研究報告　-　6巻　(1986年)

解説 - Review

6-1

ゲッターによるトリチウムプロセッシング
Tritium Processing by Getter Materials

市村憲司、渡辺国昭

Kenji ICHIMURA, Kuniaki WATANABE

論文 - Original

6-2

黒鉛による水素同位体の捕獲と再放出　−鉄不純物の影響及び再結合係数−
Capture and Thermal Release of Hydrogen Isotopes by/from Graphite --Effect of Iron Impurity Doped to Graphite Surface and Recombination Factors--

芦田　完、渡辺国昭

Kan ASHIDA, Kuniaki WATANABE

6-3

Zr-V-Fe合金による実験室規模でのトリチウムの供給と回収
Supply and Recovery of Tritium Gas by Zr-V-Fe Alloy for Laboratory Experiments

松山政夫、三宅　均、市村憲司、芦田　完、渡辺国昭

Masao MATSUYAMA, Hitoshi MIYAKE, Kenji ICHIMURA, Kan ASHIDA, Kuniaki WATANABE

6-4

制動Ｘ線計測によるトリチウムガスの非破壊測定
Non-Destructive Measurement of Amount of Tritium by Bremsstrahlung Counting

松山　政夫、三宅　均、芦田　完、渡辺　国昭、伍島　伸五、藤田　良成、中谷　秀夫

Masao MATSUYAMA, Hitoshi MIYAKE, Kan ASHIDA, Kuniaki WATANABE, Shingo GOSHIMA, Yoshinari FUJITA, Hideo NAKAYANI

6-5

環境同位体から見た南極東クイーンモードランド地域内陸部の氷床堆積環境
Isotope Study of Depositional Environment in East Queen Maud Land, Antarctica

佐竹　洋、川田　邦夫、津島　健、佐藤　暢子

Hiroshi SATAKE, Kunio KAWADA, Takeshi TSUSHIMA, Nobuko SATO

ノート - Notes

6-6

赤外分光法による[Co(en)3]Cl3・3T2Oの分解過程
Infrared Study on Decomposition Process of [Co(en)3]Cl3・3T2O

金坂　績、西村　裕幸、金森　寛、川井　清保、市村　憲司、渡辺　国昭

Isao KANESAKA, Hiroyuki NISHIMURA, Kan KANAMORI, Kiyoyasu KAWAI, Kenji ICHIMURA, Kuniaki WATANABE

6-7

吸着トリチウムのリアルタイムイメージング（�T）−マイクロチャンネルプレートの可能性−
Real-Time Imaging of Adsorbed Tritium (�T) −Potential of Microchannel Plate−

市村　憲司、渡辺　国昭

Kenji ICHIMURA, Kuniaki WATANABE

6-8

燃焼法による黒鉛中のトリチウム・インベントリーの評価
Determination of Tritium Inventory in Graphite by Combustion Method

芦田　完、松山　政夫、渡辺　国昭

Kan ASHIDA, Masao MATSUYAMA, Kuniaki WATANABE

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研究報告6-1
解説

　In the research and development of nuclear fusion, getter materials have been widely applied to tritium processing and/or handling techniques such as evacuation, recovery, storage, supply, purification, enrichment, and separation. Some getters have been already developed and applied to tritium handling as well as impurity control in tokamaks. In this paper, we have described the present status of getter applications: (1) plasma-vacuum conditioning, (2) storage-supply-recovery, (3) purification, enrichment and separation, (4) removal and waste management.
  The improvement of getter properties, however, is required so as to apply them to a wider variety of the unit processes of the tritium handling techniques. It has been pointed out that there is a need for investigations on (1) the activation-deactivation mechanism, (2) absorption-desorption properties and mechanism, (3) durability and/or reactivity against impurity gases, (4) isotope effect and (5) alloying effect.

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研究報告6-2
論文

　To know the effect of metallic impurities deposited over the graphite first wall of thermonuclear fusion devices on the trapping-detrapping processes of fuel particles, the desorption processes of hydrogen isotope implanted into the graphite doped with iron (3at.%) was studied using XPS and TDS. Hydrogen isotope ions were implanted into a sample at room temperature with 5 keV using a conventional ion gun. An impurity modification phenomenon was found for the thermal desorption process. Namely, a new desorption peak (denoted as [Fe/C]-peak) appeared for the graphite doped with iron. The desorption mechanism for [Fe/C]-peak was explained by the second order surface recombination of trapped hydrogen atoms. The rate constants were determined as

k(H₂)=(7x10^-4)exp(-59x10³/RT)

k(D₂)=(4x10^-4)exp(-59x10³/RT)

k(T₂)=v_d(T₂)exp(-59x10³/RT)

where the frequency factor and activation energy are [1/molec・sec] and [cal/mol] unit, respectively. The recombination factor for hydrogen isotopes were estimated as

k_r(H₂)=(1.5x10^-15)exp(-59x10³/RT)[cm₄/molec・sec]

k_r(D₂)=(9.6x10^-15)exp(-59x10³/RT)

k_r(T₂)=v_d(T₂)x(2.6x10^-12)exp(-59x10³/RT)

 

　It was concluded that the impurity modification on the trapping-detrapping process is due to the increase in electronic charge on carbon caused by the presence of iron dopant.

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研究報告6-3
論文

　Supply and recovery techniques of tritium gas (T₂) on a laboratory scale is important for experimental studies using a large amount of tritium gas. From this view point, we examined the potential of the Zr-V-Fe alloy as material for the supply and recovery of tritium gas.
  The amount of tritium gas used was 5 Ci in each run, and that of the alloy used was 47mg. It was revealed that the alloy was excellent for purifying tritium gas containing such impurities as ³He, tritiated water and methane: the gas released by heating from the alloy consisted of T₂ (85%), HT (15%) and trace amounts of water and hydrocarbons.
  The pressure (P) of tritium gas released from the alloy obeyed the following equation,

Log P=2.7+log q²-6300/T,

where q and T denote the amount of absorption and temperature, respectively. This equation agree with that obtained by using ultra-high vacuum systems. It indicates that the alloy is applicable to recover tritium gas from even conventional vacuum systems that not so good.
  An absorption-desorption cycle of over 40 times confirmed the durability of the alloy against residual gases mainly consisting of water and carbon monoxide.
  These results indicate that the Zr-V-Fe alloy is excellent for the purification, recovery, storage, and supply of tritium gas in conventional vacuum systems.

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研究報告6-4
論文

　To establish techniques for in-situ and non-destructive measurement of a large amount of tritium gas, we examined the bremsstrahlung counting method of determine the amount of tritium in glass or aluminum alloy tubes. The wall thickness of glass tubes used was 0.5, 1.0, 1.2, 1.5 and 2.0 mm, and that of aluminum ally tube was 1.0 mm. The outer diameter of each tube was 10 mm. The pressure of tritium in the tubes was controlled in a range from 2 to 160 Torr, which corresponds to a range from 40 mCi to 3.5 Ci.
  It was observed that the counting rate of the bremsstrahlung X-rays was proportional to the pressure or the amount of tritium gas in the tubes. The half-thickness varied from 40 to 140 mg/cm², depending on the wall thickness of the glass tubes used in the present study. However, the present results indicate that the bremsstrahlung counting method is applicable to in-situ and non-destructive measurements of a large amount of tritium gas in the tritium handling systems.

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研究報告6-5
論文

　Firn cores from East Antarctica were analyzed regarding their depth hoar level, grain size, density, tritium concentration, δD and δ¹⁸O value so as to find the age of the firn cores and to study post-depositional changes of isotopic composition. In the 1.2m deep firn core collected at γ 1 Station, a clear stratigraphic boundary was observed at the 26cm depth. Above the boundary grain size of firn is small (2.5) and depth hoar is poorly crystallized (DHL=1). On the contrary, below the boundary the grain size is large (4-5.5) and depth hoar is well crystallized (DHL=3-4.5). This stratigraphic observation suggests the absence of semidimentation for a considerably long period. Tritium concentration in the firn above the boundary is 18-25TU, although less than 8TU below the boundary. Tritium concentration in the upper layer is almost equal to that in the present snow observed at Mizuho Station. From these results, it can be inferred that the lower layer was formed before 1950 prior to the nuclear test. The d-parameter changes from 11 to 18 and shows a good correlation with depth hoar level. This change in d-parameter suggests that in a layer lower than 30cm, 25-40% of firn is vaporized during post-depositional firnification. Tritium concentration in 10m deep firn core obtained at the Advance Camp Station ranges from 8TU to 301TU. From the surface to the 1.4m depth, the tritium content is 54-80 TU and increases rapidly up to 301TU (maximum) at 2.6m. Then, it decreases gradually to 17TU until the 4m depth, and is almost constant at a depth lower than 4m. This vertical profile reflects the temporal variation of tritium concentration in precipitation. The firn at 2.6m, having the maximum tritium concentration, is inferred to have been deposited in 1966. The accumulation rate at the Advance Camp Station is estimated to be 14cm/year.

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研究報告6-6
ノート

　The decomposition of [Co(en)₃]Cl₃・3T₂O over a period of 5 months was studied by infrared spectroscopy. The spectrum changed drastically with the disappearance of the bands due to ethylenediamine and the appearance of some new bands. The decomposition process of en → 2NH₃+HCCH was analyzed using two models regarding the concentration of T₂O. These reveal that about one thousand ethylenediamines decompose due to one β particle in the initial state.

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研究報告6-7
ノート

　To investigate microscopic processes of trapping and diffusion of tritium on/through materials, autoradiography has been widely applied. This technique, however, gives us only qualitative information. One aim of this study is to examine the potential of a microchannel plate for in-situ measurements of the amounts of adsorbed tritium and its distribution on sample surfaces.
  Microchannel plates (MCP, Hamamatsu Photonics Ltd.) were mounted in an oil-free ultra-high vacuum chamber. By use of a MCP with a phosphorescent anode plate, the image of the thermal electrons from a hot filament was observed. When the applied voltage and electron fluence were above 1.5 kV and 10e-/sec, respectively, it was possible to obtain in-situ image of hot electrons with real-time. These results indicate that tritium of over 10^-9 Ci can be detected. This means that tritium of 10^-3 in the coverage is detectable. Therefore, the above-mentioned imaging apparatus is applicable to in-situ measurements of the distribution of adsorbed tritium. In addition, the combination of the lens system and image processing one will provide us a powerful technique to investigate the distribution of tritium adsorbed on materials and its motion.

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研究報告6-8
ノート