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Journal Articles

Effect of surface conditions of the filament used in thermal ionization mass spectrometry on an uranium isotopic measurement

Taguchi, Shigeo; Miyauchi, Hironari*; Horigome, Kazushi; Yamamoto, Masahiko; Kuno, Takehiko

Bunseki Kagaku, 67(11), p.681 - 686, 2018/11

In thermal ionization mass spectrometry, de-gassing is one of the important treatments to release impurities of filaments and to minimize the influence of background. In this work, the effect of the surface change in the tungsten filament induced by the conductively heating treatment on uranium isotopic ($$^{235}$$U/$$^{238}$$U) measurement has been investigated. It was found that the conductively heating treatment of the filament has the effect of smoothing the surface of the filament and also has the effect of improving the deposition of the sample on the filament surface. As a result of either these effects, the precision of uranium isotopic ($$^{235}$$U/$$^{238}$$U) measurement was improved.

Journal Articles

First-principles study of solvent-solute mixed dumbbells in body-centered-cubic tungsten crystals

Suzudo, Tomoaki; Tsuru, Tomohito; Hasegawa, Akira*

Journal of Nuclear Materials, 505, p.15 - 21, 2018/07

 Times Cited Count:1 Percentile:38.14(Materials Science, Multidisciplinary)

Tungsten (W) is considered as a promising candidate for plasma-facing materials for future nuclear fusion devices, and selecting optimal alloying constituents is a critical issue to improve radiation resistance of the W alloys as well as to improve their mechanical properties. We conducted in the current study a series of first-principles calculations for investigating solvent-solute mixed dumbbells in W crystals. The results suggested that titanium (Ti), vanadium (V), and chromium (Cr) are favorable as solutes for W alloys from irradiation-effect perspectives because these elements are expected to promote vacancy-interstitial recombination without causing radiation-induced precipitation that reduces ductility of irradiated materials.

Journal Articles

Recent advances in modeling and simulation of the exposure and response of tungsten to fusion energy conditions

Marian, J.*; Becquart, C. S.*; Domain, C.*; Dudarev, S. L.*; Gilbert, M. R.*; Kurtz, R. J.*; Mason, D. R.*; Nordlund, K.*; Sand, A. E.*; Snead, L. L.*; et al.

Nuclear Fusion, 57(9), p.092008_1 - 092008_26, 2017/06

 Times Cited Count:32 Percentile:0.46(Physics, Fluids & Plasmas)

Under the anticipated operating conditions for demonstration magnetic fusion reactors beyond ITER, structural materials will be exposed to unprecedented conditions of irradiation, heat flux, and temperature. While such extreme environments remain inaccessible experimentally, computational modeling and simulation can provide qualitative and quantitative insights into materials response and complement the available experimental measurements. For plasma facing components such as the first wall and the divertor, tungsten (W) has been selected as the best candidate material due to its superior high-temperature and irradiation properties. In this paper we provide a review of recent efforts in computational modeling of W both as a plasma-facing material as well as a bulk structural material subjected to fast neutron irradiation. We highlight several of the most salient findings obtained via computational modeling and point out a number of remaining future challenges.

Journal Articles

Suppression of radiation-induced point defects by rhenium and osmium interstitials in tungsten

Suzudo, Tomoaki; Hasegawa, Akira*

Scientific Reports (Internet), 6, p.36738_1 - 36738_6, 2016/11

 Times Cited Count:10 Percentile:35.13(Multidisciplinary Sciences)

Modeling of the evolution of radiation-induced defects is important for finding radiation-resistant materials, which would be greatly appreciated in nuclear applications. We apply the first principles method combined with kinetic Monte Carlo to indicate a mechanism to mitigate the effect of radiation by adding particular solute elements that change the migration dimension of interstitials in W crystals. The resultant mechanism is applicable to any body-centered-cubic (BCC) metals whose SIAs have one-dimensional (1D) motion and is expected to provide a general guideline for computational design of radiation-resistant alloys in the field of nuclear applications.

Journal Articles

Deuterium permeation behavior for damaged tungsten by ion implantation

Oya, Yasuhisa*; Li, X.*; Sato, Misaki*; Yuyama, Kenta*; Oyaizu, Makoto; Hayashi, Takumi; Yamanishi, Toshihiko; Okuno, Kenji*

Journal of Nuclear Science and Technology, 53(3), p.402 - 405, 2016/03

 Times Cited Count:5 Percentile:23.48(Nuclear Science & Technology)

The deuterium (D) permeation behaviors for ion damaged tungsten (W) by 3 keV D$$_{2}$$$$^{+}$$ and 10 keV C$$^{+}$$ were studied. The D permeability was obtained for un-damaged W at various temperatures. For both D$$_{2}$$$$^{+}$$ and C$$^{+}$$ implanted W, the permeability was clearly reduced. But, for the D$$_{2}$$$$^{+}$$ implanted W, the permeability was recovered by heating at 1173 K and it was almost consistent with that for un-damaged W. In the case of C$$^{+}$$ implanted W, the permeability was not recovered even if the sample was heated at 1173 K, indicating that the existence of carbon would prevent the recovery of permeation path in W. In addition, TEM observation showed the voids were grown by heating at 1173 K and not removed, showing the existence of damages would not largely influence on the hydrogen permeation behavior in W in the present study.

Journal Articles

Migration of rhenium and osmium interstitials in tungsten

Suzudo, Tomoaki; Yamaguchi, Masatake; Hasegawa, Akira*

Journal of Nuclear Materials, 467(Part 1), p.418 - 423, 2015/12

AA2015-0099.pdf:0.62MB

Tungsten is expected to be a promising plasma-facing material for future fusion devices, but radiation-induced precipitation (RIP), which leads the material to hardening, is a concern at their practical use. One of the keys to accurate prediction of the emergence of RIP is migration of solute atoms, rhenium and osmium, that are produced by nuclear transmutation through irradiation. We conduct a series of numerical simulations using an atomic kinetic Monte Carlo method and investigate the migration of these solute atoms in the form of tungsten-rhenium and tungsten-osmium mixed dumbbells, considered to be the most efficient "carriers" of the solute atoms. We find that the low rotation energy barrier of these mixed dumbbells leading to three-dimensional migration greatly influences their diffusivities. The result also suggests that, although these dumbbells have three-dimensional motion, one cannot simply reduce their migration behavior to that of vacancy-like spherical objects.

Journal Articles

Modification of vacuum plasma sprayed tungsten coating on reduced activation ferritic/martensitic steels by friction stir processing

Tanigawa, Hiroyasu; Ozawa, Kazumi; Morisada, Yoshiaki*; Noh, S.*; Fujii, Hidetoshi*

Fusion Engineering and Design, 98-99, p.2080 - 2084, 2015/10

 Times Cited Count:6 Percentile:28.02(Nuclear Science & Technology)

The vacuum plasma spray (VPS) technique has been investigated as the most practical method to form Tungsten (W) layer as a plasma facing material in fusion devices. The issues are the thermal conductivity and the strength of VPS-W, i.e., the thermal conductivity of VPS-W were significantly lower than that of the bulk W, and the hardness of VPS-W is much less than that of the bulk W. These are mainly caused by the porous structure of VPS-W. In order to solve these issues, friction stir processing (FPS) was applied on VPS-W in this study. It was suggested that FSP can contribute to significant improvement both in mechanical and thermal properties of VPS-W coating.

Journal Articles

Issues and approaches for ITER with the full tungsten divertor from Day One

Nakano, Tomohide

Purazuma, Kaku Yugo Gakkai-Shi, 91(3), p.191 - 196, 2015/03

no abstracts in English

Journal Articles

Structural and gasochromic properties of WO$$_{3}$$ films prepared by reactive sputtering deposition

Yamamoto, Shunya; Hakoda, Teruyuki; Miyashita, Atsumi; Yoshikawa, Masahito

Materials Research Express (Internet), 2(2), p.026401_1 - 026401_8, 2015/02

 Times Cited Count:2 Percentile:85.43(Materials Science, Multidisciplinary)

The effects of deposition temperature and film thickness on the structural and gasochromic properties of tungsten trioxide films used for the optical detection of diluted cyclohexane have been investigated. The tungsten trioxide films were prepared on SiO$$_{2}$$ substrates by magnetron sputtering, with the deposition temperature ranging from 300 to 550$$^{circ}$$C in an Ar and O$$_{2}$$ gas mixture. The gasochromic properties of the films, coated with a catalytic Pt layer, were examined by exposing them up to 5% cyclohexane in N$$_{2}$$ gas. We found that (001)-oriented monoclinic tungsten trioxide films, with a columnar structure, grew at deposition temperatures between 400 and 450$$^{circ}$$C. The gasochromic characterization of the tungsten trioxide films revealed that (001)-oriented tungsten trioxide films, with cauliflower-like surface morphology, were appropriate for the optical detection of cyclohexane.

Journal Articles

Development of an H$$^{-}$$-ion source for the High-Intensity Proton Accelerator (J-PARC)

Oguri, Hidetomo; Ueno, Akira; Namekawa, Yuya*; Ikegami, Kiyoshi*

Review of Scientific Instruments, 77(3, Part2), p.03A517_1 - 03A517_3, 2006/03

 Times Cited Count:5 Percentile:64.74(Instruments & Instrumentation)

The J-PARC Project was started in 2001 as a joint project carried out by JAERI and KEK. At the first stage of the J-PARC, the linac will accelerate the H- ion beam current of 30 mA with a duty factor of 1.25 %. The J-PARC H- ion source driven with a LaB6 filament has regularly delivered more than 35 mA beam with a duty factor of 0.9 % without resorting to cesium. Although the operated duty factor is about 1/3 of the requirement, the filament is not replaced for a half year. At the J-PARC, the lifetime of the tungsten (W) filament was measured by using another H- ion source, which can produce a 72 mA with cesium seeded. The experimental results showed that there is a possibility of the W filament satisfying the lifetime of more than 500 hours, which is J-PARC requirement. We consider the W driven plasma ion source is one of the candidates for the J-PARC source. At present, we are performing the beam test of the cesium free ion source driven with W. We will present the experimental data of the beam test in this conference.

Journal Articles

Progress in the blanket neutronics experiments at JAERI/FNS

Sato, Satoshi; Verzilov, Y. M.; Ochiai, Kentaro; Nakao, Makoto*; Wada, Masayuki*; Kubota, Naoyoshi; Kondo, Keitaro; Yamauchi, Michinori*; Nishitani, Takeo

Fusion Engineering and Design, 81(8-14), p.1183 - 1193, 2006/02

 Times Cited Count:12 Percentile:29.12(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Design study of fusion DEMO plant at JAERI

Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Sato, Masayasu; Isono, Takaaki; Sakurai, Shinji; Nakamura, Hirofumi; Sato, Satoshi; Suzuki, Satoshi; Ando, Masami; et al.

Fusion Engineering and Design, 81(8-14), p.1151 - 1158, 2006/02

 Times Cited Count:100 Percentile:0.63(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Experimental studies on tungsten-armour impact on nuclear responses of solid breeding blanket

Sato, Satoshi; Nakao, Makoto*; Verzilov, Y. M.; Ochiai, Kentaro; Wada, Masayuki*; Kubota, Naoyoshi; Kondo, Keitaro; Yamauchi, Michinori*; Nishitani, Takeo

Nuclear Fusion, 45(7), p.656 - 662, 2005/07

 Times Cited Count:8 Percentile:66.28(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Compatibility of lithium oxide single crystals with tungsten sputtered films; The Effect of passivation films

Nasu, Shoichi*; Nagata, Shinji*; Yoshii, Kiichiro*; Takahiro, Katsumi*; Kikuchi, Naoto*; Kusano, Eiji*; Moto, Shintaro*; Yamaguchi, Sadae*; Ohashi, Kentaro*; Noda, Kenji; et al.

Funtai Oyobi Fummatsu Yakin, 52(6), p.427 - 429, 2005/06

no abstracts in English

Journal Articles

Neutronics experiments using small partial mockups of the ITER test blanket module with a solid breeder

Sato, Satoshi; Verzilov, Y. M.; Nakao, Makoto*; Ochiai, Kentaro; Wada, Masayuki*; Nishitani, Takeo

Fusion Science and Technology, 47(4), p.1046 - 1051, 2005/05

 Times Cited Count:12 Percentile:30.66(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Filament lifetime test of the negative ion source for the high intensity proton accelerator

Oguri, Hidetomo; Namekawa, Yuya*

JAERI-Tech 2004-053, 35 Pages, 2004/07

JAERI-Tech-2004-053.pdf:1.33MB

The high intensity proton accelerator facility project (J-PARC) aims to pursue frontier science in materials science, nuclear physics and nuclear technology, using an accelerator complex at the highest beam power in the world. An H$$^{-}$$ ion source for the project is required to produce a beam current of $$>$$60 mA and an emittance of $$<$$0.20 $$pi$$mm.mrad with a duty factor of 2.5 %. In addition, the ion source must be run for 500 h continuously without maintenance. As a result of the beam test, the beam current and the emittance of 72 mA and 0.15 $$pi$$mm.mrad were achieved in the Cs seeded operation, respectively. Because a lifetime of the filament cathode is one of the main restrictions for the maintenance cycle, we started to perform a filament lifetime test. As the result of the test, we succeeded for 258 h arc operation at the arc power of 30 kW with the duty factor of 3 %. Moreover, the results showed that there is a possibility of achievement $$>$$800 h lifetime by change the connection between filament and arc power supply and the optimization of the filament shape.

Journal Articles

Neutronics experiments for DEMO blanket at JAERI/FNS

Sato, Satoshi; Ochiai, Kentaro; Hori, Junichi; Verzilov, Y. M.; Klix, A.; Wada, Masayuki*; Terada, Yasuaki*; Yamauchi, Michinori*; Morimoto, Yuichi*; Nishitani, Takeo

Nuclear Fusion, 43(7), p.527 - 530, 2003/07

 Times Cited Count:11 Percentile:59.96(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Tritium permeation study through tungsten and nickel using pure tritium ion beam

Nakamura, Hirofumi; Shu, Wataru; Hayashi, Takumi; Nishi, Masataka

Journal of Nuclear Materials, 313-316(1-3), p.679 - 684, 2003/03

 Times Cited Count:13 Percentile:29.96

no abstracts in English

Journal Articles

Impact of armor materials on tritium breeding ratio in the fusion reactor blanket

Sato, Satoshi; Nishitani, Takeo

Journal of Nuclear Materials, 313-316, p.690 - 695, 2003/03

 Times Cited Count:6 Percentile:53.71

no abstracts in English

Journal Articles

Mechanical properties of HIP bonded W and Cu-alloys joint for plasma facing components

Saito, Shigeru; Fukaya, Kiyoshi*; Ishiyama, Shintaro; Sato, Kazuyoshi

Journal of Nuclear Materials, 307-311(2), p.1542 - 1546, 2002/12

 Times Cited Count:28 Percentile:12.12

no abstracts in English

94 (Records 1-20 displayed on this page)