Hidehisa Hagiwara, Katsuaki Hayakawa, Ittoku Nozawa

Abstract
N-doped LaTa₂O₇ nanosheets (LTON-BP) were prepared by polygonal barrel-plasma surface modification method using N₂ plasma. X-ray photoelectron spectroscopy measurements suggest that nitrogen atoms were added at the interstitial crystal lattice sites of the N₂ plasma-treated photocatalyst. The photocatalytic activity of LTON-BP for H₂ production from triethanolamine aqueous solution was found to be 3.3 times higher than that of N-doped LaTa₂O₇ nanosheets prepared by a conventional method, which is attributed to the high oxidation ability of LTON-BP stemming from its band structure.

Mitsuhiro Inoue, Hironori Nakajima, Takayuki Abe

Abstract
Thermally self-sustaining CO₂ methanation reaction was investigated using highly active TiO₂-supported Ru (Ru/TiO₂) catalysts prepared by the polygonal barrel-sputtering method. The experiments were conducted using a lab-scale reactor covered with an inner heater for the direct heating + a thermal insulator and an outer heater for the simulation of outside temperature + a thermal insulator. When the CO₂ methanation was carried out by setting the inner and outer heater temperatures at 180 and 90 °C, respectively, the reaction temperature was increased from 183.6 °C to 191.1 and 195.6 °C by increasing the flow rate of a feeding CO₂ + H₂ gas (CO₂/H₂ ratio = 1/4 vol./vol.) from 6.7 ml/min to 35.0 and 54.7 ml/min. According to this result, the thermally self-sustaining reaction was evaluated by supplying the CO₂ + H₂ gas at 50 ml/min. At the outer heater temperature of 180 °C, the reaction temperature was stable at 230 °C for over 6 h after the inner heater of 180 °C was switched off at 40 min. Similar result was obtained at the outer heater temperature of 170 °C, and the reaction temperature was kept at 210 °C. However, under the outer heater temperature conditions of ≤160 °C, the reaction temperature after switching off the inner heater was rapidly decreased and the stable temperature trend was not observed. It is noted that the thermal transfer simulation based on the lab-scale experimental conditions presented possibility of the thermally self-sustaining reaction without the external heating using a thermal insulator having the thermal conductivity of 8.12 × 10^-3 W/(m K). However, this conductivity was ＜ 1/10 time of conventional thermal insulators. In contrast, the simulation for a large-scale reactor indicated that a cooling needs to keep a constant reaction temperature of 250 °C under the flow rate conditions of CO₂: 250 ml/in and H₂: 1000ml/min. This result implies that for our catalysts, the thermally self-sustaining reaction without both the external heating and the insulators can be achieved by increasing the heat of reaction due to the high flow rates of the reactant gases.

Akira Taguchi,Takumi Nakamori

Abstract
Highly crystalline pure-SiO₂ zeolites with CHA-type framework were prepared from three different silica sources of an alkoxide (tetraethyl orthosilicate), colloidal silica (AS-40) and fumed silica (Cab-O-Sil M5) in fluoride media. Single-phase CHA-type zeolites were successfully obtained with H₂O/SiO₂ molar ratios in the range of 1.2 – 1.3 in the final gel.

Hatano Yuji, Toyama Takeshi

Abstract
Tungsten is a primary candidate of plasma-facing material (PFM) of a future fusion reactor.As PFM, tungsten will be exposed to deuterium-tritium plasma while irradiated with high energy neutrons. Trapping of tritium at neutron-induced defects needs to be understood for accurate evaluation of tritium inventory in a vacuum vessel of a reactor. From these viewpoints, the conceptual design of the capsule to realize neutron irradiation of tungsten in an existing fission reactor in a hydrogen gas atmosphere was proposed in this report. The irradiation conditions were supposed to be 400 ℃ and 0.1 MPa. Vanadium hydride was selected as a hydrogen source from the viewpoint of equilibrium hydrogen pressure, reaction rate and thermal stability.Molybdenum was chosen as the capsule material due to its low hydrogen permeability.

Satoshi Akamaru, Katsuhiko Nishimura

Abstract
A hydrogen ion irradiation apparatus was constructed, and the amount of implanted hydrogen in a Ti sheet was evaluated. A focused hydrogen ion beam having a spot area of approximately 3×3 mm² was used to irradiate a Ti sheet. After hydrogen irradiation for 12 h, the Ti sheet surface showed an irradiated mark. The thermal desorption spectrum indicated that hydrogen was possibly soluble in the Ti metal without Ti hydride formation. As the irradiation time was extended to 36 h, the amount of implanted hydrogen increased. These results proved that the Ti sheet captured the irradiated hydrogen.

Masanori HARA, Ryota Uchikawa, Kenichi Kato, Takeshi Ito

Abstract
Low energy X-ray detectors have been used for the beta-ray induced X-ray spectrometry (BIXS) in tritium analysis. However, the energy calibration of detector has been done with using the X-ray from radionuclides such as ⁵⁵Fe, ⁵¹Cr and ⁵⁷Co. These radionuclides generate limited energy lines of X-ray. The other calibration method was proposed in this study. The beta ray induced X-ray with beta radionuclide such as ⁹⁰Sr and ¹³⁷Cs was used. A metal plate was constituted desirable elements which generate adequate X-ray lines for the calibration. To generate X-ray, the metal plate was irradiated by beta particles from ⁹⁰Sr or ¹³⁷Cs. The spectrum of X-ray generated was measured to obtain the relationship between the energy of X-ray and the pulse height (channel). The relationship taken by this calibration method could give more precise calibration factor in comparison with the conventional method.