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Journal Articles

Phase-field model for crystallization in alkali disilicate glasses; Li$$_2$$O-2SiO$$_2$$, Na$$_2$$O-2SiO$$_2$$ and K$$_2$$O-2SiO$$_2$$

Kawaguchi, Munemichi; Uno, Masayoshi*

Journal of the Ceramic Society of Japan, 128(10), p.832 - 838, 2020/10

 Times Cited Count:0

This study developed phase-field method (PFM) technique in oxide melt system by using a new mobility coefficient ($$L$$). The crystal growth rates ($$v_0$$) obtained by the PFM calculation with the constant $$L$$ were comparable to the thermodynamic driving force in normal growth model. The temperature dependence of the $$L$$ was determined from the experimental crystal growth rates and the $$v_0$$. Using the determined $$L$$, the crystal growth rates ($$v$$) in alkali disilicate glasses, Li$$_2$$O-2SiO$$_2$$, Na$$_2$$O-2SiO$$_2$$ and K$$_2$$O-2SiO$$_2$$ were simulated. The temperature dependence of the $$v$$ was qualitatively and quantitatively so similar that the PFM calculation results demonstrated the validity of the $$L$$. Especially, the $$v$$ obtained by the PFM calculation appeared the rapid increase just below the thermodynamic melting point ($$T_{rm m}$$) and the steep peak at around $$T_{rm m}$$-100 K. Additionally, as the temperature decreased, the $$v$$ apparently approached zero ms$$^-1$$, which is limited by the $$L$$ representing the interface jump process. Furthermore, we implemented the PFM calculation for the variation of the parameter $$B$$ in the $$L$$. As the $$B$$ increased from zero to two, the peak of the $$v$$ became steeper and the peak temperature of the $$v$$ shifted to the high temperature side. The parameters $$A$$ and $$B$$ in the $$L$$ increased exponentially and decreased linearly as the atomic number of the alkali metal increased due to the ionic potential, respectively. This calculation revealed that the $$A$$ and $$B$$ in the $$L$$ were close and reasonable for each other.

Journal Articles

The Evaluation of the properties of the collision-plate-type jet mill for dry recycling of MOX powder

Kawaguchi, Koichi; Segawa, Tomoomi; Yamamoto, Kazuya; Makino, Takayoshi; Iso, Hidetoshi; Ishii, Katsunori

Funtai Kogakkai-Shi, 57(9), p.478 - 484, 2020/09

A collision plate type jet mill is assumed to be a pulverizer that can control the particle size for nuclear fuel fabrication. The collision plate type jet mill consists of two modules, a classifier and a mill chamber. Coarse component of powder is cycled in the equipment and finally pulverized into objective particle size. In this report, simulated crushed powders were classified and pulverized step by step, and particle size distribution were compared. The collision plate type jet mil can produce objective size particles with low overgrinding.

Journal Articles

Signatures of the vortical quark-gluon plasma in hadron yields

Taya, Hidetoshi*; Park, A.*; Cho, S.*; Gubler, P.; Hattori, Koichi*; Hong, J.*; Huang, X.-G.*; Lee, S. H.*; Monnai, Akihiko*; Onishi, Akira*; et al.

Physical Review C, 102(2), p.021901_1 - 021901_6, 2020/08

 Times Cited Count:0 Percentile:100(Physics, Nuclear)

Journal Articles

Development of a multiphase particle method for melt-jet breakup behavior of molten core in severe accident

Wang, Z.; Iwasawa, Yuzuru; Sugiyama, Tomoyuki

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 12 Pages, 2020/08

Journal Articles

Enhancing emergency response in the field based on analysis of workload distribution at Fukushima Daiichi Nuclear Power Station

Yoshizawa, Atsufumi*; Oba, Kyoko; Kitamura, Masaharu*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 18(2), p.55 - 68, 2019/06

This study aims to improve the potential of an emergency response by analyzing the workload management during the accident at the Emergency Response Center (ERC) of TEPCO's Fukushima Daiichi Nuclear Power Plant. Specifically, the research focused on the response of the ERC during the time between the discontinuation of Unit 3 core water injection and its recovery. It identified the different types of workload at the ERC had and how they had been managed based on the record of a TV conference. It also deduced the casual factors of the responses, supplementing the interview record of the director of ERC at the time by applying workload management analysis. On the basis of these findings, lessons to enhance the potential of the on-site emergency response have been obtained for ERC and outside organizations.

Journal Articles

Development on high-power spallation neutron sources with liquid metals

Futakawa, Masatoshi

Proceedings of 13th International Symposium on Advanced Science and Technology in Experimental Mechanics (13th ISEM'18) (USB Flash Drive), 6 Pages, 2018/10

Issues on the engineering technologies relating to high-power spallation neutron sources with liquid metals are introduced. The present status on research activities and results was reviewed.

Journal Articles

Thermal-hydraulics technological strategy roadmap 2017; An Approach for continuous safety improvement of LWRs

Itoi, Tatsuya*; Iwaki, Chikako*; Onuki, Akira*; Kito, Kazuaki*; Nakamura, Hideo; Nishida, Akemi; Nishi, Yoshihisa*

Nippon Genshiryoku Gakkai-Shi, 60(4), p.221 - 225, 2018/04

no abstracts in English

JAEA Reports

System management for aggregation of knowledge on marine geological survey in coastal areas

Takahashi, Tadao*; Sato, Toshinori; Masunaga, Kosuke

JAEA-Review 2017-030, 60 Pages, 2018/01

JAEA-Review-2017-030.pdf:4.32MB

The amount of the information such as the data, models and analysis results related to geological environment has been enormous. It is believed that an appropriate organization of the information is useful for conducting geological environment survey work at the candidate sites of geological disposal. The Survey on Geological Disposal Technology projects commissioned by METI that started in FY2015 handles various information such as the data, models, analysis results, etc. of geological environment. In this project, in preparation for collection and compilation of the information on geological environment in coastal areas, we have made clear the current status of the existing systems including databases. At the same time, we have created measures for centralized information management for the purpose of organizing a huge amount of information as well as sharing the information and information management systems among the related organizations.

JAEA Reports

Inspection and repair techniques in reactor vessel of the experimental fast reactor JOYO; Development of devices for retrieving bent MARICO-2 subassembly and completion of retrieval work

Ashida, Takashi; Nakamura, Toshiyuki*; Ito, Hideaki

JAEA-Technology 2017-024, 198 Pages, 2017/11

JAEA-Technology-2017-024.pdf:55.8MB
JAEA-Technology-2017-024-appendix(CD-ROM)-1.zip:298.09MB
JAEA-Technology-2017-024-appendix(CD-ROM)-2.zip:210.77MB

In the experimental fast reactor Joyo, the disconnecting of an irradiation test subassembly MARICO-2 (Material Testing Irradiation Rig with Temperature Control) from its holding mechanism was conducted in May 2007. After the operation, the rotating plug was rotated despite the fact that the test subassembly was not disconnected completely. Consequently, top of wrapper tube of the MARICO-2 subassembly was bent onto the in-vessel storage rack. Since the overhanging part of the subassembly was in the height in which contacts with the upper core structure, it had damaged the bottom surface of the upper core structure. As the result, it was necessary to replace the damaged upper core structure and to retrieve the bent MARICO-2 subassembly for Joyo restart. Retrieval devices for MARICO-2 subassembly consist of a gripper mechanism to lift subassembly together with transfer pot, a guide tube built-in a pantograph mechanism to adjust lifting axis and safety mechanisms to prevent or mitigate falling of MARICO-2 subassembly, a retrieval cask and so on. Design of the retrieval devices have been verified in ex-vessel partial or full-scale mock-up tests and in-vessel function tests. In 2014, MARICO-2 subassembly was successfully retrieved from the reactor vessel by applying these retrieval devices. Then, retrieved subassembly was transported to a hot-cell facility for post-irradiation examinations. Devices have demonstrated expected performance under the actual environmental conditions of a sodium cooled fast reactor. This is a synthetic report about the retrieval work of the deformed and irradiated test subassembly in Joyo. This report includes the detail design and fabrication of the special retrieval device, results of tests for confirmation including the mock-up tests in manufacturer's factory, and results of MARICO-2 retrieval work from the reactor vessel.

Journal Articles

Challenges for enhancing Fukushima environmental resilience, 2; Features of radionuclide release and deposition with accident progress

Saito, Kimiaki; Nagai, Haruyasu; Kinase, Sakae; Takemiya, Hiroshi

Nippon Genshiryoku Gakkai-Shi, 59(6), p.40 - 44, 2017/06

no abstracts in English

Journal Articles

Thermal-hydraulics technological strategy roadmap that improves safety of LWRs

Arai, Kenji*; Umezawa, Shigemitsu*; Oikawa, Hirohide*; Onuki, Akira*; Nakamura, Hideo; Nishi, Yoshihisa*; Fujii, Tadashi*

Nippon Genshiryoku Gakkai-Shi, 58(3), p.161 - 166, 2016/03

no abstracts in English

JAEA Reports

MOSRA-SRAC; Lattice calculation module of the modular code system for nuclear reactor analyses MOSRA

Okumura, Keisuke

JAEA-Data/Code 2015-015, 162 Pages, 2015/10

JAEA-Data-Code-2015-015.pdf:3.99MB
JAEA-Data-Code-2015-015-appendix(CD-ROM).zip:3.38MB

MOSRA-SRAC is a lattice calculation module of the Modular code System for nuclear Reactor Analyses (MOSRA). This module performs the neutron transport calculation for various types of fuel elements including existing light water reactors, research reactors, etc. based on the collision probability method with a set of the 200-group cross-sections generated from the Japanese Evaluated Nuclear Data Library JENDL-4.0. It has also a function of the isotope generation and depletion calculation for up to 234 nuclides in each fuel material in the lattice. In these ways, MOSRA-SRAC prepares the burn-up dependent effective microscopic and macroscopic cross-section data to be used in core calculations.

Journal Articles

Study on application of kriging to evaluation of radioactivity concentration for ensuring compliance with the criterion of site release

Ishigami, Tsutomu; Shimada, Taro

Journal of Nuclear Science and Technology, 52(9), p.1186 - 1204, 2015/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

In the field of decommissioning of nuclear facilities, a reliable method for ensuring compliance with the criterion of site release is an important technical issue to be resolved in Japan. Considering that kriging can consider the spatial correlation of radioactivity concentrations, we propose a method of applying kriging to ensure compliance with the site release criterion. Estimated radioactivity concentrations exhibit uncertainty, which results in a certain probability of the occurrence of decision errors regarding site release. We describe a method for calculating the uncertainty and establish a minimum number of measurement points required. We applied the proposed method and a conventional statistical method to two sample cases. It was observed that the proposed method appropriately estimated the mean radioactivity concentration and led to an efficient measurement requiring fewer measurement points relative to the conventional method when spatial correlation existed.

Journal Articles

Analytic cross sections for electron impact collisions with nitrogen molecules

Tabata, Tatsuo*; Shirai, Toshizo*; Sataka, Masao; Kubo, Hirotaka

Atomic Data and Nuclear Data Tables, 92(3), p.375 - 406, 2006/05

 Times Cited Count:56 Percentile:6.01(Physics, Atomic, Molecular & Chemical)

no abstracts in English

Journal Articles

Pedestal conditions for small ELM regimes in tokamaks

Oyama, Naoyuki; Gohil, P.*; Horton, L. D.*; Hubbard, A. E.*; Hughes, J. W.*; Kamada, Yutaka; Kamiya, Kensaku; Leonard, A. W.*; Loarte, A.*; Maingi, R.*; et al.

Plasma Physics and Controlled Fusion, 48(5A), p.A171 - A181, 2006/05

 Times Cited Count:61 Percentile:9.5(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Characterization of Type-I ELMs in tangential co-, balanced- and counter-plus perpendicular NBI heated plasmas on JT-60U

Kamiya, Kensaku; Urano, Hajime; Koide, Yoshihiko; Takizuka, Tomonori; Oyama, Naoyuki; Kamada, Yutaka; JT-60 Team

Plasma Physics and Controlled Fusion, 48(5A), p.A131 - A139, 2006/05

 Times Cited Count:20 Percentile:39.65(Physics, Fluids & Plasmas)

Effects of plasma rotation and ripple loss on the Type-I ELMs have systematically studied in the JT-60U tokamak, scanning combinations of NBI at the three kinds of plasma volumes. New findings on the Type-I ELMs confirm to be smaller ELM energy loss per pedestal stored energy, DWELM/Wped, and faster ELM frequency, fELM, in the counter-NBI than co-NBI, keeping the power of ELM, PELM, per heating power crossing the separatrix, PSEP, constant. Balanced-NBI case is also intermediate between co- and counter-NBI. In addition, the product of PELM/PSEP decreases according to increase in the plasma volume, suggesting an increase in the inter-ELM transport due mainly to an enhancement in the ripple loss of fast ion.

Journal Articles

Comparisons of small ELM H-mode regimes on the Alcator C-Mod and JFT-2M tokamaks

Hubbard, A. E.*; Kamiya, Kensaku; Oyama, Naoyuki; Basse, N.*; Biewer, T.*; Edlund, E.*; Hughes, J. W.*; Lin, L.*; Porkolab, M.*; Rowan, W.*; et al.

Plasma Physics and Controlled Fusion, 48(5A), p.A121 - A129, 2006/05

 Times Cited Count:15 Percentile:49.68(Physics, Fluids & Plasmas)

Dedicated experiments were carried out to compare the properties, fluctuation behaviour and access conditions of these regimes. A common shape was developed which scaled the plasma boundary except for aspect ratio. Scans of density and input power were carried out at several values of q95, so as to achieve ranges of dimensionless parameters. A striking similarity of access conditions was seen. These results suggest common physical mechanisms for the H-mode regimes, which do not depend critically on aspect ratio over this range. On the other hand, several differences in the details of the edge fluctuations were found, and will be reported. The effect of wall conditioning via boronization on the H-mode regimes will also be discussed.

Journal Articles

Replica symmetry breaking for the Ising spin glass within cluster approximations

Yokota, Terufumi

Physica A, 363(2), p.161 - 170, 2006/03

 Times Cited Count:6 Percentile:55.88(Physics, Multidisciplinary)

Within a class of cluster approximations, the Ising spin glass model on a d-dimensional hypercubic lattice is solved near the spin glass transition temperature. Spin glass order parameter function and Almeida-Thouless line are obtained.

Journal Articles

Reduced divertor heat loads, plasma shape effects, and radial electric field structures in JFT-2M HRS H-mode plasmas

Kamiya, Kensaku; Kawashima, Hisato; Ido, Takeshi*; Oyama, Naoyuki; Bakhtiari, M.*; Kasai, Satoshi; Kusama, Yoshinori; Miura, Yukitoshi; Ogawa, Hiroaki; Tsuzuki, Kazuhiro; et al.

Nuclear Fusion, 46(2), p.272 - 276, 2006/02

 Times Cited Count:3 Percentile:87.79(Physics, Fluids & Plasmas)

An attractive operational regime without any large ELMs, namely High Recycling Steady (HRS) H-mode, was found on JFT-2M during Y2000 campaign after boronization. Recent experiments have concentrated on the studies of the access conditions for the HRS regime, in terms of the pedestal parameters. The HRS regime was more likely at higher edge density and lower edge temperature, which corresponds to the normalized electron collisionality of 1 in the plasma edge region.

Journal Articles

Experimental and theoretical elastic cross sections for electron collisions with the C$$_{3}$$H$$_{6}$$ isomers

Makochekanwa, C.*; Kato, Hidetoshi*; Hoshino, Masamitsu*; Tanaka, Hiroshi*; Kubo, Hirotaka; Bettega, M. H. F.*; Lopes, A. R.*; Lima, M. A. P.*; Ferreira, L. G.*

Journal of Chemical Physics, 124(2), p.024323_1 - 024323_9, 2006/00

 Times Cited Count:15 Percentile:50.48(Chemistry, Physical)

no abstracts in English

251 (Records 1-20 displayed on this page)