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Kato, Masato; Oki, Takumi; Watanabe, Masashi; Hirooka, Shun; Vauchy, R.; Ozawa, Takayuki; Uwaba, Tomoyuki; Ikusawa, Yoshihisa; Nakamura, Hiroki; Machida, Masahiko
Journal of the American Ceramic Society, 107(5), p.2998 - 3011, 2024/05
Times Cited Count：0 Percentile：0.01(Materials Science, Ceramics)Kawamoto, Keisuke*; Ochiai, Asumi*; Takeda, Ayaka*; Nakano, Yuriko*; Yokoo, Hiroki*; Oki, Takumi*; Onuki, Toshihiko*; Ohara, Yoshiyuki; Fukuyama, Kenjin; Utsunomiya, Satoshi*
no journal, ,
In the Ningyo-toge uranium mine, Okayama, Japan, various toxic elements such as U, As, and Ra are present in the mine wastewaters, of which the concentration except for Ra in the wastewater decrease below the regulatory limit by transport to the slag dumping pond. The mechanisms of decreasing their concentrations in the wastewaters are not fully understood. In order to understand the fundamental processes of natural attenuation at this site, we have investigated the wastewaters and solids from upstream to the pond at the downstream. Wastewater was contacted with oxygenated water and the amount of dissolved oxygen increased. Simultaneously dissolved ferrous iron was oxidized to form ferrihydrite nanoparticles, which are associated with silica colloids, As and U. The ferrihydrite nanoparticles as suspended colloids were transported to the pond in downstream, where the waste stream is completely oxidized. In the slag dumping pond, Mn dioxide, birnessite, dominantly occurs forming a mixture with ferrihydrite + silica colloid, which has a potential to adsorb Ra
. Consequently, Fe hydroxides nanoparticles and Mn dioxides in Ningyo-toge play a key role on removing U, As and Ra from the wastewater.
Yokoo, Hiroki*; Kawamoto, Keisuke*; Oki, Takumi*; Uehara, Motoki*; Onuki, Toshihiko*; Ohara, Yoshiyuki; Fukuyama, Kenjin; Hochella, M. F. Jr.*
no journal, ,
no abstracts in English
Oki, Takumi; Kato, Masato; Ikusawa, Yoshihisa; Hirooka, Shun
no journal, ,
The thermal conductivity in high temperature range considering Bredick transition was studied based on the irradiation test data, and the irradiation behavior was evaluated using our analytical code. The thermal conductivity considering Bredick transition increases from around 1500 K and peaks around 2200 K. By evaluating the irradiation behavior using this thermal conductivity, it was confirmed that the fuel center temperature from low temperature range to just below the melting point reproduced the measured value.
Kato, Masato; Hirooka, Shun; Watanabe, Masashi; Vauchy, R.; Oki, Takumi
no journal, ,
no abstracts in English
Oki, Takumi; Kato, Masato; Ikusawa, Yoshihisa
no journal, ,
JAEA has been developing a MOX(Mixed Oxide) fuel irradiation behavior analysis code based on a scientific fuel property model for the development of future fast reactor fuels. In this study, we investigated a new MOX thermal conductivity model incorporating the dependence of the Bredig transition on plutonium and minor actinide content, and evaluated the results of post-irradiation examinations of MOX fuel irradiated in JOYO using the irradiation behavior analysis code. As a result, it was expected that the thermal conductivity model can reproduce the measured fuel center temperature from low temperature to just below the melting point, as well as the fuel restructuring.
