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image crystalSerizawa, Hiroyuki; Oishi, Yuji*; Kaji, Yoshiyuki; Yamanaka, Shinsuke*
New Research Trends of Fluorite-Based Oxide Materials, p.243 - 262, 2015/01
The image crystal is a shape controllable negative crystal which is sometimes reported by mineralogist. The negative crystals formed in a large single-crystal mass have attracted interest as expensive jewelry because of their mysterious appearance and rarity. Nonetheless, for many scientist, the cavity has been nothing else than a volume defect which occurs in a single crystal by chance. However, the authors found unexpectedly that the image crystal is formed in UO when helium is enclosed in the gas bubble. They also found that the shape of the image crystal changes dramatically with the conditions of helium precipitation, which implies that the shape of the cavity should change depending on the inner pressure. A truncated octahedron-type, an octa-triacontahedron-type and a pentacontahedron-type negative crystal were observed. Recent study clarified that the growth process of the image crystal can be explained by a step free energy model rather than an attachment energy.
Serizawa, Hiroyuki; Kaji, Yoshiyuki
Journal of the American Ceramic Society, 97(4), p.1187 - 1193, 2014/04
Times Cited Count：1 Percentile：6.69(Materials Science, Ceramics)The longitudinal and transverse wave velocities of polycrystalline MgO were successfully measured simultaneously and five types of elastic moduli, the Debye temperature, and the Gruneisen parameter were evaluated as functions of temperature from 298 K to 1764 K. An aluminum foil was used as a couplant between the MgO specimen and waveguide. Both acoustic waves were successfully propagated into the specimen through the solid and liquid aluminum layers. In particular, no influence of melted aluminum foil on the acoustic wave velocities was observed. With increasing temperature, the Young's, shear, and bulk moduli decreased monotonically and the Gruneisen parameter and Poisson's ratio increased monotonically, which indicated a decrease in the ionic bonding strength. The Debye temperature decreased almost linearly with increasing temperature, which showed the effect of thermal expansion.
powder induced by helium precipitationSerizawa, Hiroyuki; Matsunaga, Junji*; Shirasu, Noriko; Nakajima, Kunihisa; Kashibe, Shinji*; Kaji, Yoshiyuki
Journal of Asian Ceramic Societies (Internet), 1(3), p.289 - 295, 2013/09
This report addresses the precipitation of helium in polycrystalline UO, which deforms the morphology of the grains and their surfaces Helium was injected into pulverized UO particles at 1473 K by hot isostatic pressing (HIP). The specific surface area measured by volumetric gas adsorption instrument implied that small pores should exist on the as-helium-treated sample surface. Field-emission scanning electron microscopy observations showed that numerous shallow basins (approximately 500 nm in radius) with hexagonal fringe were formed on the surface. The basin resembles a ruptured blister whose lid has been forced open. SEM observations showed a uniform polygonal-shaped section of the gas bubble on the fracture surface; this implies that precipitated helium forms a negative crystal in the grain.
Serizawa, Hiroyuki; Matsunaga, Junji*; Haga, Yoshinori; Nakajima, Kunihisa; Akabori, Mitsuo; Tsuru, Tomohito; Kaji, Yoshiyuki; Kashibe, Shinji*; Oishi, Yuji*; Yamanaka, Shinsuke*
Crystal Growth & Design, 13(7), p.2815 - 2823, 2013/07
Times Cited Count：5 Percentile：42.72(Chemistry, Multidisciplinary)Since the shape of the negative crystal closely relates to the morphology of the crystal habits, the formation and the growth mechanism is important subject in a field of the physical science. Whereas, the negative crystal formed in a large single crystal mass has been arousing interest as an expensive jewelry because of its mysterious appearance and rarity. However, it is difficult to control the shape of this polyhedral cavity embedded in a solid medium arbitrary. Here we report the recent discovery on the growth process of the negative crystal. We found that precipitated helium forms the negative crystal in UO; the shape changes drastically with the condition of the helium precipitation. The transformation mechanism was discussed in this article. Our investigation implies that the shape of the negative crystal can be arbitrary controlled by controlling the precipitation condition.
Akie, Hiroshi; Sato, Isamu; Suzuki, Motoe; Serizawa, Hiroyuki; Arai, Yasuo
Journal of Nuclear Science and Technology, 50(1), p.107 - 121, 2013/01
Times Cited Count：2 Percentile：18.63(Nuclear Science & Technology)A simple formula is developed for the evaluation of the helium production amount in the fast reactor fuel. For the subroutine use in the existing fuel behavior analysis code, the formula is designed putting emphasis on simplicity and quickness rather than accuracy. The accuracy of the formula is confirmed by comparing with the detailed calculation with SWAT code, and also with the post irradiation examination (PIE) results of the fuel pin irradiated at the experimental fast reactor JOYO. As a result, the formula is found to evaluate the helium amount with the difference of less than about 10% from the detailed calculation and from the PIE results. Based on these results, the formula is installed in the fuel behavior analysis code for the simulation of helium behavior in fast reactor fuels.
Nakajima, Kunihisa; Serizawa, Hiroyuki; Shirasu, Noriko; Haga, Yoshinori; Arai, Yasuo
Journal of Nuclear Materials, 419(1-3), p.272 - 280, 2011/12
Times Cited Count：24 Percentile：85.64(Materials Science, Multidisciplinary)The solubility and diffusion coefficient of helium in the single-crystal UO samples were determined by a Knudsen-effusion mass-spectrometric method. The measured helium solubilities were found to lie within the scatter of the available data, but to be much lower than those for the polycrystalline samples. The diffusion analysis was conducted based on a hypothetical equivalent sphere model and the simple Fick's law. The helium diffusion coefficient was determined by using the pre-exponential factor and activation energy as the fitting parameters for the measured and calculated fractional releases of helium. The optimized diffusion coefficients were in good agreement with those obtained by a nuclear reaction method reported in the past. It was also found that the pre-exponential factors of the determined diffusion coefficients were much lower than those analyzed in terms of a simple interstitial diffusion mechanism.
Arai, Yasuo; Serizawa, Hiroyuki; Nakajima, Kunihisa; Takano, Masahide; Sato, Isamu; Katsuyama, Kozo; Akie, Hiroshi; Suzuki, Motoe; Shirasu, Noriko; Haga, Yoshinori; et al.
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 8 Pages, 2011/12
High amount of He is generated in MA-bearing fuel during irradiation and storage periods compared with that in U or U-Pu fuel. Laboratory scale experiments, post irradiation examinations and modeling study were carried out in order to understand the He behavior in MA-bearing oxide fuel. Diffusion characteristics of He in single-crystal UO were investigated by the Knudsen effusion mass spectrometry. Effects of the He accumulation on lattice and bulk expansion of oxide pellets were examined by use of alpha-decay of 
Cm. Post irradiation examinations of 0.5%Am-MOX fuel irradiated at a fast test reactor JOYO were carried out, concentrating on the He behavior in the fuel pellets. A model describing the He behavior in MA-MOX fuel was constructed based on the principle processes, such as generation, diffusion, equilibrium and release to outer gaseous phase. By use of the model as a subroutine of a conventional fuel behavior analysis code, the He behavior in MA-MOX fuel for fast reactors was simulated.
Serizawa, Hiroyuki; Matsunaga, Junji*; Haga, Yoshinori; Nakajima, Kunihisa; Kashibe, Shinji*; Iwai, Takashi
JAEA-Research 2011-025, 32 Pages, 2011/11
JAEA-Research-2011-025.pdf:10.17MB
This report deals with the precipitation of helium in UO matrix to deform the microstructure. The examination was performed using single and polycrystalline UO sample. The helium-treated samples under 900 atm at 1473 K were reheat-treated at much more high temperature, 1573 K or 1973 K to release the infused helium. The microstructure of the sample was examined by FIB, FE-STEM and FE-TEM. It was confirmed that precipitated helium atoms form a negative crystal in the grain or the matrix of the single crystal. At 1573 K, helium can be released without formation of intergranular tunnel since the surface diffusion coefficient of helium is large. However, some open grain boundaries were observed in the sample heat-treated at 1973 K. This might be related to the activity of helium in the grain boundary region. The structure of the negative crystal was analyzed from the view point of the thermodynamics of the surface growth.
Rintsu, Yuko*; Serizawa, Shigeru*; Yamazaki, Tetsuo*; Umeyama, Nobuaki*; Moriuchi, Shigeru*; Handa, Hiroyuki*; Onishi, Ryoichi*; Takemura, Morio*; Chino, Masamichi; Nagai, Haruyasu; et al.
Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10
no abstracts in English
Serizawa, Hiroyuki; Fukuhara, Mikio*; Nakajima, Kunihisa; Iwai, Takashi; Arai, Yasuo
Proceedings of 8th Asian Thermophysical Properties Conference (ATPC '07) (CD-ROM), 6 Pages, 2007/08
Longitudinal and transverse wave velocities, five kinds of elastic moduli, Debye temperature and Gruneisen parameter have been simultaneously measured as functions of temperature from 298 to 1764 K in polycrystalline MgO, by help of aluminum couplant. Young, shear, bulk moduli, and Gruneisen parameter and Poisson's ratio decreased and increased monotonically with increasing temperature, respectively, showing a lowering of ionic bonding strength. Lame parameter versus temperature slope is almost zeroing in the whale temperature region. The behavior was interpreted as an interlocking associated with network of short Mg-O bonds, based on three-dimensional volume-nonpreserving shear.
Osaka, Masahiko; Serizawa, Hiroyuki; Kato, Masato; Nakajima, Kunihisa; Tachi, Yoshiaki; Kitamura, Ryoichi; Miwa, Shuhei; Iwai, Takashi; Tanaka, Kenya; Inoue, Masaki; et al.
Journal of Nuclear Science and Technology, 44(3), p.309 - 316, 2007/03
Times Cited Count：30 Percentile：87.22(Nuclear Science & Technology)no abstracts in English
Osaka, Masahiko; Serizawa, Hiroyuki*; Kato, Masato; Inoue, Masaki; Nakajima, Kunihisa*; Tachi, Yoshiaki; Kitamura, Ryoichi; Oki, Shigeo; Miwa, Shuhei; Iwai, Takashi*; et al.
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
Development of minor actinide containing fuel/target, i.e., (Pu,Am)O-MgO, (Pu,Np)O-MgO, (U,Pu,Np)O, (U,Pu,Np)N and (Pu,Np,Zr)N, for the use in a future integrated system of fast reactor and accelerator driven system is underway as a collaborative work between JAERI and JNC. The present statuses of fabrication test and property measurements are given. Irradiation test in the experimental fast reactor JOYO is also mentioned.
Nakajima, Kunihisa; Iwai, Takashi; Kikuchi, Hironobu; Serizawa, Hiroyuki; Arai, Yasuo
JAERI-Research 2005-027, 42 Pages, 2005/09
JAERI-Research-2005-027.pdf:4.15MB
Nitride fuel pins containing inert matrix such as ZrN and TiN were fabricated for the irradiation test at JMTR, aiming at understanding irradiation behavior of nitride fuel for transmutation of minor actinides. Minor actinides are surrogated by plutonium in the present fuel pin. This report describes the preparation and characterization of fuel pellets, and fabrication of fuel pins. The irradiation for 11 cycles from May 2002 to November 2004 at JMTR was completed without any failure of fuel pins.
Serizawa, Hiroyuki; Kikuchi, Hironobu; Iwai, Takashi; Arai, Yasuo; Kurosawa, Makoto; Mimura, Hideaki; Abe, Jiro
JAERI-Tech 2005-039, 23 Pages, 2005/07
JAERI-Tech-2005-039.pdf:2.89MB
A high-temperature ultrasonic measuring system had been designed and installed in a glovebox (711-DGB) to study a mechanical property of nuclear fuel containing trans-uranium (TRU) elements. A figuration apparatus for the cylinder-type sample preparation had also been modified and installed in an established glovebox (142-D). The system consists of an ultrasonic probe, a heating furnace, cooling water-circulating system, a cooling air compressor, vacuum system, gas supplying system and control system. An A/D converter board and an pulsar/Receiver board for the measurement of wave velocity were installed in a personal computer. The apparatus was modified to install into the glovebox. Some safety functions were supplied to the control system. The shape and size of the sample was revised to minimize the amount of TRU elements for the use of the measurement. The maximum sample temperature is 1500 
C. The performance of the installed apparatuses and the glovebox were confirmed through a series of tests.
-ZrO pseudo-binary phase diagramAlbiol, T.*; Serizawa, Hiroyuki; Arai, Yasuo
Journal of Nuclear Science and Technology, 39(Suppl.3), p.834 - 837, 2002/11
no abstracts in English
Sawa, Kazuhiro; Tobita, Tsutomu*; Takahashi, Masashi; Saito, Takashi; Iimura, Katsumichi; Yokouchi, Iichiro; Serizawa, Hiroyuki; Sekino, Hajime; Ishikawa, Akiyoshi
JAERI-Research 2001-043, 52 Pages, 2001/09
JAERI-Research-2001-043.pdf:14.92MB
no abstracts in English
solid solution with magnesium and europium oxidesFujino, Takeo*; Sato, Nobuaki*; Yamada, Kota*; Nakama, Shohei*; Fukuda, Kosaku; Serizawa, Hiroyuki; Shiratori, Tetsuo*
Journal of Nuclear Materials, 297(3), p.332 - 340, 2001/09
Times Cited Count：4 Percentile：33.39(Materials Science, Multidisciplinary)Oxygen potential of solid solution Mg
Eu
U
O
was examined as a function of O/Metal ratio at 1000, 1100 and 1200C. The O/Metal ratio which gave the steepest change of the oxygen potential(GOM) was 1.995 for y=0.05, z=0.1 and y=0.05, z=0.05. The position decreased to 1.908 at higher Mg
concentration of y=0.1, z=0.05. The GOM did not change with temperature in a range 1000-1200C. At GOM, a friction of 0.473 of total Mg occupy the interstitial position of the fluorite lattice.
in comparison with undoped UO, Mg-Nb doped UO and Ti doped UOFujino, Takeo*; Shiratori, Tetsuo; Sato, Nobuaki*; Fukuda, Kosaku; Yamada, Kota*; Suzuki, Yasufumi; Serizawa, Hiroyuki
Journal of Nuclear Materials, 297(2), p.176 - 205, 2001/08
Times Cited Count：20 Percentile：79.16(Materials Science, Multidisciplinary)no abstracts in English
Fujino, Takeo*; Sato, Nobuaki*; Yamada, Kota*; Okazaki, Manabu*; Fukuda, Kosaku; Serizawa, Hiroyuki; Shiratori, Tetsuo*
Journal of Nuclear Materials, 289(3), p.270 - 280, 2001/03
Times Cited Count：2 Percentile：19.66(Materials Science, Multidisciplinary)no abstracts in English
Serizawa, Hiroyuki; Nakajima, Kunihisa; Arai, Yasuo; Yamashita, Toshiyuki; Kuramoto, Kenichi; Kinoshita, H.*; Yamanaka, Shinsuke*; Uno, Masayoshi*; Kurosaki, K.*
Progress in Nuclear Energy, 38(3-4), p.237 - 240, 2001/02
Times Cited Count：5 Percentile：38.97(Nuclear Science & Technology)no abstracts in English
