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Journal Articles

Thermal expansion of PuO $_{2}$

Uchida, Teppei; Sunaoshi, Takeo*; Konashi, Kenji*; Kato, Masato

Journal of Nuclear Materials, 452(1-3), p.281 - 284, 2014/09

https://doi.org/10.1016/j.jnucmat.2014.05.039

Times Cited Count：9 Percentile：57.01(Materials Science, Multidisciplinary)

Experiment and simulation studies on physical properties of actinide oxides have been carried out. Thermal expansion is important data to evaluate the various properties from molecular dynamics (MD) simulation. In this study, thermal expansion of PuO $_{2}$ was evaluated by experiment and MD simulation. In the experimental study, thermal expansion of PuO $_{2.00}$ pellet was determined by a dilatometer in the temperature range of 300-1923 K. In the MD simulation, Born-Mayer-Huggins interatomic potential with a partially ionic model and Morse potential were employed. Lattice constants of PuO $_{2}$ were evaluated in the temperature range of 300-2800 K by MD simulation, and thermal expansion was evaluated. The experimental data was good agreement with the MD simulation result. Evaluation formula for thermal expansion of PuO $_{2}$ in the temperature range of 300-2800 K was derived from both data.

Journal Articles

Thermal expansion measurement and heat capacity evaluation of hypo-stoichiometric PuO $_{2.00}$

Kato, Masato; Uchida, Teppei; Matsumoto, Taku; Sunaoshi, Takeo*; Nakamura, Hiroki; Machida, Masahiko

Journal of Nuclear Materials, 451(1-3), p.78 - 81, 2014/08

https://doi.org/10.1016/j.jnucmat.2014.03.021

Times Cited Count：9 Percentile：57.01(Materials Science, Multidisciplinary)

Linear thermal expansion of PuO $_{2-x}$ was measured by dilatometry in an oxygen partial pressure-controlled atmosphere. The measured data of PuO $_{2-x}$ slightly increased with deviation . The linear thermal expansion of PuO $_{2-x}$ was determined as a function of temperature and O/M ratio, and the equation for the thermal expansion coefficient was derived. Heat capacity of PuO $_{2-x}$ was evaluated using this equation. The effect of O/M ratio on heat capacity was small. In addition to the vibration and dilatational terms, it is important to analyze the Schottky term in evaluating heat capacity of PuO $_{2}$ .

Journal Articles

Melting temperatures of the ZrO $_{2}$ -MOX system

Uchida, Teppei; Hirooka, Shun; Sugata, Hiromasa*; Shibata, Katsuya*; Sato, Daisuke*; Kato, Masato; Morimoto, Kyoichi

Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.1549 - 1553, 2013/09

Journal Articles

Effect of oxygen-to-metal ratio on properties of corium prepared from UO $_{2}$ and zircaloy-2

Hirooka, Shun; Kato, Masato; Morimoto, Kyoichi; Komeno, Akira; Uchida, Teppei; Akashi, Masatoshi

Journal of Nuclear Materials, 437(1-3), p.130 - 134, 2013/06

https://doi.org/10.1016/j.jnucmat.2013.01.334

Times Cited Count：5 Percentile：38.34(Materials Science, Multidisciplinary)

Journal Articles

Measurement of oxygen chemical diffusion in PuO $_{2-x}$ and analysis of oxygen diffusion in PuO $_{2-x}$ and (Pu,U)O $_{2-x}$

Kato, Masato; Uchida, Teppei; Sunaoshi, Takeo*

Physica Status Solidi (C), 10(2), p.189 - 192, 2013/02

https://doi.org/10.1002/pssc.201200454

Times Cited Count：5 Percentile：89.73(Materials Science, Multidisciplinary)

Journal Articles

Effect of oxygen-to-metal ratio on densification behavior in the sintering process of PuO $_{2}$ pellet

Uchida, Teppei; Sunaoshi, Takeo*; Kato, Masato

Physica Status Solidi (C), 10(2), p.193 - 196, 2013/02

https://doi.org/10.1002/pssc.201200475

Times Cited Count：4 Percentile：86.2(Materials Science, Multidisciplinary)

Journal Articles

Melting temperature and thermal conductivities of corium prepared from UO $_{2}$ and zircalloy-2

Kato, Masato; Uchida, Teppei; Hirooka, Shun; Akashi, Masatoshi; Komeno, Akira; Morimoto, Kyoichi

Materials Research Society Symposium Proceedings, Vol.1444, p.91 - 96, 2012/09

https://doi.org/10.1557/opl.2012.987

Times Cited Count：1 Percentile：56.57(Materials Science, Multidisciplinary)

Journal Articles

Thermal expansion of corium prepared from UO and zircalloy-2

Hirooka, Shun; Akashi, Masatoshi; Uchida, Teppei; Morimoto, Kyoichi; Kato, Masato

Materials Research Society Symposium Proceedings, Vol.1444, p.97 - 101, 2012/09

https://doi.org/10.1557/opl.2012.1004

Times Cited Count：0 Percentile：0.11(Materials Science, Multidisciplinary)

Journal Articles

Thermal properties of UO $_{2}$ by molecular dynamics simulation

Uchida, Teppei; Sunaoshi, Takeo*; Kato, Masato; Konashi, Kenji*

Progress in Nuclear Science and Technology (Internet), 2, p.598 - 602, 2011/10

https://doi.org/10.15669/pnst.2.598

Interatomic potential function of UO $_{2}$ was determined and thermal expansion, specific heat and thermal conductivity were evaluated by molecular dynamics (MD) simulation. For thermal expansion, a dilatometry was conducted and a measurement result was compared with a result of MD simulation. Thermal expansion value was in good agreement with MD simulation. Specific heat and thermal conductivity was also in good agreement with literature data when the supercell contained Schottky defects. Thermal conductivity, especially, was affected at low temperature range and decreased with increasing Schottky defect concentration. It was considered that vacancies scattered phonon vibrations. The interatomic potential function of UO $_{2}$ was considered usable.

Journal Articles

Oxygen potential of (U $_{0.88}$ Pu $_{0.12}$ )O $_{2pm x}$ and (U $_{0.7}$ Pu $_{0.3}$ )O $_{2pm x}$ at high temperatures of 1673-1873 K

Kato, Masato; Takeuchi, Kentaro; Uchida, Teppei; Sunaoshi, Takeo*; Konashi, Kenji*

Journal of Nuclear Materials, 414(2), p.120 - 125, 2011/07

https://doi.org/10.1016/j.jnucmat.2011.01.042

Times Cited Count：21 Percentile：82.54(Materials Science, Multidisciplinary)

Many studies on oxygen potentials have been reported, but their data were scattered and the data at high temperatures are limited. In this work, the oxygen potential of (U $_{0.88}$ Pu $_{0.12}$ )O $_{2pm x}$ and (U $_{0.7}$ Pu $_{0.3}$ )O $_{2pm x}$ was measured at high temperatures of 1673-1873 K using gas equilibrium method using thermo-gravimetry. The influence of Pu addition on the oxygen potential of MOX was discussed. The oxygen potential and the O/M ratio were decided by in-situ analysis. The oxygen partial pressure was adjusted by controlling the ratio of $_{H_{2}}$ / $_{H_{2}}$ O in the flowing gas atmosphere, and the oxygen potential was determined. The oxygen potentials measured by the point defect model. The deviation x varied with the relation of in the near stoichiometric composition region. The oxygen potential increased with increasing Pu content. The values of stoichiometric MOX containing 12% and 30%Pu were determined to be -334 kJ/mol and -296 kJ/mol, respectively, at 1773 K.

Journal Articles

The Phase state at high temperatures in the MOX-SiO $_{2}$ system

Nakamichi, Shinya; Kato, Masato; Sunaoshi, Takeo*; Uchida, Teppei; Morimoto, Kyoichi; Kashimura, Motoaki; Kihara, Yoshiyuki

Journal of Nuclear Materials, 389(1), p.191 - 196, 2009/05

https://doi.org/10.1016/j.jnucmat.2009.01.028

Times Cited Count：2 Percentile：17.63(Materials Science, Multidisciplinary)

Japan Atomic Energy Agency researchers have developed mixed oxide (MOX) fuels containing minor actinides (MA). These fuels were irradiated for ten minutes in the FBR Joyo in some short-term irradiation tests. The Si-condensed phases were observed at the center of the pellets in the post irradiation examination. Si impurities came to be mixed into the raw materials in the ball milling process, because Si rubber was used as the lining of the milling pot. Content of Si in the pellets was within the specification of the fuel. It is important to investigate the Si state in MOX at high temperatures like the reactor operating temperature of the fuel to evaluate irradiation behavior. In the present work, MOX specimens with mixed SiO $_{2}$ impurity were prepared. The ratio of MOX to SiO $_{2}$ was controlled at a mol fraction of 3 to 1. The specimens were first heated at 1973K in atmospheres of three different oxygen partial pressures to adjust the O/M ratio. Then these specimens were sealed in a tungsten capsule, and heated at 2273K or 2673K. Compounds consisting of Pu and Si were observed at grain boundaries of the MOX matrix in specimens after heat treatment. These compounds were not observed in grain interior and MOX matrix was not affected significantly by Si impurity. These compounds tended to form in specimens with low O/M ratio and in specimens heated at higher temperatures.

Oral presentation

Phase state in the PuO $_{2}$ -SiO $_{2}$ system

Uchida, Teppei; Nakamichi, Shinya; Sunaoshi, Takeo*; Morimoto, Kyoichi; Kato, Masato; Kihara, Yoshiyuki

no journal, ,

no abstracts in English

Oral presentation

Elucidation of precipitation condition of Si compound in the MOX fuel

Uchida, Teppei

no journal, ,

no abstracts in English

Oral presentation

Thermal properties of UO $_{2}$ by molecular dynamics simulation

Uchida, Teppei; Nakamichi, Shinya; Kato, Masato; Konashi, Kenji*

no journal, ,

no abstracts in English

Oral presentation

Thermal conductivity of UO $_{2}$ by molecular dynamics simulation

Uchida, Teppei

no journal, ,

In this study, thermal expansion and thermal conductivity of UO $_{2}$ containing Schottky defects were evaluated as a first step of evaluating thermal properties of MOX fuel containing MA by molecular dynamics simulation. Compared to thermal conductivity of perfect crystal UO $_{2}$ , that of UO $_{2}$ containing Schottky defects were lower. It is considered that defect structures scattered phonon vibrations and thermal conductivity decreased.

Oral presentation