Papers - 2010

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[2010_01]

Distribution and Mobility of Tritium in Type 316 Stainless Steel

R.-D. Penzhorn, Y. Torikai, S. Naoe, K. Akaishi, A. Perevezentsev, K. Watanabe, M. Matsuyama

Fusion Science and Technology Vol.57 Number3 Apr.2010, 185-195

[2010_02]

30 years R&D Activities on a Large Amount of Tritium Handling Technology and its Future Subjects
1. Construction of Faculity Handling Large Amount of Tritium - The Dawn of Tritium Research Studies and Construction of Tritium Handling Faculity(written in Japanese)

MATSUYAMA Masao, YAMAHISA Toshihiko

Journal of Plasma Fusion Research. Vol.86, No.2(2010) 97-103

[2010_03]

Accomplishment of the Large Amount of Tritium Handling Technology(1)
-Accumulation of the Safety Operation Experiences of Tritium Handling Facilities and the Related Safety Studied-

HATANO Yuji, YAMADA Masayuki, HAYASHI Takumi

Journal of Plasma Fusion Research. Vol.86, No.3(2010) 173-184

[2010_04]

30 years R&D Activities on a Large Amount of Tritium Handling Technology and its Future Subjects
-Maintenance and Renewal of a Radiation Facility, Bringing-up of the Tritium Handling Researchers and Toward the Establishment of a New Tritium Core Facility-(written in Japanese)

MATSUYAMA Masao, HAYASHI Takumi, YAMAHISA Toshihiko

Journal of Plasma Fusion Research. Vol.86, No.7(2010) 431-435

[2010_05]

Methanol oxidation on carbon-supported Pt-Ru and TiO₂ (Pt-Ru/TiO₂/C) electrocatalyst prepared using polygonal barrel-sputtering method

Kazuki Hirakawa, Mitsuhiro Inoue and Takayuki Abe

Electrochimica Acta 55 (2010) 5874-5880

[2010_06]

Suppression of Potential Oscillations in PEFCs by Using Anode Catalyst Prepared by Polygonal Barrel-Sputtering Method

M. Inoue, K. Hirakawa, M. Umeda, T. Abe

FUEL CELLS 10, 2010, No.4, 556-562

[2010_07]

Visualization of Diffusive Hydrogen

Takahito Watakabe, Goroh Itoh, Yuji Hatano

Materials Science Forum Vols.654-656(2010) 2903-2906

[2010_08]

Crystal structure change of Li_2+xTiO_3+y tritium breeder under moist air

Masanori Hara, Yuka Togashi, Masao Matsuyama, Yasuhisa Oya, Kenji Okuno

Journal of Nuclear Materials 404 (2010) 217-221

[2010_09]

Study of the Plasma Driven Permeation of Hydrogen through a Nickel Membrane in RF and Ohmic Plasmas in the Spherical Tokamak QUEST

Sanjeev K. SHARMA, Hideki ZUSHI, Ikuji TAKAGI, Yuki HISANO, Mizuki SAKAMOTO, Yuta HIGASHIZONO, Taichi SHIKAMA, Sigeru MORITA, Tetsuo TANABE, Naoaki YOSHIDA, Kazuaki HANADA, Makoto HASEGAWA, Osamu MITARAI, Kazuo NAKAMURA, Hiroshi IDEI, Kohnosuke N. SATO, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA, Yousuke NAKASHIMA, Nobuyuki NISHINO, Yuji HATANO, Akira SAGARA, Yukio NAKAMURA, Naoko ASHIKAWA, Takashi MAEKAWA, Yasuaki KISHIMOTO, Yuichi TAKASE and QUEST Group

Journal of Plasma Fusion Research.SERIES, Vol.9(2010) 142-146

[2010_10]

Preparation of Mg and Al phosphate coatings on ferritic steel by wet-chemical method as tritium permeation barrier

Kun Zhang, Yuji Hatano

Fusion Engineering and Design 85(2010)1090-1093

[2010_11]

Absolute Determination of Tritium Amount by Highly Sensitive Calorimeter

Masao Matsuyama

Netsu Sokutei 37 (4) 147-153

[2010_12]

Sensitivity of a specially designed calorimeter for absolute evaluation of tritium concentration in water

Masao Matsuyama, Kenichi Takatsuka, Masanori Hari

Fusion Engineering and Desing 85 (2010) 2045-2048

[2010_13]

Improvement of high temperature stability of Pd coating on Ta by HfN intermediate layer

Teo Nozaki, Yuji Hatano, Eriko Yamakawa, Asuka Hachikawa, Kazuyoshi Ichinose

International journal of hydrogen energy 35 (2010) 12454-12460

[2010_14]

Exposure of tungsten nano-structure to TEXTOR edge plasma

Y. Ueda, K. Miyata, Y. Ohtsuka, H.T. Lee, M. Fukumoto, S. Brezinsek, J.W. Coenen, A. Kreter, A. Litnovsky, V. Philipps, B. Schweer, G. Sergienko, T. Hirai, A. Taguchi, Y. Torikai, K. Sugiyama, T. Tanabe, S. Kajita, N. Ohno, The TEXTOR team

J.Nucl.Mater. 2010 (in press)

[2010_15]

Retention behavior of hydrogen isotopes in boron film deposited on SS-316 for LHD first wall

K.Okuno, S.Suzuki, M.Kobayashi, R.Kurata, M.Matsuyama, N.Ashikawa, A.Sagara,Y.Oya

Fusion Engineering and Design, 85 (2011) 2328-2330

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[2010_01]

Fusion Science and Technology Vol.57 Number3 Apr.2010, 185-195

   Exposure of Type 316 stainless steel to tritium-containing hydrogen at an elevated temperature causes diffusion of the majority into the bulk and trapping of a small fraction in a thin oxide layer on the surface at concentrations far exceeding those in the bulk. The uptake by the bulk and surface layer is temperature and pressure dependent. After chemical erosion of the tritium-rich layer, the concentration of tritium on the topmost surface is slowly and asymptotically restored even at 298 K. Isothermal heating at 373 or 473 K until substantial release of the bulk tritium is associated with a comparatively much smaller liberation from the surface layer suggesting different retention and liberation mechanisms. The tritium inventory and profile evolution of homogeneously loaded Type 316 stainless steel caused by chronic release at the ambient temperature and radioactive decay were followed experimentally over several years and modeled successfully by a diffusion mechanism. The model has been adapted to specimens nonhomogeneously loaded with tritium only up to the subsurface. It simulates profile and inventory changes well even after prolonged aging. Chronic release constitutes an aging loss of tritium comparable to that of radioactive decay that should be taken into account for the assessment of tritium-contaminated stainless steel waste.

Keywords:tritium, stainless steel, aging

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[2010_02]

Journal of Plasma Fusion Research. Vol.86, No.2(2010) 97-103

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[2010_03]

Journal of Plasma Fusion Research. Vol.86, No.2(2010) 97-103

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[2010_04]

Journal of Plasma Fusion Research. Vol.86, No.7(2010) 431-435

Keywords:tritium, core facility, broader approach, DEMO Reactor, thermonuclear fusion

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[2010_05]

Electrochimica Acta 55 (2010) 5874-5880

   Methanol oxidation performance of a carbon-supported Pt-Ru alloy catalyst used at the direct methanol fuel cell (DMFC) anode is improved by adding TiO₂. However, the methanol oxidation performance of the electrocatalyst described above must be enhanced further to realize practical application in DMFCs. In this study, we used our original surface-modifying technique termed the "polygonal barrel-sputtering method" to prepare a carbon-supported Pt-Ru and TiO₂ (Pt-Ru/TiO₂/C) electrocatalyst offering higher methanol oxidation performance. The obtained results show that the methanol oxidation performance of the prepared Pt-Ru/TiO₂/C is superior to that using wet process as the TiO₂ deposition method. Furthermore, for our sputtering method, the peak current of methanol oxidation on the Pt-Ru/TiO2/C is enhanced by increasing the TiO₂ deposited amount up to 2.8 wt.%. These results suggest that a Pt-Ru/TiO₂ interface area is increased using the polygonal barrel-sputtering method, providing the high methanol oxidation performance of Pt-Ru/TiO₂/C.

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[2010_06]

FUEL CELLS 10, 2010, No.4, 556-562

   In this study, we investigated the suppression of potential oscillations that occur while feeding H₂ gas including a large amount of CO to polymer electrolyte fuel cells. A carbon-supported Pt-Ru alloy (Pt-Ru/C) sample was prepared by the polygonal barrel-sputtering method. Electrochemical measurement was conducted in 1 N H₂SO₄electrolyte solution saturated with H₂ gas including CO of 1,000 ppm. From the measurement, it was found that the prepared Pt-Ru/C sample showed higher CO tolerance than a commercially available sample, and therefore, potential oscillations in the case of the prepared sample occurred for slightly longer intervals. Additional samples were prepared by sputtering different amounts of Ru on the prepared Pt-Ru/C sample, and it was observed that the average interval of potential oscillations increased with the amount of Ru. This result suggests that in the case of the polygonal barrel-sputtering method, Ru plays an important role in suppressing potential oscillations and influences the CO tolerance of Pt-Ru/C.

Keywords: Anode Catalyst, CO Oxidation, Polygonal Barrel-Sputtering Method, Polymer Electrolyte Fuel Cells, Potential Oscillations, Pt-Ru/C

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[2010_07]

Materials Science Forum Vols.654-656(2010) 2903-2906

   In recent years, the use of hydrogen as a clean energy has been paid attention to in terms of the prevention of global warming. Tanks composed solely of steel and cylinders consisting of aluminum liner reinforced with C-FRP in the surrounding are used to store high-pressure hydrogen gas in hydrogen stations and in fuel cell vehicles, respectively. On the other hand, hydrogen embrittlement has been known to occur in some metallic materials under several certain conditions. Also, it has been generally known that the environmental hydrogen that invades the material during services plays major role in hydrogen embrittlement. For this reason, investigations on the behavior of environmental hydrogen in metallic materials are needed. In this study, the behavior of environmental hydrogen in pure aluminum, 6061 aluminum alloy and 7075 aluminum alloy has been investigated by means of tritium autoradiography.

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[2010_08]

Journal of Nuclear Materials 404 (2010) 217-221

   To investigate the aging behavior of Li_2+xTiO_3+y, the materials Li_2.0TiO_3+y, Li_2.2TiO_3+y and Li_2.4TiO_3+y were stored under moist air at ambient temperature. Under these conditions the weight of Li_2.0TiO_3+y increased by only 1% in 100 days, which provides evidence for the high chemical stability of Li₂TiO₃. In comparison, under the same storage conditions the weights of Li_2.2TiO_3+y and Li_2.4TiO_3+yincreased by 14% and 18%, respectively. The observed weight gain is attributed to the uptake of water, and to the reaction of a by-product of Li_2+xTiO_3+y with water and carbon dioxide. The weight gain curves were evaluated by the Jander equation. From the analysis, it was possible to obtain the diffusion coefficient of water through Li₂TiO₃ particles at ambient temperature. The determined value was 2 × 10^-17 m²/s.

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[2010_09]

Journal of Plasma Fusion Research. SERIES, Vol.9(2010) 142-146

   Particle retention and recycling are still major issues for the long pulse fusion devices. Plasma driven permeation(PDP) is one of the main reason behind the particle retention/recycling in these devices. To enhance the understanding of the particle retention under various discharge parameters, the PDP of hydrogen through a 30 μm thick Ni membrance heated at 523 K has been studied in RF and ohmic plasmas in the spherical tokamak QUEST. The permeation has been allowed by reflected neutral atoms by using a baffle before the Ni membrance to avoid any impurity deposition. The baffle before the Ni membrance also provides a way to simulate the particles retension behind plasma facing components(PFC) inside the tokamak chamber. It has been observed that the PDP fluence (Q_PDP)increases linearly with RF power (P_RF) and the chamber pressure. A linear relationship with scattered date between Q_PDP and Hα fluence (Qα) is found in all dischaeges, which suggests the fundamental proportionality of Q_PDP to the incident atomic fluence. For the longer discharges pulse, the PDP flux(Γ_H2) tends to saturate at τ ≈ 30 s, though the incidene ion flux to the chamber wall is ~5× 10²¹ m^-2 s^-1. Q_PDP is also found proportional to the plasma discharge widths(τ ›5s).

Keywords: plasma driven permeation, PDP, recycling, retention, tritium

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[2010_10]

Fusion Engineering and Design (in press)

   Layers of Mg or Al phosphate were prepared on type 430 ferritic stainless steel (SS430) by wet-chemical methods as tritium permeation barrier. Disk-type specimens of SS430 were first coated with ZrO₂/ZrO₂ or ZrO₂/Al₂O₃ layers (100 nm) by sol-gel and electrolytic deposition techniques. Then, the phosphate layers were prepared by dip-coating method; the total thickness of coating was 200 nm. The permeation rate of hydrogen was measured at 300-600 ℃ under driving pressure of 0.1 MPa. The Mg or Al phosphate layers provided significant barrier effects, and the permeation reduction factor observed under the present conditions was 200-3000 against that of Pd coated 430 specimen. Further investigation, however, was required to improve the stability at high temperatures.

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[2010_11]

   From viewpoint of establishment of a standard system to determine the absolute amount and/or concentration of high-level tritium which is used as fuel of a future fusion reactor and one of radioactive materials, the appllicability of a specially designed twin type conduction calorimeter has been examined at the tritium handling facility in Hydrogen Isotope Research Center, University of Toyama. Two examples of the examinations were shown: one is the measurement of a given amount of tritium stored in ZrNi alloy powder, and the other is the measurement of tritiated water. Both examinations gave enough results as a standard device. lt was seen, therefore, that the present calorimeter has high potential for measurement of the absolute amount of tritium. Furthermore, an example that the present calorimeter was applied to nondestructive measurement of the amount of tritium in a glass ampoule was described.

Keywords: tritium, calorimeter, absolute measurement, non-destructive measurement, fusion reactor

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[2010_12]

   Applicability of a specially designed high-sensitivity conduction calorimeter has been examined to determine the absolute amount of tritium in tritiated water. A given concentration of tritiated water was prepared for examinations. Prior to measurements by the calorimeter, the concentration of tritium was measured by a liquid scintillation counter, and it was determined as 46.0±0.5MBq/cm³. This tritiated water, 20cm³, was loaded into a sample cell of the calorimeter. The concentration of tritium determined by the calorimeter was 45.± 2.0MBq/cm³, and it agreed with that by the liquid scintillation counter within a few percent. In addition, detection limit of the present calorimeter was evaluated to be 40 MBq, considering the standard deviation of background level measured without tritiated water. It was concluded, therefore, that the present calorimeter can be utilized as a standard device for determination of the absolute amount of tritium in tritiated water.

Keywords: Calorimeter, Tritiated water, Measurement, Liquid scintillation counter

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[2010_13]

   Hafnium nitride (HfN) was chosen as a material for non-porous intermediate layer to improve the high temperature stability of Pd-Ta composite membranes for hydrogen separation. A layer of dense HfN (70 nm) was prepared between Ta substrate and thin Pd film (300 nm), and the high temperature stability of Pd coating was examined by hydrogen absorption experiments at 573 K after the heat treatments at 873 and 973 K. The HfN layer showed obvious hydrogen permeability, though the permeation rate in HfN appeared to be smaller than that in Pd and Ta. In addition, the degradation in coating effects of Pd at elevated temperatures was substantially retarded by HfN layer. Such improved stability was ascribed to retardation of open porosity development in Pd films and interdiffusion between Pd and Ta. It was concluded that HfN is a potential candidate material for intermediate layer to improve high temperature stability of Pd-group 5 metal composite hydrogen separation membranes.

Keywords: Hydrogen separation, Permeation membranes, Composite materials, Palladium, Tantalum, Nitrides

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[2010_14]

   W nano–structures (fuzz), produced in the linear high plasma device, NAGDIS, were exposed to TEXTOR edge plasmas (ohmic He/D mixed plasma and pure D plasma) to study formation, erosion and C deposition on W fuzz in tokamak plasmas for the first time. Fuzz layers were either completely eroded or covered by C deposit. There was no clear indication of W fuzz growth under the present conditions. There was no significant difference of C deposition between 'thick' fuzz (500–600 nm in thickness) and 'thin' fuzz (300–400 nm) in the He/D plasma. On the W fuzz surface, C deposition was enhanced probably due to reduction of effective sputtering yield and effective reflection coefficient of carbon ions, similar to roughness effects. Formation and erosion of W fuzz in tokamak devices and role of impurities are discussed.

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[2010_15]

    The chemical states and the deuterium retention of boron films deposited on type 316 stainless steel used as first wall of LHD, which contained 52% oxygen, were studied by means of XPS and TDS. The high oxygen concentration in the boron film could be attributed to oxygen in the surface oxide layer of the stainless steel. The major chemical state of boron with 52% oxygen concentration was B₂O₃. The B₂O₃ structure was decomposed to B–B and B–O bonds by the energetic deuterium irradiation. It was found that the deuterium could remain in boron films under operation temperature in the first wall of LHD. The deuterium retention in the boron film deposited on SS was smaller compared to that in the boron film deposited on silicon substrate with 36% oxygen concentration. As the oxygen concentration in boron films increased, the amount of sputtered oxygen was clearly increased, indicating that more heavy water was formed by reacting with implanted deuterium and released, resulting in the smaller deuterium retention in the boron films. The knowledge for the tritium retention in boron films which cannot remove in the operation temperature and the release of tritiated water should be required for the D–D discharge in LHD.

Keywords: Boronization, LHD, SS316, XPS, TDS