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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：17.52(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 600
C, 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.
Iwai, Yasunori; Kubo, Hitoshi*; Sato, Katsumi; Oshima, Yusuke*; Noguchi, Hiroshi*; Taniuchi, Junichi*
Proceedings of 7th Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT-7) (USB Flash Drive), 2 Pages, 2014/06
Hydrophobic platinum catalysts have been developed especially for combustion of hydrogen isotopes released in a nuclear facility. A new type of hydrophobic hydrogen combustion catalyst commercially named TKK-KNOITS catalyst is hardly susceptible to water mist and water vapor in the atmosphere and water produced by hydrogen combustion. It is capable of maintaining the activity even at relatively low temperatures. The TKK-KNOITS catalyst is superior to other previous hydrophobic catalysts in applicability to wide range of hydrogen concentration from very thin to dense. The catalyst which carrier is composed of inorganic oxide has thermal stability up to 873 K.
Iwai, Yasunori; Sato, Katsumi; Taniuchi, Junichi*; Noguchi, Hiroshi*; Kubo, Hitoshi*; Harada, Nobuo*; Oshima, Yusuke*; Yamanishi, Toshihiko
Journal of Nuclear Science and Technology, 48(8), p.1184 - 1192, 2011/08
Times Cited Count：34 Percentile：91.82(Nuclear Science & Technology)The inorganic-based hydrophobic Pt-catalyst named H1P has been developed especially for efficient oxidation of a tracer level of tritium in the ambient temperature range even in the presence of saturated water vapor. The overall reaction rate constant for H1P catalyst in the ambient temperature range was considerably larger than that for traditionally applied Pt/Al
O
catalyst. Moreover, the decrease in reaction rate for H1P in the presence of saturated water vapor compared with in the absence of water vapor was slight due to its excellence in hydrophobic performance. Oxidation reaction on the catalyst surface is the rate-controlling step in the ambient temperature range and diffusion in a catalyst substratum above 313 K due to its fine porosity. The overall reaction rate constant in the ambient temperature range was dependent on the space velocity and hydrogen concentration in carrier.
Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko; Taniuchi, Junichi*; Noguchi, Hiroshi*; Kubo, Hitoshi*; Harada, Nobuo*; Oshima, Yusuke*
no journal, ,
The inorganic-based hydrophobic Pt-catalyst named H1P has been developed especially for efficient oxidation of a tracer level of tritium at room temperature even in the presence of saturated water vapor. Overall reaction rate constant of tritium oxidation on a H1P catalyst in a flow-through system were determined as a function of space velocity, hydrogen concentration in carrier, temperature of catalyst, water vapor concentration in carrier. The overall reaction rate constant for H1P catalyst at room temperature was considerably larger than that for traditionally applied Pt-alumina catalyst. The overall reaction rate constant at room temperature was dependent on the space velocity and hydrogen concentration in carrier. The overall reaction rate constant under the dry and wet conditions was proportional to hydrogen concentration in carrier to the power 0.33 and 0.44, respectively.
Iwai, Yasunori; Sato, Katsumi; Kubo, Hitoshi*; Oshima, Yusuke*; Noguchi, Hiroshi*; Taniuchi, Junichi*
no journal, ,
To enhance the reliability of tritium handling technologies for a fusion reactor, hydrophobic catalysts are strongly required for sufficient tritium oxidation at the room temperature without additional heating, considering the loss of electronic supply accident in the event of a fire. Traditional hydrophilic catalysts have lost its activity at room temperature due to the formation of water layer on the surface of the catalysts. JAEA and TKK have jointly researched and developed some inorganic-based hydrophobic catalysts for tritium oxidation at room temperature. The tritium oxidation performance of newly developed Hydrophobic Regular Pt Catalyst was independent on the moisture concentration in atmosphere. The reaction on the surface was the rate-controlling step at the room temperature. The tritium (hydrogen) concentration affected strongly the overall reaction rate coefficient. Research to improve catalyst activity is the next step for Hydrophobic Regular Pt Catalyst.
Kubo, Hitoshi*; Oshima, Yusuke*; Noguchi, Hiroshi*; Taniuchi, Junichi*; Sato, Katsumi; Iwai, Yasunori
no journal, ,
Regarding the fusion plants, radioactive tritium is a recyclable fuel. Tritium release into the environment should be controlled as low as possible even in case of a severe accident. In a severe accident in a light water reactor accompanied with loss of electricity, serious damage of the containment and safety-relevant components by detonation of the hydrogen-air mixture should be prevented. Oxidation of hydrogen in a catalytic reactor is considered a reliable way to remove hydrogen and tritium. The typical hydrophilic catalysts are useless due to the loss of activity by exposure to moisture at room temperature. The existing polymer-based hydrophobic catalysts have disadvantage of burnable. In the presentation, fabrication technique for inorganic-based hydrophobic catalysts to achieve a good balance of thermal stability and oxidation activity at room temperature is discussed.
Iwai, Yasunori; Sato, Katsumi; Kubo, Hitoshi*; Oshima, Yusuke*; Noguchi, Hiroshi*; Taniuchi, Junichi*
no journal, ,
Taking an accident such as loss of electric power into consideration, a hydrophobic catalyst, over which tritium and oxygen can react efficiently at room temperature, will contribute greatly to the fusion safety. Japan Atomic Energy Agency and Tanaka Kikinzoku Kogyo K.K. has jointly developed the hydrophobic platinum catalyst TKK-KNOITS for the oxidation of very thin tritium at room temperature. The overall reaction rate constant at room temperature for TKK-KNOITS was much larger than that for TKK-H1P, previously reported. The volume of catalytic reactor can be significantly reduced when the reactor is packed with TKK-KNOITS.
Kubo, Hitoshi*; Oshima, Yusuke*; Sato, Katsumi*; Iwai, Yasunori
no journal, ,
We have developed a hydrophobic catalyst for the combustion of hydrogen for the purpose to prevent a nuclear facility from hydrogen explosion in its severe accident. The iodine-resistance of the catalyst was investigated. The Pt-Pd catalysts were prepared especially with an inorganic carrier which is chemically treated to be hydrophobic. The hydrogen combustion tests were carried out in the presence of iodine in air. Tritium was mixed in air to improve the analytical accuracy of reaction by radioactivity counting. The Pt-Pd catalyst manufactured by noble acetylacetonate technique lost its catalytic activity in the presence of iodine in air. The Pt-Pd catalyst manufactured by the newly proposed technique with noble chloride salt maintained its catalytic activity in the presence of not only iodine but methyl iodide and chlorine gas. The developed catalyst will be a promising catalyst for nuclear facility due to its iodine-resistance and capability for hydrogen combustion at room temperature
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 1.38
10 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.
Iwai, Yasunori; Kondo, Akiko*; Edao, Yuki; Sato, Katsumi; Kubo, Hitoshi*; Oshima, Yusuke*
no journal, ,
Effect of halogenated gas on detritiation efficiency of the detritiation system has been investigated taking an event of off normal event such as fire into consideration. Concerning the activity of platinum catalyst for oxidation of tritium, we have evaluated the steep decrease in activity of platinum catalyst in the presence of halogenated gas. In order to avoid the steep decrease in activity, a noble catalyst alloyed with platinum and palladium showed an outstanding proof. In addition, the halogenated acid produced over catalyst surface affects the activity of catalyst. As for water absorber, a molecular sieve decreased its water absorbing capacity in the presence of halogenated gas.
