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研究報告7-1
解説
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.
研究報告7-2
論文
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.
研究報告7-3
論文
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.
研究報告7-4
論文
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.
研究報告7-5
論文
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, ao, 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,
ao, then a pronounced normal isotope effect was observed. At
ao =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.
研究報告7-6
論文
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.
研究報告7-7
論文
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.
研究報告7-8
論文
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.
研究報告7-9
ノート
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.
研究報告7-10
ノート
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.