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Journal Articles

Fuel restructuring behavior analysis of MA-bearing MOX fuels irradiated in a fast reactor

Ozawa, Takayuki; Ikusawa, Yoshihisa; Kato, Masato

Transactions of the American Nuclear Society, 113(1), p.622 - 624, 2015/10

A recycle system for minor actinides (MAs), in which MAs are recycled by reprocessing and irradiating them in a fast reactor, is studied to reduce the degree of hazard and the amount of high-level radioactive wastes. MAs would be used as mixed oxide (MOX) fuels with plutonium and uranium in fast reactors. Since MA content of MA-bearing MOX (MA-MOX) to be used in fast reactors is assumed to reach $$sim$$5 wt%HM, the effects on not only fuel properties but also fuel behaviors have to be estimated to use MA-MOX as fast reactor fuels. As the MOX fuels to be used will be irradiated at a comparably high linear power and the fuel center temperature would be assumed to be over 2,273 K during irradiation in the fast reactors, fuel restructuring would take place due to void migration towards the fuel center under the radial temperature gradient, and a central void would be formed. Since the fuel center temperature would be decreased by the effect of formation of the central void, the fuel restructuring is one of the most important behaviors for fast reactor fuels. In this study, the effect of MA content on fuel restructuring behavior was estimated from the results of irradiation experiments such as B11 and B14 performed in Joyo to study the irradiation behaviors of MA-MOX and the calculation results using a fuel restructuring model which can take into account MA-MOX dependence on vapor pressure.

Journal Articles

Physical property model for advanced oxide fuels

Kato, Masato; McClellan, K.*

Transactions of the American Nuclear Society, 113(1), p.613 - 614, 2015/10

A joint study on advanced oxide fuels is being carried out under the Civil Nuclear Energy Working Group (CNWG) bilateral collaboration between the U.S. Department of Energy and the Japan Atomic Energy Agency. The main goal of this study is to support development and validation of a science-based fuel analysis code for minor actinide (MA) bearing MOX fuel. In analysis and evaluation of fuel performance, it is essential to understand the physical properties of the advanced oxide fuels. Therefore, we are investigating physical properties of (U,Pu)O$$_{2}$$, (U,Ce,)O$$_{2}$$, PuO$$_{2}$$, CeO$$_{2}$$ and other related compounds to prepare a physical property database and to construct an integrated mechanistic physical property model. In this paper, we describe the derivation of a model to represent heat capacity and thermal conductivity of (U,Pu)O$$_{2-x}$$ that is based on the experimental database.

Journal Articles

Early-in-life fuel restructuring behavior of Am-bearing MOX fuels

Tanaka, Kosuke; Sasaki, Shinji; Katsuyama, Kozo; Koyama, Shinichi

Transactions of the American Nuclear Society, 113(1), p.619 - 621, 2015/10

In order to evaluate the microstructural change behavior of Am-MOX fuels at the initial stage of irradiation, detailed investigations using image analysis were performed on X-ray Computed Tomography (X-ray CT) images and on ceramographs from fuels irradiated in both B11 and B14.

Journal Articles

Sintering behavior of (U,Ce)O$$_{2}$$ and (U,Pu)O$$_{2}$$

Nakamichi, Shinya; Hiroka, Shun; Sunaoshi, Takeo*; Kato, Masato; Nelson, A.*; McClellan, K.*

Transactions of the American Nuclear Society, 113(1), p.617 - 618, 2015/10

Cerium dioxide has been used as a surrogate material for plutonium dioxide. Dorr et al reported the use of hyper-stoichiometric conditions causes the start of shrinkage of (U,Ce)O$$_{2}$$ at low temperature compared with the sintering in reducing atmosphere. However, the precise stoichiometry of the samples investigated was not controlled or otherwise monitored, preventing any quantitative conclusions regarding the similarities or differences between (U,Ce)O$$_{2}$$ and (U,Pu)O$$_{2}$$. The motivation for the present work is therefore to compare the sintering behavior of MOX and the (U,Ce)O$$_{2}$$ MOX surrogates under controlled atmospheres to assess the role of oxygen defects on densification in both systems.

Oral presentation

Thermophyisical properties of (U,Ce)O$$_{2pm x}$$

White, J.*; Hiroka, Shun; Murakami, Tatsutoshi; Nelson, A.*; McClellan, K.*; Kato, Masato

no journal, , 

Use of CeO$$_{2}$$ as a surrogate to better understand the behavior of MOX fuels requires a fundamental investigation of the thermophysical properties to assess the appropriate use. The challenge in performing thermophysical property measurements on oxygen non-toichiometric MOX is in handling the kinetics at elevated temperatures and also in determining a reference state from which to measure the oxygen:metal ratio (O:M). This study integrated the use of identical gas handling systems installed on a thermogravimetric analyzer and the property measurement system (differential scanning calorimeter and laser flash analyzer) to control the partial pressure of oxygen, PO$$_{2}$$, between the system and maintain stoichiometry from ambient temperature to 1200$$^{circ}$$C.

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