W.M. Shu, K. Watanabe

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

Abstract

    The effects of erosion on tritium permeation and mobile inventory in an ITER divertor were examined by an analytic model taking into account multiples structures and temperature gradient. The erosion accelerates the tritium permeation for both Be/Cu and W/Cu options. However, it affects tritium inventory in different ways. For the Be/Cu divertor, the tritium inventory in the Be layer dominates the total, resulting in the reduction of the inventory with decreasing Be thickness. For the W/Cu divertor, on the other hand, the tritium inventory gradually decreases initially and then increases sharply with increasing operation time. This distinct behavior is mainly caused by the difference in relative magnitudes of tritium solubility between Be and Cu, and between W and Cu.

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

    To estimate depth profiles and the amount of tritium captured in materials, the applicability of a bremsstrahlung counting method was examined. Two kinds of materials were used as model samples. One was a tritium source made of an organic polymer and the other was a disk of ZrNi-alloy containing tritium. For both samples, bremsstrahlung X-ray spectra showed a single broad peak. The maximum intensity of each peak appeared at 〜 7-8 keV. The intensities were 19 counts s^-1 for the polymer source and 240 counts s^-1 for the ZrNi disk. To evaluate the detection depth, the observed spectra were compared with those by numerical analysis. The spectral shape and peak position obtained by computer simulation agreed quite well with those of the spectrum observed for the polymer source, whereas for the ZrNi disk, a significant difference was observed at the higher side of the peak. The difference could be attributed to the superposition of bremsstrahlung and characteristic X-rays arising from nickel. The detection depth was determined to be 〜 1 mm for a polymer source consisting mainly of carbon atoms, and 〜 0.1 mm for the ZrNi disk. The present method is highly promising for non-destructively measuring tritium captured deep in materials and to estimate tritium concentration profiles.

Kuniaki Watanabe, Masao Matsuyama, Tohru Kobayashi, Wei Min Shu

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

Abstract

    A new type of chromatography for hydrogen isotope separation was developed employing a Pd-Pt alloy (8 at.% Pt) as functional material. It could separate a H₂-D₂ mixture into H₂ and D₂ in the temperature range of 274-297 K in a short time with simple operation procedures without introducing any replacement gas. An elusion mechanism plays an important role in the separation, and a replacement mechanism and/or a mixing effect may also be participating. A good separation can be expected under conditions of moderate operation temperature, a high carrier gas pressure and a slow flow rate. The new chromatography has potential for application in isotope separation systems for thermonuclear fusion devices.

K. Ashida^a, K. Watanabe^a, S. Ikeno^b, K. Mori^b

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

^b Materials Science and Engineering, Faculty of Engineering, Toyama University, Gofuku 3190, Toyama, 930-8555, Japan

Abstract

   Zr₃Al₂ alloy was used as a model substrate to prepare surface protective layers of Pd with an electroless plating methods. Effects of the Pd-overlayer on the kinetics of deuterium ab/desorption and durability against N₂ and CO₂ were investigated. The rate determining step of absorption and desorption and desorption in/from Zr₃Al₂ were not altered by Pd-plating. The absorption obeyed the first order, and the desorption obeyed the second order kinetics. The durability tests against N₂ and CO₂ showed that exposure to these gases caused a reduction of the absorption rate of deuterium. The extent of the reduction for Pd/Zr₃Al₂, however, was smaller than that of bare Zr₃Al₂. Namely, the surface modification by the Pd-layer is effective against gases, and applicable for processing of fuel gases containing a non-negligible amount of impurity gases.

K. Watanabe, W.M. Shu, E. Motohashi, M. Matsuyama

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

Abstract

    Decomposition of methane on Zr₇Ni₁₀, ZrNi, Zr₂Ni, Zr₄Ni and Zr was investigated in the temperature range 573-823 K. The alloy of Zr₄Ni efficiently removed methane by over 99% in 105s at 673 K. The pressure reduction of methane approximately obeyed the first order kinetics for all samples. The activation energy of the decomposition rate was determined to be 49 kj mol^-1. The specific decomposition rate increased with the zirconium content for the four alloys, while that of Zr is smaller than that of Zr₄Ni. The decomposition rate also depended on the surface conditions.