研究報告

第25巻(2005)

研究報告25 - 1 総論 - Review

富山大学におけるトリチウム取り扱い技術の研究・開発
R&D in Tritium Handling Technilogy for 25 Years at Toyama University

渡辺国昭

富山大学水素同位体科学研究センター、〒930-8555 富山市五福3190

K. Watanabe

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


Abstract

 Use of gaseous tritium at Toyama University was started in 1956 to investigate reaction kinetics and mechanisms of heterogeneous catalysis. Owing to this experience and achievements,the Tritium Research Center was established in 1980 for study on fundamental phenomena concerning safe and efficient handling techniques of tritium required for tritium handling technology has been carried out, althogh the center has undergone reorganization twice in the past 25 years and has been renamed the Hydrogen Isotope Research Center. The research topics have been basically hydrogen isotope - meterial interactions, which concerns with technical aspects such as tritium trapping - detrapping by first wall meterials, permeation through structural materials, detritiation of contaminated meterials, recobery - storage - supply by metals and alloys, hydrogen isotope separation, measuring techniques and so on. This review article provides a brief summary carried out at Toyama University over a period of 25 years since 1980.

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研究報告25 - 2 論文 - Original

清浄Nb表面への水素の吸着と偏析
Adsorption and Segregation of Hydrogen on Clean Nb Surface

波多野雄治1)、V. Alimov2)、A. Livshits2)、中村幸男3)、大藪修義3)、松山政夫1)

1)富山大学水素同位体科学研究センター、〒930-8555 富山市五福3190
2)Bonch-Bruyevich University of Telecommunications 61 Moika, St. Petersberg 191186, Russia
3)核融合科学研究所、〒509-5292 岐阜県土岐市下石町322-6

Y. Hatano1), V. Alimov2), A. Livshits2), Y. Nakamura3), N. Ohyabu3), M. Matsuyama1)

1)Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
2)Bonch-Bruyevich University of Telecommunications 61 Moika, St. Petersberg 191186, Russia
3)National Institute for Fusion Science, Oroshi-cho, Toki 509-5292, Japan


Abstract

 Sticking coefficient of H2, α , on a clean Nb surface was measured as a function of specimen temperature (25 - 477 ˚C) and hydrogen uptake. The initial value of sticking coefficient at negligible hydrogen uptake was ca. 0.25 and was independent of surface temperature. At any temperature examined, α showed a significant reduction with increase in hydrogen uptake, although the extent of reduction decreased with increasing temperature. Such reduction in α was ascribed to the increase in the surface coverage of hydrogen due to surface segregation and was explained by a model assuming equilibrium partitioning of hydrogen between the surface and the solid solution phase in the bulk.

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研究報告25 - 3 論文 - Original

SS316 ステンレス鋼のトリチウムの除染(3)—エッチングによる表面除染後のトリチウムの挙動—
Removal of tritium from 316 stainless steel (3) -Behavior of tritium after surface decontamination-

村田大樹、鳥養祐二、R.-D. Penzhorn、赤石憲也、渡辺国昭、松山政夫

富山大学水素同位体科学研究センター、〒930-8555 富山市五福3190

D. Murata, Y. Torikai, R.-D. Penzhorn, K. Akaishi, K. Watanabe, M. Matsuyama

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


Abstract

 In order to understand the mechanism of tritium release from Type 316 stainless steel, surface tritium concentration was examined by β-ray-induced X-ray spectrometry (BIXS) for the specimen that was etched by acid. Before etching, the surface tritium concentration was 158 kBq/cm2, while it became 1.1 kBq/cm2 after etching. The surface tritium concentration was found to increase with time, and it became as large as 83 kBq/cm2 in 4,500 hours after etching. During this period, tritium chronic release was observed. The result should that tritium segregated from the bulk to the surface and SS316 surface was re-contaminated with time.

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研究報告25 - 4 論文 - Original

SS316 ステンレス鋼のトリチウムの除染(4)—エッチング表面における水素捕獲と放出のモデリング—
Removal of tritium from 316 stainless steel (4) -Modeling of hydrogen trapping and release in chemically etched surface of tritium occluded stainless steel sample-

赤石憲也、村田大樹、R.-D. Penzhorn、鳥養祐二、渡辺国昭、松山政夫

富山大学水素同位体科学研究センター、〒930-8555 富山市五福3190

K. Akaishi, D. Murata, R.-D. Penzhorn, Y. Torikai, K. Watanabe, M. Matsuyama

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


Abstract

 When a stainless-steel sample occluded with tritium was dissolved the thickness a few 10 μm chemically, it was observed by a coauthor, Murata that tritium concentration at the newly formed top surface increased with time, while tritium release occurred from the surface to the gas phase. In this paper, a model to explain tritium accumulation and release at the etched surface is described. For the modeling, it was assumed that some of the segregated tritium atoms from the bulk to the surface are trapped on adsorption sites and become immobile, and that some of them are released from the top surface to the gas phase. By solving a one-dimensional diffusion equation, the rates of accumulation and release of tritium were estimated, and compared with experimental results. The comparison showed good agreement between experimental result and theoretical calculation.

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研究報告25 - 5 論文 - Original

In-situ measurements of tritium desorption from a vanadium alloy by β-ray-induced Χ-ray spectrometry (BIXS)

Xiang Liu1), H. Homma2), Y. Hatano2), M. Matsuyama2)

1)Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, Sichuan, China
2)Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan


Abstract

 Thermal release of tritium from a vanadium alloy was investigated by means of β-ray-induced X-ray spectrometry (BIXS). The sample tested was a V-4Cr-4Ti alloy recrystallized by annealing at 1000 ˚C for 2 h. A tritium gas diluted with hydrogen was characterized with a quadrupole mass spectrometer and a small ionization chamber, and the concentration of tritium was evaluated to be 0.14%. The sample was exposed to the tritium gas at 400 ˚C. The total concentration of hydrogen isotopes absorbed in the sample was 0.17 at%, and the corresponding tritium concentration was 2.4 appm, respectively. Tritium started to desorb at 350 ˚C. The duration of time required for desorption was much longer than that expected from the diffusion coefficient of tritium in the alloy, indicating that the rate of tritium release was controlled by a surface recombination process.

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研究報告25 - 6 論文 - Original

高感度熱量計によるトリチウム量の絶対測定(1)—熱量測定システムの設計・製作及び性能試験—
Absolute Measurement of Tritium by High-Snsitivity Calorimater(1) -Construction of Calorimetric System and its Performance Tests-

松山政夫

富山大学水素同位体科学研究センター、〒930-8555 富山市五福3190

M. Matsuyama

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


Abstract

 A calorimetric system for evaluation of the absolute amount of tritium was designed and constructed, and its basic performance was tested. A calorimeter can be used to measure total energy of radiations as a calorific value. The present calorimetric system consists of a twin-type thermal conductivity calorimeter equipped with a vacuum shielding, a tritium container, total pressure gauges, a quadrupole mass spectrometer, and high-vacuum systems. A calibration curve of the calorimeter was prepared at first using two samples enclosed a given amount of Zr-Ni alloy powder only, and the following linear relation was obtained: Eout = (0.2694±0.0010) Qin, where Eout is the output (μV) from the heat sensors and Qin is the input power (μW) by Joule heating to the sample cell. In addition, the lower detection limit was estimated to be 0.15 μW from stability of the calorimeter, which corresponds to the tritium amount of 0.16 GBq. As an initial test, Zr-Ni alloy powder loaded with a given amount of tritium was used and the amount of tritium was estimated to be 26.3 GBq, which was slightly less than the tritium activity determined previously by using a small ionization chamber.

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研究報告25 - 7 論文 - Original

液体シンチレーションカウンターの計数特性とクエンチング校正
Determination of Quench Curve and Evaluation of Accuracy of Counting on Liquid Scintilation Counter

原 正憲1)、中澤良太2)、岡部俊夫2)、松山政夫1)

1)富山大学水素同位体科学研究センター、〒930-8555 富山市五福3190
2)富山大学 理学部、〒930-8555 富山市五福3190

M. Hara1), R. Nakazawa2), T. Okabe2), M. Matsuyama1)

1)Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
2)Faculty of Science, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan


Abstract

 Liquid scintillation process is conversion of the energy of radioactive decay into photons. The conversion efficiency depends on the sample conditions such as existence of a quencher and color of the sample. To determine the activity of an unknown sample by using a liquid scintillation counter, the conversion efficiency must be accurately determined. The conversion efficiency for two liquid scintillation counters, which is called a quench curve, was measured using two series of tritium standard samples. Accurate quench curves for both counters were obtained. The quench curves differed from each other because the energy window of tritium on multi-channel analyzers differed. The characteristics of the quench curves were essentially similar to each counter systems. The quench curves indicated that the accuracy of counting decreased with strengthening of quenching for both liquid scintillation counters. On the other hand, the quench curves were independent of the activity of tritium.

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