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Kitamura, Akane; Yamaki, Tetsuya*; Yuri, Yosuke*; Koshikawa, Hiroshi*; Sawada, Shinichi*; Yuyama, Takahiro*; Usui, Aya; Chiba, Atsuya*
Nuclear Instruments and Methods in Physics Research B, 460, p.254 - 258, 2019/12
Times Cited Count：2 Percentile：23.19(Instruments & Instrumentation)Poly(vinylidene-fluoride) (PVDF) film is suitable for investigation of the size of etchable ion tracks because we can clearly judge the finish of the track etching and the surrounding bulk area remains due to the high chemical stability. Thereby we can measure the radius of ion tracks of each ion. In this study, we focused on two irradiation conditions for controlling the size of etchable ion tracks of PVDF films. One was irradiation in an oxygen atmosphere and the other was a fullerene (C
) cluster beam irradiation. SEM observation showed that the size of pores became larger by irradiation in an oxygen atmosphere. It was found that the oxidation of ion tracks widened the size of etchable ion tracks. The C irradiation caused larger etchable tracks on the PVDF surface. The result could represent the effect of local and simultaneous collisions by the swift aggregated ions.
Chikazawa, Yoshitaka; Uzawa, Masayuki*; Usui, Shinichi*; Tozawa, Katsuhiro*; Kotake, Shoji
Nuclear Technology, 177(3), p.293 - 302, 2012/03
Times Cited Count：3 Percentile：24.98(Nuclear Science & Technology)JSFR is a concept of a commercial sodium-cooled fast reactor which has been being studied in Fast Reactor Cycle Technology Development (FaCT) project since 2006. For the JSFR fuel handling, various fuel handling systems (FHSs) were investigated and an advanced FHS with an ex-vessel storage tank (EVST) has been selected. The other FHS concepts investigated are evolutional FHSs without an EVST. The result has indicated that the construction cost of the evolutional systems do not reduce the construction cost dramatically, which is mainly due to additional safety measures required higher decay heat handling in gas atmosphere and due to the necessity of separated fresh and failed fuel storage. From an economical point of view, a longer plant outage of the evolutional systems offsets its advantage of the lower construction cost. On the basis of the results of this comparative study, JSFR has selected the FHS with an EVST.
-like spin resonance in the iron-based nodal superconductor BaFe
(As
P
) observed using inelastic neutron scatteringIshikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; Suzuki, Katsuhiro*; et al.
Physical Review B, 84(14), p.144517_1 - 144517_5, 2011/10
Times Cited Count：26 Percentile：70.69(Materials Science, Multidisciplinary)We performed inelastic neutron scattering on a powder sample of iron-based superconductor BaFe(AsP) with 
= 30 K. Although this system is expected to have line nodes in its superconducting order parameter, we have observed spin resonance at the same scattering vector as that appeared in the -wave iron-based superconductors without line nodes. Moreover, the resonance enhancement, which can be a measure of the area of sign reversal between the hole and electron Fermi surfaces (FSs), is comparable to those without line nodes. These facts indicate that the sign reversal between the FSs is still dominant in this system, and the line nodes should create only limited area of sign-reversal on a single FS. Hence the system can hold higher Tc than the other iron-based superconductors with nodal symmetry, such as LaFePO
and KFeAs (
10 K).
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08
Times Cited Count：51 Percentile：88.4(Physics, Fluids & Plasmas)Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m
for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 
2 m for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.
Chikazawa, Yoshitaka; Uzawa, Masayuki*; Usui, Shinichi*; Tozawa, Katsuhiro*; Kotake, Shoji
Proceedings of 2010 International Congress on Advances in Nuclear Power Plants (ICAPP '10) (CD-ROM), p.10142_1 - 10142_9, 2010/06
Ikeda, Yoshitaka; Hanada, Masaya; Kamada, Masaki; Kobayashi, Kaoru; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Inoue, Takashi; Honda, Atsushi; Kawai, Mikito; et al.
IEEE Transactions on Plasma Science, 36(4), p.1519 - 1529, 2008/08
Times Cited Count：12 Percentile：41.25(Physics, Fluids & Plasmas)The JT-60SA N-NBI system is required to inject 10 MW for 100 s at 500 keV. Three key issues should be solved for the JT-60SA N-NBI ion source. One is to improve the voltage holding capability. Recent R&D tests suggested that the accelerator with a large area of grids may need a high margin in the design of electric field and a long time for conditioning. The second issue is to reduce the grid power loading. It was found that some beamlets were strongly deflected due to beamlet-beamlet interaction and strike on the grounded grid. The grids are to be designed by taking account of beamlet-beamlet interaction in three-dimensional simulation. Third is to maintain the D- production for 100 s. A simple cooling structure is proposed for the active cooled plasma grid, where a key is the temperature gradient on the plasma grid for uniform D- production. The modified N-NBI ion source will start on JT-60SA in 2015.
Usui, Shinichi; Mihara, Takatsugu; Obata, Hiroyuki; Kotake, Shoji
Proceedings of 2008 International Congress on Advances in Nuclear Power Plants (ICAPP '08) (CD-ROM), p.512 - 518, 2008/06
Refueling operation of sodium fast reactor (SFR) is one of major technical issue due to the chemical activities and opaqueness of sodium coolant properties in comparison with that of LWR. In the Japan Atomic Energy Agency (JAEA) sodium cooled Fast Reactor (JSFR) design study, the further reliable and rational fuel handling system (FHS) has been developing based on the experience of safe and reliable fuel handling operation in the existent SFR plants. Some of advanced concepts for the FHS have being studied in order to increase economic competitiveness further by attempting reduction of the amount of the material and the refueling time, and are scheduled to execute elemental tests and/or mock-up tests to confirm their feasibilities.
Oshima, Katsumi; Okano, Fuminori; Honda, Atsushi; Shinozaki, Shinichi; Usui, Katsutomi; Noto, Katsuya; Kawai, Mikito; Ikeda, Yoshitaka
JAEA-Technology 2007-044, 27 Pages, 2007/06
JAEA-Technology-2007-044.pdf:26.9MB
In the positive ion based NBI (P-NBI) system, we have developed a protection system to protect the power supply facilities from over load during long pulse operation. The protection system monitors the voltage (V) and current (I) in the power supply facilities, and calculates the parameters of V2t and I2t in real-time, where T is the pulse duration. It turns off the power supply facilities when V2t and I2t are beyond the critical values. After two development stages, we have completed the protection system using a package typed PLC (Programmable Logic Controller) which has a high expandability of multi-unit operation. Moreover, we have constructed a user-friendly system by using a SCADA (Supervisory Control and Data Acquisition) system.
Aizawa, Kosuke; Chikazawa, Yoshitaka; Usui, Shinichi; Konomura, Mamoru; Ando, Masato*
JAEA-Research 2007-042, 105 Pages, 2007/06
JAEA-Research-2007-042.pdf:3.64MB
Various conceptual design studies of sodium cooled small reactor have been performed in the feasibility study. In FY2005 study, a 300MWe modular reactor which adopts metal-fueled and 1 loop cooling system in order to pursues economical competitiveness was investigated. Transient analyses were performed to show core safety under the large pipe break accident that was found to be the severest accident in case of a 1 loop cooling system. From the analysis results, it was showed a possibility to maintain the core safety without the reactor scram. Transient analyses of the natural circulation decay heat removal system were also performed, and it was showed a possibility to maintain the core safety after the reactor scram. The in-vessel storage (IVS) was adopt to eliminate the ex-vessel storage and the design of the distribution flow adjustment device in IVS is studied. It was showed that the IVS could be introduced without modifying in the reactor design in FY2004. The rationalization of the fuel handling system is investigated taking advantage of co-location plant in which the reactor, the recycle plant and the fuel fabrication plant are co-located in a site. As a result of rationalization, the volume of the reactor building becomes 0.85 times as much as that of the design in FY2004.
Hanada, Masaya; Ikeda, Yoshitaka; Kamada, Masaki; Kikuchi, Katsumi; Komata, Masao; Mogaki, Kazuhiko; Umeda, Naotaka; Usui, Katsutomi; Grisham, L. R.*; Kobayashi, Shinichi*
IEEE Transactions on Dielectrics and Electrical Insulation, 14(3), p.572 - 576, 2007/06
Times Cited Count：5 Percentile：33.65(Engineering, Electrical & Electronic)Voltage holding capability of a 500 keV 22 A negative ion accelerator for JT-60U was experimentally examined. Voltage holding capability was strongly correlated with intensity of the light emitted inside the accelerator by applying the acceleration voltage. Namely, stable voltage holding was realized when the light emission was well suppressed. To examine the origin of the light emission, the correlation between the light intensity and the dark current was measured. The light intensity was linearly varied with the dark current. Further, it was indicated from the direction of the dark current that electrons were emitted from cathode grids by applying the acceleration voltage. In addition, the spectroscopy measurement of the light showed that the light had a broad peak at 420 nm. No particular spectra of hydrogen, oxygen and carbon have been observed. Therefore, the light emission seemed to be originated by electron excitation of FRP itself. From these results, it was thought that the voltage holding capability of the JT-60U negative ion accelerator could be improved by suppressing the electron emission from the cathode grids.
Chikazawa, Yoshitaka; Usui, Shinichi; Hayafune, Hiroki; Konomura, Mamoru
JAEA-Research 2007-001, 91 Pages, 2007/02
JAEA-Research-2007-001.pdf:9.42MB
In Feasibility Study on Commercialized Fast Breeder Reactor Cycle Systems, Large and Middle scale sodium cooled reactors which have an upper inner structure (UIS) with a slit have been studied for the size reduction of reactor structure. A new fuel handling machine (FHM) which is suitable for the UIS with a slit has been developed in this study. The FHM is required not to contact to UIS under the earthquake condition when its arm is extended into the slit. In the previous study, it is confirmed that the reduction of clearance in bearing of FHM is effective to reduce the deflection of FHM unit. But the general lubricant such as grease can not be used for the bearing because that of FHM will be set in argon gas atmosphere of the reactor vessel. In FY2005, the performance test of large-sized bearing with the selected lubrication specification has been performed in the high temperature argon gas atmosphere.
Chikazawa, Yoshitaka; Usui, Shinichi; Konomura, Mamoru; Sadahiro, Daisuke*; Tozawa, Katsuhiro*; Hori, Toru*; Toda, Mikio*; Kotake, Shoji*
Proceedings of 14th International Conference on Nuclear Engineering (ICONE-14) (CD-ROM), 7 Pages, 2006/07
A seismic analysis has been performed showing that the seismic interaction between the UIS and the FHM can be avoided adopting gapless bearings at the FHM arm joint. An angular contact ball bearing is suitable for the new FHM since it can eliminate gaps by preload pressure. A major problem of the FHM bearings is lubrication since the contact pressure between steel rings and ball increases because of ball bearing. Additionally, FHM operating temperature is about 200 deg-C and normal grease is not applicable under argon gas with sodium vapor. A endurance test with 1/10 scale bearings in the air has been performed to show applicability of angular contact ball bearings to the FHM arm joint. The results with 20,000 cycle showed that bearings with combination of MoS
coating steel rings and ceramics balls can be tolerable as the FHM operating condition. A real scale bearing test in argon gas with sodium vapor has also been demonstrated to reveal bearing size and sodium vapor effects.
Chikazawa, Yoshitaka; Usui, Shinichi; Konomura, Mamoru; Ikeda, Hirotsugu
JAEA-Research 2006-032, 202 Pages, 2006/04
JAEA-Research-2006-032.pdf:38.12MB
In the feasibility study on commercialized fast breeder cycle system, fuel handling systems for sodium cooled reactors has been studied. In FY 2004 study, a fuel handling system with an EVST for a twin large scale reactor power plant is designed and key issues about the system are identified. A manipulator type fuel handling machine suitable for the upper internal structure with a slit designed and seismic analyses show that it can treat spent fuels without interaction with upper internal structure in earthquakes. Fuel handling time is reduced adopting a sodium pot which can carry 2 subassemblies in onetime. Spent fuels are stored at an EVST while their decay heat are reduced to be 5kW/subassembly. A new fuel handling system for fuels with minor actinide is designed considering 1kW/subassembly heat and shielding. A innovative concept without an EVST is also studied. A fuel handling system adopting fuel transfer without a sodium pot is constructed to reduce material mass. A fuel handling system for a metal fuel reactor plant has been design. From the result of a survey on a gas storage, a water pool storage with helium cans and EVST, a system with EVST is selected because of its economical and safety advantage. Fuel handling condition is briefly reviewed considering commercialized reactor fuel specifications such as minor actinide content and ODS cladding.
Hishida, Masahiko; Murakami, Tsutomu*; Kisohara, Naoyuki; Fujii, Tadashi; Uchita, Masato*; Hayafune, Hiroki; Chikazawa, Yoshitaka; Usui, Shinichi; Ikeda, Hirotsugu; Uno, Osamu; et al.
JAEA-Research 2006-006, 125 Pages, 2006/03
JAEA-Research-2006-006.pdf:11.55MB
In Phase I of the "Feasibility Studies on Commercialized Fast Reactor Cycle Systems (F/S)", an advanced loop type reactor has been selected as a promising concept of sodium-cooled reactor, which has a possibility to fulfill the design requirements of the F/S. In Phase II, design improvement for further cost reduction and the establishment of the plant concept has been performed. In this study, reactor core design and large-scale plant design have been performed by adopting the modified fuel assembly with inner duct structure and double-wall straight tube steam generator (SG), which concepts were chosen at the interim review of FY 2003. For this SG, safety logics have been studied and the structural concept has been established. And the plant designs improving the in-service inspection (ISI) and repair capability have been performed. Furthermore, elaborate confirmation of the design has been performed reflecting the development of elemental technology, back-up concepts have been proposed. Besides, cost reduction measures have been studied by reducing reactor grade materials, introducing autonomous standardizations, simplifying the design due to deregulation and adopting systemized standards for BOP and NSSS. From now on, reflecting the results of elemental experiments, in-depth design studies and examination of critical issues will be carried out and the plant concept will accomplish in preparation for the final evaluation in Phase II.
Chikazawa, Yoshitaka; Kisohara, Naoyuki; Usui, Shinichi; Konomura, Mamoru; Sawa, Naoki*; Sato, Mitsuru*; Tanaka, Toshihiko
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
A small reactor has a potential to be utilized as a power source applicable to diversified social needs and reduce capital risks. In remote sites where the population is small and plants can not be economically connected to a power grid, power sources without refueling whose capacities are lower than 50 MW-electric are required because fuel transfer cost is expensive in such sites. In the present study, a small sodium cooled core with 30 years lifetime has been developed and a simple plant system without refueling has been sketched. Dimensions of major components are determined to evaluate its economical potential. Transient analyses show that self actuated shutdown system (SASS) enhances the passive safety features to maintain the reactor integrity in anticipate transient without scram events.
Chikazawa, Yoshitaka; Usui, Shinichi; Hayafune, Hiroki; Konomura, Mamoru
JNC TN9400 2005-046, 160 Pages, 2005/08
JNC-TN9400-2005-046.pdf:24.19MB
Large and Medium scale sodium cooled reactors which has a upper inner structure (UIS) with a slit have been developed in the "Feasibility Study on Commercialized Fast Breeder Reactor Cycle Systems". In this study, a new fuel handling machine (FHM) which is suitable for the UIS with a slit has been developed. In the FY2004 study, 1/10 scale bearing tests have been performed and a test rig for real scale bearing have been manufactured.
Chikazawa, Yoshitaka; Hori, Toru*; Usui, Shinichi; Konomura, Mamoru; Nishiguchi, Yohei
JNC TY9400 2005-009, 329 Pages, 2005/07
JNC-TY9400-2005-009.pdf:24.1MB
In the feasibility study on commercialized fast breeder cycle system, fuel handling systems for sodium cooled reactors has been studied. In FY 2003 study, a fuel handling system with an EVST for a power plant with 4 medium scale modular reactors is designed and key issues about the system are identified. A manipulator type fuel handling machine suitable for the upper internal structure with a slit designed and seismic analyses show that it can treat spent fuels without interaction with upper internal structure in earthquakes. Fuel handling time is reduced adopting a sodium pot which can carry 2 subassemblies in onetime.In this study, a innovative concept without an EVST is also studied. In this concept, the total mass is not dramatically reduced comparing a system with an EVST because several fuel transfer machines with gas cooling systems are needed for safety point of view.
Chikazawa, Yoshitaka; Kisohara, Naoyuki; Usui, Shinichi; Konomura, Mamoru; Tanaka, Toshihiko
JNC TY9400 2005-004, 189 Pages, 2005/06
JNC-TY9400-2005-004.pdf:9.33MB
A conceptual design of various small metal fuel sodium cooled reactors has been studied in the feasibility study on commercialized fast breeder reactor cycle system. In FY2004 study, a 50 MWe power plant for remote places with a long life core without refueling and a 300 MWe modular reactor which pursues standardization for learning effect and reduction of capital risks.In the small reactor with a long life core, the reactor vessel is minimized without a permanent fuel handling system and the cooling system is simplified adopting 1 loop. The total mass of the reactor vessel and the cooling system is dramatically reduced and the concept has a potential to be an attractive power source for remote places.In the 300 MWe modular reactor, the cooling system adopts 1 loop and the ex-vessel fuel storage tank for spent fuels is eliminated adapting the in-vessel storage (IVS) which has a capacity for a 4 year storage. The reactor building is minimized without the ex-vessel storage This concept has a potential to be an power source for key grids with modular constructions and a first plant with a small fuel cycle facility can demonstrate the metal fuel fast reactor cycle
Usui, Shinichi; Chikazawa, Yoshitaka; Konomura, Mamoru; Tanaka, Toshihiko; Hori, Toru*; Ohkubo, Toshiyuki*
Proceedings of 2005 International Congress on Advances in Nuclear Power Plants (ICAPP '05) (CD-ROM), 0 Pages, 2005/05
The Japan Nuclear Cycle Development Institute and the Electric Utilities have been studying for concepts of commercialized FBR plant system. In this study, a small sized sodium cooled reactor has been studied from standpoints of having a potential to use a power source applicable to diversified social needs and reduced capital risks. The concept is pursued to satisfy various requirements: economical competitiveness, reactor safety, very long lived core, etc. The electrical power is set to 165 MWe based on previous studies of small sized sodium cooled reactor which was aim of cost reduction of the plant pursued. A three regional Zr concentration with one Pu enrichment core has been designed. The burn-up reactivity is kept 1.17% dk/k and the core refueling occurs after 20 years operation with 77,000 MWd/t average burn-up. The reactor system is enhanced a passive safety to avoid a core melt even an ATWS and the design has possible capability to withstand UTOP and ULOHS events, although it requires reactor shutdown action by operator within a certain time. Tank-type primary system has been designed. A circular type IHX and a primary EMP are located in series inside of the reactor vessel. The steam generator and the secondary EMP are located outside of the reactor vessel and connected to the IHX by piping. A diameter of the core is minimized in order to reduce a reactor vessel size. Two PRACS driven by natural circulation is chosen as a decay heat removal system in order to satisfy a heat removal condition of Category IV in Japanese standard.The construction cost of the whole plant evaluates to be achieved an economical goal considering a mass production.
