Kuniaki WATANABE, Masao MATSUYAMA
Hydrogen Isotope Research Center, Toyama University,Gofuku 3190, Toyama 930
(Received July 31, 1992; accepted November 7, 1992)

Abstract
Vast amounts of tritium will be used for thermonuclear fusion reactors. Without establishing safe handling techniques for large amounts of tritium, undoubtedly the fusion reactors will not be accepted. Japanese activity on tritium related research has considerably developed in the last 10 years. This review paper gives a brief summary of safe handling techniques developed by Japanese research groups.

Osamu YAMAMOTO
Department of Biology, Faculty of Sciences, Hiroshima University, 1-3 Kagamiyama, Higashi-Hiroshima 724, JAPAN
(Received July 15, 1992; accepted November 7, 1992)

Abstract
A building was recently constructed which has facilities specially designed for exclusive use of HTO studies.

As chemical evidences of HTO, a specific UV spectrum, the luminescence exhibition only with luminol but without peroxydase and the epoxide formation from mesityl oxide were found, from which it was concluded that the radiolytic reaction of water with HTO is [H₂O→H₂O^*→H₂＋O ] followed by [O＋M→(MO),(MO)＋H₂O→M(OH) ₂ or ・MOH＋・OH], [O＋O→O₂] and [O＋H₂O→H₂O₂]. This was supported by low oxygen effects observed in thymine and adenine radiolysis with HTO.
  Low-dose-rate effect (Kada effect) was reconfirmed using the transfection system of M13 phage DNA irradiated, and then it could be explained by that the ratios of [O＋M→(MO),(MO)＋H₂O→M(OH) ₂ or ・MOH＋・OH] to [O＋O→O₂] increases with the decrease of dose rate.
  RBE higher than one was obtained also in the case of the killing of radioresistant E.coil TG1. It was concluded that this is due to the high reactivity of nascent O which can act resembling two OH.
  LD50/30 was estimated to be 5.6x10⁸Bq (8Gy) for C57BL/6N female young mice and 9.3x10⁸ Bq (13Gy) for (C57BL/6NxC3H/He) F₁ young female mice by single-injection of HTO. At doses lower than 5.6x10⁸ Bq (8Gy), mice died inducing leukemias with higher doses and other solid tumors with lower doses.
  In continuous administration of HTO, (C57BL/6NxC3H/He) F₁ female adult mice died of haematopoietic failure with in 50 days at dose rates more than 0.48 Gy/day, while the appearance of lymphomas changed to that of various non-lymphoma tumors with the decrease of dose rate to less than 0.24 Gy/day and surviving over 150 days.

Masao MATSUYAMA, Hitoshi MIYAKE, Kan ASHIDA, Kuniaki WATABANE
Hydrogen Isotope Research Center, Toyama University,Gofuku 3190, Toyama 930，JAPAN
(Received July 31, 1992; accepted November 9, 1992)

Abstract
Waste aluminum is recycled and reused as aluminum raw material. Another way of recycling is possible for aluminum. It decomposes water at room temperature to produce hydrogen and aluminum hydroxide under certain conditions. The present paper described preliminary results of a study on factors affecting the rate of hydrogen production using pure aluminum and Al-Mg alloy. The results showed : (1)Cold-rolling is effective to enhance the reaction, indicating that defect structures play important roles, (2)Alloying magnesium to aluminum is much more effective to increase the reaction rate than the cold-rolling of pure aluminum, (3)An important factor to affect the reaction rate appears to be corrosion cracking patterns through formation of fresh surfaces and/or active sites.

Kan ASHIDA^*1, Kuniaki WATANABE^*1, Shotaro MOROZUMI^*1, Kenji MATSUDA^*2, Sizuo TADA^*2
*1Hydrogen Isotope Research Center, Toyama University
^*2Material Science and Engineering, Faculty of Engineering, Toyama University
Gofuku 3190, Toyama 930, JAPAN
(Received July 31, 1992; accepted November 9, 1992)

Abstract
　Hydrogen storage materials lose their effectiveness in the presence of small amounts of impurity gases in hydrogen owing to the formation of oxide and/or carbide layers on the surface of materials. To avoid this impairment, applicability of Pd coating as protective layer was examined. Zr and Zr₃Al₂ were selected as model substrates and coated with Pd with electroless plating method. The characteristics of the Pd coating were examined with scanning electron microscopy (SEM), electron probe microanalysis (EPMA), x-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). SEM observations showed that dense and relatively smooth Pd-overlayers could be prepared with this method on combination with vacuum annealing. EPMA and XPS revealed that mutual diffusion of the relevant elements took place above 600℃ As a consequence, the elements of the substrates on the surface. Zr, however, was present as ZrC, whereas, Pd was kept in its pure metallic state. TDS showed that Zr played no important role in absorption and desorption of deuterium and only the Pd-overlayer took part in the ab/desorption processes, indicating that the Pd layer acts as permeation window for hydrogen and can protect the inner substrate from impurity gases.

Hitoshi MIYAKE, Kuniaki WATANABE
Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930, JAPAN
(Received July 31, 1992; accepted November 9, 1992)

Abstract
　Tritium containers are commonly made of conventional types of stainless steel. Use of these materials, however, causes problems such as high permeation rate of tritium, contamination of tritium with protium, which is dissolved in stainless steel and so on. To solve these problems, the inner walls of such containers were passivated with anodic oxidation. As a first step to evaluate the effect of the passivation layers on the above problems, ad/absorption and desorption characteristics of deuterium were examined with thermal desorption spectroscopy. Such developed container showed smaller gas release and smaller amount of solved hydrogen compared commercial stainless steel containers. This property, however, arose from differences in materials themselves or in manufacturing processing of the containers. The oxide layers grown on a container with twice anodic oxidation processing did not act as barrier for the deuterium ad/absorption. The oxide layers grown by repeating the process four times, however, showed about one order of magnitude smaller ad/absorption, suggesting that these oxide layers will act as barrier for tritium ad/absorption and permeation.

Kiyoshi HASEGAWA, Hiroshi FUSUMAE, Shoichi MIYAHARA, Manabu SHINOHARA, Masao MATSUYAMA^*, Kuniaki WATANABE^*
Faculty of Engineering, Toyama University
^*Hydrogen Isotope Research Center, Toyama University
Gofuku 3190, Toyama 930, JAPAN
(Received July 31, 1992; accepted November 9, 1992)

Abstract
　The effect of carbon tetrachloride on the UV-stimulated HT oxidation was examined. Mixture gases (H₂, HT, O₂ and CCl₄) were irradiated by high pressure mercury lamp with varying the pressure of carbon tetrachloride. Total tritium concentration of HTO and TCl increased with increasing the pressure of carbon tetrachloride and increased acceleratedly with time when higher pressure of carbon tetrachloride was used. The enhancement effect was examined by measuring the acidity of the water in which HTO and HCl (TCl) were trapped and by considering additional elementary reactions by the addition of carbon tetrachloride. The acidity of the trapped water was proportional to the irradiation time. The quantity of TCl was calculated from that of HCl formed. Substraction of the TCl concentration from the total tritium concentration showed accelerated increase in HTO with time. The acceleration is not ascribed to the catalytic action of HCl (TCl) for the exchange reaction H₂O and HT. Main paths for the formation of HTO are discussed.

Kenji SHIMIZU, Takako FUJII, Masao MATSUYAMA^*, Kuniaki WATANABE^*
Faculty of Education, Toyama University
^*Hydrogen Isotope Research Center, Toyama University
Gofuku 3190, Toyama 930, JAPAN
(Received July 31, 1992; accepted November 9, 1992)

Abstract
　The compound Er₂Fe₁₄B was hydrogenated to Er₂Fe₁₄BHx up to x=2.2 under a hydrogen pressure of ～0.1 atm. The average volume expansion per hydrogen atom was found to be 3.8A³/H for Er₂Fe₁₄B_1.0 and Er₂Fe₁₄BH_1.8 compound. The ¹⁶⁷Er NMR measurements were also done on Er₂Fe₁₄BH_1.0 by means of spin echo method. The Er hyperfine fields at the f and g sites in the hydride slightly decrease when compared with those in Er₂Fe₁₄B. The electric quadrupole interaction parameters for Er at the f and g sites remain almost constant within the range of accepted uncertainties.