K. Ashida^b, K. Kanamori^a, M. Matsuyama^a, K. Watanabe^a

^a Tritium Research Center

^b Department of Chemistry, Faculty of Science Toyama University, Gofuku 3190 Toyama 930, Japan

Kenji Ichimura, Kan Ashida, Kuniaki Watanabe

Tritium Research Center. Toyama University, Gofuku 3190, Toyama 930, Japan

Abstract

    To apply hydrogen storage materials (getters) to tritium recovery and storage, it is important to understand the activation process of the getters and their pumping characteristics not only for tritium gas, but also impurity gases such as HTO. From this viewpoint, the activation process of the Zr-V-Fe getter (St-707, SAES Getters) and absorption process of D₂O were investigated with XPS-SIMS. An as-received getter surface was observed to be covered with H₂O, CO, O₂, and hydrocarbons. In addition, the getter components formed respective oxides on the surface. The activation, which consisted of vacuum heating above 500℃, caused the disappearance of the adsorbed impurities from the surface, forming a metallic surface consisting of Zr (87 at.%) and V (13 at. %). Exposure to D₂O vapor at 25℃ resulted in the absorption of D₂O as D₂O(a) and/or OD(a). In addition, a part of the surface was oxidized. Elevation of the exposure temperature to 300℃ caused the disappearance of the D₂O(a) and/or OD(a). Consequently the O-coverage decreased, although the partially oxidized surface remained. We conclude that both Zr and V function as the active sites for the decomposition of D₂O (a) and/or OD (a). However, the Zr sites work more actively for the decomposition reaction than the V sites do. Consequently, these Zr sites determine the absorption rate.

K. Ichimura, M. Matsuyama, K. Watanabe, T. Takeuchi

Tritium Research Center, Toyama University, Gofuku 3190, Toyama 930, JAPAN

Abstract

    The rates of ab/desorption of water vapor for Zr-V-Fe getter were investigated by means of mass analyzed thermal desorption spectroscopy. The absorption rate obeyed first order kinetics with respect to the pressure of water vapor. The activation energies for absorption were determined as 1.8 (H₂O), 2.7 (D₂O), and 3.2 (T₂O) kcal/mol. Only hydrogen was desorbed by heating the getter in which water was absorbed. The desorption obeyed second order kinetics with respect to the amount of absorption. The activation energies for desorption were determined as 28.0 (H₂O), 28.6 (D₂O), and 29.3 (T₂O) kcal/mol. It is concluded that the rate determining step for absorption is the dissociation reaction of adsorbed water molecules or hydroxyl groups on the surface. The rate determining step for desorption is the association reaction of hydrogen atoms which diffuse from the bulk to the surface.

Osamu Takayasu, Masatoshi Takagi, Toyosaburo Takeuchi

Faculty of Science, Toyama University, Toyama930, Japan

Abstract

    Previous work on the enrichment of tritium in TH-H₂ and TD-D₂ systems by means of thermal diffusion columns showed that the equation proposed by Waldmann for enrichment in a column of parallel plates is made applicable to that in a column of Clusius type by the addition of two parameters. One parameter is constant irrespective of the gas system, but the other parameter depends on the gas system. In this study, the enrichment of tritium was performed on the three systems, T₂-H₂, T₂-He, and TH-He, and the values of the parameters were obtained. The results reveal that the former parameter is 1.7 as a geometric constant of the column and the latter can be replaced by 1.4 times the thermal diffusion coefficient of each system.

M. Matsuyama^a, K. Ichimura^a, K. Ashida^a, K. Watanabe^a, H. Sato^b

^a Tritium Research Center, Toyama University, Gofuku 3190, Toyama 930, Japan

^b Research and Development Laboratory, Aloka Co. Ltd., 1-22-6 Mure, Mitaka, Tokyo, Japan

Abstract

    The contamination of three ionization chambers (Cu, Ni-plated, and Au-plated chambers) due to exposure to HT or HTO was measured. Considerable contamination took place for all of the chambera due to exposure to HTO. This is caused by the physical adsorption of HTO. The extent of the contamination differed from each other (Ni > Au > Cu), being considered due to difference in their surface roughness. In case of the exposure to HT, the Cu-chamber was contaminated in room air, whereas the Ni-chamber did in dry air atmosphere. This is considered due to the adsorption of HTO (being formed with catalytic exchange reaction between HT and H₂O) on the Cu-chamber and that of HT on the Ni-chamber. The Au-chamber was not contaminated with the exposure to HT. This is because neither the adsorption of HT nor the catalytic exchange reaction takes place on this surface.

Kenji Ichimura, Naoya Inoue, Kan Ashida, Masao Matsuyama, Hitoshi Miyake, Kuniaki Watanabe

Tritium Research Center, Toyama University, Gofuku 3190, Toyama-shi 930

Kenji Ichimura^a, Kuniaki Watanabe^a, Hidenari Kato^b, Isao Kanesaka^b, Kiyoyasu Kawai^b

^a Tritium Research Center, Toyama University, Gofuku 3190, Toyama 910, Japan

^b Department of Chemistry, Faculty of Science, Toyama University, Gofuku 3190, Toyama 930, Japan

渡辺国昭, 市村憲司

富山大学トリチウム科学センター