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Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Al
GaO
scintillators by gamma-ray-induced positron annihilation lifetime spectroscopyFujimori, Kosuke*; Kitaura, Mamoru*; Taira, Yoshitaka*; Fujimoto, Masaki*; Zen, H.*; Watanabe, Shinta*; Kamada, Kei*; Okano, Yasuaki*; Kato, Masahiro*; Hosaka, Masahito*; et al.
Applied Physics Express, 13(8), p.085505_1 - 085505_4, 2020/08
Times Cited Count：5 Percentile：33.01(Physics, Applied)To clarify the existence of cation vacancies in Ce-doped GdAlGaO (Ce:GAGG) scintillators, we performed gamma-ray-induced positron annihilation lifetime spectroscopy (GiPALS). GiPAL spectra of GAGG and Ce:GAGG comprised two exponential decay components, which were assigned to positron annihilation at bulk and defect states. By an analogy with Ce:YAl
O, the defect-related component was attributed to Al/Ga-O divacancy complexes. This component was weaker for Ce, Mg:GAGG, which correlated with the suppression of shallow electron traps responsible for phosphorescence. Oxygen vacancies were charge compensators for Al/Ga vacancies. The lifetime of the defect-related component was significantly changed by Mg co-doping. This was understood by considering aggregates of Mg
ions at Al/Ga sites with oxygen vacancies, which resulted in the formation of vacancy clusters.
Osaki, Hirotaka; Shimazaki, Yosuke; Sumita, Junya; Shibata, Taiju; Konishi, Takashi; Ishihara, Masahiro
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 8 Pages, 2015/05
For the design on the VHTR graphite components, it is desirable to employ graphite material with higher strength. IG-430 graphite has been developed as an advanced candidate for VHTR. However, the new developed IG-430 does not have enough databases for the design of HTGR. In this paper, the compressive strength (Cs) of IG-430, one of important strengths for design data, is statistically evaluated. The component reliability is evaluated based on the safety factors defined by the graphite design code, and the applicability as the VHTR graphite material is discussed. It was found that IG-430 has higher strength (about 11%) and lower standard deviation (about 27%) than IG-110 which is one of traditional graphites used for HTGR, because the crack in IG-430 would not easy to propagate rather than IG-110. Since fracture probability for IG-430 is low, the higher reliability of core-component will be achieved using IG-430. It is expected that IG-430 is applicable for VHTR graphite material.
Kamiyama, Kenji; Konishi, Kensuke; Sato, Ikken; Toyooka, Junichi; Matsuba, Kenichi; Suzuki, Toru; Tobita, Yoshiharu; Pakhnits, A. V.*; Vityuk, V. A.*; Vurim, A. D.*; et al.
Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 8 Pages, 2014/12
Kamiyama, Kenji; Konishi, Kensuke; Sato, Ikken; Toyooka, Junichi; Matsuba, Kenichi; Zuyev, V. A.*; Pakhnits, A. V.*; Vityuk, V. A.*; Vurim, A. D.*; Gaidaichuk, V. A.*; et al.
Journal of Nuclear Science and Technology, 51(9), p.1114 - 1124, 2014/09
Times Cited Count：12 Percentile：67.4(Nuclear Science & Technology)Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Kunimoto, Eiji*; Yamaji, Masatoshi*; Eto, Motokuni*; Konishi, Takashi*; Sawa, Kazuhiro
Nuclear Engineering and Design, 271, p.314 - 317, 2014/05
Times Cited Count：11 Percentile：64.59(Nuclear Science & Technology)In this study, in order to develop evaluation method for material properties and to evaluate the irradiation-induced property changes under higher neutron doses for IG-430, the oxidation and densification effects on elastic modulus of IG-430 were investigated. Moreover, the correlation of the microstructure based on the X-ray tomography images and the material properties was discussed. It was shown that the elastic modulus of the densified graphite depends on only the closed pores and it is possible to evaluate the material properties of graphite by using X-ray tomography method. However, it is necessary to take into account of the change in the number and shape of closed pores in the grain to simulate the elastic modulus of the highly oxidized and irradiated materials by the homogenization analysis.
Fujita, Ichiro*; Eto, Motokuni*; Osaki, Hirotaka; Shibata, Taiju; Sumita, Junya; Konishi, Takashi; Yamaji, Masatoshi; Kunimoto, Eiji
JAEA-Research 2013-004, 20 Pages, 2013/07
JAEA-Research-2013-004.pdf:2.4MB
Graphite components in HTGR and VHTR may be oxidized by impurities in coolant helium-gas even at normal operation, as well as by air at air-ingress accident. In this study, by air-oxidation test at 520-900
C, oxidation characteristics of IG-110 and IG-430 graphites, and associated decrease in compressive strength were examined. The following results were obtained. (1) The activation energy of the air-oxidation for IG-430 is 176 kJ/mol being almost same as for IG-110, though the oxidation rate for IG-430 is less than a half of that for IG-110. (2) There are correlations between density change and decrease in compressive strength. Decrease in strength is the largest in case that the oxidation temperature is lower than 600 C where the homogenous oxidation occurs. (3) In the process of oxidation, amorphous binder regions are predominantly oxidized. It suggests that peeling-off of cokes grains is necessary to be considered for oxidation weight loss, as well as gasification.
Kamiyama, Kenji; Konishi, Kensuke; Sato, Ikken; Toyooka, Junichi; Matsuba, Kenichi; Zuyev, V. A.*; Pakhnits, A. V.*; Vurim, A. D.*; Gaidaichuk, V. A.*; Kolodeshnikov, A. A.*; et al.
Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 7 Pages, 2012/12
In order to eliminate energetics potential in the case of postulated core disruptive accidents (CDAs) of sodium-cooled fast reactors, introduction of a fuel subassembly with an inner duct structure has been considered. Recently, a design option which leads molten fuel to discharge upward is considered to minimize developmental efforts for the fuel subassembly fabrication. In this paper, a series of out-of-pile tests and one in-pile test were presented. The out-of-pile tests were conducted to investigate the effects of driving pressures on upward discharge, and the in-pile test was conducted to demonstrate a sequence of upward discharge behavior of molten-fuel. Based on these experimental results, it is concluded that the most of molten-fuel is expected to complete discharging upward before core melting progression, and thereby, introduction of the fuel subassembly with the upward discharge duct has the sufficient potential to eliminate energetics events.
Matsuba, Kenichi; Kamiyama, Kenji; Konishi, Kensuke; Toyooka, Junichi; Sato, Ikken; Zuev, V. A.*; Kolodeshnikov, A. A.*; Vasilyev, Y. S.*
Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 7 Pages, 2012/12
A series of fragmentation tests (FR tests) for molten oxide was conducted to obtain experimental knowledge on the distance for fragmentation of molten core material discharged into the lower sodium plenum. Approx. 7
14 kg of molten alumina was discharged into a sodium pool (depth: 1.3 m, diameter: 0.4 m, temperature: approx. 673 K) through a duct (inner diameter: 4063 mm). The test results showed that the molten alumina was fragmented into particles within 1 m from the surface of the sodium pool. The estimated distances for fragmentation in the FR tests were roughly 6070% lower than the predictions by the existing representative correlation. The experimental knowledge confirms the possibility that the distance for fragmentation of the molten core material can be significantly reduced due to thermal interactions in the lower sodium plenum.
Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Kunimoto, Eiji*; Yamaji, Masatoshi*; Eto, Motokuni*; Konishi, Takashi*; Sawa, Kazuhiro
Proceedings of 6th International Topical Meeting on High Temperature Reactor Technology (HTR 2012) (USB Flash Drive), 6 Pages, 2012/10
In this study, in order to develop evaluation method for material properties and to evaluate the irradiation-induced property changes under higher neutron doses for IG-430, the oxidation and densification effects on elastic modulus of IG-430 were investigated. Moreover, the correlation of the microstructure based on the X-ray tomography images and the material properties was discussed. It was shown that the elastic modulus of the densified graphite depends on only the closed pores and it is possible to evaluate the material properties of graphite by using X-ray tomography method. However, it is necessary to take into account of the change in the number and shape of closed pores in the grain to simulate the elastic modulus of the highly oxidized and irradiated materials by the homogenization analysis.
Kojima, Keiji*; Onishi, Yuzo*; Watanabe, Kunio*; Nishigaki, Makoto*; Tosaka, Hiroyuki*; Shimada, Jun*; Aoki, Kenji*; Tochiyama, Osamu*; Yoshida, Hidekazu*; Ogata, Nobuhisa; et al.
JAEA-Research 2011-033, 126 Pages, 2012/02
JAEA-Research-2011-033.pdf:31.33MB
The next advancements for the research of radioactive waste repository was started to improve and systematize the investigation and evaluation techniques on geological environment in consideration of intra-field of science and technology. Intra-field means the various fields among each study area of (a) geological environment, (b) design and engineering, (c) safety evaluation for radioactive waste repository, here. The following items were studied and discussed this year. (1) To Reconstruct Near Field (NF) Concept in consideration of coupled phenomena on geological environment. (2) To develop systematic investigation techniques on the geological environment in consideration of intra-field among each study area above mentioned (a), (b) and (c). Regarding (1), examination of NF concept focused on the realistic crystalline rock was carried out. Also through the overall discussion in the committee, comments from the all commissioners in relation to the intra-field of their study area were made to reflect on reconstruction of NF concept. Regarding (2), the research and development in consideration of NF and intra-field among each study area were conducted.
Sumita, Junya; Shibata, Taiju; Kunimoto, Eiji*; Yamaji, Masatoshi*; Konishi, Takashi*; Sawa, Kazuhiro
IOP Conference Series; Materials Science and Engineering, 18(16), p.162012_1 - 162012_4, 2011/09
Times Cited Count：1 Percentile：52.78(Materials Science, Ceramics)For control rod element of Very High Temperature Reactor, carbon fiber reinforced carbon matrix composite (C/C composite) is one of the major candidate materials for its high strength and thermal stability. The development of a property prediction model of the two-dimensional (2D)-C/C composite is one of the most important subjects for the design methodology for control rod. Since the property of the 2D-C/C composite is strongly dependent on its microstructure, fiber/matrix, it would be possible to evaluate the properties of the 2D-C/C composite from its microstructure. In this study, in order to develop the property prediction model of the 2D-C/C composite base on its microstructure, pore distribution was investigated by using the X-ray computed tomography (X-ray CT) images and developed image based voxcel model. The compressive strength of the 2D-C/C composite was measured and evaluated by the voxcel model. This study shows that the pore distribution in the 2D-C/C composite can be confirmed visually and the volume and shape of the pores can be estimated from X-ray CT images. It is also shown that evaluation of the compressive strength by using the voxel model is useful to simulate the trend of the stress distribution of the 2D-C/C composite. However, it is necessary to characterize the property of the 2D-C/C composite and to set up the appropriate mesh to simulate the absolute stress value precisely.
Eto, Motokuni*; Konishi, Takashi*; Shibata, Taiju; Sumita, Junya
IOP Conference Series; Materials Science and Engineering, 18(16), p.162003_1 - 162003_6, 2011/09
Times Cited Count：4 Percentile：87.38(Materials Science, Ceramics)High Temperature Gas-cooled Reactor (HTGR) and Very High Temperature Reactor (VHTR) are attractive nuclear reactors to obtain high temperature helium gas to the reactor outlet. To enhance the thermal efficiency, the core internals of HTGR/VHTR are subjected to the very severe high temperature condition. The carbon fiber reinforced carbon-carbon composite (C/C composite) is one of the advanced material candidates for the control rod sheath of the reactors because of its excellent thermal resistance and stability in the severe condition. The R&Ds on the C/C composite application to HTGR have been carried out since 1990'. JAEA and Toyo Tanso have been in collaboration with each other in the R&Ds. The development of control rod made of C/C composite is recently focused as one of the important subjects to develop the VHTR in the international R&Ds. The scheme of the development of JAEA is categorized as the following phases; (1) Database establishment, (2) Design and manufacturing of component and (3) Demonstration test by HTTR. At the initial stage of the development in 1990' in JAERI, the feasibility of the control rod using C/C composite was demonstrated by a conceptual design. The phase (2) is planned to be completed within 5 years. This paper presents the review of the development of the control rod made of C/C composite and the recent R&D results.
collisions at 
= 200 GeVAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07
Times Cited Count：29 Percentile：72.31(Astronomy & Astrophysics)We report on the event structure and double helicity asymmetry (
) of jet production in longitudinally polarized collisions at = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured = -0.0014 
0.0037 at the lowest 
bin and -0.0181 0.0282 at the highest bin. The measured is compared with the predictions that assume various 
distributions.
collisions at = 200 and 62.4 GeVAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06
Times Cited Count：184 Percentile：99.44(Physics, Nuclear)Transverse momentum distributions and yields for 
, and 
in collisions at = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different collisions. We also present the scaling properties such as 
and 
scaling and discuss the mechanism of the particle production in collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.
Sato, Ikken; Tobita, Yoshiharu; Konishi, Kensuke; Kamiyama, Kenji; Toyooka, Junichi; Nakai, Ryodai; Kubo, Shigenobu*; Kotake, Shoji*; Koyama, Kazuya*; Vassiliev, Y. S.*; et al.
Journal of Nuclear Science and Technology, 48(4), p.556 - 566, 2011/03
In the JSFR design, elimination of severe recriticality events in the Core Disruptive Accident (CDA) is intended as an effective measure to assure retention of the core materials within the reactor vessel. The design strategy is to control the potential of excessive void reactivity insertion in the Initiating Phase selecting appropriate design parameters such as maximum void reactivity on one hand, and to exclude core-wide molten-fuel-pool formation, which has been the main issue of CDA, with introduction of Inner Duct on the other hand. The effectiveness of these measures are reviewed based on existing experimental data and evaluations performed with validated analysis tools. It is judged that the present JSFR design can exlude severe power burst events.
+ collisions at = 200 GeV and scaling properties of hadron productionAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03
Times Cited Count：175 Percentile：98.48(Astronomy & Astrophysics)The PHENIX experiment at RHIC has measured the invariant differential cross section for production of 
, 
, 
and 
mesons in collisions at = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, 
and 
, determining the high 
and characterizing the low regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.
Kojima, Keiji*; Onishi, Yuzo*; Watanabe, Kunio*; Nishigaki, Makoto*; Tosaka, Hiroyuki*; Shimada, Jun*; Aoki, Kenji*; Tochiyama, Osamu*; Yoshida, Hidekazu*; Ogata, Nobuhisa; et al.
JAEA-Research 2010-049, 282 Pages, 2011/02
JAEA-Research-2010-049.pdf:29.88MB
This report summarizes studies that have been carried out with the aim of assessing and systemizing the technology used for the investigation and analysis of the deep underground geological environment in relation to the disposal of radioactive waste. The main studies were: (1) a study on the research and development (R&D) topics proven to have practical application for the investigation, and analysis and understanding of the deep underground geological environment, and, (2) a study on leading edge technology that can provide the advanced technical basis for the investigation, analysis and understanding of the deep underground geological environment. Regarding the R&D topics (1, above), specific investigations, measurements, numerical analyses and chemical analyses were performed and reviewed with respect to the topics, (a) Repository design, engineering technology (b) Geological environment and (c) Safety evaluation. Based on the result of the review, topics requiring collaboration research in overlapping research fields, including safety assessment, were identified. Also, the near field concept (NFC) was reconsidered in terms of its realistic construction model. Regarding advanced technology (2, above), based on the objectives of the JAEA (Japan Atomic Energy Agency) research project, the study was implemented considering previous R&D results and detailed research result at the research site and thus an assessment of the need for advanced technical basis for investigation and analysis. This study contributed to the R&D development and its practical application.
Toyooka, Junichi; Kamiyama, Kenji; Konishi, Kensuke*; Tobita, Yoshiharu; Sato, Ikken
Proceedings of 7th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-7) (CD-ROM), 7 Pages, 2010/11
In this study, the heat flux from the molten core materials to the outer surface of the inner duct (the pool-to-duct heat flux) was evaluated based on all the EAGLE-1 in-pile experiments available. Through the evaluation, it was understood that the pool-to-duct heat flux was so high in all the in-pile experiments that the duct wall failed without coolant boiling in its behind. It was also indicated that the presence of steel in the molten core mixture played a key role in this high heat flux. Application of the SIMMER-III code for these tests suggested that some model improvements were necessary to simulate pool-to-duct heat transfer behavior in a mechanistic way.
Sumita, Junya; Shibata, Taiju; Kunimoto, Eiji*; Yamaji, Masatoshi*; Konishi, Takashi*; Sawa, Kazuhiro
Journal of Nuclear Science and Technology, 47(4), p.411 - 420, 2010/04
Times Cited Count：4 Percentile：30.63(Nuclear Science & Technology)Two dimensional carbon fiber reinforced carbon composite (2D-C/C composite) is one of the candidate materials for a reactor internals, e.g. control rod element, of Very High Temperature Reactor (VHTR) because of its high strength at high temperature and thermal stability. From the viewpoint of its application to the reactor internals of VHTR, it is important to investigate the anisotropy effect on its properties for the design and safety analysis of VHTR. Moreover, the property of 2D-C/C composite is strongly related to its microstructure, therefore, it is necessary to observe the internal microstructure to investigate the relationship between the microstructural change and the property change. This study has shown that the X-ray tomography could be applied to observe the microstructural change of thermally 2D-C/C composite. The relationship between the thermal conductivity and the coefficient of thermal expansion (CTE) change and burn-off of thermally oxidized 2D-C/C composite could be expressed by the empirical exponential decay formula in both directions perpendicular and parallel to lamina. It could be explained the direction of hexagonal graphite crystal structure from carbon atoms and microstructural change of 2D-C/C composite.
