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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：49 Percentile：92.61(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：7 Percentile：17.93(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.
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, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Minato, Kazuo; Shiwaku, Hideaki; Komamine, Satoshi*; Fukui, Toshiki*; Nitani, Hiroaki*; Nomura, Masaharu*
no journal, ,
Chemical state analysis of Ru element scattered in an imitative glass matrix was performed by using the Imaging XAFS technique. Information on distribution of Ru element in the matrix was obtained from contrast values of CCD images before and after the Ru K-absorption edge. It is confirmed that the feature of the distributed element can be examined by getting XAFS spectra from the contrast information. We can get two kinds of XAFS spectra corresponding to Ru metal and oxide separately in the Imaging XAFS analysis.
Okamoto, Minoru*; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
no abstracts in English
Okamoto, Minoru*; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
no abstracts in English
Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Minato, Kazuo; Shiwaku, Hideaki; Yaita, Tsuyoshi; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; et al.
no journal, ,
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. It can be seen that Ru element scattered in the glass sample exists as oxide RuO.
Okamoto, Minoru; Maruyama, Toshiki; Tatsumi, Toshitaka*; Yabana, Kazuhiro*
no journal, ,
In low-density nuclear matter, non-uniform structures called "nuclear pasta" are expected. So far, most works on nuclear pasta have used the Wigner-Seitz (WS) cell approximation with geometrical symmetry, which reduces the calculation into one-dimensional space. However, this approximation brings about limitation of the structure within typical pasta structures. On the other hand, some works report possibilities of more complicated structures such as gyroid, double-diamond, etc. In this context we perform fully three-dimensional calculations of nuclear matter based on the relativistic mean-field model and the Thomas-Fermi approximation. We demonstrate that pasta structures, previously given by the WS cell approximation, also appear in the three-dimensional calculation. The most stable structure of matter with and without WS cell approximation are compared. We also present newly observed structures which may appear as exited states of matter.
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
no abstracts in English
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
no abstracts in English
Okamoto, Minoru; Maruyama, Toshiki; Yabana, Kazuhiro*; Tatsumi, Toshitaka*
no journal, ,
In low-density nuclear matter which is relevant to the crust region of neutron stars and collapsing stage of supernovae, non-uniform structures called nuclear pasta are expected. Such pasta structures may play important roles, cooling process of neutron stars and the equation of state. So far, most works on nuclear pasta have used Wigner-Seitz cell approximation. We perform three-dimensional calculation of non-uniform nuclear matter based on the relativistic mean field model and the Thomas-Fermi approximation without any geometrical symmetry. Introducing a large cubic cell with periodic boundary conditions, we numerically solve the coupled field equations for mesons and the Coulomb potential. We demonstrate that the typical pasta structures appear in the three-dimensional calculations. The most stable structure and the EOS of matter with and without WS cell approximation are compared. Then we present newly observed structures which may appear as exited states of matter.
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 numerically explore the pasta structures and properties of low-density nuclear matter without any assumption on the geometry. We observe conventional pasta structures, while a mixture of the pasta structures appears as a metastable state at some transient densities and discuss these results. We have observed the fcc lattice structure of droplets instead of the bcc lattice, which is against the results of previous works. This difference comes from our fully consistent treatment of the lattice structure and the droplet.
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.
