芦田　完、渡辺　国昭
〒930　富山大学五福3190

Kan ASHIDA, Kuniaki WATANABE
Tritium Research Center, Toyama University , Gofuku 3190, Toyama 930, JAPAN
(Received December 24, 1987)

Abstract
Various candidate materials for the first wall of the magnetically confined thermonuclear fusion devices have been widely investigated. Among these candidates, graphite is one of the most promising materials because of its low-z, refractory nature, high heat conductivity, and ease in fabrication, etc. In spite of graphite’s superb properties, many problems which would obstruct its actual use are still left to be solved.
  In this paper, the present status and the current objectives of a graphite first wall which concern fuel recycling and inventory are reviewed from the viewpoint of [1] surface characterization and radiation damages caused by ion bombardment, [2] trapping and remission of hydrogen isotope atoms, [3] trapped states, thermal desorption behaviors and recombination factors of hydrogen isotopes, and [4] surface modification by other elements.

松山　政夫、渡辺　国昭
富山大学トリチウム科学センター
〒930　富山市五福3190

Masao MATSUYAMA, Kuniaki WATANABE
Tritium Research Center, Toyama University, Gofuku 3190, Toyama 930, JAPAN

Abstract

Knowledge about the amount of adsorption and/or adsorption states of tritium in various materials is of great importance to the development of safety handling systems free from the serious contamination of tritium gas. The amount of tritium adsorbed on materials has been usually measured by an apparatus isolated from the tritium gas exposure system. Therefore, the amount of tritium observed deviates from the original value because of desorption into the ambient atmosphere and its reaction with atmospheric components. From this viewpoint, we developed a measuring system equipped with a small detector attached directly to the tritium exposure system, and examined performance if the system.
  The detector employed in the present counting device was a hemispherical G-M tube covered with a tungsten mesh in place of a thin mica window. The efficiency of the present counting device was remarkably affected by absorption of β-rays in the working gas (mixture of helium and 1% isobutane) and its geometrical configuration. These effects on the observed counting rate were checked by using a polymer source labeled with tritium. As a result, the efficiency significantly decreased with the absorption ofβ-rays in the working gas rather than as a result of its geometrical configuration. From the absorption curve, it was determined that the absorption coefficient of β-rays was 2.16 cm^-1 for the ambient gas. From these results, the overall efficiency (F) was shown as F=exp(-2.46h), where h is the distance from the sample surface to the detector. The practical examination was carried out by using small nickel and iron plates exposed to tritium gas at room temperature. A great difference in the amount of adsorbed tritium between both metal samples was clearly recognized irrespective of the small surface areas less than 1cm². In addition, the results showed that the present counting device could measure the coverage less than 10^-6.

青木　正義、岡部　茂、西川　嗣雄、渡辺　国昭^*、松山　政夫^*
福井大学工学部
〒910　福井市文京3-9-1
^*富山大学トリチウム科学センター
〒930　富山市五福3190

Masayoshi AOKI, Shigeru OKABE, Tsuguo NISHIKAWA, Kuniaki WATANABE^*,Masao MATSUYAMA^*
Faculty of Engineering, Fukui University,Bunkyo 3, Fukui 910, JAPAN
^*Tritium Research Center, Toyama University,Gofuku 3190, Toyama 930, JAPAN
(Received December 25, 1987)

Abstract

Thermally stimulated exoelectron emission (TSEE) from BeO was studied by irradiating its surface with a variety if β-rays such as polymer tritium, ⁶³Ni, ¹⁴⁷Pm, ²⁰⁴Tl and ⁹⁰Sr.⁹⁰Y. It was found that the efficiency of TSEE (i.e. the ratio of the number of emitted exoelectrons to the number of incident β-particles) of BeO decreased with an increase in β radiation energy and was approximately proportional to the stopping power dE/dx in Al. The mean energy of the β-rays from the polymer tritium source was roughly estimated to be 3.8 keV by some simple assumptions.

三宅　均、松山　政夫、渡辺　国昭
富山大学トリチウム科学センター
〒930　富山市五福3190

Hitoshi MIYAKE, Masao MATSUYAMA, Kuniaki WATABANE
Tritium Research Center, Toyama University,Gofuku 3190, Toyama 930, JAPAN
(Received December 25, 1987)

Abstract
To understand the compatibility of the spinning rotor gauge with tritium handling during fusion experiments, tritium gas and/or gas mixtures of hydrogen isotopes were measured with the spinning rotor gauge in pressure ranges of 10^-5 to 10 Pa.
  It was observed that it is possible to determine the absolute pressure of tritium gas and/or gas mixtures of hydrogen isotopes within several percent errors as well as determining the absolute pressure of pure gas by using the mole fraction of the component gases in the mixture. Additionally, it was found that the sensitivity and the offset value do not change with a tritium exposure amounting to 1.9x10⁵ Pa・s. Therefore, we concluded that the spinning rotor gauge is free from any tritium β-ray effects. From this result, it was concluded that a spinning rotor gauge is quite useful to tritium handling systems, including thermonuclear fusion devices, as a transfer standard and/or absolute pressure gauge.

森　克徳、笠井　希一郎^*、佐藤　清雄^*、石川　義和、芦田　完^**、渡辺　国昭^**

富山大学教養部
^*富山大学理学部
^**富山大学トリチウム科学センター
〒930　富山市五福3190

Katsunori MORI, Kiichiro KASAI^*, Kiyoo SATO^*, Yoshikazu ISHIKAWA, Kan ASHIDA^**, Kuniaki WATANABE^**
College of Liberal Arts, Toyama University
^*Faculty of Science, Toyama University
^**Tritium Research Center, Toyama University
(Received December 25, 1987)

Abstract
The variation in the superconducting critical temperature, Tc, between NbHx, PdHx and NbDx films, prepared by H-reactive sputtering at room temperature, were investigated. The prepared films were about 5000A in thickenss. The X-ray diffraction experiments were carried out and the lattice parameters, a_o, were calculated. To obtain the value of Tc, the electrical resistance was measured. If we assume that the same composition in NbHx and NbDx correspond to the same lattice parameters, a_o, then a pronounced normal isotope effect was observed. At a_o =3.4A, hydrogen absorption reduces Tc by 2.8K while deuterium absorption reduces Tc by 3.9K.
  For PdHx, however, all the samples did not become superconductors above 1.4K, even for film which was sputtered in 100% hydrogen gas.

東　直人、宮崎　哲郎、芦田　完^*、渡辺　国昭^*、古川　勝敏^**、大野　新一^**
名古屋大学工学部合成化学科
〒464　名古屋市千種区不老町
^*富山大学トリチウム科学センター
〒930　富山市五福3190
^**日本原子力研究所東海研究所化学部
〒319-11　茨城県那珂郡東海村

Naoto AZUMA, Tetsuo MIYAZAKI, Kan ASHIDA^*, Kuniaki WATANABE^*
Katsutoshi FURUKAWA^**, Shin-ichi OHNO^**
Faculty of Engineering, Nagoya University,Furo-cho, Chikusa-ku, Nagoya 464, JAPAN
^*Tritium Research Center, Toyama University,Gofuku 3190, Toyama 930, JAPAN
^**Department of Chemistry, Japan Atomic Energy Research Institute,Tokai-mura, Ibaraki 319-11, JAPAN
(Received December 25, 1987)

Abstract
When silica is irradiated by 80 keV D⁺ ions or RF plasma of D₂ gas, deuterium is trapped in the silica forming≡Si-OD bonds. This phenomenon has been detected by infrared Fourier transform spectrometer (TFIR). The deuterium, trapped as OD bonds, is desorbed from the silica upon heating. The thermal desorption mechanisms of the trapped deuterium were studied here with FTIR and thermal programmed desorption mass spectrumeter (TPDMS). The thermal desorption rate of the trapped deuterium, that is the decrease in the rate of OD bonds upon heating, was measured by FTIR. The desorption products, such as HD, D₂, HDO, and D₂O, were measured by TPDMS. HD and D₂ were produced at a temperature range of 550-700℃, while HDO and D₂O were produced above 750℃. The thermal desorption spectra of both hydrogen (HD and D₂) and water (HDO and D₂O) corresponded to the thermal decrease spectra of the OD bonds. Thus it was concluded that the desorption products of both hydrogen and water are produced by the thermal decomposition of the OD bonds.

佐竹　洋、竹内　誠治
富山大学理学部地球科学教室
〒930　富山市五福3190

Hiroshi SATAKE, Seiji TAKEUCHI
Department of Earth Sciences, Toyama University,Gofuku 3190, Toyama University
(Received December 25, 1987)

Abstract
The capability of Ni-Ni and Fe-Ni electrodes for electrolytic enrichment of tritium are evaluated. The tritium separation factors for Ni-Ni and Fe-Ni electrodes are in a range of 5-25 and 20-40, respectively. The tritium separation factor with a Fe-Ni electrode is systematically higher than that with a Ni-Ni electrode when the electrolysis is conducted under the same conditions. For Fe-Ni electrode, samples having the same final volume show almost the same tritium concentration factor even if the tritium separation factor of these samples are different by about 20. This is not the case for Ni-Ni electrode because most of tritium separation factors are lower than 20. For the Fe-Ni electrode, the tritium enrichment factor of each sample may be obtained simply from the final volume, without the time consuming procedure for the measurement of the deuterium concentration factor.

宇佐美　四郎、松山　政夫^*、渡辺　国昭^*、竹内　豊三郎^*、野上　英明、浅井　祐二、長谷川　淳
富山大学工学部
^*富山大学トリチウム科学センター
〒930　富山市五福3190

Shiro USAMI, Masao MATSUYAMA^*, Kuniaki WATANABE^*, Toyosaburo TAKEUCHI^*, Hideaki
NOGAMI, Yuji ASAI, Kiyoshi HASEGAWA Faculty of Engineering, Toyama University
^*Tritium Research Center, Toyama University
Gofuku 3190, Toyama 930, JAPAN
(Received December 25, 1987)

Abstract
Knowledge concerning the conversion rate of tritium gas to tritiated water in the environment is basic data needed for estimating the risk of exposure to tritium gas. The conversion rate is affected by various factors such as the tritium concentration, dust and moisture in the atmosphere, bacteria in the soil, and solar rays, etc. However, the influence of solar rays on the conversion rate has not been investigated hitherto. From this viewpoint, we examined the influence of ultra-violet (UV) irradiation on the conversion rate of room temperature.
  The reaction vessel (RV) used in the present study was spherical flask made of Pyrex or quartz. A given amount of the mixture of oxygen and tritium diluted with hydrogen was introduced into the RV and then UV-irradiation was carried out. The partial pressure of the tritium gas was kept constant at 0.6 Torr (5μCi/ml) and the oxygen pressure was varied from 20 to 160 Torr. A high pressure mercury lamp was used as a light source. The conversion rate was determined by the amount of the tritiated water formed. This was measured by a liquid scintillation counter.
  Only tritium gas was introduced to clarify the contribution of the exchange reaction with the trace amount of water in the RV, however, little tritiated water was formed. The initial conversion rate of the gas mixture without UV-irradiation was of an order of magnitude of 0.01%/day, which corresponded to the tritium decay rate. From these results, it was revealed that the exchange rate of tritium gas with the water adsorbed on inner wall of the RV was negligibly small in comparison to the conversion rate, and that most of the tritiated water formed came from the β-radiation-induced oxidation.
  In addition, it was observed that with UV-irradiation the conversion rate was about 1000 times greater than that of nonirradiation. In particular, wave lengths ranging from 200 to 300 nm were effective for converting tritium gas. The primary conclusion was that solar rays would play an important role in the conversion rate of tritium gas in the environment.

金坂　績、高橋　英之、川井　清保、渡辺　国昭^*

富山大学理学部
^*富山大学トリチウム科学センター
〒930　富山市五福3190

Isao KANESAKA, Hideyuki TAKAHASHI, Kiyoyasu KAWAI, Kuniaki WATANABE^*

Faculty of Science, Toyama University
^*Tritium Research Center, Toyama University
Gofuku 3190, Toyama 930, JAPAN
(Received December 25, 1987)

Abstract

The decomposition process in the MeOH-T₂O system was studied over a period of 10 months by infrared spectroscopy. The main product was CO with a small amount of CH₄ and HCO₂ Me. The process was kineticly analyzed, which clarifying that the decomposition of MeOH and CO almost obeys first- and second-order kinetics, respectively. The G value derived for decomposition was -3.5 for MeOH and -11 for CO. These values are different from those received from radiolysis. The reason for this will be discussed.

対馬　勝年、塚田　秀一、芦田　完^*、渡辺　国昭^*

富山大学理学部地球科学教室
^*富山大学トリチウム科学センター
〒930　富山市五福3190

Katutoshi TSUSHIMA, Shuichi TSUKADA, Kan ASHIDA^*, Kuniaki WATANABE^*

Department of Earth Sciences, Faculty of Science, Toyama University
^*Tritium Research Center, Toyama University
Gofuku 3190, Toyama 930, JAPAN
(Received December 25, 1987)

Abstract

To investigate ice surface properties near the melting points, a tritium diffusion method was designed, developed and applied to laboratory-grown, single crystal ice. A quasi-liquid layer existing at the interface between the glass tube and the ice specimen served as a high speed path for the tritium diffusion. The experimental setup was focused to estimate the diffusion coefficient of tritium in a quasi-liquid layer at the interface. Preliminary results of the laboratory measurements conducted show that a quasi-liquid layer does exist, serving as a high speed diffusion path and that the diffusion coefficient is estimated to range from 10^-13 to 10^-12 m²/s at -0.8℃. Furthermore, separate experimental investigations are planned to obtain the numerical values of the diffusion coefficient and the layer thickness.