Takayuki Abe, Tomoyuki Tachikawa, Yuji Hatano, Kuniaki Watanabe

Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    A cyclic voltammogram (CV) of amorphous MgNi clearly showing the hydrogen absorption-emission processes of amorphous MgNi was obtained by using a micropaste electrode technique. The hydrogen absorption was observed as an increase in the cathodic current below -0.9 V vs. Hg/HgO, and the emission as a broad anodic peak at ~-0.9 V. These processes were considerably affected by immersion of the electrode in a KOH solution prior to measurements. The ring part of the cathodic current shifted to the cathodic direction depending on the immersion time. A decrease in the anode peak current and a remarkable shift of the anode peak potential were also observed. Using X-ray diffraction analyses, the deterioration of such electrode properties was attributed to formation of Mg(OH)₂ by the alkaline immersion. Potential step measurements gave an apparent diffusion constant (D _app) of the hydrogen in the material of 6.8-9.4x10 ^-10 cm ²/s, irrespective of the immersion time. These results show that the Mg(OH)₂ formed has almost no effect on the diffusion of hydrogen but disturbs electron transfer processes on the electrode surface.

Keywords: Rechargeable hydrogen batteries; Micropaste electrode technique; Amorphous MgNi; Mg(OH)₂

Yuji Hatano, Tomoyuki Tachikawa, Daobin Mu, Takayuki Abe, Kuniaki Watanabe, Shotaro Morozumi

Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    The mechanism underlying degradation of an amorphous MgNi electrode was studied. Amorphous MgNi powder was prepared by mechanical alloying, and a charge/discharge cycle test was carried out in 6 M KOH solution. The amount of hydrogen absorbed in the charge process was determined by vacuum hydrogen extraction. The discharge capacity decreased rapidly with progress of the cycle test. The results of the hydrogen extraction indicated that almost all hydrogen absorbed in the charge process was released in the discharge process. X-ray diffraction analyses showed that Mg(OH)₂ was formed on the surfaces of MgNi particles after the cycle test. It was deduced that the reduction in the discharge capacity was mainly due to the degradation in absorption capability in the charge process caused by retardation of electron transfer by Mg(OH)₂ layer. The cyclic stability of the discharge capacity was improved by heat treatment in Ar at 573 K.

Keywords: Nickel/metal hydride battery; Anode; Magnesium; MgNi; Amorphous; Mg(OH)₂

D. Mu, Y. Hatano, T. Abe, K. Watanabe

Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    Amorphous MgNi alloy was prepared by ball-milling of Mg2Ni and Ni powders. Current density dependence of the discharge capacity was studied in the range from 5 to 250 mA/g for the MgNi electrode by charge-discharge cycle tests in 6 M KOH electrolyte using a conventional two-electrode system. The amount of hydrogen used for the discharge decreased with cycles. The extent of capacity degradation at a given cycle increased with increasing discharge current density. The capacity degradation curves could be expressed by ¢(t)=¢+(¢0¢)exp[kt], where ¢(t) is the discharge capacity at time t, that is the period of time in which the electrode was immersed in the electrolyte solution, ¢0 the ideal discharge capacity expected for the virgin electrode, ¢ the final steady discharge capacity after a number of cycles, and k the apparent rate constant for the degradation. The rate constant increased linearly with the current density. According to diffusion analyses of discharge curves under different current densities, the hydrogen diffusion in the bulk is not the rate-determining step for the measured discharge rate, but surface processes play dominant roles in affecting the MgNi electrode properties.

Keywords: MgNi alloy; Discharge current density; Hydrogen diffusion; Degradation

Kaoru Dokko^a, Soichi Horikoshi^a, Takashi Itoh^a, Matsuhiko Nishizawa^a, Takayuki Abe^b, Minoru Umeda^a, Isamu Uchida^a

^a Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Aramaki-Aoba 07, Aoba-ku, Sendai 980-8579, Japan

^b Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    A microelectrode technique was applied to investigate the electrochemical properties of LiMn₂O₄ particles at elevated temperatures. Cyclic voltammograms of LiMn₂O₄ were measured after the particles were exposed to the electrolytes. This technique results in rapid and precise evaluation of the redox behavior of the materials. A significant capacity fading was observed in 1 M LiPF₆/EC+PC electrolytic solution, which indicates that both LiMn₂O₄ and LiPF₆ participate in the reaction to produce an inert material on the particle surface. Next, the capacity fading for two different BET surface area particles were compared using 1 M LiPF₆/EC+PC at 50 ﾟC. The reaction was found not to be controlled by the surface area. Finally, a Li_1.1Mn_1.9O₄ particle was employed. The fading in discharge was ca. 10% for 50 cycles even at 50 ﾟC, which means that the particle substitution of Mn in LiMn₂O₄ by Li substantially enhanced the capacity stability.

Keywords: Microelectrode technique; Lithium manganese oxide spinel; Charge/discharge properties; Elevated temperature

Masao Matsuyama, Tadayuki Murai, Kuniaki Watanabe

Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    To make a nondestructive measurement of tritium retained on/in materials surfaces, conversion efficiency of b-ray to characteristic X-rays in an argon atmosphere has been examined. For this purpose, various tritium-containing graphite plates were prepared at first by ion implantation. After the tritium implantation, measurements of an X-ray spectrum from the graphite plates were carried out in the argon atmosphere. A good linear relation was observed between the intensity of Ar(Ka) characteristic X-rays and the total amount of tritium determined by full-combusion. The apparent conversion efficiency was determined as 4.15x10 ^-6 counts/s/Bq. To determine the intrinsic conversion efficiency for argon atoms, relevant correction factors such as geometrical efficiency, absorption of X-rays, effects of a tritium depth profile and a photoelectric effect were experimentally evaluated through numerical calculations. Taking into account these correction factors, the intrinsic conversion efficiency was determined to be 3.1x10 ^-4 photons/b-particle.

Yuji Torikai^a, A. N. Perevezentsev^b, Masao Matsuyama^a, Kuniaki Watanabe^a

^a Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, Japan

^b UKAEA　JET Facilities Abingdon, OX 14 3EA, UK

Abstract

    To establish efficient decontamination methods for tritium-contaminated stainless steels, the desorption of tritium was studied for SS-316 in dry and wet argon gas carries at different temperatures. The specimen was exposed to tritium at 523 K for 3 hours. The tritium inventory was in a range from 2 to 12 M Bq. The desorption at elevated temperatures was measured by using a liquid scintillation counter. In addition, the tritium depth profiles in the specimen were evaluated by beta-ray induced X-ray spectrometry. It was found that the decontamination efficiency was enhanced by the presence of moisture. This effect was ascribed to the isotope exchange reaction on the surface. The depth profile measurements revealed the pressure of tritium-rich subsurface layer and the bulk with lower tritium concentration. The majority of tritium was, however, found in the bulk, indicating that extraction of bulk tritium is essential for the decontamination of SS-316 exposed to tritium at high temperatures.

Takeshi Itoh^a, Satoshi Ueda^a, Katsuyoshi Tatenuma^a, Yuji Torikai^b, Masao Matsuyama^b, Kuniaki Watanabe^b

^a KAKEN Co. Ltd, Horimachi 1044, Mito, Ibaraki 310-0903, Japan

^b Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 933-8555, Japan

Abstract

    With regard to tritiated contaminants, effective and simple dry decontamination method using ozone gas were proposed. By the treatment in ozone gas of 400 ppmv at 400 K, in the cases of stainless steel, the decontamination efficiencies of over 99% were obtained for 1 hours, and the decontamination efficiencies of aluminum were 80-86 %. By the treatment of ozone gas, the quantity of the carbon atom on the surface and in inside layer were decreased, and the oxidation on the surface and in inside was proceeded, which may be assumed and expected that the recombination, release and diffusion to the surface of tritium are prevented by a rigid oxide layer generated. The ozone gas treatment is easy to use and apply in practice with a simple and safe operation. Furthermore, gas-phase decontamination technology has many advantages over conventional wet methods, in particular, its simple control processes and small secondary waste. The proposed decontamination technology has the sufficient ability and potential to simplify a decontamination operation and reduce the large volumes waste.

S. Ueda^a, Y. Nanjou^a, T. Itoh^a, K. Tatenuma^a, M. Matsuyama^b, K. Watanabe^b

^a KAKEN Co. Ltd, Horimachi 1044, Mito, Ibaraki 310-0903, Japan

^b Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 933-8555, Japan

Abstract

   To improve the efficiency of gas chromatography for hydrogen isotope separation near room temperature, feasibility of new columns was examined for H-D and H-D-T mixture gases. One kind of the column was the mixture of Pd-Pt alloy and Cu powders as the previous study. But special attention was paid for preparing the separation column; Pd-Pt alloy particles below 200 mesh was mixed with copper powder of 150-200 mesh and packed into a loading tube of stainless steel as uniform as possible. The separation for H-D mixture gases could be remarkably improved by this column even at temperatures around 300 K. This column also could separate tritium as T2 from H-D-T mixture gas containing only 0.13 % T. The other column was prepared by Pd-Pt alloy supported by porous SiC powder for economical use of the expensive alloy. Although this column gave similar separation chromatograms, the separation efficiency was still insufficient and further studies are required.

A. Perevezentsev^a, K. Watanabe^b, M. Matsuyama^b, Y. Torikai^b

^a UKAEA Culham Science Centre, Abingdon, OX14, 3DB, UK

^b Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    Various techniques, such as wiping, gas-purge at elevated temperatures, heating by flame simultaneously with air-purge, have been tested for decontamination of stainless steel samples exposed to tritium-containing hydrogen at room and elevated temperatures. Effectiveness of the decontamination techniques is compared depending on the history of the sample loading with tritium, treatment after the loading, the sample thickness, etc.

A. Perevezentsev^a, K. Watanabe^b, M. Matsuyama^b, Y. Torikai^b

^a UKAEA Culham Science Centre, Abingdon, OX14, 3DB, UK

^b Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    Tritium distribution in stainless steel type 316 exposed to hydrogen containing 32% of tritium at room and elevated temperatures was studied using thermal desorption, analysis of bremsstrahlung spectrums and acid etching techniques. All samples exhibit a large fraction of the overall tritium inventory concentrated in a thin sub-surface layer of @15mm thickness where tritium concentration is by @2 order of magnitude larger than that in the bulk. Observed tritium depth profiles are in contradiction with a classical mechanism of hydrogen penetration to metals by atomic diffusion.

Y. Jin, M. Hara, J.L. Wan, M. Matsuyama, K. Watanabe

Hydrogen Isotope Research Center, Toyama Univ., Gofuku 3190, Toyama 930-8555, Japan

Abstract

    Isotope effects on hydrogen absorption were investigated for a Pd-4at.%Pt alloy by using a high vacuum microbalance. The absorption kinetics were well explained by a assuming comparative contributions of the dissociative adsorption and associative desorption on the surface, and the diffusion into the bulk. The activation energies for adsorption were determined to be 29.1 and 32.8 kJmol^-1 (H₂, D₂) for protium and deuterium , respectively. The activation energies for desorption were 18.1 kJmol^-1 (H₂) and 49.0 kJmol^-1 (D₂). Accordingly, the heat of absorption was evaluated to be -19.0 kJmol^-1 (H₂) for protium and -16.2 kJmol^-1 (D₂) for deuterium. The activation energies for diffusion were determined to be 28.7 kJmol^-1 (H, D) for both protium and deuterium, but the frequency factor for deuterium was about 1.5 times greater than that for protium.

Keywords: Hydrogen; Isotope effect; Absorption; Desorption; Diffusion; Pd-Pt alloy

Alexander I. Livshits, Yuji Hatano, Kuniaki Watanabe

Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, Japan

Abstract

    Superpermeable membranes based on Group Va metals can be applied in fusion devices for a short way separation of D/T mixtures from He, for an active control of particle fluxes and as a general-purpose D/T pump that may be used in particularly in tritium handling systems. Superpermeable membranes being used for D/T separation from helium are able to drastically reduce the tritium load on the He pump (cryopump), while tritium accumulation in the membrane itself does not exceed a few g for a machine of ITER scale. A possible way to decrease the tritium inventory in the membrane is to combine a higher dissociative barrier at the upstream surface with the operation at higher temperature. Compression of permeating D/T attainable with superpermeable membranes is totally determined by the sticking coefficient of thermal hydrogen molecules at the upstream surface. The degree of compression has a significant effect on the tritium inventory and the inventory dependence on the state of the downstream surface.

Yuji Hatano, Kuniaki Watanabe

Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, Japan

Abstract

    Hydrogenation of MgNi₂ by atomic hydrogen was examined at elevated temperatures. Mg₂Ni powder was compacted into a disk and heated in vacuum at 773 K for outgassing. During this heat treatment, Mg₂Ni was transformed into MgNi₂ by evaporation of Mg. This specimen was hydrogenated at 573, 673 and 773 K by hydrogen gas of 30 Pa and atoms produced by rf-discharge. No significant hydrogenation took place by hydrogen gas. On the other hand, the specimen was hydrogenated by the exposure to atoms at 773 K up to [H]/[M]=0.14 within 25 ks. New peaks appeared in the diffraction pattern of Cu Kα　X-ray at 2θ=34.0, 42.0, 48.9 and 86.6. This observation indicated that the hydride formed was in a cubic structure.

Keywords: magnesium; nickel; intermetallic compound; hydrogen; hydrogen atom; hydride; plasma

Ryo Hayakawa^a, Yuji Hatano^a , Katsuhiko Fujii^b, Ken-ichi Fukumoto^c, Hideki Matsui^c, Kuniaki Watanabe^a

^a Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

^b Institute of Nuclear Safety System, 64 Sata. Mihamacho, Mikata-gun, Fukui 919-1205, Japan

^c Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan

Abstract

    The oxidation and reduction of surface oxides of the V-4%Ti alloy were examined by X-ray photoelectron spectroscopy. A specimen sheet of the alloy covered by oxide films was heated between 513 and 1223 K for 10 min in vacuum. Vanadium oxides started to be reduced the metallic state at 673 K owing to oxygen dissolution in the bulk., while titanium remained in oxidized states up to 983 K. Titanium segregated to the surface above this temperature, and the surface concentration reached up to 40% at 1223 K. The specimen surface enriched in Ti was thus prepared and oxidized at 573 and 773 K under oxygen pressures between 10^-5 and 10^-3 Pa. At 573 K, titanium was selectively oxidized at 10^-5 Pa, while vanadium remained in a metallic state. Such selective oxidation of Ti took place also at 775 K under the pressure of 10^-4 Pa. Titanium segregating to the surface appeared to provide the barrier effect against tritium inventory and permeation under high temperature, low oxygen partial pressure conditions through selective oxidation.

Yuji Hatano^a, Miyuki Takamori^a, Kenji Matsuda^b, Susumu Ikeno^b, Katushiko Fujii^c, Kuniaki Watanabe^a

^a Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

^b Department of Material Systems Engineering and Life Science, Faculty of Enginnering, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

^c Institute of Nuclear Safety System, 64 Sata, Mihamacho, Mikata-gun, Fukui 919-1205

Abstract

    The solid state reaction between tungsten and amorphous carbon was studied at 973, 1073 and 1173 K. An amorphous carbon film was deposited onto a tungsten sheet by vacuum evaporation. The specimens thus prepared were heated at given temperatures, and the time dependence of carbide growth was examined by means of X-ray diffraction. No carbide appeared at 973 K within 240 min. On the other hand, the peaks of W₂C appeared at 1073 and 1173 K after an induction period, although W₂C is not thermodynamically stable at these temperatures. The intensities of W₂C peaks increased with elapse of time and then decreased owing to the decomposition of W₂C. No diffraction peaks from WC were detected at both temperatures. It was concluded that the rates of nucleation and growth of W₂C are significantly higher than those of WC at these temperatures.

S. Fukuda^a, R.A. Anderl^b, Y. Hatano^c, S.T. Schuetz^b, R.J. Pawelko^b, D.A. Petti^b, G.R. Smolik^b, T. Terai^d, M. Nishikawa^a, S. Tanaka^d, A. Sagara^e

^a Kyushu University, Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan

^b Idaho National Engineering and Environmental Laboratory, INEEL, Idaho Falls, ID 83415, USA

^c Toyama University, Gofuku, Toyama 930-8555, Japan

^d The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

^e National Institute for Fusion Sciences, Shitaishi-cho, Toki 509-5292, Japan

Abstract

    Flibe-tritium experiment in the Japan-US joint project (JUPITER-II) was initiated in 2001. H/D isotonic exchange experiments were conducted to select a Flibe-facing material. Because of hydrogen isotope interactions with carbon, Ni crucibles were selected for Flibe/Tritium behavior experiments. A Flibe-tritium pot with two Ni (or Cu) permeable probes was designed. The rate of the overall tritium permeation through the Flibe-facing Ni or Cu was estimated by numerical simulation using TMAP4 code. Diffusion in bulk Flibe was found to be the rate-determining step for purified Flibe.

Keywords: Flibe; Tritium; Permeation; Nickel; Glassy Carbon; Hydrocarbon; JUPITER-II; TMAP4

Susumu Ikeno^a, Tokimasa Kawabata^a, Hiroaki Hayashi^a, Kenji Matsuda^a, Seiichi Rengakuji^a, Toshiaki Suzuki^b, Yuji Hatano^c, Katsuyoshi Tanaka^d

^a Faculty of Engineering, Toyama University, Toyama 933-8555, Japan

^b Application & Research Center, JEOL Ltd., Akishima 196-8558, Japan

^c Hydrogen Isotope Research Center, Toyama University, Toyama 933-8555, Japan

^d Shin-Nikkei Co. Ltd., Tokyo 141-0032, Japan

Abstract

    TiO₂ films were formed on aluminum plates by a dip-coating in an advanced sol-gel precursor solution, and the effect of sintering conditions on the photocatalytic properties of the oxide were investigated by UV adsorption. The samples prepared in this way exhibit photocatalytic activity in a range of suitable sintering conditions compatible with the region of crystallization of anatase characterized by X-ray diffraction. The surface morphology and adhesion between the TiO₂ nano-film and aluminum plate were confirmed by energy filtering transmission electron microscopy, and the surface morphology was found to affect the photocatalitic activity. The TiO₂ film was 30 nm thick and was confirmed to be finely crystallines with a mean diameter of 12nm.

Keywords: photocatalyst; titanium dioxide; aluminum; advanced sol-gel method; anatase

Teijun Ma, Yuji Hatano, Takayuki Abe, Kuniaki Watanabe

Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, Japan

Abstract

    Amorphous MgNi  was modified by ball milling with perylene and its effects on the charge/discharge capacity were examined by using a conventional two-electrode cell. It was found that both the ball milling time and perylene/MgNi ratio had great influence on the discharge capacity and cycle life of MgNi. Three types of effects were identified, depending on ball milling conditions. One of them was the increase in the discharge capacity at the first cycle, the second type was the deceleration of the degradation of the discharge capacity with charge/discharge cycle, and the last type was the reduction in the charge/discharge capacity. Chemical states of modified surfaces were analyzed by Auger electron spectroscopy (AES) as well as ab-initio calculation. Both AES and ab-initio calculations indicated that carbon atoms can form bonding with both magnesium and nickel atoms, but bonding with magnesium atoms is most preferable. The change in the charge/discharge capacity is attributed to such kind of reactions, and the three distinct effects are ascribed to the presence of different MgNi-perylene composites, formed during the ball milling on the surface, resulting in the retardation or acceleration of Mg(OH)₂ formation on the electrode.

Keywords: magnesium; nickel; aromatic compound; surface modification; battery electrode

Hitoshi Hanada, Yuji Hatano^a, Kanetsugu Isobe^b, Kan Sakamoto, Masayasu Sugisaki

Kyushu University, Fukuoka, Japan 812-8581, (92)642-3795

^aPresent address: Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, Japan

^bPresent address: Japan Atomic Energy Research Institute, Tritium Engineering Laboratory, Tokai, Ibaraki, 319-1195, Japan

Abstract

    The hydrogen distribution in the oxidized Zircaloy-2 was related to its microstructure by tritium microautoradiography based on a cathodic tritium charging method. It was found out that hydrogen atoms were concentrated in the intermetallic precipitates such as Zr(Fe, Cr)₂ and Zr₂(Fe, Ni) existing in the oxide film, and on the grain boundary of zirconium matrix. It was also found out that hydrogen atoms were scarcely present in the thin metallic region adjacent to the oxide layer, the thickness of which was about 10-15 μm.

M. Matsuyama^a, T. Murai^a, K. Yoshida^a, K. Watanabe^a, H. Iwakiri^b, N. Yoshida^b

^a Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

^b Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580, Japan

Abstract

    Trapping and diffusion of tritium implanted into tungsten at room temperature were examined by b-ray-induced X-ray spectrometry. One of two thin tungsten plates used was previously irradiated with ions. After the tritium irradiation, X-ray spectra from a W sample were measured in an argon atmosphere, and changes in the X-ray spectra with time were followed for five months at room temperature. The observed X-ray spectra consisted of three characteristic X-ray peaks and a bremsstrahlung X-ray peak. For the W sample without He pre irradiation all characteristic X-ray intensities decreased with time, while those for the sample with He pre-irradiation were almost constant, indicating that the He irradiation strongly affects the migration of tritium. Furthermore, the X-ray spectra were analyzed by computer simulation to estimate tritium depth profile. From those results, the diffusion coefficient of tritium at room temperature and effects of He pre-irradiation on trapping of tritium were evaluated.

M. Matsuyama

Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, Japan

Abstract

    Recently developed techniques for nondestructive measurement of tritium, separation of hydrogen isotopes, and decontamination of tritium-contaminated materials at the Hydrogen Isotope Research Center (HRC) in Toyama University were introduced. As a nondestructive measuring technique for high level tritium, b-ray-induced X-ray spectrometry (BIXS) was applied to the evaluation of elemental, oxidized, and ad/absorbed tritium, and it was concluded that this technique is fairly available for determination of tritium in gaseous, liquid, and solid states. A new separation technique by gas chromatography using the Pd-based alloy was proposed, which can be operated near room temperature. Performance of the present separation technique was examined by using a mixture of H, D, and T species. Finally, an example of the thermal behavior of tritium absorbed in stainless steel type 316 was shown.

Keywords: self handling techniques of tritium; nondestructive measurement of tritium; b-ray-induced X-ray spectrometry; separation of hydrogen isotopes; decontamination of tritium

T. Abe^a, H. Shima^a, K. Watanabe^a, Y. Ito^b

^a Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

^b TOYO Corporation 1-6, Yaesu 1-Chome, Chuo-Ku, Tokyo 103-8284, Japan

Abstract

    The effect of cell temperature on the performance of a polymer electrolyte fuel cell was examined in the present study. Measurements using the current interrupt and AC impedance methods showed that membrane resistance increased as the cell temperature was reduced, The change transfer resistance, determined by the AC impedance method, also increased with decreasing cell temperature. The results of electrochemical analysis showed that the temperature of the cell strongly affected the performance of the membrane-electrode assembly in the cell. In addition, the water balance calculated from dew points of fuel gases changed with cell temperature, At a cell temperature of 80 ℃, ca. 80% of the water generated on the cathode passed through the membrane to the anode, while at a cell temperature of 40 ℃, only ca. 20% of the water on the cathode passed through the membrane to the anode.

Hajime Aoyama^a, Tetsutaro Seki^a, Kazuyoshi Ishikawa^a, Shunsuke Hosokawa^b, Takeshi Itoh^c, Katsuyoshi Tatenuma^c, Masao Matsuyama^d, Kuniaki Watanabe^d

^a Fuji Heavy Industries LTD, Robots Development Dept., 1-1-11 Younan, Utsunomiya, Tochigi 320-8564, Japan

^b Masuda Institute Co., 2-4-11 Hongo Bunkyo-ku, Tokyo 113-0033, Japan

^c KAKEN Co. Ltd, Horimachi 1044 Mito, Ibaraki 310-0903, Japan

^d Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    For a routine cleaning and a primary decontamination of tritiated contaminants in the case of decommissioning, a decontamination robot based on dry method utilizing ozone gas treatment was developed. The robot sized of 720(W)x850(D)x1,050(H) mm with a remote and automatic system consists mainly of 5 different part, a flat decontamination port of about 1,000 cm² for ozone gas exposure with a heater and surrounding rubber curtain to isolate the inside circumstance, an ozone gas generator utilizing creeping discharge method, a gas cooler for the hot air containing tritiated vapor to be trapped, an adsorption vessel packing molecular-sieves for tritium trap, and a circulation pump. The amount of suction air is larger than that of the exposure air, therefore non of the contaminants are scattered out from the adsorption port, and this is one of the main characteristic of the robot.

Y. Namjou^a, S. Ueda^a, T. Itoh^a, K. Tatenuma^a, M. Matsuyama^b, K. Watanabe^b

^a Kaken Co., Hori 1044, Mito Ibaraki, 310-0903, Japan

^b Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

    In order to improve the efficiency in gas chromatographic isotope separation technology, porous SiC supporting palladium -platinum (Pd-Pt) alloy as a column material was developed. It was confirmed that the utilization of the column material developed enabled higher recovery yield of 90% and the higher purity of 97% for deuterium isotopic separation comparing with the method using conventional column materials such as the mixture of Pd-Pt alloy filler under 100 mesh and Cu powder from 40 to 80 mesh.