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Journal Articles

Evaluation of oxidation efficiency of hydrophobic palladium catalyst for $$^{3}$$H monitoring in radioactive gaseous waste

Furutani, Misa; Kometani, Tatsunari; Nakagawa, Masahiro; Ueno, Yumi; Sato, Junya; Iwai, Yasunori*

Hoken Butsuri (Internet), 55(2), p.97 - 101, 2020/06

https://doi.org/10.5453/jhps.55.97

Herein, an oxidation catalyst was introduced after heating it to 600$$^{circ}$$C to oxidize tritium gas (HT) existing in exhaust into tritiated water vapor (HTO). This study aims to establish a safer $$^{3}$$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$$_{2}$$), and platinum/aluminum oxide (Pt/Al$$_{2}$$O$$_{3}$$) 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$$_{2}$$ and Pt/Al$$_{2}$$O$$_{3}$$ catalysts could oxidize HT into HTO at 25$$^{circ}$$C.

Journal Articles

Evaluation of oxidation efficiency of hydrophobic palladium catalyst for $$^{14}$$C monitoring in gaseous radioactive waste

Ueno, Yumi; Nakagawa, Masahiro; Sato, Junya; Iwai, Yasunori

Hoken Butsuri, 51(1), p.7 - 11, 2016/03

https://doi.org/10.5453/jhps.51.7

In the Nuclear Science Research Institute, Japan Atomic Energy Agency (JAEA), in order to oxidize $$^{14}$$C, which exists in various chemical forms in exhaust, into $$^{14}$$CO$$_{2}$$, a copper oxide (CuO) catalyst is introduced after heating to 600$$^{circ}$$C. Our goal was to establish a safer $$^{14}$$C monitoring system by lowering the heating temperature required for the catalyst; therefore, we developed a new hydrophobic palladium/silicon dioxide (Pd/SiO$$_{2}$$) catalyst that makes the carrier's surface hydrophobic. In these experiments, catalysts CuO, platinum/aluminum oxide (Pt/Al$$_{2}$$O$$_{3}$$), palladium/zirconium dioxide (Pd/ZrO$$_{2}$$), hydrophobic Pd/SiO$$_{2}$$, and hydrophilic Pd/SiO$$_{2}$$ 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$$_{2}$$ catalyst had the best oxidation efficiency. By substituting the currently used CuO catalyst with the hydrophobic Pd/SiO$$_{2}$$ catalyst, we will be able to lower the working temperature from 600$$^{circ}$$C to 300$$^{circ}$$C and improve the safety of the monitoring process.

Journal Articles

Radiation dose of aircrews during a solar proton event without ground-level enhancement

Kataoka, Ryuho*; Nakagawa, Yumi*; Sato, Tatsuhiko

Annales Geophysicae (Internet), 33(1), p.75 - 78, 2015/07

https://doi.org/10.5194/angeo-33-75-2015
 Times Cited Count：8 Percentile：27.53(Astronomy & Astrophysics)

A significant enhancement of radiation dose is expected for aircrews during ground-level enhancement (GLE) events, while the possible radiation hazard remains open question during on-GLE solar energetic particle (SEP) events. Using a new air shower simulation driven by the proton flux data obtained from GOES satellites, we show the possibility of significant enhancement of the effective dose rate of up to 4.5 $$mu$$Sv/h$$^{-1}$$ at conventional flight altitude of 12 km during the largest SEP event which did not cause a GLE. As a result, new GOES-driven model is proposed to give the upper limit of the radiation dose in the stratosphere during non-GLE SEP events.

JAEA Reports

Survey of radiation protection creiteria following the accident at the Fukushima Dai-ichi Nuclear Power Plant

Yamada, Katsunori; Fujii, Katsutoshi; Kanda, Hiroshi; Higashi, Daisuke; Kobayashi, Toshiaki; Nakagawa, Masahiro; Fukami, Tomoyo; Yoshida, Keisuke; Ueno, Yumi; Nakajima, Junya; et al.

JAEA-Review 2013-033, 51 Pages, 2013/12

JAEA-Review-2013-033.pdf:2.73MB

After the accident at Fukushima Dai-ichi Nuclear Power Plant, various numerical criteria relevant to radiation protection were defined. We surveyed these criteria through internet. As a result of survey, the following 13 items were identified: (1) criteria for taking stable iodine tablets, (2) criteria for the screening of surface contamination, (3) evacuation area, sheltering area, etc., (4) activity concentrations in food, drinking water, etc., (5) dose limit for radiation workers engaged in emergency work, (6) guideline levels of radioactive substances in bathing areas, (7) criteria for use of school buildings and schoolyards, (8) restriction on planting rice, (9) acceptable activity concentrations in feedstuff, (10) acceptable activity concentrations in compost, (11) criteria for export containers and ships, (12) criteria for contaminated waste, (13) standards for radiation workers engaged in decontamination work. In this report, the basis of and issues on these criteria are summarized.

Oral presentation

Evaluation of oxidation efficiency of hydrophobic palladium catalyst used for monitoring $$^{3}$$He in radioactive gaseous waste

Kometani, Tatsunari; Furutani, Misa; Nakagawa, Masahiro; Ueno, Yumi; Sato, Junya

no journal, , 

no abstracts in English

Oral presentation

Evaluation of oxidation efficiency of hydrophobic palladium catalyst for $$^{14}$$C monitoring in gaseous radioactive waste in reprocessing plant and RI using facilities

Ueno, Yumi; Nakagawa, Masahiro; Sato, Junya; Iwai, Yasunori

no journal, , 

no abstracts in English

6 (Records 1-6 displayed on this page)
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