Papers - 2008

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[2008_01]

Comparative study of the tritium disribution in metals

A. N. Perevezentsev, A. C. Bell, L. A. Rivkis, V. M. Filin, V. V. Gushin, M. I. Belyakov,
I. M. Kravchenko, I. A. Ionessian, Y. Torikai, M. Matsuyama, K. Watanabe, A. I. Markin

Journal of Nuclear Materials 372 (2008) 263-276

[2008_02]

Preparation and Physical and Electrochemical Properties of Carbon-Supported Pt-Ru (Pt-Ru/C) Samples Using the Polygonal Barrel-Sputtering Method

Mitsuhiro Inoue, Hiroshi Shingen, Tomohito Kitami, Satoshi Akamaru, Akira Taguchi, Yasuhisa Kawamoto, Akio Tada, Kazuhiko Ohtawa, Kanji Ohba, Masao Matsuyama, Kuniaki Watanabe, Iwao Tsubone, Takayuki Abe

J. Phys. Chem. C 2008, 112, 1479 -1492

[2008_03]

Surface modification of carbon nanofibers with platinum nanoparticles using a"polygonal barrel-sputtering"system

Hironari Yamamoto, Kazuki Hirakawa,Takayuki Abe

Materials Letters 62 (2008) 2118-2121

[2008_04]

On the mechanism of tritium desorption from stainless steel

K.Akaishi, Y.Torikai, D.Murata, R.-D.Penzhorn, Tomohito Kitami, M.Matsuyama

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films -- May 2008 -- Volume 26, Issue 3, pp. 321-327

[2008_05]

Thermodynamic and Magnetic Properties of GdPd Hydride

Masanori Hara, Takayuki Nakazawa, Satoshi Akamaru, Kuniaki Watanabe, Katsuhiko Nishimura, Katsunori Mori, Masao Matsuyama

Materials Transactions, Vol.49 No.06 (2008) pp.1428-1433

[2008_06]

Transport of Tritium in SS316 at Moderate Temperatures

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

Fusion Science and Technology, Vol.54, Number 2, August 2008, 515-518

[2008_07]

Standardization of Tritium Measuring Devices Based on a High-Sensitivity Calorimeter

Masao Matsuyama, Masanori Hara

Fusion Science and Technology, Vol.54, Number 1 ,July 2008,182-185

[2008_08]

Influence of Oxygen on Permeation of Hydrogen Isotopes Through Group 5 Metals

Yuji Hatano, Andrei Busnyuk, Vasily Alimov, Alexander Livshits, Yukio Nakamura, Masao Matsuyama

Fusion Science and Technology, Vol.54, Number 2, August 2008,526-529

[2008_09]

Tritium Diffusion in V-4Cr-4Ti Alloy

K. Hashizume, J.Matsuda, K.T.Otsuka, T.Tanabe,Y.Hatano, Y.Nakamura, T.Nagasaka,T.Muroga

Fusion Science and Technology, Vol.54, Number 2, August 2008,553-556

[2008_10]

Surface Coating on Aluminum Flakes with Titanium Nitride Layer by Barrel-Sputtering Techniques

Satoshi Akamaru, Yuji Honda, Akira Taguchi,Takayuki Abe

Materials Transactions, Vol.49 No.07 (2008) pp.1638-1643

[2008_11]

Hydrogen Release Rate of SUS316 in Ar Gas Flow and Vacuum

Yuji Torikai, Shogo Naoe, Kenya Akaishi, Ralf-Dieter Penzhorn, Kuniaki Watanabe, Masao Matsuyama

J. Vac. Soc. Jpn. Vol.51, No.9, 2008

[2008_12]

Development of a new detection system for monitoring high-level tritiated water

Masao Matsuyama

Fusion Engineering and Design 83 (2008) 1438-1441

[2008_13]

Measurement of tritium permeation in flibe(2LiF-BeF₂)

P. Calderoni, P. Sharpe, M. Hara, Y. Oya

Fusion Engineering and Design 83 (2008)1331-1334

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[2008_01]

Journal of Nuclear Materials 372 (2008) 263-276

 Coupons of stainless steel, Inconel, beryllium, copper and alminium broze were exposed to tritium in hydrogen gas mixtures over a wide range of parameters:temperature up to 770K, pressure from 1×10 ^-4MPa to 0.05MPa, tritium concentration from 1at.%to 98at.%. The tritium concentration on the surface and distribution thtough the metals were measured using radiography, radioluminography, β-ray induced X-ray spectroscopy and acid etching methods. The effect of metal processing, such as forging, polishing and heat treatment on the tritium distribution was studied along with parameters relating to the exposure of the metal to tritium.

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[2008_02]

J. Phys. Chem. C 2008, 112, 1479 -1492

 Carbon-supported Pt-Ru alloy (Pt-Ru /C) catalysts were prepared using the "polygonal barrel-sputtering method". From the preparation of a Pt-Ru alloy with Pt/Ru = ca. 50:50 atom % on a glass plate as support, the optimum sputtering conditions were an Ar gas pressure of 0.9-0.7 Pa and room temperature. The amount of the sputtered Pt-Ru alloy was controlled by changing the ac power and the sputtering time. Subsequently, the Pt-Ru/C samples were prepared under the given optimum conditions. The Pt-Ru alloy was dispersed extensively in the form of nanoparticles on a carbon support. For the ac power levels of 130, 100, and 50 W, the size distributions were narrower when the ac power was lowered. The respective average particle sizes were 4.1 nm (130 W), 3.3 nm (100 W), and 2.2 nm (50 W). In the case of 30 W, however, the size distribution and the average particle size were almost identical to those for 50 W. In addition, when the Pt-Ru/C samples were prepared by changing the sputtering time, only the dispersion density of the alloy nanoparticles increased in the Pt and the Ru deposited without changing the particle size. The atomic ratios of Pt and Ru in individual Pt-Ru alloy nanoparticles for the prepared samples were similar to the sputtering ratio and homogeneous compared with those for the commercially available samples. With regard to the electrochemical properties for the prepared samples, the hydrodynamic voltammograms for H2 oxidation were identical to that of the commercially available sample. However, for CO oxidation, the peak shapes and the peak potentials for the prepared samples were sharper and ca. 20 mV lower than those for the commercially available samples, due to the uniform Pt and Ru atomic ratios of the individual alloy particles for the prepared samples. The coulomb charges of the CO oxidation reaction per amount of Pt and Ru for the prepared samples increased linearly in the reversed average particle sizes, while on the other hand, the charges for the commercially available samples were not proportional to the reversed sizes. This shows that the Pt-Ru alloy for the prepared samples was more efficiently utilized for electrochemical reactions rather than were the commercial ones. In addition, the cell performances for the alloy loading of 0.08 or 0.02 mg/cm2 using the prepared Pt-Ru /C samples were similar to those for 0.50 mg/cm2 using the commercially available sample.

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[2008_03]

Materials Letters 62 (2008) 2118-2121

 Carbon nanofibers (CNFs) modified with Pt nanoparticles have been prepared using a new RF sputtering instrument called a "polygonal barrel-sputtering" system. The prepared samples were characterized by optical microscopy, field emission scanning microscopy (FE-SEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluorescence (XRF), X-ray diffraction (XRD), and transmission electron microscopy (TEM) with energy-dispersive X-ray spectrometry (EDS). When only the CNFs were placed in the system, large CNF aggregates with sizes of 5–15 mm were observed and Pt was deposited non-uniformly. In addition, microscopic observations revealed that ca. 40% of the CNFs were still unmodified. In contrast, when pieces of bent columnar stainless steel were placed in the system with the CNFs, large CNF aggregates were not observed in the Pt deposited sample. In this sample, CNFs modified with highly dispersed Pt nanoparticles were obtained successfully, and unmodified CNFs were absent. The sizes of the Pt nanoparticles were in a narrow range of 1.7–3.5 nm, and their mean size was 2.5 nm.

Keywords: Coatings; Deposition; Nanocomposites; Nanomaterials

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[2008_04]

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films -- May 2008 -- Volume 26, Issue 3, pp. 321-327

 Stainless-steel specimens (15×15×0.5 mm³) containing homogeneously distributed tritium were used for the experiments. To investigate the fate of tritium in the surface region, about 70 μm were chemically etched and the regrowth of tritium on the top surface layer determined as function of time by -ray-induced x-ray spectrometry. Simultaneously, the specimen was flushed with an argon gas stream at ambient temperature and the released tritium collected in water bubblers. The chronically liberated tritium retained in the bubblers was quantified in regular intervals using a liquid-scintillation counting technique. It was found to consist predominantly of tritiated water (99%); the rest probably being tritium-containing hydrogen. In this work, a model for the transport of hydrogen is proposed that allows quantitative evaluation of the experimental results. It is demonstrated that the numerical simulation accurately predicts the amount of tritium progressively trapped on the surface and that slowly released at ambient temperature from the bulk of the stainless-steel material.

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[2008_05]

Materials Transactions, Vol.49 No.06 (2008) pp.1428-1433

 Thermodynamic and magnetic properties of GdPd hydride (deuteride) were studied. Each of the pressure-composition isotherms of GdPd-Q (Q=H or D) systems showed a plateau region in 0.05 < [Q]/[GdPd] < 0.4, though hydrogen induced disproportionation of GdPd was observed above [Q]/[GdPd] > 0.4. The disproportionation products were determined to be GdQ₂ and Gd₃Pd₄. Enthalpy changes for GdPd hydride formation at [Q]/[GdPd] = 0.2 were evaluated from the isotherms to be
Δ H_f°= -130 kJ/mol_H2and -122 kJ/mol_D2. Magnetization measurements revealed that the effective magnetic moments of GdPd and its hydride were approximately the same as that of Gd³⁺. This indicates that magnetic properties of GdPd and its hydride are governed by gadolinium atoms. In fact, the magnetic ordering temperature and the paramagnetic Curie temperature were also found to be almost invariable with hydrogen content, revealing that electrons from the 1s orbital of absorbed hydrogen bring little influence on the nature of 4f-electrons of gadolinium.

Key words: rare-earth, palladium, GdPd, hydride formation, disproportionation, isotherm, magnetic ordering temperature, curie temperature, effective magnetic moment

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[2008_06]

Fusion Science and Technology, Vol.54, Number 2, August 2008, 515-518

 From tritium release experiments with stainless steel 316 carried out at several temperatures and tritium depth profiles of tritium-depleted specimen information on the transport of tritium by two diverse techniques was obtained. The results could be interpreted by a one dimensional diffusion model. The activation energy for the diffusion of tritium through stainless steel was found to be 61.3 kJ/mol.

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[2008_07]

Fusion Science and Technology, Vol.54, Number 1 ,July 2008,182-185

 A twin type thermal conduction calorimeter has been specially designed and constructed for absolute measurement of tritium, and then its performance was examined using two kinds of tritium samples, i.e., ZrNi alloy powders loaded with a given amount of tritium. Total amounts of tritium in the ZrNi alloy powders were previously estimated by a small ionization chamber. Changes in radioactivity of two samples were followed for three years, and it was seen that the activity changes obeys the half-life of 4505 days. The initial tritium amounts estimated by the small ionization chamber agreed well with the extrapolated values from the activity changes evaluated by the calorimeter. Namely, it was suggested that the small ionization chamber is able to be used as a secondary standard of the tritium measuring devices. The -ray-induced X-ray counter was also calibrated for non-destructive measurements of high-level tritium by using the present small ionization chamber.

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[2008_08]

Fusion Science and Technology, Vol.54, Number 2, August 2008,526-529

 Group 5 metals (V, Nb and Ta) are potential candidates of tube material in vacuum permeator for tritium recovery from Pb-17Li liquid blanket system. From this viewpoint, the influence of oxygen on the surface reaction rates of hydrogen on V and Ta were examined in an ultra-high vacuum apparatuses at elevated temperatures, and the results were compared with the data on Nb acquired in a previous study. The surface reaction rates of hydrogen on V and Ta, and consequently permeation rates, decreased with increasing oxygen concentration in the bulk as previously observed for Nb. These observations were ascribed to the increase in surface oxygen coverage with increasing bulk oxygen concentration. The weakest influence of oxygen on hydrogen permeation rate was observed for V. The expected permeation rate through V under typical blanket conditions, however, was not necessarily high due to high oxygen solubility in V. The evaluation indicated that the highest permeation rate should be obtained with Nb under typical blanket conditions.

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[2008_09]

Fusion Science and Technology, Vol.54, Number 2, August 2008,553-556

 Characteristics of the tritium diffusion coefficient DT in V-4Cr-4Ti alloy, including a bending in the Arrhenius plot of DT, are examined. Based on a trap model, the possible trap sources and their binding energies for tritium in the alloy are evaluated using the experimental data of DT in pure V, which are measured with a tritium tracer method, and the literature data of protium diffusion in V-Ti and V-Cr alloys. The result of the evaluation suggests the presence of two trap sources in the alloy. The first would be attributed to a trap at each substitutional alloying atom which is likely to be Ti. The binding energy EB of 0.08 eV gives the best fit to the observed value of DT above 300 K. The bending in the Arrhenius plot below 300 K is caused by a second trap site with a higher EB, and a lower concentration than those of each alloying atom. The trap is probably formed by the alloying atoms presence to neighboring Ti atoms. The contribution of Cr atom to the trap effect seems to be rather small in this alloy.

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[2008_10]

Materials Transactions, Vol.49 No.07 (2008),1638-1643

 A twin type thermal conduction calorimeter has been specially designed and constructed for absolute measurement of tritium, and then its performance was examined using two kinds of tritium samples, i.e., ZrNi alloy powders loaded with a given amount of tritium. Total amounts of tritium in the ZrNi alloy powders were previously estimated by a small ionization chamber. Changes in radioactivity of two samples were followed for three years, and it was seen that the activity changes obeys the half-life of 4505 days. The initial tritium amounts estimated by the small ionization chamber agreed well with the extrapolated values from the activity changes evaluated by the calorimeter. Namely, it was suggested that the small ionization chamber is able to be used as a secondary standard of the tritium measuring devices. The -ray-induced X-ray counter was also calibrated for non-destructive measurements of high-level tritium by using the present small ionization chamber.

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[2008_11]

J. Vac. Soc. Jpn. Vol.51, No.9, 2008

 To understand the mechanism of hydrogen release from materials used in vacuum technology,the release behavior of tritium from stainless steel SUS316 previously loaded with this gas was investigated isothermally at 423 K either under a stream of argon or under vacuum conditions. Depth profiles of the heated specimens were determined by chemical etching. The diffusion coefficients used to fit the depth profiles of specimens heated under vacuum at 423 K were non-discernible from those obtained with specimens heated under a stream of Ar at the same temperature.

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[2008_12]

Fusion Engineering and Design 83 (2008) 1438-1441

 To monitor high-level tritiated water in a fusion fuel circulation system, a new detection system for non-destructive measurements of tritium concentration was specially design and fabricated. A twin-type X-ray detector, which works as a detector of the low energy X-rays induced by β-Rays from tritiated water, was equipped with the new detection system. Tritiated water flows in a narrow space surrounded by two X-ray detectors. Basic performance of the new detection system was examined using a poly-methylmethacrylate disk labeled with tritium and tritiated water. It was found that the present detection system satisfied the basic performance for measurements of the low energy X-rays and it is applicable to non-destructive measurements of high-level tritiated water in a flow system.

Keywords: High-level tritiated water, Non-destructive measurement, Tritium concentration, β-Ray-induced-X ray spectrometry, Fusion fuel circulation system

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[2008_13]

Fusion Engineering and Design 83 (2008) 1331-1334

  This paper reports on the experimental investigation of tritium permeation in flibe (2LiF?BeF2) at the Safety and Tritium Applied Research facility of the Idaho National Laboratory. A stainless steel cell formed by two independent volumes separated by a 2-mm thick nickel membrane is maintained at temperatures between 500 and 700 °C. A controlled amount of T2 gas is flown in excess of argon in the source volume in contact with the bottom side of the nickel membrane, while a layer of molten salt is in contact with the top side. The tritium permeating above the liquid surface is carried by an argon flow to a diagnostic system comprised of a quadrupole mass spectrometer, a gas chromatographer and a proportional counter. Tritium permeability in flibe as a function of temperature is determined by the measured permeation flow rates reached in steady-state conditions, while the diffusivity is determined by fitting the transient process with the analytical solution for the diffusion process. As a result, the solubility of tritium in flibe as a function of temperature is also determined.

Keywords: Fusion; Tritium; Molten salt; Diffusivity; Solubility