百島則幸
熊本大学理学部
〒860-8555熊本市黒髪2丁目39-1

Noriyuki Momoshima
Faculty of Science, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555

Abstract
　Environmental tritium was first observed in a helium fraction at a liquid air production facility in Germany in 1949. During the 1950s and early 1960s, huge amounts of artificial tritium were released into the atmosphere by nuclear testing. The environmental tritium level increased to more than 200 times the natural tritium level. Since the signing of a test ban treaty in 1963, the environmental tritium level has decreased, and analysis of recent Japanese rain samples has shown that the environmental tritium level is close to that before the nuclear testing. Tritium released from nuclear bombs into the atmosphere has been used as a global-scale tracer in studies on water mass movement in the ocean, groundwater flow and atmospheric air mass movement. Useful and valuable results have been obtained in those studies. In the atmosphere, tritium exists in three different chemical forms: hydrogen (HT), water vapor (HTO) and hydrocarbons (CH₃T). The concentration of HT the highest, followed by those of CH₃T and HTO. The most interesting feature of these chemical species is their significantly different specific activities. HT has 10⁶ TU, CH₃T has 10⁴ TU and HTO has 10 TU, suggesting that HT and CH₃T have been released from nuclear facilities. Vegetation is sensitively responds to a change in environmental HTO level by rapid exchange of water molecules between leaf water and atmospheric water vapor. HTO vapor released into the air slowly contaminates soil water. A nuclear fusion facility is planed to use a large quantity of tritium that is comparable to natural tritium on the earth, indicating the necessity to maintain tritium in a nuclear fusion facility and the necessity to carefully monitor the environmental tritium level.

原　正憲、金子義信、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

M. Hara, Y. Kaneko, K. Watanabe
Hydrogen Isotope Research Center, Toyama University Gofuku 3190, Toyama 930-8555, Japan

Abstract
　The kinetics of hydrogen absorption by a Pd-4 at%Pt alloy was studied in the temperature range of 0 to 80 C and pressure from 0.1 to 10 Torr by using a vacuum microbalance. The absorption kinetics extending over the entire absorption curve be analyzed by a diffusion model assuming notable contributions from dissociative adsorption of hydrogen molecules and associative desorption of adsorbed hydrogen atoms on the surface. The activation energies for absorption and desorption were determined to be 4.6 and 9.0 kcal/mol (H₂), respectively. Based on these values, the heat of the hydrogen solution was evaluated to be -4.6 kcal/mol (H₂), which is in good agreement with the value obtained by thermodynamic study. In addition, the activation energy for diffusion was determined to be 7.1 kcal/mol (H), causing slower hydrogen diffusion in the alloy than Pd.

金　瑩、原　正憲、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

Y. Jin, M. Hara, K. Watanabe
Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, JAPAN

Abstract
　Hydrogen absorption kinetics of palladium alloys was studied by using a vacuum microbalance system. The data analysis procedures were shown in detail in the present paper for a spherical sample as an example, where the second order hydrogen adsorption and desorption were assumed to have occurred on the sample surface. The factors that may influence hydrogen absorption curves and kinetic parameters are discussed.

波多野雄治、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
高森美幸、松田健二、池野進
富山大学工学部物質生命システム工学科
〒930-8555　富山市五福3190

Y. Hatano, K. Watanabe
Hydrogen Isotope Research Center, Toyama University
Gofuku 3190, Toyama 930-8555, Japan
M. Takamori, K. Matsuda, S. Ikeno
Department of Material System Engineering and Life Science, Faculty of Engineering, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract
　Solid state reaction between tungsten and carbon film was examined at 1073K. Carbon film was deposited onto tungsten sheet by vacuum evaporation at room temperature and analyzed by means of X-ray photoelectron spectroscopy. Carbon and tungsten beneath the carbon film were detected, whereas only trace amount of impurities such as oxygen were present. The binding energy of W 4f electrons indicated that tungsten was in a metallic state at the interface. These observations suggested that no impurity layer existed at the interface. Analysis using transmission electron microscopy showed that carbon was in an amorphous state. The specimen was heated at 1073 K in vacuum, and change in crystal structure was analyzed by means of X-ray diffraction. The peak of W₂C appeared after an induction period for ca. 1 min, although W₂C is not thermodynamically stable at 1073 K. The peak intensity ratio of W₂C to metallic tungsten increased in proportion to the square root of time to take the maximum value at 50 min and then decreased with elapse of time. No peak of WC was observed. These results indicate that the nucleation rate of W₂C was much faster than that of WC at 1073 K. The decomposition of W₂C was ascribed to the reaction between carbon in W₂C and H₂O in residual gas.

芦田　完、波多野雄治、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. Ashida, Y. Hatano, K. Watanabe
Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract
　Kinetic analyses were performed for solid-state reactions between a hydrogen-containing carbon film and substrate metals to form metallic carbide of Me₂C (Me=Be, Mo, W). Isothermal and non-isothermal reaction curves could be explained by a random nucleation and two-dimentional crystal growth model. The kinetic equation can be approximated well by -ln(1-x)= k_appt^2, where x is the extent of reaction and kapp the apparent rate constant. The temperature dependence of the rate constants are given as

k_app(Be)=3.10 exp(-109.[kJ/mol]/RT) [1/sec²],

k_app(Mo)=231. exp(-161.[kJ/mol]/RT),

k_app(W) =516. exp(-183.[kJ/mol]/RT),

for Be-C, Mo-C and W-C systems, respectively, where the apparent activation energy is considered to be the sum of those for nucleation and diffusion. Linear relations were found between the apparent activation energy and the melting point of substrate metals as well as the bond strength of Me-C (Me=Be, Mo, W).

松山政夫、村井忠幸、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
都築和泰、野田信明
核融合科学研究所
〒509-5292　土岐市下石町322-6

M. Matsuyama, T. Murai, K. Watanabe
Hydrogen Isotope Research Center, Toyama University
Gofuku 3190, Toyama 930-8555, Japan
K. Tsuzuki, N. Noda
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi 509-5292, Japan

Abstract
　Tritium retention in boron-coated graphite (B/Graphite) irradiated with tritium ions at room temperature and at high temperatures was examined by beta-ray-induced X-ray spectrometry (BIXS). The results of analyses by X-ray diffraction and X-ray photoelectron spectroscopy for an unirradiated sample suggested that boron coated on the graphite surface formed an amorphous structure and that it contained impurities such as oxygen and carbon. Both a sharp intense peak and a broad weak peak induced by beta-rays appeared in the observed X-ray spectra. It was seen from the X-ray spectra that most of tritium implanted into the B/Graphite at room temperature was retained on the surface and in subsurface layers. In addition, it was seen that the implanted tritium can be easily removed at a relatively low temperature and that the retention amount decreased to 1/3 by heating at 300゜C for 30 min. However, a considerable increase in tritium retention was observed when the irradiation temperature was increased to more than 300C, indicating adsorption of tritium on the bare surface graphite.

二村嘉明
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
河村　弘、土谷邦彦
日本原子力研究所
〒311-1394　茨城県東茨城郡大洗町成田町新堀3607

Yoshiaki FUTAMURA
Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, JAPAN
Hiroshi KAWAMURA^* and Kunihiko TSUCHIYA^*
*Japan Atomic Energy Research Institute, Shinbori 3607, Narita-cho,Oarai-machi, Higashi-Ibaragi
Gun, Ibaragi 311-1394, JAPAN

Abstract
　This up-to-date compilation of data for ceramic breeding materials (Li₂O, Li₂TiO₃, Li₂ZrO₃, and Li₄SiO₄) is part of a study to construct a database for tritium breeding materials of fusion reactor blankets in which existing data for breeding materials and neutron multipliers have been collected from as many sources possible.
 The data compiled include data on physical and thermal properties, mechanical properties, chemical stability and compatibility, tritium solubility and transport, irradiation effects, afterheat characteristics, thermal cycling effects, waste disposal, and other miscellaneous properties of ceramic breeding materials, such as Li₂O, Li₂TiO₃, Li₂ZrO₃, and Li₄SiO₄. As a result of this compilation, the status of existing data can be recognized.