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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.
Edao, Yuki; Sato, Katsumi; Iwai, Yasunori; Hayashi, Takumi
Journal of Nuclear Science and Technology, 53(11), p.1831 - 1838, 2016/11
Times Cited Count:8 Percentile:59.58(Nuclear Science & Technology)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
Fusion Engineering and Design, 98-99, p.1796 - 1799, 2015/10
Times Cited Count:5 Percentile:39.50(Nuclear Science & Technology)Hydrophobic platinum catalysts have been widely applied in the field of nuclear fusion for the exchange reactions of hydrogen isotopes between hydrogen and vapor in the water detritiation system, and for the oxidation of tritium on the atmospheric detritiation system. 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 upgrade 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 upgrade 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 upgrading in catalytic activity of Pt/SDB catalyst.
Isobe, Kanetsugu; Kawamura, Yoshinori; Iwai, Yasunori; Oyaizu, Makoto; Nakamura, Hirofumi; Suzuki, Takumi; Yamada, Masayuki; Edao, Yuki; Kurata, Rie; Hayashi, Takumi; et al.
Fusion Engineering and Design, 98-99, p.1792 - 1795, 2015/10
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)Activities on Broader Approach (BA) were started in 2007 on the basis of the Agreement between the Government of Japan and the EURATOM. The period of BA activities consist of Phase1 and Phase2 dividing into Phase 2-1 (2010-2011), Phase 2-2 (2012-2013) and Phase 2-3 (2014-2016). Tritium technology was chosen as one of important R&D issues to develop DEMO plant. R&D activities of tritium technology on BA consist of four tasks. Task-1 is to prepare and maintain the tritium handling facility in Rokkasho BA site in Japan. Task 2, 3 and 4 are main R&D activities for tritium and these are focused on: Task-2) Development of tritium accountancy technology, Task-3) Development of basic tritium safety research, Task-4) Tritium durability test. R&D activities of tritium technology in Phase 2-2 were underway successfully and closed in 2013.
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:17.42(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.
Hayashi, Takumi; Nakamura, Hirofumi; Kawamura, Yoshinori; Iwai, Yasunori; Isobe, Kanetsugu; Yamada, Masayuki; Suzuki, Takumi; Kurata, Rie; Oyaizu, Makoto; Edao, Yuki; et al.
Fusion Science and Technology, 67(2), p.365 - 370, 2015/03
Times Cited Count:1 Percentile:9.61(Nuclear Science & Technology)Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko
Fusion Engineering and Design, 89(7-8), p.1534 - 1538, 2014/10
Times Cited Count:8 Percentile:53.05(Nuclear Science & Technology)The ion exchange membrane such as Nafion is a key material for electrolysis cells of the Water Detritiation System. Long-term exposure of Nafion ion exchange membrane into 1.3810Bq/kg of tritiated water was conducted at room temperature for up to 2 years. The ionic conductivity of Nafion ion exchange membrane after immersed in tritiated water was changed. The change in color of membrane from colorless to yellowish was caused by active radical reactions. Infrared Fourier transform spectrum of the membrane immersed in tritiated water revealed a small peak for bending vibration of C-H situated at 1437 cm demonstrating the formation of hydrophobic functional group in the membrane. The high-resolution solid state F NMR spectrum of the membrane after immersed in tritiated water was similar to that of membrane irradiated with -rays. From the F NMR spectrum, any distinctive degradation in the membrane structure by interaction with tritium was not measured.
Kawamura, Yoshinori; Edao, Yuki; Iwai, Yasunori; Hayashi, Takumi; Yamanishi, Toshihiko
Fusion Engineering and Design, 89(7-8), p.1539 - 1543, 2014/10
Times Cited Count:8 Percentile:53.05(Nuclear Science & Technology)Tritium recovery system using adsorption or catalytic isotope exchange has already been proposed for a solid breeding blanket system of a nuclear fusion reactor. Synthetic zeolite is often used as an adsorbent or a substrate of chemical exchange catalyst. And, it is well known that its properties are changed easily by exchanging their cations. So, in this work, adsorption capacities of hydrogen isotope and water vapor on cation-exchanged mordenite with transition metal ion were investigated. Ag ion-exchanged mordenite (Ag-MOR) has indicated considerably large hydrogen adsorption capacity in lower pressure range at 77 K. And, adsorption capacity of water vapor did not so vary with exchaned cation in comparison with hydrogen adsorption. The discussion from the viewpoint of adsorption rate is still remaining, but more compact cryosorption column for tritium recovery system is possible to design if Ag-MOR is adopted.
Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko
Fusion Science and Technology, 66(1), p.214 - 220, 2014/07
Times Cited Count:4 Percentile:30.65(Nuclear Science & Technology)We have developed a honeycomb Pd catalyst applicable for the oxidation of the tritiated hydrocarbons. In this study, honeycomb Pd catalysts of three different densities, 2, 5 and 10 g/L, were prepared to investigate the effect of density on reaction rate. Tritiated methane was selected as a typical hydrocarbon. Overall reaction rate constant for tritiated methane oxidation on honeycomb Pd catalyst were determined with a flow-through system as a function of space velocity from 1000 to 6300 h, methane concentration in carrier from 0.004 to 100 ppm, temperature of catalyst from 322 to 673 K. The density of palladium deposited on the base material had little effect on reaction rate for tritiated methane oxidation. The overall reaction rate constant was proportional to the space velocity. The overall reaction rate constant was independent on the methane concentration when it was less than 10 ppm.
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.
Ueno, Yumi; Koarashi, Jun; Iwai, Yasunori; Sato, Junya; Takahashi, Teruhiko; Sawahata, Katsunori; Sekita, Tsutomu; Kobayashi, Makoto; Tsunoda, Masahiko; Kikuchi, Masamitsu
Hoken Butsuri, 49(1), p.39 - 44, 2014/03
The Japan Atomic Energy Agency has conducted a monthly monitoring of airborne C discharge at the forth research building (RI facility) of the Tokai Research and Development Center. In the current monitoring, C, which exists in various chemical forms in airborne effluent, is converted into CO with CuO catalyst and then collected using monoethanolamine (MEA) as CO absorbent. However, this collection method has some issues on safety management because the CuO catalyst requires a high heating temperature (600C) to ensure a high oxidation efficiency and the MEA is specified as a poisonous and deleterious substance. To establish a safer, manageable and reliable method for monitoring airborne C discharge, we examined collection methods that use different CO absorbents (MEA and Carbo-Sorb E) and oxidation catalysts (CuO, Pt/Alumina and Pd/ZrO). The results showed 100% CO collection efficiency of MEA during a 30-day sampling period under the condition tested. In contrast, Carbo-Sorb E was found to be unsuitable for the monthly-long CO collection because of its high volatile nature. Among the oxidation catalysts, the Pd/ZrO showed the highest oxidation efficiency for CH at a lower temperature.
Kawamura, Yoshinori; Iwai, Yasunori; Munakata, Kenzo*; Yamanishi, Toshihiko
Journal of Nuclear Materials, 442(1-3), p.S455 - S460, 2013/11
Times Cited Count:13 Percentile:69.19(Materials Science, Multidisciplinary)Zeolite easily exchanges its cation to another. In this work, synthetic mordenite type zeolite (Na-MOR) was used as start material. And, its cation (Na) has been exchanged by Li, K, Mg and Ca. Then, adsorption capacities of H and D on them were investigated at 77 K, 159 K, 175 K and 195 K. Adsorption capacities on Li-MOR and Ca-MOR became larger than that on Na-MOR at low pressure range. Oppositely, that on K-MOR became smaller. In case of alkaline metal, cation with small atomic number may lead to large adsorption capacity.
Yamanishi, Toshihiko; Kawamura, Yoshinori; Iwai, Yasunori; Isobe, Kanetsugu
Fusion Engineering and Design, 88(9-10), p.2272 - 2275, 2013/10
Times Cited Count:2 Percentile:18.46(Nuclear Science & Technology)The multi-purpose RI equipment has been constructed at Rokkasho site in DEMO R&D building until 2011. The equipment is the first and unique facility in Japan, where tritium, RI species, and beryllium can simultaneously be used. The amounts of tritium used and stored are 3.7 TBq per day and 7.4 TBq, respectively. The material of the column of the micro gas chromatograph has been studied. The calorimeter has also been studied as a possible tritium measurement method. A set of basic data on the interaction between materials and tritium has been measured especially for pure Fe. As for the tritium behavior in the blanket materials, the tritium release after neutron irradiation was studied. As a study for the tritium durability, the endurance of ion exchange membrane has been tested by using high concentration tritium water. The data of tritium water were well consistent with those obtained by irradiation.
Iwai, Yasunori; Sato, Katsumi; Kawamura, Yoshinori; Yamanishi, Toshihiko
Fusion Engineering and Design, 88(9-10), p.2319 - 2322, 2013/10
Times Cited Count:4 Percentile:32.11(Nuclear Science & Technology)The Nafion ion exchange membrane is a key material for electrolysis cells of the water detritiation system. Endurance of ion exchange membrane immersed into high-concentration tritiated water has been demonstrated under the Broader Approach activities, as a R&D on endurance of fuel cycle components at high tritium exposure. Long-term exposure of Nafion ion exchange membrane into 1.38 TBq/kg of tritiated water was conducted at room temperature for up to 2 years. The curves of percent elongation at break vs. dose and tensile strength vs. dose for the Nafion membranes immersed into tritiated water were well consistent with those for Nafion membranes irradiated to an equivalent dose with rays and electron beams. The results of ferric Fenton test indicated that the degradation directly by radiation was dominant at room temperature compared with that by reactions with radicals produced from water radiolysis. The curve of ion exchange capacity vs. dose for the Nafion membranes immersed into tritiated water was also well consistent with that for Nafion membranes irradiated to an equivalent dose with rays and electron beams. These results showed that the irradiation tests with rays and electron beams were effective to predict a degradation behavior of ion exchange membrane immersed into high-concentration tritiated water.
Edao, Yuki; Kawamura, Yoshinori; Ochiai, Kentaro; Hoshino, Tsuyoshi; Takakura, Kosuke; Ota, Masayuki; Iwai, Yasunori; Yamanishi, Toshihiko; Konno, Chikara
JAEA-Research 2012-040, 15 Pages, 2013/02
Tritium generation and recovery studies on LiTiO as a solid breeding material under neutron irradiation carried out in the Fusion Neutron Source (FNS) facility. A capsule with LiTiO packed bed was put in a system which simulated an actual blanket system which built in beryllium blocks and lithium titanate ones. Estimated values of the amount of tritium generation by a numerical calculation agreed closely with experimental values. The capsule was heated up to 300C, and helium, helium with water vapor, hydrogen or hydrogen/water vapor were selected as purge gas. In the case of purge by helium added water vapor, the ratio of HTO to total tritium release was 98%. In helium with hydrogen/water vapor purge, the ratio of HTO to total tritium release was 80%, which was confirmed that HTO released by isotope exchange reaction between water vapor and tritium. In helium with hydrogen purge, the ratio of HT to total tritium release was 6070%, which was shown that HT released by isotope exchange reaction between hydrogen gas and tritium. HTO released by water generation reaction between hydrogen in purge gas and oxygen in LiTiO although water vapor was not added in purge gas. The ratio of HTO release seemed to be small under the deoxidized condition of the LiTiO surface. Tritium release behavior in the LiTiO depended on the composition of purge gas, and its chemical form was affected by the surface conditions of LiTiO.
Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko
Fusion Engineering and Design, 87(7-8), p.946 - 950, 2012/08
Times Cited Count:7 Percentile:48.00(Nuclear Science & Technology)The catalytic performance should be maintained in any off normal events. Fire accident is the typical off normal event. In the fusion plant, typical combustibles are evaluated to be polymeric low-halogen cables. Produced gases from burned low-halogen cable may affect the activity of catalysts for the oxidation of tritium. We experimentally demonstrated the influence of produced gases from burned low-halogen cable on the activity of catalyst using tritium gas. Our analyzed result showed that ethylene, methane and benzene were major produced gases. The activity of catalysts for the oxidation of tritium during a fire event was evaluated using two types of commercial Pt catalysts which are the hydrophilic Pt/AlO and the new type hydrophobic catalyst named TKK-H1P especially developed for the room temperature conversion of tritium to tritiated vapor. The temperature of catalytic reactor was selected to be 423 or 293 K. At 423 K, no considerable decrease in catalytic activity was observed for both catalysts even in the presence of produced gases from burned low-halogen cable. At 293K, considerable increase in catalytic activity was initially observed for both catalysts due to the effect of produced hydrogen. Then the temporary decrease was observed, however the catalytic activity was gradually recovered to be the original activity. Consequently, the irreversible decrease in activity of the catalysts during a fire event was not observed.