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Journal Articles

Hydrophobic platinum honeycomb catalyst to be used for tritium oxidation reactors

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:0 Percentile:0.01(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.

Journal Articles

Hydrophobic Pt catalyst for combustion of hydrogen isotopes at low temperatures

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.

Journal Articles

Room-temperature reactor packed with hydrophobic catalysts for the oxidation of hydrogen isotopes released in a nuclear facility

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:26 Percentile:90.28(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$$_{2}$$O$$_{3}$$ 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.

Oral presentation

Tritium oxidation performance of hydrophobic Pt-catalyst developed for room temperature recombiner

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.

Oral presentation

Tritium oxidation performance of hydrophobic regular Pt catalyst

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.

Oral presentation

Hydrophobic catalysts for the oxidation of tritium (hydrogen) at room temperature

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.

Oral presentation

Development of hydrophobic Pt catalyst KNOITS for oxidation of tritium at room temperature

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.

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