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Journal Articles

Catalyst technology of Tanaka Kikinzoku Kogyo

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$$^{circ}$$C, which is much higher than the 70$$^{circ}$$C 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.

Journal Articles

Development of hydrophobic platinum catalyst for the effective collection of tritium in fusion plants

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$$^{circ}$$C, which is much higher than the 70$$^{circ}$$C 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.

Journal Articles

Distinctive radiation durability of an ion exchange membrane in the SPE water electrolyzer for the ITER water detritiation system

Iwai, Yasunori; Yamanishi, Toshihiko; Isobe, Kanetsugu; Nishi, Masataka; Yagi, Toshiaki; Tamada, Masao

Fusion Engineering and Design, 81(1-7), p.815 - 820, 2006/02

 Times Cited Count:14 Percentile:27.6(Nuclear Science & Technology)

Solid-polymer-electrolyte (SPE) water electrolysis is attractive in electrolytic process of water detritiation system (WDS) in fusion reactors because it can electrolyze liquid waste directly, but radioactive durability of its ion exchange membrane is a key point. Radioactive durability of Nafion, a typical commercial ion exchange membrane, was experimentally investigated using Co-60 irradiation facility and electron beam irradiation facility at Takasaki Radiation Chemistry Research Establishment of JAERI. Nafion is composed of PTFE (Polytetrafluoroethylene) main chain. However the degradation of its mechanical strength by irradiation was significantly distinguished from that of PTFE and no serious damage was observed for its ion exchange capacity up to 530 kGy, the requirement of ITER. Atmospheric effects such as soaking and oxygen on degrading behaviors were discussed from the viewpoint of radical reaction mechanism. Dependencies of operating temperature and radioactive source are also demonstrated in detail.

Journal Articles

Intelligible seminar on fusion reactors, 8; Fuel cycling system for tritium recovery

Fukada, Satoshi*; Hayashi, Takumi

Nippon Genshiryoku Gakkai-Shi, 47(9), p.623 - 629, 2005/09

no abstracts in English

Journal Articles

Durability of irradiated polymers in solid-polymer-electrolyte water electrolyzer

Iwai, Yasunori; Yamanishi, Toshihiko; Nishi, Masataka; Yagi, Toshiaki; Tamada, Masao

Journal of Nuclear Science and Technology, 42(7), p.636 - 642, 2005/07

 Times Cited Count:18 Percentile:21.92(Nuclear Science & Technology)

Radioactive durability of organic polymers in solid-polymer-electrolyte water electrolyzer was investigated by $$gamma$$-ray irradiation. Serious deteriorations for tensile strength and ion exchange capacity of ion exchange membrane (Nafion) were not observed up to 850 kGy. No serious damage was also observed for the gasket materials (Aflas) up to 500 kGy. PFA and FEP, insulator materials, lost their tensile strength at 300 kGy or less. As the result, it is concluded that the electrolyzer could be used up to around 500 kGy in the case where PFA and FEP are replaced by the polyimide resin whose durability is well demonstrated. Two degrading mechanisms were supposed. One is direct degradation by energy of radial rays. The other is that by the attack of radicals. It was demonstrated that the effect of radicals on the membrane was not dominant. The quantity of dissolved fluorine in water was found to correlate with the tensile strength and ion exchange capacity. Hence, it is possible to evaluate the degradation of the membrane by monitoring the quantity of dissolved fluorine.

Journal Articles

Application of pressure swing adsorption to water detritiation process

Iwai, Yasunori; Yamanishi, Toshihiko; Nishi, Masataka; Suzuki, Yutaka*; Kurita, Koichi*; Shimazaki, Masanori*

Journal of Nuclear Science and Technology, 42(6), p.566 - 572, 2005/06

 Times Cited Count:6 Percentile:56.45(Nuclear Science & Technology)

Pressure swing adsorption has been studied as a new water processing method for a future fusion power plant which will have a large amount of tritiated water to be processed. A series of adsorption and dehydration experiments was carried out for a typical adsorbent of NaX zeolite and it was clearly observed that break through time differs in H$$_{2}$$O and HTO, that is, it is certain that NaX zeolite can separate into the tritium concentrated water and the tritium reduced water. The quick dehydration is attained by decompression and purge gas flowing. It was observed that a part of the water released by decompression was transferred by the purge gas, and the rest water was adsorbed on the adsorbent again and was gradually released by the diffusion. It is demonstrated that enlargement of pressure difference between adsorption and dehydration is effective to obtain high dehydration ratio. Furthermore, it was also verified that enough vapor removal capacity of purge gas is quite necessary to obtain high dehydration ratio.

Oral presentation

Research and development on radiation durability of core components of water detritiation system for fusion reactors

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$$times$$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 $$gamma$$ 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.

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