Reduction and phase transformation of Ce-doped zirconolites

Hayashizaki, Kohei; Hirooka, Shun; Yamada, Tadahisa*; Sunaoshi, Takeo*; Murakami, Tatsutoshi; Saito, Kosuke

Ceramics (Internet), 8(1), p.24_1 - 24_12, 2025/03

https://doi.org/10.3390/ceramics8010024

Sintering and microstructural behaviors of mechanically blended Nd/Sm-doped MOX

Hirooka, Shun; Horii, Yuta; Sunaoshi, Takeo*; Uno, Hiroki*; Yamada, Tadahisa*; Vauchy, R.; Hayashizaki, Kohei; Nakamichi, Shinya; Murakami, Tatsutoshi; Kato, Masato

Journal of Nuclear Science and Technology, 60(11), p.1313 - 1323, 2023/11

https://doi.org/10.1080/00223131.2023.2192725

Additive MOX pellets are fabricated by a conventional dry powder metallurgy method. NdO and SmO are chosen as the additive materials to simulate the corresponding soluble fission products dispersed in MOX. Shrinkage curves of the MOX pellets are obtained by dilatometry, which reveal that the sintering temperature is shifted toward a value higher than that of the respective regular MOX. The additives, however, promote grain growth and densification, which can be explained by the effect of oxidized uranium cations covering to a pentavalent state. Ceramography reveals large agglomerates after sintering, and Electron Probe Micro-Analysis confirms that inhomogeneous elemental distribution, whereas XRD reveals a single face-centered cubic phase. Finally, by grinding and re-sintering the specimens, the cation distribution homogeneity is significantly improved, which can simulate spent nuclear fuels with soluble fission products.

Manufacturing and property measurements of homogeneous simulated FP (Nd/Sm/Gd/Zr)-doped MOX

Horii, Yuta; Hirooka, Shun; Vauchy, R.; Hayashizaki, Kohei; Uno, Hiroki*; Tamura, Tetsuya*; Sunaoshi, Takeo*; Owada, Hideaki*; Yamada, Tadahisa*; Murakami, Tatsutoshi

no journal, , 

Fission products (FPs), which are generated and stored in fuel matrix by irradiating nuclear fuels, affect thermo-physical fuel properties. To improve accuracy of computer simulation of irradiation behaviors, studies on the fuel properties containing FPs are needed. However, only a limited number of studies on the irradiated fuel properties, especially MOX fuels, have been reported in the world due to difficulties in handling of the irradiated fuels. Moreover, the effect of individual FP cannot be evaluated because many kinds of FPs are stored in the irradiated fuels. Thus, an alternative method should be suggested to easily study the effects of FPs on the fuel properties. In this study, fuel properties were measured to evaluate the effects of FPs by using simulated FP-doped MOX specimens instead of a real irradiated fuel. For the measurement, the homogeneity of FP in a specimen is also important, as well as uranium and plutonium. To obtain homogeneous specimens, re-grinding and re-sintering processes were repeated and the improvement was confirmed by EPMA and XRD at each set of the process. A specimen with suitable homogeneity for measurement was prepared by repeating the series of processes three times. SmO, GdO and ZrO, which are major and soluble FPs in irradiated MOX fuels, were selected as simulated FPs. The effect of individual FP on the properties, such as thermal conductivity and thermal expansion, was evaluated on the specimens. In addition, NdO, SmO and GdO co-doped MOX was also prepared to compare the influence of containing multiple lanthanides.

Study on powder adhesion prevention by surface micro-fabrication of stainless steel

Hayashizaki, Kohei; Omi, Koyo; Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Satone, Hiroshi*; Suzuki, Michitaka*

no journal, , 

To reduce the retention of the nuclear fuel materials in the glove box and the external exposure dose, the technology of the powder adhesion prevention by the surface micro-fabrication on the glove box components has been developed. In this study, a stainless steel specimen, which is a glovebox component material, was subjected to surface microfabrication, and measurements and evaluations were carried out concerning adhesion and powder adhesion prevention effects. A stainless steel specimen that was unmachined and several specimens with different surface roughnesses that had been micro-fabricated on their surfaces were used to perform surface roughness and adhesion measurement tests by atomic force microscopy. The average adhesion force tended to decrease as the surface roughness increased. In this study, it was found that surface micro-fabrication of stainless steel had a certain effect on preventing powder adhesion.

Synthesis of zirconolite with U-Ce mixed oxide for stable storage of nuclear fuel materials

Hayashizaki, Kohei; Hirooka, Shun; Akiyama, Daisuke*; Kirishima, Akira*; Saito, Kosuke

no journal, , 

Sintering behavior of microwave de-nitrated or dry-recycled MOX powders

Hirooka, Shun; Hayashizaki, Kohei; Owada, Hideaki*; Sunaoshi, Takeo*; Tamura, Tetsuya*; Saito, Kosuke

no journal, , 

no abstracts in English

Study on stable storage of nuclear fuel materials, 1; Synthesis of zirconolite with U-Ce mixed oxide

Hayashizaki, Kohei; Hirooka, Shun; Akiyama, Daisuke*; Kirishima, Akira*; Murakami, Tatsutoshi

no journal, , 

no abstracts in English

Sintering behavior of dry-recycled MOX powder with various particle size distribution

Hayashizaki, Kohei; Hirooka, Shun; Sunaoshi, Takeo*; Nakamichi, Shinya; Murakami, Tatsutoshi

no journal, , 

no abstracts in English