芦田　完^*、西出　善宗^**、市村　憲司^***、渡辺　国昭^***、松浦　郁也^**
*富山大学放射性同位元素総合実験室
^**富山大学理学部化学科
^***富山大学トリチウム科学センター
〒930　富山市五福3190

Kan ASHIDA^*, Yoshimune NISHIDE^**, Kenji ICHIMURA^***,Kuniaki WATANABE^***, Ikuya MATSUURA^**
*Radio-Isotope Laboratory, Toyama University
^**Faculty of Science, Toyama University
^***Tritium Research Center, Toyama University
Gofuku 3190, Toyama 930, JAPAN

Abstract
Recovery and storage of tritiated water is one of the most important problems for experiments using tritium. As a first step to apply the hydration phenomenon of inorganic compounds for this purpose, we investigated the hydration and dehydration process of CuSO₄ with H₂O, D₂O and HTO (93μCi/cc) by using thermal desorption spectroscopy. Three desorption peaks appeared in the desorption spectra for CuSO₄5H₂O and CuSO₄5D₂O at 60, 80 and 180℃. It indicates that there are three distinct bound states of absorbed water molecules (denoted as Ⅰ, Ⅱ and Ⅲ). The ratio among the amounts of absorption in each of the states were 2:2:1. With respect to CuSO₄5HTO, the first and second peaks appeared at the same temperature as those for H₂O, whereas the third peak was observed at 183℃, being 3℃ higher than that of H₂O. Tritiated water was homogeneously distributed among the three states at first and redistributed during storage at room temperature in a closed container for several days. The concentration of the tritiated water in state Ⅰ decreased and that in state Ⅲ increased.
  The analysis of desorption spectra made it clear that the rate determining step for the dehydration was a random nucleation processes for each of the absorbed states. The actovation energies were 20, 23 and 35 kcal/mol for state Ⅰ, Ⅱ and Ⅲ, respectively. No isotope effect was observed in this term. The kinetic isotope effect only appeared in the frequency factor for the desorption of water in state Ⅲ: that is, the frequency factor for state Ⅰ and Ⅱ were 1.1x10¹⁰ and 1.1 x10¹¹ sec^-1, respectively: they were valid for the three kinds of water molecules. On the other hand, those for H₂O and D₂O in state Ⅲ were 8.3x10¹³ sec^-1 and that for HTO was 5.3x10¹³ sec^-1.
  During storage of the sample in a closed container, HTO removed from state Ⅰ to state Ⅲ via the gas phase, being concentrated in state Ⅲ.

松山　政夫、三宅　均、渡辺　国昭、加藤　一真^*、前川　寛^*、佐藤　博夫^*
富山大学トリチウム科学センター
^*アロカ株式会社
〒181　東京都三鷹市牟礼6-22-1

Masao MATSUYAMA, Hitoshi MIYAKE, Kuniaki WATANABE, Kazuma KATO^*,Hiroshi MAEKAWA^*, Hiroo SATO^*
Tritium Research Center, Toyama University,Gofuku 3190, Toyama 930
Research and Development Laboratory, Aloka Co. Ltd.
Mure 6-22-1, Mitaka, Tokyo 181, JAPAN
(Received December 25, 1984)

Abstract
Ionization chambers are widely used for measuring tritium in the gas phase. Recently, however, it has been perceived that the contamination of the chamber wall due to the adsorption of tritium significantly impairs the reliability of the ionization chambers when they are used for measuring tritium at high concentrations. As a first step to overcome this difficulty, we studied the contamination of ionization chambers with tritium gas (HT) and/or tritiated water vapor (HTO) by using different component materials (Cu, Ni-plated, and Au-plated chambers).
  In case of the Cu chamber, the concentration of tritium gas in the chamber decreased exponentially with time due to purge by fresh air to a certain level. Then, the decrease rate slowed down drastically (the memory effect). This is caused by adsorption of tritiated water on the surface of the material; the tritiated water being formed in the chamber due to exchange reaction with water vapor. In case of the Ni-plated chamber, the memory effect was also observed; however, this is not due to the adsorbed tritiated water. Instead, it is thought to due to adsorbed tritium such as T(a) or HT(a). With respect to the Au-plated chamber, no memory effect took place when it was exposed to tritium gas (HT).
  On the other hand, when the chambers were exposed to tritiated water vapor, all showed a large memory effect. It was clarified that the memory effect principally arose from the physically adsorbed tritiated water.
  In conclusion, the Au-plated chamber is most preferable for measuring tritium gas. However, the memory effect due to the adsorption of tritiated water vapor is as large as that for the other two. Therefore, it is necessary to develop suitable decontamination methods for the contamination will have to be avoided by the selection of more suitable materials.

朝野　武美、桐谷　玲子、藤田　慎一
大阪府立放射線中央研究所
大阪府堺市新家町704

Takeyoshi ASANO, Reiko KIRITANI, Shinichi FUJITA
Radiation Center of Osaka Prefecture,Shinke-cho, Sakai, Osaka, JAPAN
(Received December 25, 1984)

Abstract
A study for improving the yield in the synthesis of ［2-¹⁴C，5-³H］cytosine was made using a preferable condition for the reaction between ［2-¹⁴C，5-Br］ cytosine and tritium gas. Using ［2-¹⁴C］ cytosine as the starting material, 29% of radioactive cytosine was recovered after bromination and tritiation. Tritium labeled in the product obtained was determined to 86%. Thus, the degree of double labeling was calculated as 70% on the basis of the radioactive content of the starting cytosine (81%).

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 WATANABE
Tritium Research Center, Toyama University
(Received December 25, 1984

Abstract
We have investigated the diffusion, solution and permeation of hydrogen isotopes in/through organic polymers to search for the suitable membrane materials for tritium separation. In our previous research, the permeation and diffusion constants of tritium for polycarbonate coated with stainless steel (SS) film, prepared by rf-sputtering, differed considerably from those of the order isotopes, where experimental methods and conditions for tritium differed from those for the others: tritium permeation was measured by means of β-ray counting, whereas the others were measured by ionization gauge. In this study, we measured the permeation of hydrogen isotopes at 0.4-10 KPa using a mass spectrometer by means of the time-lag method and investigated the mechanism of permeation so as to understand the previous results.
 The large difference as observed previously was not detected in the present study. The ratio of the diffusion and permeation constants among the three isotope were D(H₂) : D(D₂) : D(T₂)=1.21 : 1.71 : 1, and KD(H₂) : KD(D₂) : KD(T₂)=1 : 1.03 : 2.77, where D, K and KD are the diffusion, solution and permeation constants, respectively. Three hydrogen isotopes appeared as H₂, D₂ and T₂ after permeation through the SS film, which mainly consisted of oxides and/or carbides of Fe and Cr, as hydrogen atoms or irons. Then, they recombine at the down-stream side of the SS film to form hydrogen molecules and permeate through polycarbonate as they stand. The present results indicated that the previous ones are due to the influence of the counting gas on the behavior of tritium in the polymer or the pressure dependence of the solution and/or diffusion constants.

市村　憲司、芦田　完^*、松山　政夫、渡辺　国昭、竹内　豊三郎
富山大学トリチウム科学センター
^*富山大学RI総合実験室
〒930　富山市五福3190

Kenji ICHIMURA, Kan ASHIDA^*, Masao MATSUYAMA, Kuniaki WATANABE, Toyosaburo TAKEUCHI
Tritium Research Center, Toyama University , Gofuku 3190, Toyama 930
(Received December 25, 1984)

Abstract
Recovery and storage of tritiated water is one of the important problems for the safe handling of large amounts of tritium, because it is anticipated that a considerable amount of tritium becomes tritiated water once tritium is introduced into the handling system. From this viewpoint, we have studied the absorption/desorption phenomena of water (H₂O and D₂O) for Zr-V-Fe getter (St-707, SAES Getters) by means of mass analyzed thermal desorption spectroscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry.
  The absorption rate of water vapor changed linearly with exposure pressure. The activation energies and frequency factors were determined as Ea(H₂O)=1.8kcal/mol and νa(H₂O)=2.1cc/sec・cm² (projected area), and Ea(D₂O)=2.7kcal/mol and νa(D₂O)=4.0 cc/sec・cm² (projected area), respectively. Only hydrogen molecules (H₂ or D₂) was desorbed when the getter was heated after exposure to water. The desorption obeyed second order kinetic with respect to the amount of water absorption. The activation energies and frequency factors were the same as those observed for desorption of hydrogen after hydrogen exposure. The XPS analysis made it clear that the surface mainly consisted of metallic Zr and V; a part of them, however, was oxidized due to exposure to water. In the SIMS measurement, ZrOD⁺, VOD⁺, VOD⁺₂, and OD^- peaks appeared after exposure to D₂O vapor. The intensities of these peaks and intensities of the oxide peaks of Zr3d_5/2 and V2p_3/2 decreased as the exposure temperature increased.
  It was concluded that: (1) the rate determining steps for the absorption and desorption were the surface decomposition reaction of adsorbed water molecules or hydroxyl groups and surface association reaction of hydrogen atoms diffused to the surface from the bulk; (2) both Zr and V work as active sites for absorption where the Zr-site plays a more important role than the V-site; and (3) the Zr-V-Fe getter is suitable for the recovery and storage of tritiated water as well as tritium gas.

草開　清志、久保　孝、竹田　美緒子、大岡　耕之、松山　政夫^*、渡辺　国昭^*

富山大学工学部金属工学科
^*富山大学トリチウム科学センター
富山市五福3190

Kiyoshi KUSABIRAKI, Takashi KUBO, Mioko TAKEDA, Takayuki OOKA, Masao MATSUYAMA^*, Kuniaki WATANABE^*
Department of Metallurgical Engineering, Faculty of Engineering, Toyama University
^*Tritium Research Center, Toyama University
Gofuku 3190, Toyama 930, JAPAN
(Received December 25, 1984)

Abstract
In order to locate hydrogen trapped in the microstructure of stainless alloys and/or steels, tritium autoradiographical studies have been carried out. We improved the techniques for autoradiography with the use of a corrosion inhibitor, NaNO₂, during photographic processing, and obtained clear autoradiographs of tritium on iron. The techniques lead to the

following conclusions:

1. The distinct autoradiographs for iron can be obtained by inhibiting the corrosion of the specimens by using a photographic processing solution containing sodium nitrite.
2. The resolution of the autoradiograph is higher than that obtained by the previous techniques, and the processing is simpler, because colloidon film is not used.
3. The grain boundaries and inclusions in cold worked and annealed iron act as trapping sites for hydrogen.
4. By using the techniques improved in this study, TEM and SEM as well as optical microscopy can be used to identify the trapping sites of tritium in iron in connection with its microstructure.

三木　俊克、池谷　元伺、松山　政夫^*、渡辺　国昭^*

山口大学工業短期大学部
宇部市常盤台2557
^*富山大学トリチウム科学センター
富山市五福3190

Toshikatsu MIKI, Motoji IKEYA, Masao MATSUYAMA^*, Kuniaki WATANABE^*
Technical College, Yamaguchi University,Tokiwadai, Ube 755, JAPAN
^*Tritium Research Center, Toyama Universit,Gofuku 3190, Toyama 930, JAPAN

Abstract
The decay of the electret charge due to tritium β-rays was studied to determine the sensitivity of electret dosimeters for atmospheric tritium. The electret charge decreases proportionally in relation to the tritium activity and to the exposure time with a sensitivity of about 1x10^-18 C/pCi・s, corresponding to the theoretical response of electret dosimeters in the ionization chamber mode. This high sensitivity leads us to consider using the electret dosimeter as a promising devise for the measurement of tritium.

佐竹　洋、木津　暢彦、水谷　義彦

富山大学理学部地球科学教室
〒930　富山市五福3190

Hiroshi SATAKE, Nobuhiko KIZU, Yoshihiko MIZUTANI
Department of Earth Sciences, Toyama University,Gofuku 3190, Toyama 930, JAPAN
(Received December 25, 1984)

Abstract
The tritium content of the river water samples from five large rivers in the Hokuriku district in Japan were measured. The averaged tritium content of the Sho River during April 1980 to March 1983 was 20 TU. Those of the other four rivers ranged from 24 to 26 TU. All five rivers had a large tritium content relative to precipitation. This suggests that the precipitation polluted by past nuclear weapon test is still present in the fquiferous water and is being discharged to some extent into the rivers. The tritium contents of these five rivers do not decrease during the spring thaw, though the discharge of river water increases in this period. This suggests that the proportion of runoff to the discharge is relatively small even during the spring thaw.