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Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Uenomachi, Mizuki*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.
Nuclear Instruments and Methods in Physics Research A, 971, p.164118_1 - 164118_8, 2020/08
Times Cited Count:7 Percentile:66.68(Instruments & Instrumentation)Kotake, Shoji*; Chikazawa, Yoshitaka; Takaya, Shigeru; Otaka, Masahiko; Kubo, Shigenobu; Arai, Masanobu; Kunogi, Kosuke; Ito, Takaya*; Yamaguchi, Akira*
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04
A maintenance management required to prototype nuclear power reactors is proposed. Monitoring and control of sodium impurity and thermal transient are extremely important for sodium boundary maintenance for sodium-cooled fast reactors. At the fast stage of the prototype reactor Monju operation, degradation mechanism on the piping should be demonstrated based on operation experiences. Therefore inspection on a representative position for crack indication and pipe thickness is proposed. Due to less experience of SFR plants, early detection of boundary failure is considered. For a matured operation stage, when degradation mechanism is well demonstrated based on inspection data, inspection cycle could be extended. And for commercial reactors, maintenance without inspection will be established based on accumulated operation experiences including those of the prototype reactor Monju.
Yoshiasa, Akira*; Arima, Hiroshi; Fukui, Hiroshi*; Okube, Maki*; Katayama, Yoshinori; Otaka, Osamu*
Nihon Kessho Gakkai-Shi, 51(1), p.66 - 69, 2009/02
We have determined a precise P-T phase diagram of AgI by high-temperature high-pressure synchrotron experiments. X-ray diffraction and X-ray absorption measurements were performed using a multi-anvil high pressure apparatus at SPring-8 synchrotron radiation facility. In a disordered rock-salt phase, Ag ions occupy both octahedral and tetrahedral sites. The occupancy of tetrahedral site has a maximum value, 20%, at 2 GPa. A change from rock-salt structure to disordered rock-salt structure is gradual in the X-ray diffraction measurements while it is clearly observed in the X-ray absorption measurements. Analysis of EXAFS Debye-Waller factor is useful because the force constant can be decided directly even at high pressure and high temperature. Pressure influences greatly the effective potential and anharmonicity decreases with increasing pressure.
Arima, Hiroshi*; Otaka, Osamu*; Hattori, Takanori; Katayama, Yoshinori; Utsumi, Wataru; Yoshiasa, Akira*
Journal of Physics; Condensed Matter, 19(7), p.076104_1 - 076104_7, 2007/02
Times Cited Count:16 Percentile:57.78(Physics, Condensed Matter)no abstracts in English
Ogawa, Kazuma*; Mukai, Takahiro*; Arano, Yasushi*; Otaka, Akira*; Ueda, Masashi*; Uehara, Tomoya*; Magata, Yasuhiro*; Hashimoto, Kazuyuki; Saji, Hideo*
Nuclear Medicine and Biology, 33(4), p.513 - 520, 2006/05
Times Cited Count:54 Percentile:80.16(Radiology, Nuclear Medicine & Medical Imaging)To develop a radiopharmaceutical for the palliation of painful bone metastases based on the concept of bifunctional radiopharmaceuticals, we synthesized a bisphosphonate derivative labeled with rhenium-186 (Re) that contains a hydroxyl group at the central carbon of its bisphosphonate structure and attached a stable Re-MAMA chelate to the amino group of a 4-amino-butylidene-bisphosphonate derivative, Re-MAMA-HBP, and investigated the effect of a hydroxyl group at the central carbon of its bisphosphonate structure on the affinity for hydroxyapatite and biodistribution by conducting a comparative study with Re-MAMA-BP. Re-MAMA-HBP was prepared by a reaction with ReO and SnCl in citrate buffer after the deprotection of trityl groups of Tr-MAMA-HBP. After reversed phase HPLC, Re-MAMA-HBP had a radiochemical purity of over 95 %. Compared with Re-MAMA-BP, Re-MAMA-HBP showed a greater affinity for hydroxyapatite beads in vitro and accumulated a significantly higher level in the femur in vivo. Thus, the introduction of a hydroxyl group into Re complex-conjugated bisphosphonates would be effective in enhancing accumulation in bone. These findings provide useful information on the design of bone-seeking therapeutic radiopharmaceuticals.
Otaka, Osamu*; Arima, Hiroshi*; Fukui, Hiroyuki*; Utsumi, Wataru; Katayama, Yoshinori; Yoshiasa, Akira*
Physical Review Letters, 92(15), p.155506_1 - 155506_4, 2004/04
Times Cited Count:51 Percentile:84.23(Physics, Multidisciplinary)Local structures around germanium in liquid germanate have been investigated by means of in situ X-ray absorption measurements up to 9 GPa at 1273 K. Liquid germanate consisting of tetrahedrally coordinated germanium contracts with increasing pressure without significant changes in the local structure up to 2.5 GPa and then shows an abrupt fourfold-to-sixfold coordination change around 3 GPa. The coordination change is completed below 4 GPa where upon a high-density liquid consisting of octahedrally coordinated germanium becomes stable. The GeO octahedron in the high-density liquid is more compressible than that in solids.
Okube, Maki*; Yoshiasa, Akira*; Otaka, Osamu*; Katayama, Yoshinori
High Pressure Research, 23(3), p.247 - 251, 2003/09
Times Cited Count:5 Percentile:38.86(Physics, Multidisciplinary)In order to examine the pressure effect on anharmonic thermal vibrations of Pt, Extended X-ray Absorption Fine Structure (EXAFS) spectra near Pt K-edge and L-edge were measured in the temperature range from 300 to 800K under pressures up to 6vGPa, using large volume high-pressure devices and synchrotron radiation. We have investigated the anharmonic interatomic potentials by a cumulant expansion method. The values of EXAFS Debye-Waller factors, 2 and 3, become smaller with increase of pressure. The anharmonic effective pair potential was evaluated and the potential coefficient a at 0.1MPa and 6GPa are 4.8 and 5.0eV/, respectively. The anharmonic potential parameter decreases with increasing pressure.
Okube, Maki*; Yoshiasa, Akira*; Otaka, Osamu*; Fukui, Hiroyuki*; Katayama, Yoshinori; Utsumi, Wataru
Journal of Physics; Condensed Matter, 14(44), p.11511 - 11515, 2002/11
Times Cited Count:4 Percentile:26.13(Physics, Condensed Matter)no abstracts in English
Otaka, Osamu*; Yoshiasa, Akira*; Fukui, Hiroyuki*; Murai, Keiichiro*; Okube, Maki*; Takebe, Hitoshi*; Katayama, Yoshinori; Utsumi, Wataru
Journal of Physics; Condensed Matter, 14(44), p.10521 - 10524, 2002/11
Times Cited Count:18 Percentile:64.23(Physics, Condensed Matter)no abstracts in English
Otaka, Osamu*; Takebe, Hitoshi*; Yoshiasa, Akira*; Fukui, Hiroshi*; Katayama, Yoshinori
Solid State Communications, 123(5), p.213 - 216, 2002/08
Times Cited Count:18 Percentile:64.23(Physics, Condensed Matter)Using a multi-anvil high-pressure device and synchrotron radiation, X-ray observations of AgI high pressure and high temperature up to 6.0 GPa and 1000 K have been performed to investigate the phase relations between -AgI, rocksalt-type, disordered rocksalt-type, and liquid phases. The three phases of -AgI, disordered rocksalt-type, and liquid meet in a triple point in the vicinity of 823 K and 1.3 GPa. The melting curve of the disordered rocksalt phase is linear with a positive slope. The transition between rocksalt and the disordered rocksalt phases is a broad and diffuse disordering type within the same structure. The formation of the disordered rocksalt phase has been hence estimated with the variation of a relative intensity ratio of (111) and (200) diffraction from the rocksalt phase. With increasing pressure the rocksalt phase becomes stabel at high temperature. At 6.0 GPa the rocksalt phase directly melts without the transition to the disordered rocksalt phase.
Okube, Maki*; Yoshiasa, Akira*; Otaka, Osamu*; Fukui, Hiroshi*; Katayama, Yoshinori; Utsumi, Wataru
Solid State Communications, 121(5), p.235 - 239, 2002/02
Times Cited Count:11 Percentile:50.72(Physics, Condensed Matter)In order to examine the pressure effect on the anharmonicity of Au, EXAFS spectra near Au -edge were measured at the temperature range from 300 to 1000K under pressure up to 14GPa using large volume high-pressure devices and synchrotron radiation. The values of EXAFS Debye-Waller factors, and , become smaller with increase of pressure, which indicates that the potential width become narrower with pressure. The anharmonic effective pair potentials of Au, , at 0.1MPa, 6 and 14GPa have been calculated. The pressure dependence of the coefficient of thermal expansion has also been evaluated.
Otaka, Osamu*; Yoshiasa, Akira*; Fukui, Hiroyuki*; Murai, Keiichiro*; Okube, Maki*; Katayama, Yoshinori; Utsumi, Wataru; Nishihata, Yasuo
Journal of Synchrotron Radiation, 8(Part2), p.791 - 793, 2001/03
no abstracts in English
Yoshiasa, Akira*; Okube, Maki*; Otaka, Osamu*; Kamishima, Osamu*; Katayama, Yoshinori
Japanese Journal of Applied Physics, Part 1, 39(12A), p.6747 - 6751, 2000/12
Times Cited Count:10 Percentile:44.21(Physics, Applied)The anharmonic effective pair potentials for Br-Cu bond in and CuBr under pressure have been investigated by an extended X-ray absorption fine structure (EXAFS) technique. The EXAFS spectra near the Br K-edge were measured under high temperature and high pressure using a large-volume uniaxial press and synchrotron radiation from SPring-8. The anharmonic effective pair potential for each phase is influenced by pressure and become steeper with increasing pressure. The potential parameter for -phase at 0.1MPa increases by about 20% at the pressure of 4.8GPa. The stastical distribution of Cu in -CuBr and superionic conduction mechanism have been discussed based on the effective pair potential and distribution of Br-Cu distances.
Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Foong, W. S.*; Uenomachi, Mizuki*; Kamada, Kei*; Kin, J. Y.*; Yoshino, Masao*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.
no journal, ,
no abstracts in English
Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Foong, W. S.*; Uenomachi, Mizuki*; Kamada, Kei*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.
no journal, ,
no abstracts in English
Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Uenomachi, Mizuki*; Kamada, Kei*; Kim, J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.
no journal, ,
Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Uenomachi, Mizuki*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.
no journal, ,
The retrieval of the nuclear fuel debris, which is the substance including melted nuclear fuel and structural materials, will be started from fiscal 2021. Then, as a non-destructive analysis technology of the nuclear fuel debris, a -ray spectroscopy system is being developed to measure high energy rays due to Eu and nuclear reactions under high dose rate, which was composed of a CeBr cubic, photomultiplier tube, and fast signal processing unit. This presentation reports that the exposure study of the detector system was performed for a Co field at the dose rates of up to 750 mSv/h, and the detector response was investigated at each dose rate.