji*; Kawahata, Kazuo*; Tokuzawa, Tokihiko*; Akiyama, Tsuyoshi*; Yokoyama, Masayuki*; Shoji, Mamoru*; Michael, C. A.*; Vyacheslavov, L. N.*; Murakami, Sadayoshi*; Wakasa, Arimitsu*; et al.
Fusion Science and Technology, 58(1), p.70 - 90, 2010/07
Times Cited Count:23 Percentile:82.23(Nuclear Science & Technology)Particle confinement processes were studied in detail on LHD. Diffusion coefficients (D) and convection velocities (V) were estimated from density modulation experiments. The magnetic configuration and collisionality were widely scanned in order to investigate parameter dependences of D and V. In order to study the effect of the magnetic configuration, magnetic axis positions (R) were scanned from 3.5 m to 3.9 m. This scan changed the magnetic ripples quite significantly, enabling the effects of neoclassical properties on measured values to be widely elucidated. Dependences of electron temperature (T) and helically trapped normalized collsionality (), where =1 indicates a rough boundary between the 1/ and plateau regimes, were examined using the heating power scan of neutral beam injection (NBI). It was found out that generally larger (or smaller) contributions of neoclassical transport resulted in more hollow (or peaked) density profiles. The larger neoclassical contribution was found to be situated at a more outwardly shifted R for the same T, and higher T or lower at each R. However, it is to be noted that R=3.5 m showed different characteristics from these trends in that this case showed a more peaked density profile at higher T.
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:16 Percentile:48.84(Chemistry, Multidisciplinary)We report on the characteristic anion-exchange behavior of the superheavy element dubnium (Db) with atomic number Z = 105 in HF/HNO 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.
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:21 Percentile:77.63(Chemistry, Inorganic & Nuclear)Anion-exchange chromatography of element 105, dubnium (Db), produced in the Cm(F, 5n)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) 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 Nb Db Pa.
Nakada, Akira; Miyauchi, Toru; Akiyama, Kiyomitsu; Momose, Takumaro; Kozawa, Tomoyasu*; Yokota, Tomokazu*; Otomo, Hiroyuki*
JAEA-Data/Code 2008-018, 134 Pages, 2008/10
This report provides the data set of atmospheric discharges from Tokai reprocessing plant in Tokai-mura, Japan over the period from 1998 to 2007. Daily and weekly data are shown for Kr that is continuously monitored and for the other nuclide (Alpha emitters, Beta emitters, H, C, I, I) whose activities are evaluated based on weekly batch-samplings, respectively. The data contained in this report are expected to apply for studying the behavior of the radioactive airborne effluent in the environment.
Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Michael, C.*; Vyacheslavov, L. N.*; Yokoyama, Masayuki*; Yamada, Hiroshi*; Oyama, Naoyuki; Urano, Hajime; Kamada, Yutaka; et al.
Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10
Comparative studies were carried out in LHD heliotron and JT-60U tokamak plasmas to elucidate the most essential parameter(s) for control of density profiles in toroidal systems. A difference in the collisionality dependence was found between the two devices. In LHD, the density peaking factor decreased with decrease of the collisionality at the magnetic axis position (R) 3.6 m, while the density peaking factor gradually increased with a decreased of collisionality at R = 3.5 m. On the other hand, in JT-60U, the density peaking factor clearly increased with a decrease of the collisionality. The difference in the collisionality dependence between R = 3.5 and R = 3.6 m is likely due to the contribution of the anomalous transport. At R = 3.5 m, larger anomalous transport caused a similar collisionality dependence. Change of the fluctuation property was observed with different density profiles in the plasma core region on both devices. In JT-60U, the increase of the radial coherence was observed with higher density peaking profile suggesting enhanced diffusion and inward directed pinch. For a magnetic axis positions (R) at 3.6 m in LHD, the increase of the fluctuation power with an increase in P was observed for a hollow density profile suggesting an increase on diffusion due to anomalous processes. Change of density profiles from peaked to hollow indicates change in the convection direction. This is due to increase in neoclassical processes. The reduction of the density peaking factor with increase of P in LHD is partly due to the neoclassical effect and partly due to the anomalous effect.
Tanaka, Kenji*; Michael, C.*; Vyacheslavov, L. N.*; Yokoyama, Masayuki*; Murakami, Sadayoshi*; Wakasa, Arimitsu*; Takenaga, Hidenobu; Muraoka, Katsunori*; Kawahata, Kazuo*; Tokuzawa, Tokihiko*; et al.
Plasma and Fusion Research (Internet), 3, p.S1069_1 - S1069_7, 2008/08
Density profiles in LHD were measured and particle transport coefficients were estimated from density modulation experiments in LHD. The dataset of different magnetic axis, toroidal magnetic filed and heating power provided data set of widely scanned neoclassical transport. At minimized neoclassical transport configuration ( = 3.5 m, = 2.8 T) showed peaked density profile. Its peaking factor increased gradually with decrease of collisional frequency. This is a similar result observed in JT-60U. At other configuration, peaking factor reduced with decrease of collsional frequency. Data set showed that larger contribution of neoclassical transport produced hollowed density profile. Comparison between neoclassical and estimated particle diffusivity showed different minimum condition. Clear difference of spatial profile of turbulence was observed between hollowed and peaked density profiles. Major part of fluctuation existed in the unstable region of ion temperature gradient mode.
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:29 Percentile:84.99(Chemistry, Inorganic & Nuclear)Formation of an anionic fluoride-complex of element 104, rutherfordium (Rf) produced in the Cm(O,5n)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], was formed in the studied fluoride ion concentrations of 0.0005 - 0.013 M. Formation of [RfF] was significantly different from that of the homologues Zr and Hf, [ZrF] and [HfF]; the evaluated formation constant of [RfF] is at least one-order of magnitude smaller than those of [ZrF] and [HfF].
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:16 Percentile:70.17(Chemistry, Inorganic & Nuclear)no abstracts in English
Koarashi, Jun; Isaka, Keisuke*; Yokota, Tomokazu*; Kozawa, Tomoyasu*; Mikami, Satoshi; Akiyama, Kiyomitsu; Kobayashi, Hirohide
JNC TN8410 2005-005, 55 Pages, 2005/05
Some investigations were made for re-evaluating collection and measurement techniques in an airborne C discharge monitoring at the Tokai reprocessing plant (TRP), which include (1)collection efficiency of CO in a carbon sampler using monoethanolamine as CO absorbent;(2)affect of incorporating tritiated water into the carbon sampler on quantitative estimation of C activity in airborne effluent; (3)affect of leakage in air sampling on evaluating airborne C discharge; and (4)determination of chemical forms of C in airborne release from the TRP. The results presented not only the validity of the TRP's monitoring method, but also the technical aspects required for establishing a more reliable and effective monitoring method.
Koarashi, Jun; Yokota, Tomokazu*; Kozawa, Tomoyasu*; Isaka, Keisuke*; Mikami, Satoshi; Akiyama, Kiyomitsu; Kobayashi, Hirohide
JNC TN8410 2005-004, 73 Pages, 2005/05
Some investigations were made for re-evaluating collection and measurement techniques in an airborn H discharge monitoring at the Tokai reprocessing plant (TRP), which include (1)collection efficiency of water in a tritium sampler; (2)quench correction in H activity measurement by liquid scintillation counting; (3)affect of leakage in air sampling on evaluating airborne H discharge; and (4)determination of chemical forms of H in airborne release from the TRP. The results presented not only the validity of the TRP's monitoring method, but also the technical aspects required for establishing a more reliable and effective monitoring method.
Koarashi, Jun; Akiyama, Kiyomitsu; Asano, Tomohiro; Yokota, Tomokazu*
Journal of Radioanalytical and Nuclear Chemistry, 262(3), p.771 - 774, 2005/01
Effect of incorporating tritiated water into a C sampling system on sample preparation and C activity measurement by liquid scintillation counting were investigated. Experiments derived the limit of water content in prepared sample, and also demonstrated that C activity can be determined without any interference fromH contamination for clear-solution sample. The results enabled us to estimate permissible reelative humidity of air required for accomplishing sample preparation and C activity measurement. These showed that for sampling of air with less than the permissible relative humidity, total C activity in airborne effluent can be evaluated accurately with no dehumidification of air.
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:31 Percentile:87.03(Chemistry, Inorganic & Nuclear)no abstracts in English
Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko; Nishinaka, Ichiro; Nagame, Yuichiro; Saika, Daisuke*; Matsuo, Keishi*; Sato, Wataru*; et al.
Journal of Nuclear and Radiochemical Sciences, 5(2), p.45 - 48, 2004/12
no abstracts in English
Koarashi, Jun; Kozawa, Tomoyasu*; Yokota, Tomokazu*; Isaka, Keisuke*; Akiyama, Kiyomitsu; Asano, Tomohiro
JNC TN8410 2004-003, 49 Pages, 2004/07
Radioactive airborne effluent discharged from Tokai reprocessing plant (TRP) contains tritium, carbon-14 and radioiodine. These radionuclides are collected with appropriate methods, respectively, in stacks to monitor their concentrations and discharged amounts. This report describes (1) the methods for collecting these radionuclides in TRP; (2) evaluations of the concentrations and discharged amounts; and (3) investigations on estimating performances of the collecting methods. The investigations showed that the collecting methods used in TRP have collecting efficiencies of more than 90% for tritium and radioiodine, and almost 100% for carbon-14. Considerations concerning collection of radionuclides in airborne effluent, made in this study, provided some technical aspects required for establishing more reliable monitoring systems.
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:44 Percentile:72.46(Chemistry, Multidisciplinary)Fluoride complexation of element 104, rutherfordium (Rf), produced in the Cm(O,5n)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 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.
Matsuda, Hideo*; Omura, Ichiro*; Sakiyama, Yoko*; Urano, Satoshi*; Iesaka, Susumu*; Ohashi, Hiromichi*; Hirao, Toshio; Abe, Hiroshi; Ito, Hisayoshi; Mori, Hidenobu; et al.
JAERI-Review 2002-035, TIARA Annual Report 2001, p.11 - 13, 2002/11
no abstracts in English