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Aihara, Jun; Ueta, Shohei; Honda, Masaki*; Kasahara, Seiji; Okamoto, Koji*
JAEA-Research 2024-012, 98 Pages, 2025/02
JAEA-Research-2024-012.pdf:32.24MB
Concept of Pu-burner high temperature gas-cooled reactor (HTGR) was proposed for the purpose of more safely reducing amount of recovered Pu. In Pu-burner HTGR concept, coated fuel particle (CFP), with ZrC coated yttria stabilized zirconia (YSZ) containing PuO
(PuO-YSZ) small particle and with tri-structural isotropic (TRISO) coating, is employed for very high burn-up and high nuclear proliferation resistance. ZrC layer is oxygen getter. In research project of Pu-burner HTGR carried out from fiscal year of 2014 to fiscal year of 2017, simulated CFPs were fabricated using Ce to simulate Pu. Moreover, simulated fuel compacts were fabricated using fabricated simulated CFPs. In this report, results of microstructural observation of CeO-YSZ and ZrC layer at each fabrication step are reported.
compoundsFrazer, D.*; Saleh, T. A.*; Matsumoto, Taku; Hirooka, Shun; Kato, Masato; McClellan, K.*; White, J. T.*
Nuclear Engineering and Design, 423, p.113136_1 - 113136_7, 2024/07
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Nanoindentation based techniques can be employed on minute volumes of material to measure mechanical properties, including Young's modulus, hardness, and creep stress exponents. In this study, (U,Ce)O solid solutions samples are used to develop elevated temperature nanoindentation and nanoindentation creep testing methods for use on mixed oxide fuels. Nanoindentation testing was performed on 3 separate (Ux-1,Cex)O compounds ranging from x equals 0.1 to 0.3 at up to 800 
C: their Young's modulus, hardness, and creep stress exponents were evaluated. The Young's modulus decreases in the expected linear manner while the hardness decreases in the expected exponential manner. The nanoindentation creep experiments at 800 C give stress exponent values, n=4.7-6.9, that suggests dislocation motion as the deformation mechanism.
ceramicsVauchy, R.; Hirooka, Shun; Watanabe, Masashi; Yokoyama, Keisuke; Sunaoshi, Takeo*; Yamada, Tadahisa*; Nakamichi, Shinya; Murakami, Tatsutoshi
Ceramics International, 49(2), p.3058 - 3065, 2023/01
Times Cited Count：11 Percentile：64.70(Materials Science, Ceramics)Suzuki, Kiichi; Kato, Masato; Sunaoshi, Takeo*; Uno, Hiroki*; Carvajal-Nunez, U.*; Nelson, A. T.*; McClellan, K. J.*
Journal of the American Ceramic Society, 102(4), p.1994 - 2008, 2019/04
Times Cited Count：53 Percentile：93.43(Materials Science, Ceramics)The fundamental properties of CeO were assessed using a range of experimental techniques. The oxygen potential of CeO was measured by the thermogravimetric technique, and a numerical fit for the oxygen potential of CeO is derived based on defect chemistry. Mechanical properties of CeO were obtained using sound velocity measurement, resonant ultrasound spectroscopy and nanoindentation. The obtained mechanical properties of CeO are then used to evaluate the Debye temperature and Gruneisen constant. The heat capacity and thermal conductivity of CeO were also calculated using the Debye temperature and the Gruneisen constant. Finally, the thermal conductivity was calculated based upon laser flash analysis measurements. This result demonstrates that the thermal conductivity has strong dependence upon material purity.
pellets by 28 GHz microwave irradiationAkashi, Masatoshi; Matsumoto, Taku; Kato, Masato
Transactions of the American Nuclear Society, 118, p.1391 - 1394, 2018/06
In this study, CeO pellet sintering by irradiating microwave at a frequency of 28 GHz was carried out to investigate the effect of particle diameter of raw powder on the density of sintered pellet. The highest bulk density is 94.2 %T.D. under the condition of 30 min holding at 1473 K. The bulk density decreases with increasing the particle diameter of used raw powder. On the other hand, all of the apparent density of sintered pellet is more than 93.5 %T.D.. The difference between the bulk density and the apparent density is caused by the difference of open porosity for each sample pellet. It seems that the high density sintered pellets with porous structure are obtained because sample pellet is heated internally and uniformly in microwave sintering.
and (U,Pu)ONakamichi, Shinya; Hirooka, 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 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 and (U,Pu)O. The motivation for the present work is therefore to compare the sintering behavior of MOX and the (U,Ce)O MOX surrogates under controlled atmospheres to assess the role of oxygen defects on densification in both systems.
-CeO solid solutions around the monoclinic-tetragonal phase boundaryYashima, Masatomo*; Hirose, Teruo*; Katano, Susumu; Suzuki, Yasuo*; Kakihana, Masato*; Yoshimura, Masahiro*
Physical Review B, 51(13), p.8018 - 8025, 1995/04
Times Cited Count：121 Percentile：97.28(Materials Science, Multidisciplinary)no abstracts in English
-YO
-NdO and ZrO-YO-CeO;
Mater.Res.Bull., 21, p.1343 - 1349, 1986/00
Times Cited Count：31 Percentile：79.51(Materials Science, Multidisciplinary)no abstracts in English
; Ikawa, Katsuichi; Iwamoto, K.
Journal of Nuclear Materials, 87(1), p.40 - 48, 1979/00
Times Cited Count：3no abstracts in English
Serizawa, Hiroyuki
no journal, ,
My investigation on cavities in ceramics was triggered by the unexpected discovery of a polyhedral cavity in a UO matrix. The SEM image that attracted my attention was a cavity observed in the fracture surface of a single crystal of UO that was heat-treated in helium at 90 MPa, followed by annealing at 1573 K for 1 h. It was clear that the cavity was a negative crystal that was formed by the precipitation of helium during heat treatment after Hot Isostatic Pressing (HIP) injection. In a series of experiments, I noticed that the shape of the negative crystal changes depending on the heat-treatment history. A truncated octahedron-type, an octa-triacontahedron-type, and a pentacontahedron-type negative crystal were observed. Our study implies that the shape of the negative crystal should change depending on the helium inner pressure enclosed in the negative crystal.
Serizawa, Hiroyuki
no journal, ,
My investigation on cavities in ceramics was triggered by the unexpected discovery of a polyhedral cavity in a UO matrix. In a series of experiments, I noticed that the shape of the negative crystal changes depending on the heat-treatment history. In general, it is difficult to control arbitrarily the shapes of these polyhedral negative crystals embedded in a solid medium; however, the shape can easily be controlled using the helium injection method. Our research team named the shape controlled negative crystal as image crystal.
White, J.*; Hirooka, Shun; Murakami, Tatsutoshi; Nelson, A.*; McClellan, K.*; Kato, Masato
no journal, ,
Use of CeO 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, between the system and maintain stoichiometry from ambient temperature to 1200C.
Ishii, Katsunori; Segawa, Tomoomi; Kawaguchi, Koichi; Nishina, Masahiro; Makino, Takayoshi; Natori, Yuri*
no journal, ,
JAEA is developing simplified a plutonium and uranium mixed oxide (MOX) pellet fabrication process. In this process, agitation granulator improves flowability of MOX powder with water as binder. This granulation method has issues, including low production capacity due to criticality control for wet nuclear material. A new simple additive-free dry granulation method was proposed recently to produce tritium breeding LiO spheres for nuclear fusion reactor. In this research, results of experiments to investigate the applicability of the new granulation method to MOX powder is reported.
