研究報告　-　16巻　(1996年)

解説 - Review

16-1

JT-60U重水素実験におけるトリチウム処理
Tritium Processing in JT-60U

宮　直之、正木　圭

Naoyuki MIYA, Kei MASAKI

16-2

核融合科学研究所大型ヘリカル実験装置とトリチウム
Large Helical Device at National Institute for Fusion Science and Tritium

佐久間　洋一

Youichi SAKUMA

論文 - Original

16-3

水素同位体分離用ガスクロマトグラフのカラム材の担体と重水素との相互作用
Deuterium Interactions with Supports of Functional Materials of an Advance Gas Chromatographic Column for Hydrogen Isotope Separation

渡辺　国昭、松山　政夫、小林　徹、坂本　章

Kuniaki WATANABE, Masao MATSUYAMA, Tohru KOBAYASHI, Akira SAKAMOTO

16-4

Zr-Ni上のPd被覆膜の真空加熱による状態変化
Changes in the Chemical and Crystallographic States of Pd-overlayers on ZrNi Plate with Vacuum Heating

芦田　完、渡辺　国昭、永田　純一、森　克徳

Kan ASHIDA, Kuniaki WATANABE, Junichi NAGATA, Katsunori MORI

16-5

Zr-Ni合金によるメタンの分解特性
Methane Decomposition on Zr-Ni Alloys

舒　衛民、松山　政夫、渡辺　国昭

W. M. SHU, Masao MATSUYAMA, Kuniaki WATANABE

16-6

ZrCo不均化における同位体効果
Isotope Effect on Disproportional of ZrCo

原　正憲、小林　孝広、小林　幸司、岡部　俊夫、森　克徳、渡辺　国昭

Masanori HARA, Takahiro KOBAYASHI, Koji KOBAYASHI, Toshio OKABE, Katsunori MORI, Kuniaki WATANABE

16-7

制動X線計測法によるトリチウムの非破壊分析（�T）有機材料への適用性
Nondestructive Tritium Analysis with Bremsstrahlung Conuting Method : (�T) Applicability to Organic Polymers

松山　政夫、渡辺　国昭

Masao MATSUYAMA, Kuniaki WATANAABE

データ - Data

16-8

核融合炉ブランケットデータベース（2）
Data Base for Tritium Breeding Blanket of Fusion Reactor (2)
(Li₂TiO₃ and Li₂ZrO₃ Solid Breeding Material)

二村　嘉明、河村　弘

Yoshiaki FUTAMURA, Hiroshi KAWAMURA

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研究報告16-1
解説

　Tritium retention analysis and tritium concentration measurement have been made during the large Tokamak JT-60U deuterium operations. This work has been carried out to evaluate the tritium retention for graphite tiles inside the vacuum vessel and tritium release characteristics in the tritium cleanup operations.
  JT-60U has carried out D-D experiments since July 1991. In the deuterium operations during the first two years, about 1.7x10¹⁹ D-D fusion neutrons were produced by D(d,p)T reactions in plasma, which are expected to produce 〜31GBq of tritium. The tritium produced is evacuated by a pumping system. A part of tritium is, however, trapped in the graphite tiles.
  Several sample tiles were removed from the vessel and the retained tritium distribution in the tiles was measured using a liquid scintillator. The results of poloidal distribution showed that the tritium concentration in the divertor tiles was higher than that in the first wall tiles and it peaked in the tiles between two strike points of divertor magnetic lines. Tritium concentration in the exhaust gas from the vessel have also been measured with an ion chamber during the tritium cleanup operations with hydrogen divertor discharges and He-GDC. Total of recovered tritium during the cleanup operations was 〜7% of that generated. The results of these measurements showed that the tritium of 16-23 GBq still remained in the graphite tiles, which corresponded to about 50-70% of the tritium generated in plasma.
  The vessel is ventilated during the in-vessel maintenance works, then the atmosphere is always kept lower than the legal concentration guide level of 0.7 Bq/cm³ for radiation work permit requirements.

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研究報告16-2
解説

　Energy is a vital necessity for humans life and we have been consuming a large amount of fossil fuel especially since the beginning of the industrial revolution. Nowadays, this large consumption of energy is now threatening our daily lives and what we need now are nonfossil fuels, for instance, solar energy, biomass energy, nuclear energy, etc. Fusion energy is unlimited as an energy resource and one of the strongest candidates as a future energy source.
  At the National Institute for Fusion Science, we are developing and constructing a new fusion experimental device called the Large Helical Device. This device will be able to generate a small amount of tritium, as a fusion product. To remove it from the exhaust gases, we have designed a tritium cleanup system based on a innovational new concept. This system is mainly consists of a palladium permeator, decomposer and hydrogen absorbing alloys. It will be able to perfectly recover tritium without oxidizing it.

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研究報告16-3
論文

　Adsorption and desorption characteristics of deuterium were studied for kieselguhr, alumina and silicon carbide by means of thermal desorption spectroscopy. They are expected to be the supports of the advanced gas chromatography for the separation of hydrogen isotopes around room temperature. Kieselguhr and alumina showed considerable interactions with deuterium. The interactions were attributed to the presence of hydroxyl groups on their surfaces. They act as a sink of hydrogen and a release source of deutrated water, suggesting substantial impairment regarding separation efficiency. The alumina on which Pd was supported confirmed the role of surface hydroxyl groups as a sink for hydrogen atoms spilling over from the Pd particles. However, silicon carbide showed no evidence of any interaction with deuterium, suggesting that it is a promising material as a support for functional metals or alloys for the columns of the advanced gas chromatography for hydrogen separation.

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研究報告16-4
論文

　Pd coating on Zr-based alloys are effective in protecting the alloy surface from poisoning impurity gases. To evaluate the stability of this layer regarding heat cycles, changes in the Pd overlayer on ZrNi plates with vacuum heating were studied as a model system with X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD). XPS measurements revealed that the Pd coating caused a significant reduction in contaminant oxygen and carbon from the surface. XRD measurements of the Pd overlayer suggested that the internal stress of the Pd layers was annealed out and Ni atoms were dissolved in the layer below 800℃. At higher temperatures, PdZr was formed with the surface having a change in its nature.

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研究報告16-5
論文

　Gettering materials are promising for the removal of residual impurities in deuterium-tritium fueled Tokamaks. The decomposition of methane on Zr₇Ni₁₀, ZrNi and Zr₂Ni alloy was investigated in the temperature range from 573 to 773K. The alloy of Zr₂Ni efficiently removed methane by over 99% in 3 min at 773K. The pressure decay of methane approximately obeyed the first order kinetics for the three Zr-Ni alloys. The activation energy of the decomposition rate was determined to be 49 kJ/mol for all selected Zr-Ni alloys. The decomposition rate increased gradually, and then, rapidly with the Zr content in the alloys, in contrast to the surface areas decreased from 0.30 �u/g for Zr₇Ni₁₀, to 0.24�u/g for ZrNi and 0.10�u/g for Zr₂Ni. The decomposition rate depended also on the surface conditions.

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研究報告16-6
論文

　To understand hydrogen induced disproportionation of ZrCo, the kinetics and isotope effect were studied in isothermal and in heating-cooling cycle modes. Crystallographic change owing to the disproportionation was also examined with powder X-ray diffraction. The rate of disproportionation increased with a temperature up to 873K, but decreased at high temperatures. Similar temperature dependence was observed in the heating-cooling mode. The kinetics was analyzed following the method of Sharp et al. The analyses indicated that the reaction mechanism changed from R2 to F1 around 823K. The Arrhenius plots of the disproportionation rate gave activation energies of 154 and 159 kJ/mol for hydrogen and deuterium, respectively, and the frequency factor as 1.07 and 1.34x10¹⁰/s below 823K. However, the plots showed a negative activation energy for both hydrogens in the high temperature region, where a larger activation energy was suggested for deuterium than for Those characteristics were discussed by assuming the presence of an intermediate between the reaction and product.

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研究報告16-7
論文

　Applicability of the bremsstrahlung counting method for estimating the depth profile of tritium captured in materials has been examined. During the first step, the commercial tritium source (1 mm in thickenss) made of a poly-[³H]-methyl-methacrylate disk was employed as the emitter of the bremsstrahlung x-rays, because it was suited for numerical analysis of bremsstrahlung x-ray spectra owing to the homogeneous distribution of the tritium atoms in the emitter. The bremsstrahlung x-ray spectra observed for the tritium source showed a single broad peak having a maximum intensity of around 8 keV. Simulation of the bremsstrahlung x-ray spectra was carried out for various thicknesses of the emitter by using a calculation program mainly consisting of a tritium β-rays spectrum，energy conversion ofβ-rays to the bremsstrahlung x-rays, and the attenuation of them in the tritium source, taking into account the range of the β-rays determined experimentally as 2 μm. It was suggested from the computational simulation that the present method can measure tritium existing up to a few millimeters in thickness from surface. In addition, the peak position and shape of the bremsstrahlung x-ray spectra obtained from the computational simulations agreed very well with those of the spectra observed by the experiments. This indicates that the peak profile of a bremmstrahlung x-ray spectrum obtained from materials such as organic polymers can be reproduced by numerical analysis. Accordingly, it was revealed that the present method was thoroughly applicable to nondestructive measurement of tritium existing in significantly deeper regions than the depth measurable by the conventionalβ-rays counting method.

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研究報告16-8
データ

　This compilation of data for Li₂TiO₃and Li₂ZrO₃ ceramic breeding material is a part of a study to construct a database for breeding blanket material for a fusion reactor, consisting of breeding material, neutron multiplier compilation were collected from as many papers and reference books as possible.
  Nevertheless, there may be data were taken from past experiments than those collected in this compilation. So the authors are going to continue collecting data of this type.
  Data were arranged in matrix from to clarify the properties of insufficient data so as to be easily used. This database is expected to very useful and necessary for designing and analyzing breeding blankets.