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O solutionKumagai, Yuta; Kusaka, Ryoji; Takano, Masahide; Watanabe, Masayuki
Journal of Nuclear Materials, 625, p.156553_1 - 156553_7, 2026/04
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Uranium-zirconium oxide solid solution, (U, Zr)O, is a representative matrix phase found in fuel debris formed during severe nuclear reactor accidents. Understanding its chemical behavior in oxidative aqueous environments is important for evaluating the potential release of radionuclides during water contact. In this study, we investigated the reactivity of (U, Zr)O with hydrogen peroxide (HO) in pure water to assess its resistance to oxidative dissolution, because HO is the dominant oxidant produced by water radiolysis. The dissolution behavior of uranium and zirconium was monitored through repeated HO exposure experiments, and the solid phases were characterized using Raman micro-spectroscopy and X-ray diffraction. Kinetic modeling was performed to interpret experimental data. The results showed that uranium dissolution occurred initially but decreased significantly upon repeated HO exposure, while zirconium dissolution proceeded more slowly. Raman analysis revealed only minor surface changes, with limited formation of uranyl peroxide phases. The kinetic simulation reproduced the experimental trends by assuming a small fraction of redox-active surface sites. These findings suggest that the observed durability of (U, Zr)O against HO-induced oxidative dissolution is not due to the formation of a protective surface layer, but rather reflects the limited redox reactivity of most of the surface. This study provides a quantitative basis for understanding the HO-induced oxidation of (U, Zr)O in water, relevant to the long-term behavior of fuel debris.
Yoshida, Naoki; Ono, Takuya; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi
JAEA-Research 2021-011, 12 Pages, 2022/01
JAEA-Research-2021-011.pdf:1.49MB
In boiling and drying accidents involving high-level liquid waste in fuel reprocessing plants, emphasis is placed on the behavior of ruthenium (Ru). Ru would form volatile species, such as ruthenium tetroxide (RuO
), and could be released to the environment with coexisting gases, including nitric acid, water, or nitrogen oxides. In this study, to contribute toward safety evaluations of these types of accidents, the migration behavior of gaseous Ru into the liquid phase has been experimentally measured by simulating the condensate during an accident. The gas absorption of RuO was enhanced by increasing the nitrous acid (HNO
) concentration in the liquid phase, indicating the occurrence of chemical absorption. In control experiments without HNO, the lower the temperature, the greater was the Ru recovery ratio in the liquid phase. Conversely, in experiments with HNO, the higher the temperature, the higher the recovery ratio, suggesting that the reaction involved in chemical absorption was activated at higher temperatures.
Yoshida, Naoki; Amano, Yuki; Ono, Takuya; Yoshida, Ryoichiro; Abe, Hitoshi
JAEA-Research 2020-014, 33 Pages, 2020/12
JAEA-Research-2020-014.pdf:3.66MB
Considering the boiling and drying accident of high-level liquid waste in fuel reprocessing plant, Ruthenium (Ru) is an important element. It is because Ru would form volatile compounds such as ruthenium tetroxide (RuO) and could be released into the environment with other coexisting gasses such as nitric oxides (NOx) such as nitric oxide (NO) and nitrogen dioxide (NO). To contribute to the safety evaluation of this accident, we experimentally evaluated the effect of NOx on the decomposition and chemical change behavior of the gaseous RuO (RuO(g)). As a result, the RuO(g) decomposed over time under the atmospheric gasses with NO or NO, however, the decomposition rate was slower than the results of experiments without NOx. These results showed that the NOx stabilized RuO(g).
Ando, Masaki; Nakano, Yoshihiro; Okajima, Shigeaki; Kawasaki, Kenji
JAERI-Research 2003-029, 72 Pages, 2003/12
JAERI-Research-2003-029.pdf:3.41MB
The objectives of this study is to clarify calculation accuracy for the Doppler effect of the resonance materials; erbium (Er), tungsten (W) and thorium (ThO). Doppler effect measurements were carried out in a fast neutron spectrum (XX-2 core) and in an intermediate neutron spectrum (XXI-1D2 core) by the sample-heated and reactivity worth measurement method up to 800
C using FCA. The experiment was analyzed with the standard analysis method for fast reactor cores at FCA with the use of the JENDL-3.2. The SRAC system was also used to investigate the calculation accuracy of the system and to compare it with that of the FCA standard analysis method. The standard analysis method underestimated for the XX-2 core and agreed the experiments within the experimental errors for the XXI-1D2 core. The analysis with the SRAC system gave smaller values by 3%
10% for the Er sample and bigger values by 2%5% for the W sample than the standard analysis method.
Ando, Masaki; Nakano, Yoshihiro; Okajima, Shigeaki; Kawasaki, Kenji
Journal of Nuclear Materials, 319, p.126 - 130, 2003/06
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Doppler effect experiments on resonance materials for ROX fuels were carried out to examine the calculation accuracy in the intermediate neutron spectrum using Fast Critical Assembly (FCA) at Japan Atomic Energy Research Institute. This study is the second phase of a series of the Doppler effect experiments on the resonance materials, which is following the measurements in the fast neutron spectrum. The Doppler effect was measured as the sample reactivity change between the heated and unheated samples. The cylindrical samples of the resonance materials such as erbium (Er), tungsten (W) and thorium (ThO) were used. The sample was heated up to 800C at the center of the FCA core. The Doppler effect measurements were analyzed using the SRAC 95 code system with the use of JENDL 3.2. The calculated values agreed with the experiment within the experimental error for the W and ThO samples, while the calculation overestimated the experiment for the Er sample about 10 %.
Nakamura, Takehiko; Kusagaya, Kazuyuki*; Yoshinaga, Makio; Uetsuka, Hiroshi; Yamashita, Toshiyuki
Progress in Nuclear Energy, 38(3-4), p.379 - 382, 2001/02
Times Cited Count：8 Percentile：50.95(Nuclear Science & Technology)no abstracts in English
Yanagisawa, Kazuaki; Yamashita, Toshiyuki; Kanazawa, Hiroyuki; Amano, Hidetoshi; Muromura, Tadasumi
Journal of Nuclear Science and Technology, 36(12), p.1153 - 1159, 1999/12
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)no abstracts in English
Yanagisawa, Kazuaki; Yamashita, Toshiyuki; Kanazawa, Hiroyuki; Amano, Hidetoshi; Muromura, Tadasumi
Journal of Nuclear Science and Technology, 36(11), p.1052 - 1063, 1999/11
Times Cited Count：1 Percentile：13.15(Nuclear Science & Technology)no abstracts in English
Yanagisawa, Kazuaki; Omichi, Toshihiko*; Shirasu, Noriko; Yamashita, Toshiyuki; ; Onozawa, Atsushi; ; Kanazawa, Hiroyuki; Kanaitsuka, Fumio; Amano, Hidetoshi
JAERI-Tech 99-044, 46 Pages, 1999/05
no abstracts in English
Yanagisawa, Kazuaki; Omichi, Toshihiko*; Shirasu, Noriko; Muromura, Tadasumi;
JAERI-Tech 99-032, 65 Pages, 1999/03
no abstracts in English
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JAERI-M 82-202, 50 Pages, 1982/12
no abstracts in English
in the presence of adsorbed phthalic acidKumagai, Yuta; Jonsson, M.*
no journal, ,
Contact of water with spent nuclear fuel is anticipated in scenarios of failure of the repository system for the direct disposal of spent fuel. Upon the direct contact of water, the UO matrix of the fuel is expected to gradually dissolve due to oxidation of uranium by the action of ionizing radiation. In this study, we examined effects of organic acid on the UO dissolution by using phthalic acid as a model compound. We investigated oxidation of UO by exposure to HO in aqueous solution containing phthalic acid. Significant adsorption of phthalic acid on UO was observed. The coverage of the surface was estimated to reach 80 %. The HO-exposure experiments revealed that adsorbed phthalic acid has no significant effect on the redox reaction by HO on the UO surface, despite the high surface density. HO oxidation of UO with adsorbed phthalic acid resulted in U dissolution to similar extents with the U dissolution measured in aqueous bicarbonate solutions.
