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Journal Articles

Deuterium retention in tungsten coating layers irradiated with deuterium and carbon ions

Fukumoto, Masakatsu; Nakano, Tomohide; Ueda, Yoshio*; Itami, Kiyoshi; Kubo, Hirotaka

Journal of Nuclear Materials, 462, p.354 - 359, 2015/07

 Times Cited Count:2 Percentile:22.25(Materials Science, Multidisciplinary)

Journal Articles

Chemical binding states of carbon atoms migrated in tungsten coating layer exposed to JT-60U divertor plasmas

Fukumoto, Masakatsu; Nakano, Tomohide; Ueda, Yoshio*; Itami, Kiyoshi

Plasma and Fusion Research (Internet), 8, p.1405159_1 - 1405159_8, 2013/11

Journal Articles

In-vessel tritium

Ueda, Yoshio*; Oya, Kaoru*; Ashikawa, Naoko*; Ito, Atsushi*; Ono, Tadayoshi*; Kato, Daiji*; Kawashima, Hisato; Kawamura, Gakushi*; Kenmotsu, Takahiro*; Saito, Seiki*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 88(9), p.484 - 502, 2012/09

no abstracts in English

Journal Articles

Effects of carbon impurity on deuterium retention in VPS-tungsten coatings exposed to JT-60U divertor plasmas

Fukumoto, Masakatsu; Nakano, Tomohide; Itami, Kiyoshi; Wada, Takaaki*; Ueda, Yoshio*; Tanabe, Tetsuo*

Journal of Nuclear Materials, 415(Suppl.1), p.S705 - S708, 2011/08

 Times Cited Count:4 Percentile:36.36(Materials Science, Multidisciplinary)

Tungsten coating on the first wall in ITER is proposed to reduce in-vessel tritium retention. However, it is possibility that carbon based materials would be used at high heat load components such as limiter. To predict the tritium retention in tungsten coating, it is essential to investigate the effects of carbon impurity on deuterium retention in tungsten coating. In this study, effects of carbon impurity on deuterium retention in the tungsten coating exposed to JT-60U divertor plasmas were investigated. Deuterium was trapped by carbon which was implanted and accumulated in the tungsten coating during the plasma discharge. D/C ration of 0.04-0.08 in the tungsten coating was reached to 1/2-1/4 compared to T/C ration in carbon co-deposition layer. Therefore, simultaneous use of carbon armor materials and tungsten coating would enhance tritium retention in tungsten coating.

Journal Articles

Thermoresponsive extraction of cadmium(II) ions by poly(TPEN-NIPA) gels; Effect of chain length and branched spacer structure on gel formation and extraction behavior

Inaba, Yusuke*; Tsumagari, Takayuki*; Kida, Tatsuya*; Watanabe, Wataru*; Nakajima, Yasutaka*; Fukuoka, Sachio*; Mori, Atsunori*; Matsumura, Tatsuro; Nakano, Yoshio*; Takeshita, Kenji*

Polymer Journal, 43(7), p.630 - 634, 2011/07

 Times Cited Count:11 Percentile:39.61(Polymer Science)

${it N,N,N',N'}$-(tetrakis-2-pyridylmethyl)ethylenediamine (TPEN) derivatives bearing a polymerizable double bond in the substituent structure of the pyridine ring are synthesized and subjected to copolymerization with ${it N}$-isopropylacrylamide in the presence of AIBN. The obtained poly(TPEN-NIPA) gels show thermo-responsive swelling/shrinking behaviors and are employed for the extraction of cadmium(II) ion from the aqueous solution to examine the relationship of the gel characteristics and the extraction performance. The polymer gels composed of the TPEN derivative bearing C3, C4, C10 and branched C3 spacer chains are synthesized and temperature-dependent extraction behavior of cadmium ion is compared. These gels extract Cd(II) ion efficiently from the aqueous solution in the swelling state at 5$$^{circ}$$C, while little extraction is observed at 45$$^{circ}$$C with shrinking. It is found that poly(TPEN-NIPA) gel of branched C3 spacer (C3b) shows the excellent thermoresponsive extraction performance.

Journal Articles

Report on ITPA meeting, 33

Asakura, Nobuyuki; Ashikawa, Naoko*; Ueda, Yoshio*; Ono, Noriyasu*; Tanabe, Tetsuo*; Nakano, Tomohide; Masuzaki, Suguru*; Itami, Kiyoshi; Kawano, Yasunori; Kawahata, Kazuo*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 87(7), p.485 - 486, 2011/07

no abstracts in English

Journal Articles

Deuterium retention in tungsten coating on the CFC tiles exposed to JT-60U divertor plasmas

Fukumoto, Masakatsu; Nakano, Tomohide; Masaki, Kei; Itami, Kiyoshi; Ueda, Yoshio*; Tanabe, Tetsuo*

Journal of Plasma and Fusion Research SERIES, Vol.9, p.369 - 374, 2010/08

no abstracts in English

Journal Articles

28th report on the ITPA (International Tokamak Physics Activity) meeting

Asakura, Nobuyuki; Nakano, Tomohide; Masuzaki, Takashi*; Ashikawa, Naoko*; Ueda, Yoshio*; Tanabe, Tetsuo*; Ono, Noriyasu*

Purazuma, Kaku Yugo Gakkai-Shi, 86(2), P. 124, 2010/02

no abstracts in English

Journal Articles

Thermo-responsive extraction of cadmium(II) ion with TPEN-NIPA gel; Effect of the number of polymerizable double bond toward gel formation and the extracting behavior

Fukuoka, Sachio*; Kida, Tatsuya*; Nakajima, Yasutaka*; Tsumagari, Takayuki*; Watanabe, Wataru*; Inaba, Yusuke*; Mori, Atsunori*; Matsumura, Tatsuro; Nakano, Yoshio*; Takeshita, Kenji*

Tetrahedron, 66(9), p.1721 - 1727, 2010/02

 Times Cited Count:17 Percentile:50.38(Chemistry, Organic)

N,N,N',N'-(tetrakis-2-pyridylmethyl)ethylenediamine (TPEN) derivatives bearing the different number (1-4) of a double bond moiety on the pyridine ring are synthesized and subjected to copolymerization with N-isopropylacrylamide in the presence of AIBN. The obtained poly(TPEN-NIPA)gels show thermo-responsive swelling/shrinking behaviors and are employed for the extraction of cadmium(II) ion from the aqueous solution to examine the relationship of the gel characteristics and the extraction performance. The polymer gels composed of the TPEN derivative bearing three or four double bonds exhibit temperature-dependent change of swelling and shrinking in water. These gels extract CdII ion efficiently from the aqueous solution in the swelling state at 5$$^{circ}$$C, while little extraction was observed at 45$$^{circ}$$C with shrinking.

Journal Articles

Tungsten accumulation in H-mode plasmas of JT-60U

Nakano, Tomohide; Asakura, Nobuyuki; Kubo, Hirotaka; Yanagibayashi, Jun*; Ueda, Yoshio*

Nuclear Fusion, 49(11), p.115024_1 - 115024_10, 2009/11

 Times Cited Count:31 Percentile:76.81(Physics, Fluids & Plasmas)

It has been observed that with increasing toroidal rotation velocity inside the $$q=1$$ layer in the direction opposite to the plasma current, sawtooth activity becomes moderate and tungsten accumulation becomes significant. The tungsten accumulation level is significantly reduced from this trend in the case that electron cyclotron wave or high energy neutral beam is injected into the plasma core. In contrast, the tungsten accumulation is kept high by the electron cyclotron wave injection into the peripheral region.

Journal Articles

Experimental studies on in-vessel tritium inventory in complicated environment of fusion reactors

Ueda, Yoshio*; Hino, Tomoaki*; Ono, Noriyasu*; Takagi, Ikuji*; Nakano, Tomohide; Tanabe, Tetsuo*; Kajita, Shin*; Fukumoto, Masakatsu

Purazuma, Kaku Yugo Gakkai-Shi, 85(10), p.684 - 694, 2009/10

Relation between deuterium retention, wall temperature and hydrocarbon generation in 30-s H-mode discharges of JT-60U was described. In discharges with a density below 50% of the Greenwald density, the trend of the deuterium retention against pulse number depended on the wall temperature: with increasing pulse number, the deuterium retention decreased at a wall temperature of 300 $$^{circ}$$C, decreased gradually at 150 $$^{circ}$$C, and remained constant at 80 $$^{circ}$$C. In contrast, in discharges with high densities above 70% of the Greenwald density, the deuterium retention increased with increasing pulse number at the above three wall temperatures. In the high density discharges, the deuterium retention flux increased with increasing hydrocarbon generation flux, suggesting that the deuterium is retained in co-deposition layers of carbon, which originated from the hydrocarbons.

Journal Articles

Transport of heavy hydrocarbon and its redeposition on plasma facing walls

Oya, Kaoru*; Inai, Kensuke*; Kikuhara, Yasuyuki*; Nakano, Tomohide; Kawata, Jun*; Kawazome, Hayato*; Ueda, Yoshio*; Tanabe, Tetsuo*

Journal of Plasma and Fusion Research SERIES, Vol.8, p.419 - 424, 2009/09

Redeposition of C$$_{2}$$H$$_{4}$$ and C$$_{2}$$H$$_{6}$$ chemically eroded from carbon walls is simulated by EDDY code incorporated with the reflection on a hydrogenated and amorphized carbon surface. The redeposition rate for heavy hydrocarbons is drastically decreased by introduction of the reflection. The redeposition patterns on the surface are enlarged by the reflection, but it is narrower for the heavy hydrocarbons than for CH$$_{4}$$. The photon emissions of C$$_{2}$$ from C$$_{2}$$H$$_{4}$$ (C$$_{2}$$H$$_{6}$$) decay faster than that of CH from CH$$_{4}$$ in high-temperature ($$>$$10 eV) plasmas, which reproduces the difference of the decay of the CD and C$$_{2}$$ light intensities observed in the vicinity of the outer diverter plates of JT-60U. For such temperatures, the inverse photon-efficiency, which is defined as the ratio of the number of the launching hydrocarbons to the photoemission events of CH and C$$_{2}$$, is in good agreement with the values observed in JT-60U experiments.

Journal Articles

Report on ITPA meetings, 24

Idomura, Yasuhiro; Yoshida, Maiko; Yagi, Masatoshi*; Tanaka, Kenji*; Hayashi, Nobuhiko; Sakamoto, Yoshiteru; Tamura, Naoki*; Oyama, Naoyuki; Urano, Hajime; Aiba, Nobuyuki; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 84(12), p.952 - 955, 2008/12

no abstracts in English

Journal Articles

Localized tungsten deposition in divertor region in JT-60U

Ueda, Yoshio*; Fukumoto, Masakatsu*; Watanabe, Jun*; Otsuka, Yusuke*; Arai, Takashi; Asakura, Nobuyuki; Nobuta, Yuji*; Sato, Masayasu; Nakano, Tomohide; Yagyu, Junichi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Deposition profiles of tungsten released from the outer divertor were studied in JT-60U. A neutron activation method was used for the first time to accurately measure deposited tungsten. Surface density of tungsten in the thick carbon deposition layer can be measured by this method. Tungsten was mainly deposited on the inner divertor (around inner strike points) and on the outer wing of the dome. Toroidal distribution of the W deposition was significantly localized near the tungsten released position, while other metallic impurities such as Fe, Cr, Ni were distributed more uniformly. These data indicate that inward drift in the divertor region played a significant role in tungsten transport in JT-60U.

Journal Articles

Study on chemical reactivity control of liquid sodium; Development of nano-fluid and its property and applicability to FBR plant

Saito, Junichi; Ara, Kuniaki; Sugiyama, Kenichiro*; Kitagawa, Hiroshi*; Nakano, Haruyuki*; Ogata, Kan*; Yoshioka, Naoki*

Proceedings of 16th International Conference on Nuclear Engineering (ICONE-16) (CD-ROM), 4 Pages, 2008/05

no abstracts in English

Journal Articles

Extraction separation of Am(III) and Eu(III) with thermosensitive gel introducing TPEN derivatives

Takeshita, Kenji*; Nakano, Yoshio*; Matsumura, Tatsuro; Mori, Atsunori*

Proceedings of 3rd International ATALANTE Conference (ATALANTE 2008) (CD-ROM), 8 Pages, 2008/05

A thermal-swing chromatographic process using a thermosensitive gel copolymerized with NIPA (N-isopropylacrylamide) and TPPEN (N,N,N',N'-tetrakis(4-propenyloxy-2-pyridylmethyl)ethylenediamine) was studied for the separation of Am(III) from Eu(III). Firstly, the radiolysis of the TPPEN-NIPA gel was tested by the $$gamma$$-ray irradiation and the $$alpha$$ nuclide adsorption. The extraction separation of Am(III) was not influenced in the radioactive environment of the proposed process. Next, the TPPEN-NIPA gel was immobilized in porous silica particles and the applicability of the gel-immobilized silica to the proposed process was tested. Am(III) was extracted selectively in the gel-immobilized silica at 5$$^{circ}$$C and the separation factor of Am(III) over Eu(III) was evaluated to be 3.7. The distribution ratio of Am(III) was reduced to less than 1/20 by increasing temperature from 5$$^{circ}$$C to 40$$^{circ}$$C. These results indicate that the TPPEN-NIPA gel is applicable to the thermal-swing chromatographic process for the MA recovery.

Journal Articles

Thermal-swing extraction separation of Am(III) and Eu(III) with poly-NIPA gel crosslinked with TPEN derivative

Takeshita, Kenji*; Matsumura, Tatsuro; Nakano, Yoshio*

Journal of Nuclear Science and Technology, 44(12), p.1481 - 1483, 2007/12

 Times Cited Count:9 Percentile:57.83(Nuclear Science & Technology)

The extraction separation of trivalent minor actinides from lanthanides was examined by a thermosensitive gel, poly-NIPA (N-isopropyl acrylamide) crosslinked with a TPEN derivative, N,N,N',N'-tetrakis(4-propenyloxy-2-pyridylmethyl)ethylenediamine (tppen). The synthesized gel showed the conformational change of polymer network with temperature, which is known as the phase transition phenomena of gel, and such conformational change was repeated stably by the thermal-swing operation between 5$$^{circ}$$C and 40$$^{circ}$$C. Then, Am(III) was extracted selectively in the swollen gel at 5$$^{circ}$$C and released easily from the shrunken gel at 40$$^{circ}$$C. The distribution ratio of Am(III) and the separation factor between Am(III) and Eu(III) were evaluated as 2000 and 18 in the swollen gel. These values are sufficient to the establishment of a practical MA recovery process. Then, both the extractability and selectivity of Am were maintained stably and the selective extraction of Am was attainable by the simple thermal-swing operation. These results suggest that the proposed gel extraction process is applicable to a MA partitioning for transmutation.

Journal Articles

Separation of Actinide(III) from Lanthanide(III) by thermosensitive gel copolymerized with TPEN derivatives

Takeshita, Kenji*; Fugate, G.*; Matsumura, Tatsuro; Nakano, Yoshio*; Mori, Atsunori*; Fukuoka, Sachio*

Proceedings of International Conference on Advanced Nuclear Fuel Cycles and Systems (Global 2007) (CD-ROM), p.120 - 125, 2007/09

Extraction separation of Am(III) and Eu(III) was examined by the thermal-swing extraction technique using a thermosensitive gel, poly-$$N$$-isopropylacrylamide (NIPA) copolymerized with a TPEN derivative, $$N,N,N',N'$$-tetrakis(4-propenyloxy-2-pyridylmethyl)ethylenediamine (TPPEN). The separation of Am(III) from Eu(III) was observed in the swollen state of gel (5$$^{circ}$$C) and the separation factor of Am(III) was evaluated as about 18 at pH5.2. More than 90% of Am(III) extracted into the gel was released by the volume phase transition of gel from the swollen state (5$$^{circ}$$C) to the shrunken one (40$$^{circ}$$C). The repetition test for the thermal swing extraction of a soft metal ion, Cd(II), which was used as a substitute of Am(III), was carried out and the extraction and release of Cd(II) were repeated three times stably under the thermal-swing operation between 5$$^{circ}$$C and 40$$^{circ}$$C. The radiation effect of gel on the extraction of Am and Eu was tested by the irradiation of $$gamma$$-ray (10 kGy) and the long-term adsorption of $$alpha$$-emitter ($$^{244}$$Cm). The TPPEN-NIPA gel sustained no damage by these radiation tests. These results suggest that the thermal-swing extraction technique is applicable to the MA partitioning process indispensable for the establishment of P&T technology.

Journal Articles

Thermal-swing extraction of Cadmium(II) by thermosensitive polymer gel crosslinked with Encapsulating hexadentate ligand

Takeshita, Kenji*; Ishida, Keigo; Nakano, Yoshio*; Matsumura, Tatsuro

Chemistry Letters, 36(8), p.1032 - 1033, 2007/08

 Times Cited Count:21 Percentile:58.12(Chemistry, Multidisciplinary)

Thermal-swing extraction of Cd(II) with a thermosensitive gel, poly-N-isopropylacrylamide (NIPA) crosslinkedwith a podand, N,N,N',N'-tetrakis(4-propenyl-oxy-2-pyridylmethyl)ethylenediamine (TPPEN), was examined. Cd(II) was extracted selectively in the gel swollen at 5$$^{circ}$$C andreleased from the gel shrunken at 40$$^{circ}$$C. The difference in thedistribution ratios of Cd(II) between these temperatures wasmore than 30 times.

Journal Articles

Physics issues and simulation of the JT-60 SA divertor for large heat and particle handling

Asakura, Nobuyuki; Kawashima, Hisato; Shimizu, Katsuhiro; Sakurai, Shinji; Fujita, Takaaki; Takenaga, Hidenobu; Nakano, Tomohide; Kubo, Hirotaka; Higashijima, Satoru; Hayashi, Takao; et al.

Europhysics Conference Abstracts (CD-ROM), 31F, 4 Pages, 2007/00

Divertor design for the JT-60 SA has been progressing in order to handle large heat flux during full pulse duration of 100 s. Divertor should be suitable for single null plasma experiments with the full power injection of 41 MW. The simulation results using 2D fluid (plasma) and Monte-Carlo (neutral) code are summarized. Lower single-null divertor is designed for ITER-like plasma configuration in order to study physics concept of the ITER divertor: control of the plasma detachment. Simulation results for various divertor geometries showed that the vertical target with V-shaped corner can produce plasma detachment near the outer strike-point for medium edge plasma density. It was also demonstrated that the divertor plasma became attached to move the outer strike point above the V-corner, suggesting that recover from sever detachment can be achieved by changing the plasma location. USN divertor will be designed for high-$$beta$$ plasma experiments with the highest shaping plasma of S=6.

57 (Records 1-20 displayed on this page)