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Journal Articles

Uranium-plutonium-oxygen phase diagram; Investigating the solvus of fluorite's exsolution

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

https://doi.org/10.1016/j.jnucmat.2024.155233

Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)

The fluorite exsolution/recombination in U $_{1-y}$ Pu $_{y}$ O $_{2-x}$ (y = 0.30 and 0.45) and PuO $_{2-x}$ 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 3050 K lower than previously reported. Finally, the systematic experimental procedure allowed us refining the locus of the solvus existing in hypostoichiometric U $_{0.70}$ 0Pu $_{0.30}$ O $_{2-x}$ , U $_{0.55}$ Pu $_{0.45}$ O $_{2-x}$ , and PuO $_{2-x}$ dioxides.

Journal Articles

Oxygen potential measurement of U $_{0.85}$ Am $_{0.15}$ O $_{2}$ at 1473, 1573, and 1673 K

Watanabe, 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

https://doi.org/10.1016/j.jnucmat.2024.155232

Times Cited Count：2 Percentile：86.32(Materials Science, Multidisciplinary)

Oxygen potential data of U $_{0.85}$ Am $_{0.15}$ O $_{2-x}$ were measured at 1473, 1573, and 1673 K by thermogravimetry. In U $_{1-y}$ An $_{y}$ O $_{2-x}$ , where An stands for Pu or Am, and for a given value of y and Oxygen/Metal ratio, the oxygen potential of U $_{1-y}$ Am $_{y}$ O $_{2-x}$ is higher than that of U $_{1-y}$ Pu $_{y}$ O $_{2-x}$ . The valence of cations in the hypostoichiometric region is similar to that of Nd-doped UO $_{2}$ . At the stoichiometric composition, it is estimated to be Am $^{3+}$ , U $^{4+}$ , and U $^{5+}$ (for charge compensation of Am $^{3+}$ ). 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.

Journal Articles

Oxygen potential of neodymium-doped U $_{0.817}$ Pu $_{0.180}$ Am $_{0.003}$ O $_{2 pm x}$ uranium-plutonium-americium mixed oxides at 1573, 1773, and 1873 K

Vauchy, R.; Sunaoshi, Takeo*; Hirooka, Shun; Nakamichi, Shinya; Murakami, Tatsutoshi; Kato, Masato

Journal of Nuclear Materials, 580, p.154416_1 - 154416_11, 2023/07

https://doi.org/10.1016/j.jnucmat.2023.154416

Times Cited Count：9 Percentile：94.05(Materials Science, Multidisciplinary)

Journal Articles

Modeling and simulation of redistribution of oxygen-to-metal ratio in MOX

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.

Journal Articles

Oxygen thermochemistry of urania-rare earth system; UO-CeO

Hirooka, Shun; Murakami, Tatsutoshi; Nelson, A. T.*; McClellan, K. J.*

INL/EXT-14-33515, p.34 - 36, 2014/10

https://doi.org/10.2172/1169217

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 $^{circ}$ C, 1400 $^{circ}$ C and 1600 $^{circ}$ C. 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.

JAEA Reports

Power-to-melt evaluation of fresh mixed-oxide fast reactor fuel; Technicall improvements of the post-irradiation-experiment and the evaluation of the results for the power-to-melt test FTM-2 in "JOYO"

; ;

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.

Journal Articles

Thermodynamic properties of Th $_{0}$ $_{.}$ $_{8}$ $_{0}$ U $_{0}$ $_{.}$ $_{2}$ $_{0}$ O $_{2}$ $_{+}$ $_{x}$ solid solution

Ugajin, Mitsuhiro; ; Shiba, Koreyuki

Journal of Nuclear Materials, 116(2-3), p.172 - 177, 1983/00

https://doi.org/10.1016/0022-3115(83)90099-5

Times Cited Count：16 Percentile：82.79(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Oxygen potentials of(Th,U)O $_{2}$ $_{+}$ $_{x}$ solid solutions

Ugajin, Mitsuhiro

Journal of Nuclear Materials, 110, p.140 - 146, 1982/00

https://doi.org/10.1016/0022-3115(82)90138-6

Times Cited Count：25 Percentile：89.10(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

On the relation between lattice parameter and O/M ratio for uranium dioxide-trivalent rare earth oxide solid solution

; ; ;

Journal of Nuclear Materials, 102, p.40 - 46, 1981/00

https://doi.org/10.1016/0022-3115(81)90544-4

Times Cited Count：156 Percentile：99.69(Materials Science, Multidisciplinary)

no abstracts in English

Patent

組成分析方法及び組成分析装置、硬度算出方法及び硬度算出装置

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。

Oral presentation

Oxygen potential measurement of (U,Ce)O $_{2}$

Murakami, Tatsutoshi; Kato, Masato; Nelson, A.*; McClellan, K.*

no journal, ,

no abstracts in English

Oral presentation

Measurement and Pu-content dependence of (U,Pu)O $_{2}$ $_{pm}$ $_{x}$ oxygen potential

Horii, Yuta; Hirooka, Shun; Vauchy, R.; Sunaoshi, Takeo*; Saito, Kosuke

no journal, ,

Oral presentation

Evaluation of (U,Ce)O $_{2}$ thermal conductivity

Hirooka, Shun; Kato, Masato; Nelson, A.*; McClellan, K.*; White, J.*

no journal, ,

Thermal diffusivity of (U,Ce)O $_{2}$ was measured as a function of O/M, and the thermal conductivity was calculated. Thermal conductivity of (U,Ce)O $_{2}$ decreased more sharply with increasing temperature compared with that of (U,Pu)O $_{2}$ . Also, thermal conductivity of (U,Ce)O $_{2}$ showed the highest peak at O/M of 2 and decreased as the O/M is apart from 2 on both hypo-stoichiometric and hyper-stoichimetric regions.

Oral presentation

The Oxygen potential measurement of (U $_{0.623}$ Pu $_{0.35}$ Am $_{0.027}$ )O $_{2{pm}x}$ under high temperature

Matsumoto, Taku; Kato, Masato; Morimoto, Kyoichi; Sunaoshi, Takeo*

no journal, ,

The oxygen potentials of (U $_{0.623}$ Pu $_{0.35}$ Am $_{0.027}$ )O $_{2{pm}x}$ were measured as a function of oxygen to metal ratio (O/M) in the temperature range from 1673 to 1873 K by the gas equilibrium method using thermogravimetry. The measured oxygen potentials were analyzed by the point defect chemistry method. From this analysis, the oxygen potential of (U $_{0.623}$ Pu $_{0.35}$ Am $_{0.027}$ )O $_{2{pm}x}$ was represented as a function of O/M ratio and temperature.

Oral presentation

Evaluation of fuel behaviors by using science-based integrated models for MOX properties, 1; Evaluation of O/M redistribution

Hirooka, Shun; Kato, Masato; Watanabe, Masashi

no journal, ,

no abstracts in English

Oral presentation

Oxygen potentials of Am and Np-bearing MOX

Hirooka, Shun; Matsumoto, Taku; Kato, Masato; Sunaoshi, Takeo*

no journal, ,

Oxygen potentials of (U $_{0.553}$ Pu $_{0.285}$ Am $_{0.015}$ Np $_{0.147}$ )O $_{2-x}$ pellet sintered in the atmosphere of Ar/H $_{2}$ /H $_{2}$ O mixture gas were measured at 1600 $^{circ}$ C and 1650 $^{circ}$ C by the gas equilibrium method. The oxygen partial pressure of the atmosphere was accurately adjusted by changing H $_{2}$ O content in the gas and monitored with oxygen sensors. Simultaneously, weight change originated by oxidation or reduction was measured by thermo-gravimetry method and O/M was calculated by the weight change. The measured data showed that the substitution of minor actinide with U increased the oxygen potential, indicating that O/M could be lowered by adding minor actinide if temperature and oxygen partial pressure of the surrounding gas was preserved. The present data was analyzed together with the previous Am-MOX data and led to the results that containing 1% of Am is equivalent to 4% of Pu on the effect of oxygen potential. Similarly, 1% of Np is equivalent to 0.2% of Pu. These effects were reflected to the defect formation energies and the relation among O/M, temperature, content ratio and oxygen partial pressure was derived. This relation can evaluate O/M of MA-MOX more accurately and, therefore, is the useful fuel technology for fuel design and evaluating irradiation behaviors.