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Journal Articles

Complex chemistry with complex compounds

Eichler, R.*; Asai, Masato; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; D$"u$llmann, Ch. E.*; Even, J.*; Fangli, F.*; Goetz, M.*; et al.

EPJ Web of Conferences, 131, p.07005_1 - 07005_7, 2016/12

 Times Cited Count:1 Percentile:48.2

In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the productions and investigations of fragile single molecular species of superheavy elements. The latest highlight is the formation of very volatile hexacarbonyl compound of element 106, Sg(CO)$$_{6}$$. Following this success, second-generation experiments were performed to measure the first bond dissociation energy between the central metal atom and the surrounding ligand. The method using a tubular decomposition reactor was developed and successfully applied to short-lived Mo(CO)$$_{6}$$, W(CO)$$_{6}$$, and Sg(CO)$$_{6}$$.

Journal Articles

Decomposition studies of group 6 hexacarbonyl complexes, 1; Production and decomposition of Mo(CO)$$_6$$ and W(CO)$$_6$$

Usoltsev, I.*; Eichler, R.*; Wang, Y.*; Even, J.*; Yakushev, A.*; Haba, Hiromitsu*; Asai, Masato; Brand, H.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; et al.

Radiochimica Acta, 104(3), p.141 - 151, 2016/03

 Times Cited Count:16 Percentile:6.06(Chemistry, Inorganic & Nuclear)

Conditions of the production and decomposition of hexacarbonyl complexes of short-lived Mo and W isotopes were investigated to study thermal stability of the heaviest group 6 hexacarbonyl complex Sg(CO)$$_6$$. A tubular flow reactor was tested to decompose the hexacarbonyl complexes and to extract the first bond dissociation energies. A silver was found to be the most appropriate reaction surface to study the decomposition of the group 6 hexacarbonyl. It was found that the surface temperature at which the decomposition occurred was correlated to the first bond dissociation energy of Mo(CO)$$_6$$ and W(CO)$$_6$$, indicating that the first bond dissociation energy of Sg(CO)$$_6$$ could be determined with this technique.

Journal Articles

Impacts of friction stir processing on irradiation effects in vacuum-plasma-spray coated tungsten

Ozawa, Kazumi; Tanigawa, Hiroyasu; Morisada, Yoshiaki*; Fujii, Hidetoshi*

Fusion Engineering and Design, 98-99, p.2054 - 2057, 2015/10

 Times Cited Count:1 Percentile:86.4(Nuclear Science & Technology)

Reduced activation ferritic/martensitic steel, as typified by F82H, is a promising candidate for structural material of DEMO fusion reactors. To prevent plasma sputtering, tungsten (W) coating was essentially required. This study aims to examine the irradiation effects on hardness and microstructure of vacuum-plasma-spray coated W-F82H steel, with a special emphasis on the impacts of grain-refining induced by frictional stir processing (FSP). It was revealed that the hardness of the VPS-FSP W after ion-irradiation to 5.4 dpa at 800$$^{circ}$$C were not remarkably changed, where bulk W usually exhibited significant irradiation hardening.

Journal Articles

Determination of tungsten and molybdenum concentrations from an X-ray range spectrum in JET with the ITER-like wall configuration

Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*; Reinke, M.*; Lawson, K.*; Coffey, I.*; P$"u$tterich, T.*; Brezinsek, S.*; Lipschultz, B.*; Matthews, G. F.*; et al.

Journal of Physics B; Atomic, Molecular and Optical Physics, 48(14), p.144023_1 - 144023_11, 2015/07

 Times Cited Count:20 Percentile:16.95(Optics)

The $$mbox{W}^{45+}$$ and $$mbox{W}^{46+}$$ 3p-4d inner shell excitation lines in addition to $$mbox{Mo}^{32+}$$ 2p-3s lines have been identified from the spectrum taken by an upgraded high-resolution X-ray spectrometer. It is found from analysis of the absolute intensities of the $$mbox{W}^{46+}$$ and $$mbox{Mo}^{32+}$$ lines that W and Mo concentrations are in the range of $$sim10^{-5}$$ and $$sim10^{-6}$$, respectively, with a ratio of $$sim$$ 5% for ELMy H-mode plasmas with a plasma current of 2.0- 2.5 MA, a toroidal magnetic field of 2.7 T and a neutral beam injection power of 14-18 MW. For the purpose of checking self-consistency, it is confirmed that the W concentration determined from the $$mbox{W}^{45+}$$ line is in agreement with that from the $$mbox{W}^{46+}$$ line within 20% and that the plasma effective charge determined from the continuum of the first order reflection spectrum is also in agreement with that from the second order within 50%. Further, the determined plasma effective charge is in agreement with that determined from a visible spectroscopy, confirming that the sensitivity of the X-ray spectrometer is valid and that probably the W and the Mo concentrations are also valid.

Journal Articles

Analysis of tungsten transport in JT-60U plasmas

Shimizu, Yusuke*; Fujita, Takaaki*; Arimoto, Hideki*; Nakano, Tomohide; Hoshino, Kazuo; Hayashi, Nobuhiko

Plasma and Fusion Research (Internet), 10(Sp.2), p.3403062_1 - 3403062_4, 2015/07

Journal Articles

Influence of blistering on deuterium retention in tungsten irradiated by high flux deuterium 10-100eV plasmas

Luo, G.; Shu, Wataru; Nishi, Masataka

Fusion Engineering and Design, 81(8-14), p.957 - 962, 2006/02

 Times Cited Count:59 Percentile:2.82(Nuclear Science & Technology)

The influence of blistering on deuterium retention in W was investigated using the newly established plasma generator with controllable incident energies ranging from 100 eV down to around 10 eV and incident flux of 1$$times$$10$$^{22}$$ D/m$$^{2}$$/s. The retention in the irradiated samples was measured using a thermal desorption spectrometer (TDS) at a ramping rate of 5 $$^{circ}$$C/s. The results indicate that only one peak appears in each spectrum, with the peak temperatures ranging from 500 until 850 $$^{circ}$$C, much higher than those from the trapping sites like vacancies, grain boundaries, dislocation loops, or impurities, implying probably a direct origin from the molecules existing inside blisters, voids/bubbles. Significant decrease in the retention at a certain incident fluence after blister appearance was observed and attributed to rupturing of the blisters, consistent with the limited size and increasing number of the blisters with increasing the incident fluence, as observed by means of SEM.

Journal Articles

First wall and divertor engineering research for power plant in JAERI

Suzuki, Satoshi; Ezato, Koichiro; Hirose, Takanori; Sato, Kazuyoshi; Yoshida, Hajime; Enoeda, Mikio; Akiba, Masato

Fusion Engineering and Design, 81(1-7), p.93 - 103, 2006/02

 Times Cited Count:12 Percentile:32.43(Nuclear Science & Technology)

This paper presents an R&D activity on the plasma facing components (PFCs), such as first wall and divertor, for the fusion power plant. The PFCs of the power plant will be subjected to heavy neutron irradiation and high heat/particle flux from plasma during the continuous operation. In the present design of the PFCs, the candidate structural material is a reduced activation ferritic-martensitic steel, F82H, from the viewpoints of low activation and high robustness against neutron irradiation, and the candidate armor material is tungsten from the low sputtering yield and low tritium retention points of view. To realize the PFCs using such materials, JAERI has bee extensively conducting R&Ds on; (1) high performance cooling tube, (2) tungsten armor materials, (3) selection of a bonding technique for F82H and tungsten materials and (4) evaluation of structural integrity. Recent achievements on these R&Ds are presented.

Journal Articles

Incident energy dependence of blistering at tungsten irradiated by low energy high flux deuterium plasma beams

Luo, G.; Shu, Wataru; Nishi, Masataka

Journal of Nuclear Materials, 347(1-2), p.111 - 117, 2005/12

 Times Cited Count:70 Percentile:2(Materials Science, Multidisciplinary)

Polycrystalline tungsten samples have been irradiated at room temperature by high flux (1$$times$$10$$^{22}$$ D/m$$^{2}$$/s) deuterium plasma beams with incident energies ranging 7 $$sim$$ 98 eV/D. Surface blistering occurred at all energies. The critical fluence for blistering $$Phi$$$$_{cr}$$ was found to increase with decreasing the incident energy. At energies $$<$$ 20 eV/D, $$Phi$$$$_{cr}$$ increased more rapidly. This energy dependence of $$Phi$$$$_{cr}$$ may be explained by a proposed model dealing with the oxide barrier to deuterium uptake into and release from the bulk W. At all energies, the blisters increased in their size and number with fluence within the corresponding low fluence ranges. However the size stopped increasing at certain fluences, while the number kept increasing within the experimental fluence range, which could be attributed to rupturing of blisters at a certain size of about 2$$mu$$m.

Journal Articles

Proposal of hot-pressed, rod-shaped tungsten armor concept for ITER divertor and its high-heat-flux performances

Sato, Kazuyoshi; Ezato, Koichiro; Taniguchi, Masaki; Suzuki, Satoshi; Akiba, Masato

Journal of Nuclear Science and Technology, 42(7), p.643 - 650, 2005/07

 Times Cited Count:4 Percentile:67.11(Nuclear Science & Technology)

no abstracts in English

Journal Articles

First wall and divertor materials as plasma facing components

Suzuki, Satoshi

Koon Gakkai-Shi, 30(5), p.243 - 247, 2004/09

Selection and the development of plasma facing materials for fusion devices, mainly ITER, are presented. For the divertor, CFC (Carbon fiber reinforced carbon composite) materials are utilized as plasma facing materials in the lower part of vertical targets in ITER. Since the design maximum heat flux to the vertical targets is 20 MW/m$$^{2}$$, CFC materials, which have higher thermal conductivity than pure copper, are preferable from a heat removal point of view. On the other hand, a plasma facing material of a dome and a liner is tungsten because tungsten has low sputtering yield and has relatively high thermal conductivity among metals. First wall covers 80% of the plasma facing area of ITER. The plasma facing material of the first wall should have good compatibility with plasma. Therefore, beryllium is utilized as a plasma facing material from the low contamination and the minimization of the oxygen impurity to the plasma points of view.

Journal Articles

Irradiation test on Mo- and W-mirrors for ITER by low energy deuterium ions

Sugie, Tatsuo; Kasai, Satoshi; Taniguchi, Masaki; Nagatsu, Masaaki*; Nishitani, Takeo

Journal of Nuclear Materials, 329-333(2), p.1481 - 1485, 2004/08

 Times Cited Count:28 Percentile:12.92(Materials Science, Multidisciplinary)

In ITER, the effect of lower energy particle bombardment is important for mirrors located near the divertor where the low temperature plasma is formed. The test pieces of molybdenum mirrors and a tungsten mirror were irradiated by high flux and low energy (67-80 eV) deuterium ions using SLEIS (Super Low Energy Ion Source with High Ion Flux) facility at the temperature of around 100 $$^{circ}$$C. The molybdenum mirror manufactured by sintering and melting the thin layer of the surface by electron beam in order to eliminate holes on the surface has a higher reflectivity before irradiation than the mirrors without melting the surface, but the reflectivity decreases rapidly with the irradiation fluence due to the generation of blisters on the mirror surface. The reflectivity of molybdenum mirror manufactured by sintering only did not decrease so significantly (less than 10 % at the fluence of 1.3 $$times$$ 10$$^{25}$$ m$$^{-2}$$). The molybdenum and tungsten mirrors manufactured by sintering without melting the surface have a potential for plasma facing mirrors in ITER.

Journal Articles

Spallation terget materials development

Kikuchi, Kenji; Kawai, Masayoshi*; Ikeda, Yujiro

Proceedings of 6th International Meeting on Nuclear Applications of Accelerator Technology (AccApp '03) (CD-ROM), p.17 - 25, 2004/00

Spallation target being developed for high intensity neutron source of MW incident proton power. Mercury is a primary target material in pulsed spallation neutron sources, lead-bismuth is a candidate target material in the accelerator-driven system (ADS) for nuclear transmutation, and tungsten is a back-up solid target for pulsed spallation neutron sources and a candidate for ADS target. Current status of these project and materials issues are stated.

JAEA Reports

Measurement of doppler effect on resonance materials for ROX fuel using FCA

Ando, Masaki; Nakano, Yoshihiro; Okajima, Shigeaki; Kawasaki, Kenji

JAERI-Research 2003-029, 72 Pages, 2003/12

JAERI-Research-2003-029.pdf:3.41MB

The objectives of this study is to clarify calculation accuracy for the Doppler effect of the resonance materials; erbium (Er), tungsten (W) and thorium (ThO$$_{2}$$). Doppler effect measurements were carried out in a fast neutron spectrum (XX-2 core) and in an intermediate neutron spectrum (XXI-1D2 core) by the sample-heated and reactivity worth measurement method up to 800$$^{circ}$$C using FCA. The experiment was analyzed with the standard analysis method for fast reactor cores at FCA with the use of the JENDL-3.2. The SRAC system was also used to investigate the calculation accuracy of the system and to compare it with that of the FCA standard analysis method. The standard analysis method underestimated for the XX-2 core and agreed the experiments within the experimental errors for the XXI-1D2 core. The analysis with the SRAC system gave smaller values by 3%$$sim$$10% for the Er sample and bigger values by 2%$$sim$$5% for the W sample than the standard analysis method.

JAEA Reports

Tritium permeation evaluation through vertical target of divertor based on recent tritium transport properties

Nakamura, Hirofumi; Nishi, Masataka

JAERI-Research 2003-024, 24 Pages, 2003/11

JAERI-Research-2003-024.pdf:1.12MB

Re-evaluation of tritium permeation through vertical target of divertor under the ITER operation condition was carried out using tritium transport properties in the candidate materials such as the diffusion coefficient and the trapping factors in tungsten for armor, and the surface recombination coefficient on copper for the heat sink obtained by authors' recent investigation (authors' data), which simulated the plasma-facing conditions of ITER. Evaluation with the data set of previous evaluation was also carried out for comparison (previous data). The permeation analysis was carried out individually by classifying into the armor region (Carbon Fiber Composites and tungsten) and the slit region without armor (3% of armor surface area) assuming the incident flux and temperature for each region. As the results of the permeation analysis, estimated permeation amount with the authors' data was one order less than that with the previous data at the end of lifetime of the divertor due to authors' small diffusion coefficient of tritium in tungsten. It also indicated the possibility that permeation through the slit region of the armor tiles could dominate total permeation through the vertical target, since tritium permeation amount through tungsten armor with the authors' data was estimated to be reduced drastically smaller than that with the previous evaluation data. The result of a little tritium permeation amount through the vertical target with the authors' data ensured the conservatism of the current evaluation of tritium concentration in the primary cooling water in ITER divertor, as it indicated the possibility of direct drainage of the divertor primary cooling water.

Journal Articles

Strength proof evaluation of diffusion-jointed W/Ta interfaces by small punch test

Li, J.-F.*; Kawai, Masayoshi*; Kikuchi, Kenji; Igarashi, Tadashi*; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Kawasaki, Akira*

Journal of Nuclear Materials, 321(2-3), p.129 - 134, 2003/09

 Times Cited Count:12 Percentile:35.03(Materials Science, Multidisciplinary)

For the development of tantalum-clad tungsten targets for spallation neutron sources, the bonding strength of tantalum-tungsten interface was investigated by means of an easy-to-use and miniaturized small punch (SP) test, in which a punching load is vertically applied to the center of a jointed disk. Cracks initiated and propagated in the tungsten side for all the samples hot-isostatically pressed (HIPed) at temperatures from 1673 to 2073 K, whereas nocrack and debonding were observed in the interface, indicating that the jointed interface is strongly bonded. The re-crystallization of tungsten occurs and results in its strength reduction, consequently the crack-initiating load decreases with HIPing temperature. The finite element analysis of the measured SP testing results shows that the maximum bonding strength can exceed 1000 MPa. The present study shows that SP test is suitable for the strength evaluation of jointed tantalum-tungsten interfaces.

Journal Articles

Present research status on divertor and plasma facing components for fusion power plants

Suzuki, Satoshi; Ueda, Yoshio*; Tokunaga, Kazutoshi*; Sato, Kazuyoshi; Akiba, Masato

Fusion Science and Technology, 44(1), p.41 - 48, 2003/07

 Times Cited Count:20 Percentile:19.97(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Solid spallation target materials development

Kawai, Masayoshi*; Furusaka, Michihiro; Li, J.-F.*; Kawasaki, Akira*; Yamamura, Tsutomu*; Mehmood, M.*; Kurishita, Hiroaki*; Kikuchi, Kenji; Takenaka, Nobuyuki*; Kiyanagi, Yoshiaki*; et al.

Proceedings of ICANS-XVI, Volume 3, p.1087 - 1096, 2003/07

In order to establish the technique fabricating a thin target slab with a real size, thin tantalum-clad tungsten slab with a hole for a thermocouple was fabricated with the high-precision machinery techniques and the HIP'ing method. The ultrasonic diagnostic showed that tantalum and tungsten bond was perfect. The HIP optimum condition was certified by means of the small punch test as already reported. The electrolytic coating technique in a molten salt was developed to make a thinner tantalum cladding on a tungsten target with a complicated shape, in order to reduce radioactivity from tantalum in an irradiated target.

Journal Articles

Design of beam incident monitor for spallation neutron target of JSNS

Meigo, Shinichiro; Harada, Masahide; Teraoku, Takuji*; Maekawa, Fujio

Proceedings of ICANS-XVI, Volume 3, p.1175 - 1180, 2003/07

It is important to monitor the proton beam for the high intensity pulse spallation target. Especially for the beam halo, which may irradiate the bulk surrounding the target, it is important to be observed to prevent causing heat spot in the shielding bulk. At JSNS, a proton beam monitors are located at front of the target. These monitors are assembled with the proton beam window. Since this scheme increases the radiation on the monitor due to the beam loss at the windows, it may arise heat deposition on the monitor. Therefore, heat deposition is calculated with NMTC/JAM. It is found that the heat deposition for normal operation is less than 0.1 W/cc.

Journal Articles

Doppler effect measurement on resonance materials for rock-like oxide fuels in an intermediate neutron spectrum

Ando, Masaki; Nakano, Yoshihiro; Okajima, Shigeaki; Kawasaki, Kenji

Journal of Nuclear Materials, 319, p.126 - 130, 2003/06

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

Doppler effect experiments on resonance materials for ROX fuels were carried out to examine the calculation accuracy in the intermediate neutron spectrum using Fast Critical Assembly (FCA) at Japan Atomic Energy Research Institute. This study is the second phase of a series of the Doppler effect experiments on the resonance materials, which is following the measurements in the fast neutron spectrum. The Doppler effect was measured as the sample reactivity change between the heated and unheated samples. The cylindrical samples of the resonance materials such as erbium (Er), tungsten (W) and thorium (ThO$$_{2}$$) were used. The sample was heated up to 800$$^{circ}$$C at the center of the FCA core. The Doppler effect measurements were analyzed using the SRAC 95 code system with the use of JENDL 3.2. The calculated values agreed with the experiment within the experimental error for the W and ThO$$_{2}$$ samples, while the calculation overestimated the experiment for the Er sample about 10 %.

Journal Articles

R&D of a MW-class solid-target for spallation neutron source

Kawai, Masayoshi*; Furusaka, Michihiro*; Kikuchi, Kenji; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Li, J.*; Sugimoto, Katsuhisa*; Yamamura, Tsutomu*; Hiraoka, Yutaka*; Abe, Katsunori*; et al.

Journal of Nuclear Materials, 318, p.35 - 55, 2003/05

R&D works for MW class solid target composed of tungsten to produce pulsed intense neutron source has been made in order to construct a future scattering facility. Three methods were investigated to prevent corrosion of tungsten from water; those are hipping, brazing and electric coating in molten salt bath. Hipping condition was optimized to be 1500 degree C in the previous work: here small punch test shows highest load for crack initiation of hipped materials at the boundary of W/Ta. The basic techniques for the other two methods were developed. Erosion test showed that uncovered W is susceptible of flowing water velocity. At high velocity w is easy to be eroded. For solid target design slab type and rod type targets were studied. As long as the optimized neutron performance is concerned, 1MW solid target is better than mercury target.

53 (Records 1-20 displayed on this page)