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Hirooka, Shun; Vauchy, R.; Horii, Yuta; Sunaoshi, Takeo*; Saito, Kosuke
Proceedings of TopFuel 2025; Nuclear Reactor Fuel Performance Conference (Internet), 10 Pages, 2025/10
Reducing the oxygen-to-metal (O/M) ratio in MOX fuels plays an important role in suppressing the corrosion depth in the cladding due to fuel-cladding chemical interaction (FCCI), which is the key to determining the lifetime of fast reactor MOX fuels. Owing to a number of irradiation and post-irradiation experiments, a clear decreasing trend in the corrosion depth with lower O/M ratio in the as-fabricated MOX pellet was reported, whereas a significant redistribution of the O/M ratio in a pellet driven by the radial temperature gradient during irradiation could supply a higher oxygen potential near the pellet periphery where the FCCI should occur. The reduction of the O/M ratio in the MOX pellet fabrication processes can be achieved by heat treatment by taking high temperature, longer time, and lower oxygen partial pressure in the gas into account; the properties governing the reduction are not sufficiently studied. This study demonstrated the variation of O/M ratio in MOX pellets and the in-situ O/M ratio during the heat treatment was analyzed by using a thermogravimeter, which revealed a decreasing behavior during heating and dwell as well as an increasing behavior in the O/M ratio during the cooling step. Furthermore, the redistribution of O/M ratio, analyzed by Sari's model, was discussed to investigate the O/M ratio and the oxygen potential near the pellet periphery which is likely to have a more direct influence on the FCCI than the as-fabricated O/M ratio. By using the recent oxygen potential data on MOX, it is found that the oxygen potential profile in the radial direction is especially drastic near the pellet periphery and is sensitive to the as-fabricated O/M ratio.
Hirooka, Shun; Vauchy, R.; Horii, Yuta; Sunaoshi, Takeo*; Saito, Kosuke; Ozawa, Takayuki
Proceedings of Workshop on Fuel Performance Assessment and Behaviour for Liquid Metal Cooled Fast Reactors (Internet), 8 Pages, 2025/07
no abstracts in English
Vauchy, R.; Hirooka, Shun; Horii, Yuta; Ogasawara, Masahiro*; Sunaoshi, Takeo*; Yamada, Tadahisa*; Tamura, Tetsuya*; Murakami, Tatsutoshi
Journal of Nuclear Materials, 599, p.155233_1 - 155233_11, 2024/10
Times Cited Count：2 Percentile：38.41(Materials Science, Multidisciplinary)The fluorite exsolution/recombination in U
Pu
O
(y = 0.30 and 0.45) and PuO was investigated using differential scanning calorimetry. The results are in relatively good agreement with the literature data, except for plutonia. Our values indicate that the critical temperature of the miscibility gap in Pu-O is 30
50 K lower than previously reported. Finally, the systematic experimental procedure allowed us refining the locus of the solvus existing in hypostoichiometric U
0Pu
O, U
Pu
O, and PuO dioxides.
Am
O
at 1473, 1573, and 1673 KWatanabe, Masashi; Yokoyama, Keisuke; Vauchy, R.; Kato, Masato; Sugata, Hiromasa*; Seki, Takayuki*; Hino, Tetsushi*
Journal of Nuclear Materials, 599, p.155232_1 - 155232_5, 2024/10
Times Cited Count：3 Percentile：53.66(Materials Science, Multidisciplinary)Oxygen potential data of UAmO were measured at 1473, 1573, and 1673 K by thermogravimetry. In UAnO, where An stands for Pu or Am, and for a given value of y and Oxygen/Metal ratio, the oxygen potential of UAmO is higher than that of UPuO. The valence of cations in the hypostoichiometric region is similar to that of Nd-doped UO. At the stoichiometric composition, it is estimated to be Am
, U
, and U
(for charge compensation of Am). The experimental data were analyzed using a defect chemistry model, and a relationship connecting the oxygen-to-metal ratio, the temperature, and the equilibrium oxygen partial pressure was proposed.
Pu
Am
O
uranium-plutonium-americium mixed oxides at 1573, 1773, and 1873 KVauchy, R.; Sunaoshi, Takeo*; Hirooka, Shun; Nakamichi, Shinya; Murakami, Tatsutoshi; Kato, Masato
Journal of Nuclear Materials, 580, p.154416_1 - 154416_11, 2023/07
Times Cited Count：10 Percentile：84.29(Materials Science, Multidisciplinary)Hirooka, Shun; Kato, Masato; Watanabe, Masashi
Transactions of the American Nuclear Society, 118, p.1624 - 1626, 2018/06
This study suggested the time development of oxygen-to-metal ratio (O/M) redistribution model with oxygen-related properties in MOX. Irradiation simulation including the suggested O/M redistribution and pore migration with vaporization-condensation model which bares density redistribution was demonstrated. The simulation results showed that O/M redistribution proceeded at lower temperature than density redistribution, which indicated that oxygen diffusion got influential at lower temperature than vaporization-condensation of MOX. Another find was that O/M redistribution was very slow at the surface because temperature kept low. However, near the surface (inside from the surface) where the temperature exceeded 1000 K, O/M redistribution was rather recognizable with oxygen flown from inner region to the near-surface. The results will be evaluated by comparison with post-irradiation examination data.
-CeOHirooka, Shun; Murakami, Tatsutoshi; Nelson, A. T.*; McClellan, K. J.*
INL/EXT-14-33515, p.34 - 36, 2014/10
Collaborative study has been done on the properties of nuclear materials between the DOE and Japan and the oxygen potential of (U,Ce)O was measured in this year. Experimental measurements of the oxygen potential were conducted on Ce=20% and 30% composition rates simulating Pu content in advanced MOX fuel in JAEA by gas equilibrium method where oxygen partial pressure in the atmosphere was controlled with mixing dry/wet Ar/H gas. More than 100 data points were obtained in the O/M range of 1.945 2.000 at 1200
C, 1400C and 1600C. The experimental results were analyzed by the defect analysis and analytical equations were obtained to calculate O/M as functions of temperature and oxygen potential. From the comparison with that of (U,Pu)O, applicability of the same defect chemistry and S-style curve are common. Also, it is revealed that (U,Ce)O requires evidently higher oxygen potential for the O/M.
; ;
JNC TN9400 2000-029, 87 Pages, 1999/11
JNC-TN9400-2000-029.pdf:5.11MB
The second Power-To-Melt (PTM) test, PTM-2, was performed in the experimental fast reactor "JOYO". AIl of the twenty-four fuel pins of the irradiation vehicle, B5D-2, for the PTM-2 test, were provided for post-irradiation-experiment (PIE) to evaluate the PTM values. ln this study, the PIE technique for PTM test was established and the PTM results were evaluated. The findings are as follows: (1) The maximum fuel-melting ratio on the transverse section was 10.7%, and was within the limit of fuel-melting in this PTM test enough. Unexpected fuel-melting amount to a ratio of 11.8% was found at 24 mm below the peak power elevation in a test fuel pin, lt is possible that this arose from secondary fuel-melting. (2) Combination of metallographical observation with X-ray microanalysis of plutonium distribution was very effective for the identification of once-molten fuel zone. (3) The PTM evaluation suggested that dependence of the PTM on the fuel pellet density was stronger than that of previous foreign PTM tests, while the dependence on the pellet-cladding gap and the oxygen-to-metal ratio was indistinctly. The dependence on the cladding temperature and the fill gas composition was not shown as well.
UO
solid solutionUgajin, Mitsuhiro; ; Shiba, Koreyuki
J. Nucl. Mater., 116(2-3), p.172 - 177, 1983/00
Times Cited Count：16 Percentile：82.51(Materials Science, Multidisciplinary)no abstracts in English
solid solutionsUgajin, Mitsuhiro
J. Nucl. Mater., 110, p.140 - 146, 1982/00
Times Cited Count：25 Percentile：88.86(Materials Science, Multidisciplinary)no abstracts in English
; ; ;
J. Nucl. Mater., 102, p.40 - 46, 1981/00
Times Cited Count：163 Percentile：99.71(Materials Science, Multidisciplinary)no abstracts in English
阿部 雄太; 中桐 俊男
川上 智彦*
JP, 2018-199316 Patent licensing information Patent publication (In Japanese)
【課題】金属を主成分とする材料中のO、Bの組成や材料の硬度を非接触で精密に算出できる。 【解決手段】図5の関係より、上記の方法で算出された(B/O)/M値のみからビッカース硬度を推定することは一般的には困難である。しかしながら、試料が図5におけるZを挟んだどちらの領域にあるかを判定することができれば、(B/O)/M値からビッカース硬度を推定することができる。前記の通り、図5におけるZよりも左側の領域はOの組成比が大きい場合であり、Zよりも右側の領域はBの組成比が大きな場合に対応する。このため、前記のO/M値、B/M値に応じてこの試料がどちらの領域に属するかを認識することができる。結局、(B/O)/M値から前記の一次式を用いてビッカース硬度を算出することができる。
Hirooka, Shun; Vauchy, R.; Horii, Yuta; Akashi, Masatoshi; Sunaoshi, Takeo*; Saito, Kosuke
no journal, ,
no abstracts in English
Akashi, Masatoshi; Hirooka, Shun; Saito, Kosuke
no journal, ,
no abstracts in English
Hirooka, Shun; Vauchy, R.; Yamada, Tadahisa*; Furusawa, Naoya*; Akashi, Masatoshi; Saito, Kosuke
no journal, ,
no abstracts in English
Horii, Yuta; Hirooka, Shun; Vauchy, R.; Uno, Hiroki*; Tamura, Tetsuya*; Sunaoshi, Takeo*; Saito, Kosuke
no journal, ,
no abstracts in English
Vauchy, R.; Akashi, Masatoshi; Hirooka, Shun; Sunaoshi, Takeo*; Furusawa, Naoya*; Nakamichi, Shinya; Saito, Kosuke
no journal, ,
The O/M ratio of MOX pellets for fast reactors is adjusted by heat treatment in reducing gas. However, in mass-production sintering furnaces, O/M ratios below 1.98 cannot be achieved due to poor gas flow. In this study, we experimentally evaluated a carbothermal reduction method in which carbon powder is added to MOX powder and sintered as an alternative to the low O/M ratio adjustment technique using reducing gas.
Horii, Yuta; Hirooka, Shun; Vauchy, R.; Sunaoshi, Takeo*; Saito, Kosuke
no journal, ,
no abstracts in English
oxygen potentialHorii, Yuta; Hirooka, Shun; Vauchy, R.; Sunaoshi, Takeo*; Saito, Kosuke
no journal, ,
Murakami, Tatsutoshi; Kato, Masato; Nelson, A.*; McClellan, K.*
no journal, ,
no abstracts in English
