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Furutani, Misa; Kometani, Tatsunari; Nakagawa, Masahiro; Ueno, Yumi; Sato, Junya; Iwai, Yasunori*
Hoken Butsuri (Internet), 55(2), p.97 - 101, 2020/06
Herein, an oxidation catalyst was introduced after heating it to 600C to oxidize tritium gas (HT) existing in exhaust into tritiated water vapor (HTO). This study aims to establish a safer H monitoring system by lowering the heating temperature required for the catalyst. In these experiments, which were conducted in the Nuclear Science Research Institute, Japan Atomic Energy Agency, cupric oxide, hydrophobic palladium/silicon dioxide (Pd/SiO), and platinum/aluminum oxide (Pt/AlO) catalysts were ventilated using standard hydrogen gas. After comparing the oxidation efficiency of each catalyst at different temperatures, we found that the hydrophobic Pd/SiO and Pt/AlO catalysts could oxidize HT into HTO at 25C.
Ueno, Yumi; Nakagawa, Masahiro; Sato, Junya; Iwai, Yasunori
Hoken Butsuri, 51(1), p.7 - 11, 2016/03
In the Nuclear Science Research Institute, Japan Atomic Energy Agency (JAEA), in order to oxidize C, which exists in various chemical forms in exhaust, into CO, a copper oxide (CuO) catalyst is introduced after heating to 600C. Our goal was to establish a safer C monitoring system by lowering the heating temperature required for the catalyst; therefore, we developed a new hydrophobic palladium/silicon dioxide (Pd/SiO) catalyst that makes the carrier's surface hydrophobic. In these experiments, catalysts CuO, platinum/aluminum oxide (Pt/AlO), palladium/zirconium dioxide (Pd/ZrO), hydrophobic Pd/SiO, and hydrophilic Pd/SiO were ventilated with standard methane gas, and we compared the oxidation efficiency of each catalyst at different temperatures. As a result, we determined that the hydrophobic Pd/SiO catalyst had the best oxidation efficiency. By substituting the currently used CuO catalyst with the hydrophobic Pd/SiO catalyst, we will be able to lower the working temperature from 600C to 300C and improve the safety of the monitoring process.
Iwai, Yasunori; Kubo, Hitoshi*; Oshima, Yusuke*; Noguchi, Hiroshi*; Edao, Yuki; Taniuchi, Junichi*
Fusion Science and Technology, 68(3), p.596 - 600, 2015/10
Times Cited Count:2 Percentile:17.57(Nuclear Science & Technology)We have newly developed the hydrophobic platinum honeycomb catalysts applicable to tritium oxidation reactor since the honeycomb-shape catalyst can decrease the pressure drop. Two types of hydrophobic honeycomb catalyst have been test-manufactured. One is the hydrophobic platinum catalyst on a metal honeycomb. The other is the hydrophobic platinum catalyst on a ceramic honeycomb made of silicon carbide. The fine platinum particles around a few nanometers significantly improve the catalytic activity for the oxidation tritium at a tracer concentration. The hydrogen concentration in the gaseous feed slightly affects the overall reaction rate constant for hydrogen oxidation. Due to the competitive adsorption of hydrogen and water molecules on platinum surface, the overall reaction rate constant has the bottom value. The hydrogen concentration for the bottom value is 100 ppm under the dry feed gas. We have experimentally confirmed the activity of these honeycomb catalysts is as good as that of pellet-shape hydrophobic catalyst. The results support the hydrophobic honeycomb catalysts are applicable to tritium oxidation reactor.
Kubo, Hitoshi*; Oshima, Yusuke*; Iwai, Yasunori
JETI, 63(10), p.33 - 36, 2015/09
Tanaka Kikinzoku Kogyo provides a broad range of precious metals products and technologies. Tanaka Kikinzoku Kogyo and Japan Atomic Energy Agency have jointly developed a new method of manufacturing catalysts involving hydrophobic processing with an inorganic substance base. As a result, previous technological issues were able to be solved with the development of a catalyst that exhibited no performance degradation in response to radiation application of 530 kGy, a standard for radiation resistance, and maintenance of thermal stability at over 600C, which is much higher than the 70C temperature that is normally used. The application of this catalyst to the liquid phase catalytic exchange process is expected to overcome significant technological hurdles with regards to improving the reliability and efficiency of systems for collecting tritium from tritiated water. It is also anticipated that the hydrophobic platinum catalyst manufacturing technology used for this catalyst could be applied to a wide range of fields other than nuclear fusion research. It was verified that if applied to a hydro oxidation catalyst, hydrogen could be efficiently oxidized, even at room temperature. This catalyst can also contribute to improving safety at non-nuclear plants that use hydrogen in general by solving the aforementioned vulnerability issue.
Iwai, Yasunori; Kubo, Hitoshi*; Oshima, Yusuke*
Isotope News, (736), p.12 - 17, 2015/08
We have successfully developed a new hydrophobic platinum catalyst for collecting tritium at nuclear fusion reactors. Catalysts used to collect tritium are called hydrophobic precious metal catalysts. In Japan, hydrophobic precious metal catalysts manufactured from polymers have been used for heavy water refinement.However, this catalyst has issues related to embrittlement to radiation and thermal stability. These technological issues needed to be solved to allow for its application to nuclear fusion reactors requiring further enrichment from highly-concentrated tritiated water. We developed a new method of manufacturing catalysts involving hydrophobic processing with an inorganic substance base. As a result, previous technological issues were able to be solved with the development of a catalyst that exhibited no performance degradation in response to radiation application of 530kGy, a standard for radiation resistance, and maintenance of thermal stability at over 600C, which is much higher than the 70C temperature that is normally used. The catalyst created with this method was also confirmed to have achieved the world's highest exchange efficiency, equivalent to 1.3 times the previously most powerful efficiency. The application of this catalyst to the liquid phase catalytic exchange process is expected to overcome significant technological hurdles with regards to improving the reliability and efficiency of systems for collecting tritium from tritiated water.
Iwai, Yasunori; Kubo, Hitoshi*; Oshima, Yusuke*
Kagaku, 70(5), p.35 - 40, 2015/05
We have successfully developed a new hydrophobic platinum catalyst for collecting tritium at nuclear fusion reactors. Catalysts used to collect tritium are called hydrophobic precious metal catalysts. In Japan, hydrophobic precious metal catalysts manufactured from polymers have been used for heavy water refinement. However, this catalyst has issues related to embrittlement to radiation and thermal stability. These technological issues needed to be solved to allow for its application to nuclear fusion reactors requiring further enrichment from highly-concentrated tritiated water. We developed a new method of manufacturing catalysts involving hydrophobic processing with an inorganic substance base. As a result, previous technological issues were able to be solved with the development of a catalyst that exhibited no performance degradation in response to radiation application of 530 kGy, a standard for radiation resistance, and maintenance of thermal stability at over 600C, which is much higher than the 70C temperature that is normally used. The catalyst created with this method was also confirmed to have achieved the world's highest exchange efficiency, equivalent to 1.3 times the previously most powerful efficiency. The application of this catalyst to the liquid phase catalytic exchange process is expected to overcome significant technological hurdles with regards to improving the reliability and efficiency of systems for collecting tritium from tritiated water.
Naganawa, Hirochika; Suzuki, Hideya; Tachimori, Shoichi; Nasu, Akinobu*; Sekine, Tatsuya*
Physical Chemistry Chemical Physics, 3(12), p.2509 - 2517, 2001/06
Times Cited Count:34 Percentile:70.77(Chemistry, Physical)no abstracts in English
Naganawa, Hirochika; Suzuki, Hideya; Tachimori, Shoichi; Nasu, Akinobu*; Sekine, Tatsuya*
Bulletin of the Chemical Society of Japan, 73(3), p.623 - 630, 2000/03
Times Cited Count:6 Percentile:35.36(Chemistry, Multidisciplinary)no abstracts in English
Shirai, Osamu; *; Kihara, Sorin*
Review of Polarography, 44(2), p.76 - 92, 1998/09
no abstracts in English
Kumakura, Minoru; Tamada, Masao; Kasai, Noboru; Kaetsu, Isao*; *
Biotechnology and Bioengineering, 33, p.1358 - 1362, 1989/00
Times Cited Count:13 Percentile:50.99(Biotechnology & Applied Microbiology)no abstracts in English
; Kaetsu, Isao
Journal of Materials Science Letters, 2, p.605 - 608, 1983/00
Times Cited Count:5 Percentile:40.03(Materials Science, Multidisciplinary)no abstracts in English
;
Journal of Polymer Science; Polymer Chemistry Edition, 20, p.863 - 874, 1982/00
no abstracts in English
Kaetsu, Isao; ;
Biotechnol.Bioeng., 21(5), p.863 - 873, 1979/00
no abstracts in English
; ; Kaetsu, Isao
J.Solid-Phase Biochem., 3(3), p.175 - 183, 1978/00
no abstracts in English
Kaetsu, Isao
Kagaku No Ryoiki, 31(10), p.87 - 91, 1977/10
no abstracts in English
Iwai, Yasunori
no journal, ,
Hydrophobic platinum catalysts have been widely applied in the field of nuclear fusion such as to the exchange reactions of hydrogen isotopes between hydrogen and vapor and to the oxidation reactions of tritium. Hydrophobic platinum catalysts are hardly susceptible to water mist and water vapor. Hydrophobic platinum catalysts are produced by supporting platinum directly on hydrophobic polymer beads. For the hydrophobic polymer, styrene divinyl benzene (SDB) has been applied in Japan. It can be pointed out that the betterment in catalytic activity of hydrophobic catalyst is expected to downsize the catalytic reactor based on a hard look at a large increase in flow rate in future. The acute change in catalytic activity of two types of commercial Pt/SDB catalysts was found when they were irradiated with electron beams. After irradiation with electron beams, the catalytic activity was evaluated by means of overall reaction rate constant for the oxidation of tritium. The overall reaction rate constant increased as increase in dose. The constant showed the peak value in the dose between 500 to 1000 kGy. After the peak, the constant decreased as increase in dose. The overall reaction rate constant at the peak was 6 times larger than that evaluated with unirradiated. The mechanical strength of irradiated Pt/SDB kept sound until 1500 kGy. The irradiation is a promising method to the betterment in catalytic activity of Pt/SDB catalyst.
Iwai, Yasunori; Kubo, Hitoshi*; Oshima, Yusuke*
no journal, ,
Water detritiation technology for the Combined Electrolysis Catalytic Exchange (CECE) process has been developed over the years in Japan Atomic Energy Agency (JAEA) for the Japanese DEMO fusion reactor. The research interest is in (1) durability of a commercial polymeric ion exchange membrane for tritiated water electrolyzer and improvement of a membrane for the enhance in durability, in (2) sorption behavior of tritiated water in elastomers for promising seal materials of the electrolyzer, and in (3) development of hydrophobic catalyst for the reaction of hydrogen isotope exchange between hydrogen and water vapor in the Liquid Phase Chemical Exchange (LPCE) column. For the durability of ion exchange membrane, durability of Nafion ion exchange membrane immersed into 1.3810 TBq/kg of highly concentrated tritiated water has been demonstrated at room temperature for up to 3 years as a Broader Approach activity. The changes in mechanical strength and ion exchange capacity after immersing in tritiated water are well consistent with those irradiated to an equivalent dose with rays or electron beams. As for the sorption behavior of tritiated water in elastomers, change in sorption behavior of water in elastomers irradiated up to 1500 kGy has been evaluated for more than 8 years. For the hydrophobic catalyst, the Japan Atomic Energy Agency and Tanaka Kikinzoku Kogyo K.K developed a new method of manufacturing catalysts involving hydrophobic processing with an inorganic substance base. The catalyst created with this method has achieved the highest exchange efficiency, equivalent to 1.3 times the previously most powerful efficiency.
Ueno, Yumi; Nakagawa, Masahiro; Sato, Junya; Iwai, Yasunori
no journal, ,
no abstracts in English