Papers - 2005

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[2005_01]

Influence of microstructure of tungsten on solid state reaction rate with amorphous carbon film

Y. Hatano, M. Takamori, K. Nogita, K. Matsuda, S. Ikeno, K. Watanabe

J. of Nuclear Materials, 337-339 (2005) 902-906

[2005_02]

Helium irradiation effects on retention behavior of deuterium implanted into boron coating film by PCVD

H. Kodama, M. Oyaidzu, A. Yoshikawa, H. Kimura, Y. Oya, M. Matsuyama, A. Sagara, N. Noda, K. Okunoa

J. of Nuclear Materials, 337-339 (2005) 649-653

[2005_03]

Effects of bulk modification by Pd on electrochemical properties of MgNi

Tiejun Ma, Yuji Hatano, Takayuki Abe, Kuniaki Watanabe

J. of Alloys and Compounds, 391 (2005) 313-317

[2005_04]

Surface Segregation of Ti in a V-4Cr-4Ti Alloy and Its Influence on the Surface Reaction Rates of Hydrogen Isotopes

Yuji Hatano, Ryo Hayakawa, Kanako Nishino, Susumu Ikeno, Takuya Nagasaka, Takeo Muroga, Kuniaki Watanabe

Materials Transactions, 46(3) (2005) 511-516

[2005_05]

Hydrogen absorption capability of a niobium panel for pumping neutral atoms in divertor region

Y. Nakamura, A.I. Livshits, Y. Nakahara, Y. Hatano, A. Busnyuk, N. Ohyabu

J. of Nuclear Materials, 337-339 (2005) 461-465

[2005_07]

The toroidal pump limiter ALT-II in TEXTOR

K. H. Finken, D. Reiter, T. Denner, K. H. Dippel, J. Hobirk, G. Mank, H. Kever, G. H. Wolf, N. Noda, A. Miyahara, T. Shoji, K. N. Sato, K. Akaishi, J. A. Boedo, J. N. Brooks, R. W. Conn, W. J. Corbett, R. P. Doerner, D. Goebel, D. S. Gray, D. L. Hillis, J. Hogan, R. T. McGrath, M. Matsuyama, R. Moyer, R. E. Nygren, J. Watkins

Fusion Science and Technology, 47 (2005) 126-136

[2005_09]

A new kind of column materials for gas chromatographic hydrogen isotope separation

M. Hara, H. Shima, S. Akamaru, T. Abe, M. Matsuyama, K. Watanabe

Fusion Science and Technology, 48 (2005) 144-147

[2005_10]

A study on a tritium separation process using self-developing gas chromatography with Pd-Pt alloy

S. Kojima, M. Yokosawa, M. Matsuyama, M. Numata, T. Kato, K. Watanabe

Fusion Science and Technology, 48 (2005) 152-155

[2005_11]

Chronic release of tritium from SS316 at ambient temperature: correlation between depth profile and tritium liberation

Y. Torikai, R.-D. Penzhorn, M. Matsuyama, K. Watanabe

Fusion Science and Technology, 48 (2005) 177-181

[2005_12]

In-situ measurement of high level tritiated water by bremsstrahlung counting

M. Matsuyama, Y. Torikai, K. Watanabe

Fusion Science and Technology, 48 (2005) 324-331

[2005_13]

Development of a low-level tritium air monitor

Y. Sakuma, T. Iida, T. Koganezawa, Y. Ogata, T. Aoyama, Y. Torikai, M. Ohta, M. Takami

Fusion Science and Technology, 48 (2005) 397-400

[2005_14]

Surface modification of polymer microparticles using a hexagonal-barrel sputtering system

Takayuki Abe, S. Akamaru, K. Watanabe and Y. Honda

J. of Alloys and Compounds, 402 (2005) 227-232

[2005_15]

Tritium distribution in JET Mark IIA type divertor tiles analysed by BIXS

Y. Torikai, M. Matsuyama, N. Bekris, M. Glugla, P. Coad, W. Naegele, A. Erbe, N. Noda, V. Philipps, K. Watanabe

J. of Nuclear Materials, 337-339 (2005) 575-579

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[2005_01]

J. of Nuclear Materials, 337-339 (2005) 902-906

 Plate-type speciments were cut from three different types of tungsten sheets fabricated under distinct rolling and heat treatment conditions in the directions parallel or perpendicular to the rolling planes. Amorphous carbon films were prepared by vacuum deposition on the specimen surfaces. Then, the specimens were heated at 1073 K in vacuum, and reaction products were analyzed by means of X-ray diffraction. The carbide formed was W₂C and no peak of WC appeared. The growth rate of W₂C was independent of the cutting directions of the specimens, although the grain boundary densities at the specimen surfaces were quite different. On the other hand, the rate of W₂C growth was dependent on both reduction and heat treatment conditions, and a specimen with higher hardness showed a higher growth rate. By taking account of the observations by a transmission electron microscope, it was concluded that dislocations play important roles in W₂C growth.

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[2005_02]

J. of Nuclear Materials, 337-339 (2005) 649-653

 Helium irradiation effects on the retention of energetic deuterium implanted into the boron coating film were investigated by means of X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). It was found, by XPS, that the B 1s peak was shifted to lower binding energy side by He⁺ ion irradiation and the FWHM was extended. These facts show that the some defects were introduced into the boron coating film by He⁺ ion irradiation. From TDS experiment, the deuterium retention, especially the amount of B-D terminal bond, increased by the pre-He⁺ ion irradiation. However, it decreased by the post-He⁺ ion irradiation. These experimental results indicate that the B-D terminal bond was mainly influenced by the He+ ion irradiation because the two neighbor B-D bonds have to dissociate simultaneously for the B-D-B bridge bond.

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[2005_03]

J. of Alloys and Compounds, 391 (2005) 313-317

 An amorphous MgNi alloy was prepared by ball-milling of Mg₂Ni and Ni with 10 mol% of Pd for 80 h, and effects of the bulk modification by Pd on the electrochemical properties of amorphous MgNi were investigated by using a conventional two-electrode system. It was found through X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) analyses that Pd dissolved uniformly into the bulk of MgNi during the ball milling without affecting the amorphous structure of MgNi. As a result, the cycle life of Pd-modified MgNi in alkaline solution was significantly improved. HRTEM and XRD observations showed that a dense layer of fine grains of Mg(OH)₂ covered over the surface of unmodified MgNi powder after the immersion in alkaline electrolyte solution, whereas no appreciable extent of Mg(OH)₂ formation was observed on the Pd-modified MgNi powder. These observations demonstrate that the Pd bulk modification is very effective to suppress the formation of Mg(OH)₂ layer and hence gives rise to the remarkable improvement of the cycle life of the electrode.

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[2005_04]

Materials Transactions, 46(3) (2005) 511-516

 The change in the chemical surface state of a V-4Cr-4Ti alloy after heat treatments in vacuum at temperatures from 573 to 1273 K was investigated by means of X-ray photoelectron spectroscopy. Before heating, the surface of the as-polished alloy was covered with a V oxide film. Diffusion of oxygen into the bulk started at around 673 K, and the alloy surface gradually became metallic. Oxygen, however, did not disappear from the surface completely. Surface segregation of Ti was observed as the temperature increased. The concentration of Ti reached 20 at% at 1273 K. No significant segregation of Cr or other impurities were observed. This surface segregation of Ti significantly reduced the surface reaction rates of H₂ and D₂. The isotope effect on the surface reaction rates of H₂ and D₂ was not observed under the present experimental conditions.

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[2005_05]

J. of Nuclear Materials, 337-339 (2005) 461-465

 The capability of a niobium panel to absorb atomic hydrogen was investigated for particle control application in divertors. The absorption rate (1.3 × 10²⁰ H/m²s) stayed almost constant up to a dose of 4 × 10²³ H/m² with no hydride formation occurring. The absorption panel can be easily regenerated. The absorbed hydrogen can be retained in the panel even after 48 h at room temperature. The absorption rate was found to decrease with panel temperature for T < 200 °C, remarkably dropping in the vicinity of room temperature. This is connected most probably with the formation of a multilayer impurity coverage. The multilayer carbon coverage deposited during the panel exposure in the divertor region of LHD decreased the absorption rate, but the panel properties could be completely restored by heating at 850 °C in spite of panel carbidization.

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[2005_07]

Fusion Science and Technology, 47 (2005) 126-136

 The Advanced Limiter Test (ALT) project is the focus of a fruitful and intense International Energy Agreement collaboration on TEXTOR. The pump limiter is a mechanical boundary that is laid out for taking the full heat load of TEXTOR, namely 8 MW (assuming 2 MW radiated power) for 10 s, and provides a pumping efficiency of at least 5% of the working gas. This layout is adopted from the requirements of a fusion reactor: It is mandatory to remove both the full power that is convected to the limiter or divertor and the helium ash that is generated in the fusion process. In order to obtain pumping for all gases, the ALT-II is equipped with turbomolecular pumps. A short description of ALT-II is given, and the power and particle fluxes to the limiter surface and into the exhaust scoops are discussed. Requirements of the helium removal rate for a reactor and relevant measurements are discussed, and particle removal and the power distribution to the limiters are treated. Related topics of the ALT-II program were hydrogen recycling and the measurement of turbulence-induced anomalous particle transport in the plasma edge.

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[2005_09]

Fusion Science and Technology, 48 (2005) 144-147

 A new kind of materials that can be applied to a gas chromatographic hydrogen isotope separation system was developed to reduce the amount of Pd-Pt alloy required for making the column and to improve the separation efficiency. Pd and Pt were deposited on α- Al₂O₃ powder by using a barrel sputtering system. Prepared sample powder was characterized from surface morphology, element distributions on the surface, composition and crystallinity. The characterization showed that a uniform layer of Pd-Pt alloy with expected composition was formed on Al₂O₃ particles. The crystallinity, however, was poor, but improved after annealing at 1073 K for 2 hours. The hydrogen absorbing behavior was also improved by the annealing. A separation column was prepared from the annealed powder and was subjected to experiments on hydrogen isotope separation. The column of annealed powder gave considerably good separation efficiency around room temperature, in spite that only 0.35 g of Pd-Pt was used for the column. The amount of Pd-Pt alloy used here should be compared to previous results, where 1.5 g of Pd-Pt powder was required for high separation efficiency. The new material was quite effective to reduce the amount of Pd-Pt alloy without compromising the separation efficiency and can give further improvement.

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[2005_10]

Fusion Science and Technology, 48 (2005) 152-155

 To study the practical application of a tritium separation process using Self-Developing Gas Chromatography (SDGC) using a Pd-Pt alloy, intermediate scale-up experiments (22 mm ID x 2 m length colum) and the development of a computational simulation method have been conducted. In addition, intermediate scale production of Pd-Pt Powder has been developed for the scale-up experiments.
    The following results were obtained: (1) a 50-fold scale-up from 3 mm to 22 mm causes no significant impact on the SDGC process; (2) the Pd-Pt alloy powder is applicable to a large size SDGC process; and (3) the simulation enables preparation of a conceptual design of a SDGC process for tritium separation.

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[2005_11]

Fusion Science and Technology, 48 (2005) 177-181

 One conceivable option for the disposal of tritium- contaminated stainless steel consists in its storage at ambient temperature in a purged containment. To assess this option several stainless steel 316 specimens, previously loaded at elevated temperatures with 0.8-8.5 MBq of tritium, were flushed continuously with dry argon (water partial pressure 0.073 Pa) for extended periods of time. The released tritium (more than 99 % in the form of tritiated water (HTO)) was collected in bubblers and monitored periodically by liquid scintillation counting. After an initial fast liberation a fairly constant rate of the order of 0.2 % per day established. Tritium depth profile in the SS specimens could be simulated by a diffusion limited desorption model. The rate determining step for tritium release appears to be bulk diffusion.

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[2005_12]

Fusion Science and Technology, 48 (2005) 324-331

 The applicability of bremsstrahlung counting to in- examined. A specially desighed metallic vial fitted with a gold-coated beryllium window was prepared for the present examinations. Only tritiated water of a given amount was put into the vial. The volume dependence of the X-ray intensity showed that 5 cm³ of tritiated water is sufficient for measurements. It was found that the spectrum of X-rays induced by β-rays consisted of only bremsstrahlung. The bremsstrahlung spectrum could be reproduced quite well by computational simulation. A good linear relation between the X-ray intensity and tritium concentration was obtained in the concentration range of 4x10^-3 - 40 MBq cm^-3. Furthermore, effect of nickel added as a model impurity to tritiated water was examined, and it was found that the tritium concentration can be evaluated from the X-ray intensity without any correction in the presence of impurity below 200 ppm.

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[2005_13]

Fusion Science and Technology, 48 (2005) 397-400

 There are three components which contain tritium in the air, i.e. water vapor, molecular hydrogen and methane [1][2]. However, there is no tritium monitor, which is able to measure the concentration separately. In the light of it, we are developing a new monitor, which will be enable us to measure the tritium concentrations in two of these species, i.e. molecular hydrogen and methane. The specific activities of tritium in molecular hydrogen and in methane are very high. Then if we can collect the hydrogen and the methane, we will easily measure the tritium concentrations. We have conceptually designed a new tritium monitor and carried out several basic experiments. Based on the results of these experiments, we have estimated the performance of the monitor. For an hour counting, the monitor will be able to measure the tritium concentrations of molecular hydrogen and methane using about 4m³ air. Since the total performance of the monitor mainly depends on the capability of the proportional counter, we are developing an appropriate counter.

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[2005_14]

J. of Alloys and Compounds, 402 (2005) 227-232

 Surfaces of spherical polymer microparticles with three different sizes (50, 12 and 5 μm in diameter) were modified with platinum using the hexagonal barrel equipped RF sputtering system. It was found that the surfaces of particles could be uniformly coated with Pt layers, regardless of their sizes. It should be noticed that the present system made it possible to form a uniform Pt-layer over a polymer particle of 1 μm diameter. Cyclic voltammograms (CVs) of the Pt-coated samples gave the same CV as that of bulky Pt, indicating that electrochemical characteristics of the Pt-layers are identical with those of Pt metal.

Keywords: Hexagonal-barrel sputtering system; Surface modification of polymer microparticles

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[2005_15]

J. of Nuclear Materials, 337-339 (2005) 575-579

 Distribution of tritium concentrations on the surface and in the bulk (up to 1 mm in depth) in a complete poloidal set of divertor tiles exposed to D-T plasma shots in JET was measured by β-ray-induced X-ray spectrometry (BIXS). The observed X-ray spectra showed that tritium distribution was different not only from tile to tile but also highly non-uniform in each individual tile. The peaks of bulk tritium concentration obtained by BIXS are correlated with the corresponding one obtained previously by other methods. For the first time, tritium depth profiles in the plasma-facing surface of complete divertor tiles were obtained by BIXS and they can be classified by four types of a tritium depth profile.
Keywords: Divertor; JET; Tritium