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Hojo, Kiminobu*; Hayashi, Shotaro*; Nishi, Wataru*; Kamaya, Masayuki*; Katsuyama, Jinya; Masaki, Koichi*; Nagai, Masaki*; Okamoto, Toshiki*; Takada, Yasukazu*; Yoshimura, Shinobu*
Mechanical Engineering Journal (Internet), 3(4), p.16-00083_1 - 16-00083_16, 2016/08
Performance demonstration certification of non-destructive inspection for cast stainless steel (CASS) has been planned but the target flaw depth to be detected has not been determined yet in Japan. The target flaw size is closely connected to the allowable flaw size which is determined by flaw evaluation of the rules on fitness-for-service. For rational mitigation of the acceptable flaw size, application of probabilistic fracture mechanics (PFM) is one of the useful countermeasures compared with deterministic approach. In this paper, benchmark problems for a CASS pipe were proposed with intention applying and verifying PFM codes. As the fracture modes, fatigue crack extension, plastic collapse and ductile crack initiation were assumed. Six organizations participated in the benchmark analysis and failure probabilities from them were compared. As a result the failure probability of each problem showed good agreement and the code for application of CASS issue has been verified.
Okamoto, Minoru*; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
Physical Review C, 88(2), p.025801_1 - 025801_10, 2013/08
Times Cited Count：56 Percentile：92.99(Physics, Nuclear)In neutron star crust, non-uniform structure of nuclear matter is expected, which is called the "pasta" structure. From the recent studies of giant flares in magnetars, these structures might be related to some observables and physical quantities of the neutron star crust. To investigate the above quantities, we have numerically explored the pasta structures with a fully three-dimensional geometry and have studied the properties of low-density nuclear matter, based on the relativistic mean-field model and the Thomas-Fermi approximation. We have observed typical pasta structures for fixed proton number-fraction and droplet and rod for cold catalyzed matter. We have also explored the crystalline configuration of "pasta". Although it was believed that spherical nuclei (droplets) form a body-centred cubic lattice as a ground state, we have shown that a face-centred cubic lattice is energetically more favored than body-centred cubic lattice near the transition density to rod.
Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*
Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 81(7), p.543 - 546, 2013/07
Times Cited Count：8 Percentile：18.74(Electrochemistry)The molten state of simulated high-level waste glass and the behavior of ruthenium element in the melt were investigated by using synchrotron radiation based X-ray imaging technique. Melting, generating and moving of bubbles, condensation and sedimentation of ruthenium element were observed dynamically in continuous 12-bit gray-scale images from the CCD camera. X-ray intensity was obtained easily by digitizing gray-scale values in the image. The existence of ruthenium element is emphasized as a black color in the CCD image at X-ray energy higher than the Ru K-absorption edge. Position sensitive imaging X-ray absorption fine structure (XAFS) measurement was also performed to clarify the chemical state of ruthenium element in the melt.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
Proceedings of Science (Internet), 146, p.218_1 - 218_6, 2013/04
In low-density nuclear matter which is relevant to neutron star crust, non-uniform structures called "nuclear pasta" are expected. In most of the previous studies, the crystalline of "nuclear pasta" and uniform background electron are assumed and/or the Wigner-Seitz (WS) cell approximation is used. For matter with droplets, body-centered cubic (bcc) lattice is found to be more favored than face-centered cubic (fcc) and simple cubic. This conclusion has been obtained by comparing the Coulomb energy with a fixed size of droplets. To be more precise, we should take into account the effect of non-uniformity of electron and optimal sizes of the droplets. We perform numerical calculations of non-uniform nuclear matter based on the relativistic mean field theory and Thomas-Fermi model with fully three-dimensional geometry. The most stable structure and the equation of state of matter with and without WS cell approximation and the energy difference between fcc and bcc for droplet are compared.
Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*
Proceedings of 4th Asian Conference on Molten Salt Chemistry and Technology & 44th Symposium on Molten Salt Chemistry, Japan, p.47 - 52, 2012/09
The molten state of the simulated high-level waste glass and the behavior of ruthenium element in the melt were investigated by using synchrotron radiation based X-ray imaging technique. Melting, generating and moving of bubbles, condensation and sedimentation of ruthenium element were observed dynamically in continuous 12-bit gray-scale images from the CCD camera. The existence of ruthenium in the X-ray CCD image was emphasized over the energy of Ru K-absorption edge. X-ray intensity was obtained easily by digitalizing gray-scale values in the image. Position sensitive imaging X-ray absorption fine structure (XAFS) measurement was performed to clarify the chemical state of ruthenium element in the melt.
Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Shiwaku, Hideaki; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 11(2), p.127 - 132, 2012/06
Distribution and the chemical state of Ru element in the simulated high-level waste glass were examined by using the synchrotron radiation based X-ray imaging technique. In this technique, a direct X-ray CCD camera is used in place of an ion chamber. Position sensitive X-ray absorption spectra were obtained by analyzing gray scale in images of the X-ray CCD camera. At first, we measured a test sample containing RuO
and Ru metal powder. We successfully obtained information on the Ru distribution in the sample. In addition, the chemical state (oxide or metal ?) of each small Ru-rich spot was evaluated by the corresponding position sensitive XAFS spectrum. The imaging XAFS technique was applied to some simulated high-level waste glass samples. The Ru distribution of the glass sample and their chemical state were confirmed by image analyses. It can be seen that Ru element scattered in the glass sample exists as oxide RuO.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
Physics Letters B, 713(3), p.284 - 288, 2012/05
Times Cited Count：33 Percentile：81.70(Astronomy & Astrophysics)We numerically explore the pasta structures and properties of low-density nuclear matter without any assumption on the geometry. We observe conventional pasta structures. A mixture of two pasta structures at transient densities and some more complicated structures appear as metastable states. We also investigated the lattice structure of droplets and found that fcc lattice appears for some density region, which is different from the widely accepted bcc lattice.
Ohshima, Hiroyuki; Sakai, Takaaki; Kamide, Hideki; Kimura, Nobuyuki; Ezure, Toshiki; Uchibori, Akihiro; Ito, Kei; Kunugi, Tomoaki*; Okamoto, Koji*; Tanaka, Nobuatsu*; et al.
JAEA-Research 2008-049, 44 Pages, 2008/06
JAEA-Research-2008-049.pdf:42.3MB
Japan Atomic Energy Agency has conducted a conceptional design study of a sodium-cooled fast reactor in a frame work of the FBR feasibility study. The plant system concept for a commercial step is intended to minimize a vessel diameter to achieve an economical competitiveness. Therefore, the coolant in the vessel has relatively higher velocity and gas entrainment (GE) prevention from a liquid surface in the reactor vessel becomes one of important issues for the thermal-hydraulic design. In order to establish a design criteria for the GE prevention, the GE from vortex dimples at the liquid surface was investigated by a working group. The 1st proposal of "Design Guideline for Gas Entrainment Prevention Using CFD Method" was established based on the knowledge gained from the working group activities. This report introduces each study in the working group to clarify the basis of the design guideline.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
no abstracts in English
Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*
no journal, ,
Distribution and the chemical state of fission product elements like Zr, Mo and Ru in the simulated high-level waste glass were examined by using the synchrotron radiation based X-ray imaging technique. We used the high resolution imaging system and the high-speed CCD camera for imaging XAFS measurement of the glass sample at molten state. Position sensitive X-ray absorption spectra were obtained by analyzing gray scale in images of the CCD camera.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
We have performed three-dimensional calculation for low-density nuclear matter without any geometrical assumption and have explored its structure and property. As a result, we have confirmed the appearance of conventional pasta structures whose existence had been suggested by several authors. We also observed some exotic structures other than pasta as metastable states around the density regions where the pasta structures change. In addition, there emerged one point unlike the conventional results in the crystalline structure of spherical nuclear matter. In our self-consistent calculation, it emerges as a face-centered cubic lattice, while it has been regarded to take a body-centered cubic lattice in the previous studies.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
We have numerically performed three dimensional calculation of low-density nuclear matter without any assumption on the geometry, and explored these structures and properties. We have observed non-uniform structures called "nuclear pasta", while a mixture of the pasta structures appears as a metastable state at some transient densities. One point unlike the conventional results emerged in the crystalline of spherical nuclei. In our self-consistent calculation, ground-state matter has a face-centered cubic lattice, while it has been regarded to take a body-centered cubic lattice in the previous studies.
Okamoto, Yoshihiro; Shiwaku, Hideaki; Nakada, Masami; Takano, Masahide; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*
no journal, ,
Chemical properties and behavior of insoluble residue in the cold cap of simulated high-level waste glass was examined by using synchrotron radiation based imaging and XAFS analyses. From XAFS analyses of Zr, Mo and Ce, (1) Zr is in a complex oxide like ZrSiO
or Zr(MoO), (2) The complex MoO
ion is predominant for Mo element, (3) Redox state for cerium element was evaluated from Ce L
-edge XAFS, and (4) Chemical state of cerium was determined from Ce K-edge XAFS. Chemical state and bubble growth at molten state was investigated by using X-ray imaging analysis.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
We have numerically performed three dimensional calculation of nuclear pasta (inhomogeneous low-density nuclear matter) in beta-equilibrium without any assumption on the geometry, and explored the structures and properties. We have observed two type of nuclear pasta with different crystalline structures. One is a face-centered cubic lattice and another is a body-centered cubic lattice. So far, it has been regarded that there appears only a body-centered cubic. But in our self-consistent calculation with non-uniformity of electrons, ground-state matter has lattice structure of not only a body-centered cubic but also a face-centered cubic.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
In low-density nuclear matter like neutron star crust and previous stage of supernovae, the existence of non-uniform structure called "nuclear pasta" has been suggested. In previous studies, uniform background electron and crystalline structure of "nuclear pasta" was assumed and Wigner-Seitz cell (WS) approximation was used. For droplet structure, it has been considered that body-centered cubic (bcc) lattice is energetically favored than face-centred cubic (fcc) lattice by a small difference in Coulomb energy. We performed three-dimensional calculation on the beta-equilibrium low-density nuclear matter using a relativistic mean field model and Thomas-Fermi approximation. We explored the most energetically stable structures and the energy compositions of bcc and fcc of droplets. Then we have found that fcc lattice can emerge at some densities.
Okamoto, Minoru*; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
no abstracts in English
Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*
no journal, ,
The high level liquid waste (HLLW) generated in the reprocessing of spent nuclear fuels is disposed of as vitrified waste mixed with borosilicate glass. Chemical state of noble metals like Ru in simulated glasses was investigated by using the synchrotron based X-ray imaging analysis in the present work. The X-ray imaging measurement was performed at the NW10A of PF-AR and the BL-27B of PF, KEK. The imaging system is composed of the beam monitor (AA40 and AA50) and the CCD camera (high-speed type C9300-221 and high resolution type C11440-10C). X-ray absorption fine structure (XAFS) spetcra of Ru K-edge for very small area were obtained from the imaging intensity data. It can be seen by comparing with standard materials that Ru in the small area exists as RuO.
Okamoto, Yoshihiro; Shiwaku, Hideaki; Nakada, Masami; Takano, Masahide; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*
no journal, ,
Synchrotron based X-ray absorption fine structure analysis of Mn, Ce, Zr, Mo, Ru, Rh and Pd was performed to evaluate chemical state and the local structure in the simulated glass samples. Redox state and chemical state were confirmed from X-ray near edge structure (XANES) analysis. Information on the local structure was obtained from the extended X-ray absorption fine structure (EXAFS) analysis.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
We have numerically performed three dimensional calculation of inhomogeneous low-density nuclear matter in beta-equilibrium without any assumption on the geometry, and explored the structures and its properties. We have observed two type of nuclear pasta with different crystalline structures. One is a face-centered cubic lattice and another is a body-centered cubic lattice. So far, it has been regarded that there appears only a body-centered cubic. But in our self-consistent calculation with non-uniformity of electrons, ground-state matter has lattice structure of not only a body-centered cubic but also a face-centered cubic. We also calculated the shear modulus of neutron star crust matter using three-dimensional data we obtained. Because of the Coulomb screening, shear modulus have lower value than previous one.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
In low-density nuclear matter like neutron star crust and the collapsing stage of supernovae matter, the existence of non-uniform matter called "nuclear pasta" have been predicted. In many previous studies, uniformly distributed electron and crystalline structure of "nuclear pasta" was assumed and the Wigner-Seitz cell (WS) approximation was often used. For crystalline structure of droplets, it has been considered that a body-centred cubic (bcc) lattice is favorable than face-centred cubic (fcc) lattice by Coulomb energy. However, for precise calculation, we should take into account the non-uniformity of electron and the size of droplet corresponding to crystalline structure. We have performed three-dimensional calculation using relativistic mean-field model and Thomas-Fermi approximation for cold catalyzed low-density nuclear matter. We will discuss the ground state structure, comparison with WS approximation and the difference between bcc and fcc lattice.
