Etsuo Ishitsuka^a, Hiroshi Kawamura^a, Kan Ashida^b, Masao Matsuyama^b, Kuniaki Watanabe^b, Hiroei Ando^a, Yoshiaki Futamura^a

^a Japan Atomic Energy Research Instiute, Oarai Research Establishment, Oarai-Machi, Higashi Ibaraki-Gun, Ibaraki-Ken 311-13, Japan

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

Abstract

    Beryllium is a promising material as a neutron multiplier of the blanket and as a first wall material. To understand the detailed behavior of beryllium under fusion reactor conditions, it is important to study the material characteristics of beryllium. As a first step, we examined surface properties of hot-pressed beryllium before and after vacuum heating, as well as after deuterium ion implantation with X-ray photoelectron spectroscopy. Carbon, fluorine and oxygen were observed on the as-received sample surface, in addition to beryllium. Carbon and fluorine decreased their peak intensities with vacuum heating. The two peaks of Bels were identified as metallic and oxidized beryllium. The deuterium ion implantation caused an increase in the peak intensities of O1s and Be1s of oxide form. This is presumed to be due to impurities in deuterium gas or residual gases in the vacuum system.

Michio Watanabe^a, Chiaki Takeda^a, Shizuo Tada^a, Hiroshi Anada^a, Susumu Ikeno^b, Kan Ashida^c, Kuniaki Watanabe^c

^a Dept. Metallurgical Eng., Faculty of Eng., Toyama University, Gofuku 3190, Toyama 930, Japan

^b Center for Cooperative Res., Toyama University, Gofuku 3190, Toyama 930, Japan

^c Hydrogen Isotope Res. Center, Toyama University, Gofuku 3190, Toyama 930, Japan

Abstract

    Alloying effects on absorption and desorption kinetics of deuterium for Zr-Al alloys were studied with mass analyzed thermal desorption spectroscopy using a conventional high vacuum system. It was found that the absorption rate of deuterium was proportional to the 1/2 power of deuterium gas pressure. On the other hand, the desorption process obeyed the second order kinetics with respect to the amount of absorbed deuterium. The temperature dependence of the rate constants revealed that the activation energies for both the absorption and desorption processes were lowered by the increase in the Al content in the alloys, Through potential diagrams for the absorption and desorption of deuterium, it was also found that the heat of deuterium (hydrogen) solution decreased with increasing Al composition. In addition, the x-ray diffraction spectroscopy showed the formation of a Zr₄Al₃ phase in the Zr₃Al₂ sample owing to repeated absorption and desorption cycles. The results suggest that the electronic factors, for example, work function, electron density, d-band character and so on, play an important role for the alloying effects rather than crystallographic structures. In addition, it becomes evidence that the absorption/desorption properties for such alloys are limited not only by the side reactions with impurity gases but also changes in their crystallographic nature owing to interactions with hydrogen and/or heat cycles.

H. Miyake^a, M. Matsuyama^a, K. Watanabe^a, D. F. Cowgill^b

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

^b Tritium Research Laboratories, Sandia National Laboratories, Livermore, California 94550, U.S.A.

Abstract

    We developed a simple system using tritium tracer and thermal desorption techniques to measure the tritium adsorption and/or absorption on/in a material having typical surface conditions: namely, not cleaned surface. The tritium counting devices used were a 2π counter and conventional proportional counter. With this system, the amounts of ad/absorption could be measured without exposing the samples to air after exposing them to tritium gas.
    The overall efficiency (F) of the 2π counter was described as F = exp(-2.64 h), where h is the distance from the sample to the detector. Ad/absorption measurements were carried out for several materials used for fabricating conventional vacuum systems. The results were, in the order decreasing amounts of ad/absorption, as [fiber reinforced plastics (FRP)] > [nickel (Ni), molybdenum disulfide (MoS₂)] > [stainless steel (SS304), iron (Fe), aluminum alloy (A2219)] > [boron nitride (h-BN), silicon carbide (SiC), SS304 passivated by anodic oxidation layers (ASS) and that by boron nitride segregation layers (BBS)]. The relative amounts were about 100 for Ni and 0.1 for ASS and BSS, being normalized to Fe = 1. It was found that the passivation of SS304 with anodic oxidation layers and/or BN segregation layers should be quite valid to decreasase the tritium inventory on/in the material walls of tritium handling systems. In addition, it was estimated that this system would be capable of detecting the tritium adsorption of the order of 10^-6 in the surface coverage.

K. Hasegawa^a,H. Fusumae^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 kinetics of the UV-stimulated HT oxidation in oxygen atmosphere was studied in combination with computer simulation consisting of 30 elementary reactions. The rate of HTO formation was observed to be proportional to the pressure of O₂ and molar fraction of HT with respect to total hydrogen pressure (H₂ + HT), and 1/2 order to total hydrogen pressure. The simulation resulted in the same pressure dependence as the observed one. The contributions of elementary reactions to the HTO formation were calculated, assuming steady states for intermediate species. It was revealed that the UV-stimulated HT oxidation is initiated by photolysis of O₂ to O (³P) (λ < 242 nm) and subsequently formed O₃ and OH play important roles in the HTO formation. The present results suggest that the conversion of tritium gas to tritiated water is considerably enhanced in the stratosphere owing to the presence of UV photons having shorter wavelengths than 242 nm.

Shotaro Morozumi^a, Manabu Matsumoto^b, Hiroshi Saikawa^a, Tomoya Minegishi^a, Kuniaki Watanabe^c

^a Chiba Insititute of Technology

^b Graduate shcool, Chiba Insititute of Technology

^c Hydrogen Isotope Research Center, Toyama University

Abstract

    Being mixed with magnesium powder by up to 50%, 304 stainless steel and titanium powders were compacted under various compacting loads, respectively, and then the green compacts were sintered in a vacuum of 10 -2 Pa, finally at 1375 K where magnesium can be vaporized completely. The sintered compacts were examined as to density, compressive strength and structure. The density and compressive strength decreased with increase in the amount of magnesium powder added to the green compacts, as well as decrease in the compacting load. The process was applied to make sintered ZrNi compacts capsulated with porous sintered stainless steel compacts. Sintered titanium and nickel compacts with a graded porosity distribution were also prepared, respectively.

  Keywords:magnesium, stainless steel, titanium, nickel, porous sintered compact, powder metallurgy