Kuniaki Watanabe^a, Masanori Hara^a, Masao Matsuyama^a, Isao Kanesaka^b, Toshiaki Kabutomori^c

^a Hydrogen Isotope Research Center,
^b Department of Chemistry, Faculty of Science, Toyama University, Gofuku 3190, Toyama 930, Japan
^c Japan Steel Works, Muroran Research Laboratory, 4 Chatu-Machi, Muroran 051, Japan

Abstract

    The stability of ZrNi and ZrCo to heat cycles in hydrogen atmosphere was studied through changes in absorption-desorption characteristics and in crystallographic structures. ZrCo easily lost its absorption-desorption capacity of hydrogen below 30 heat cycles between room temperature and a given temperature in a range of 400〜600℃. X-ray diffraction analysis showed that ZrCoH₃ initially formed decomposed to ZrH₂ + ZrCo₂. On the other hand, ZrNi was more durable than ZrCo to the similar heat cycles. But, it was found that the absorption-desorption characteristics was degraded by heat cycles over 500. The X-ray analysis showed that ZrNi also disproportionated to ZrH₂ and ZrNi₃. The difference in the stabilities between the two materials appears to be due to the difference in crystallographic nature upon formation of the respective hydrides.

K. Watanabe^a, T. Kobayashi^b, M. Matsuyama^a, K. Goto^b

^a Hydrogen Isotope Research Center,
^b Dept. Chem., Faculty of Science,Toyama University, Gofuku 3190, Toyama, 930, Japan

Abstract

    To improve the hydrogen isotope separation methods by conventional low temperature chromatography and replacement chromatography above room temperature, a type of replacement chromatography was developed. It is based on the isotope effect on hydrogen absorption by Pd or Pd-Pt alloys. Both of them showed potential to separate a 50% H2 - 50% D2 mixture gas to H₂ and D₂ near room temperatures without introducing any replacement gas. This was then denominated as "self-developing replacement chromatography". The separation efficiency, however, was considerably higher for Pd-Pt than for Pd. Material characteristics were discussed along with the separation efficiency.

Masao Matsuyama^a, Kuniaki Watanabe^a, Toshinari Yamazaki^b

^a Hydrogen Isotope Research Center Toyama University, Gofuku 3190, Toyama 930, Japan
^b Faculty of Engineering Toyama University, Gofuku 3190, Toyama 930, Japan

Abstract

    A thin beryllium disk coated with a gold evaporated film of about 80 nm thickness was fabricated as an effective radiation window of bremsstrahlung X-rays. Its characteristics were examined in detail. The bremsstrahlung counting rate was proportional to the partial pressure of tritium above 0.1 Pa. The specific counting rate was evaluated as 70.8 cps/Pa. On the other hand, it decreased gradually with the total pressure above 2 kPa. This behavior was interpreted in terms of the self-absorption of β-particles in gas phase. It was revealed that the counting rate could be reproduced very well by a simple exponential function. From these results, it was concluded that the beryllium window coated with a thin gold evaporated film is a powerful device for in-situ measurements of tritium concentration in a wide range.

K. Hasegawa^a, K. Horii^a, M. Matsuyama^b, K. Watanabe^b

^a Department of Chemical and Biochemical Engineering, Faculty of Engineering, Toyama University, Gofuku 3190, Toyama 930, Japan
^b Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930, Japan

Abstract

    The rate of the UV-stimulated HT oxidation was studied in H₂(HT)-O₂-O₃ atmospheres with excess O₃. The concentration of HTO increased linearly with UV irradiation time. The formation rate of HTO was estimated to be 3.4×10^-2 Bq cm^-3s^-1, which was about 1400 times greater than that of the UV-stimulated HT oxidation in the H₂(HT)-O₂ atmosphere. Namely the excess O₃ greatly assisted the UV-stimulated HT oxidation. The HTO formation obeyed the half order kinetics to hydrogen pressure and 0.7 order with respect to photon flux. Computer simulation consisting of 33 elementary reactions was employed to make clear the mechanism of the HT oxidation. The computer simulation reproduced the same hydrogen pressure and photon flux dependences as the experimental results. It was revealed that the main path for HTO formation is as follows: 1) HT oxidation is initiated by photolysis of O₃ to O(¹D) radicals; 2) O(¹D) radicals react with H₂(HT) to form OH(OT) radicals; 3) OH(OT) radicals produce H₂O(HTO) by the reaction with H₂(HT). On the basis of computer analysis, it is concluded that the considerable increase in the rate of HTO formation is due to the increase in O(¹D) production in the presence of O₃. The present results suggest that the O₃-assisted UV-stimulated HT oxidation is expected to be applicable to non-catalytic oxidation of tritium in thermonuclear fusion reactors.

K. Ichimura^a, A. Nagoshi^a, K. Shimizu^a, H. Miyake^b, M. Matsuyama^b, K. Watanabe^b

^a Faculty of Education, Toyama University, Toyama 930, Japan
^b Hydrogen Isotope Research Center, Toyama University, Toyama 930, Japan

Abstract

    The hydrogen absorption effects in PrCo₅ have been studied from the mean Co moment (μ_Co) and the mean hyperfine field at ⁵⁹Co nuclei (H_hf). H_hf decreases gradually, while μ_Co decrease rapidly upon hydrogen absorption. The proportion of the orbital Co moment to μ_Co decreases abruptly for the single-phase hydride region.

渡辺国昭

Kuniaki Watanabe

Hydrogen Isotope Research Center and Department of Chemistry, Toyama University, Toyama 930, Japan

Abstract

    Vacuum technology is indispensable for tritium handling, but it requires further careful consideration of tritium behavior in the system, materials concerned and environment, to assure worker's and public safety. To meet the requirements, it is important to select vacuum pumps, vacuum gauges and other vacuum devices on the one hand, but on the other hand material selection is of primary importance from a view point of tritium adsorption, diffusion, permeation and ease of decontamination. Tritium compatibility should be established for all of the respective components and materials. In addition, special attention must be paid to precise measurements of tritium in a wide range from 10 G to 0.04 Bq/cm³. This paper briefly reviews the point of concern with tritium handling vacuum systems.

Keywords: tritium handling; measurement; contamination; material selection; vacuum pump