Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
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.
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 600
C, 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
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 1.38
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.
