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Journal Articles

Inner structure and inclusions in radiocesium-bearing microparticles emitted in the Fukushima Daiichi Nuclear Power Plant accident

Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*

Microscopy, 68(3), p.234 - 242, 2019/06

 Times Cited Count:4 Percentile:20.85(Microscopy)

Radiocesium-bearing microparticles (CsMPs), consisting substantially of silicate glass, were released to the environment during the Fukushima nuclear accident in March 2011. We investigated a total of nine CsMPs using transmission electron microscopy (TEM) and inferred the atmosphere in the reactors during the accident. From elemental mapping using energy-dispersive X-ray spectrometry, Fe and Zn showing radial inhomogeneities were found in the CsMPs, in addition to the Cs that had been previously reported. Four of the CsMPs included submicron crystals, which were identified as chromite, franklinite, acanthite, molybdenite, and hessite. The chromium-containing spinels, chromite and franklinite, indicated the presence of ferrous iron (Fe$$^{2+}$$), suggesting that the inside of the reactors was reductive to some extent. Electron energy-loss spectroscopy also confirmed that the CsMPs did not contain boron, and therefore the atmosphere in which they were formed might be boron-free.

Journal Articles

Conceptual design of engineering-scale plant applied the simplified MA-bearing fuel fabrication process

Yamada, Yoshikazu; Segawa, Tomoomi; Kato, Masato

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Next Generation Nuclear Systems for Sustainable Development (FR-17) (USB Flash Drive), 8 Pages, 2017/06

Japan Atomic Energy Agency (JAEA) have proposed the transmutation of minor actinides by fast reactors as a way to contribute significantly to the reduction of the volume and the potential radiotoxicity of radioactive wastes. In order to achieve this goal, it is important to introduce a fully automated and remote operation fuel fabrication plant with shielded hot cells and manipulators. JAEA's facilities including Plutonium Fuel Production Facility (PFPF) have fabricated MOX fuel. On the basis of the operational and technical experience obtained in above facilities, the conceptual design of engineering-scale plant applied the simplified MA-bearing fuel fabrication process with shielded hot cells and manipulator was done. It will be able to fabricate high MA-bearing fuel and to perform the maintenance and repairing of each equipment with manipulators. This plant will be constructed based on this concept and development plan.

Journal Articles

Current status of the next generation fast reactor core & fuel design and related R&Ds in Japan

Maeda, Seiichiro; Oki, Shigeo; Otsuka, Satoshi; Morimoto, Kyoichi; Ozawa, Takayuki; Kamide, Hideki

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Next Generation Nuclear Systems for Sustainable Development (FR-17) (USB Flash Drive), 10 Pages, 2017/06

The next generation fast reactor is being investigated in Japan, aiming at several targets such as "safety", "reduction of environmental burden" and "economic competitiveness". As for the safety aspect, FAIDUS concept is adopted to avoid re-criticality in core destructive accidents. The uranium-plutonium mixed oxide fuel, in which minor actinide elements are included, will be applied to reduce the amount and potential radio-toxicity of radioactive wastes. The high burn-up fuel is pursued to reduce fuel cycle cost. The candidate concept of the core and fuel design, which could satisfy various design criteria by design devisals, has been established. In addition, JAEA is investigating material properties and irradiation behavior of MA-MOX fuel. JAEA is developing the fuel design code especially for the fuel pin with annular pellets of MA-bearing MOX. Furthermore, JAEA is developing oxide dispersion strengthened (ODS) ferritic steel cladding for the high burnup fuel.

Journal Articles

Disposal project for LLW and VLLW generated from research facilities in Japan; A Feasibility study for the near surface disposal of VLLW that includes uranium

Sakai, Akihiro; Hasegawa, Makoto; Sakamoto, Yoshiaki; Nakatani, Takayoshi

Proceedings of International Conference on the Safety of Radioactive Waste Management (Internet), p.98_1 - 98_4, 2016/11

The radioactivity of uranium-bearing waste contaminated by refined uranium increases with the production of its progeny on a long-term timescale. Therefore, the long-term safety concept of the near surface disposal of uranium-bearing waste is very important. The Japan Atomic Energy Agency (JAEA) examines disposal safety by controlling the average uranium radioactivity concentration in each section of disposal facility and performing safety assessment for very conservative assumptions.

Journal Articles

Development on rubber bearings for sodium-cooled fast reactor, 1; Examination plan

Yamamoto, Tomohiko; Kawasaki, Nobuchika; Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Somaki, Takahiro*; Samejima, Yusuke*; Masaki, Nobuo*

Proceedings of 2015 ASME Pressure Vessels and Piping Conference (PVP 2015) (Internet), 7 Pages, 2015/07

Since a SFR (Sodium-cooled Fast Reactor) has thin-walled component structures, a seismic isolation system is employed to mitigate the seismic force. Seismic isolation system for applying the SFR consists of the laminated rubber bearing considering characteristics of SFR structures. This paper describes a basic mechanical characteristic examination with a 1/8 scale model and a characterization examination plan of half-scale laminated rubber.

Journal Articles

Development on rubber bearings for sodium-cooled fast reactor, 2; Fundamental characteristics of half-scale rubber bearings based on static test

Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Yamamoto, Tomohiko; Kawasaki, Nobuchika; Somaki, Takahiro*; Sakurai, Yu*; Masaki, Nobuo*

Proceedings of 2015 ASME Pressure Vessels and Piping Conference (PVP 2015) (Internet), 10 Pages, 2015/07

This paper described the results of static loading tests using a half-scale rubber bearing model to investigate the fundamental characteristics such as restoring force of a rubber bearing applied to a Sodium-Cooled-Fast-Reactor (SFR). Since the SFR has thin-walled structures, a seismic isolation system is employed to mitigate the seismic force. The static loading tests were performed using the half-scale rubber bearing with a diameter of 800 mm in the range which exceeds a linear limit of horizontal direction and a yield stress of vertical direction to investigate the horizontal and vertical of each stiffness and damping ratio. The fundamental characteristic of rubber bearing employed to the SFR and the validity of a design formula became clear through the static tests.

Journal Articles

Aging deterioration test of seismic isolation applied to fusion experimental reactor

Takeda, Nobukazu; Nakahira, Masataka; Kakudate, Satoshi; Takahashi, Hiroyuki*; Shibanuma, Kiyoshi; Yabana, Shuichi*; Matsuda, Akihiro*

Proceedings of 9th World Seminar on Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures (CD-ROM), p.299 - 306, 2005/00

For the ITER, a fusion experimental reactor, it is planned to use rubber bearings in order to enhance the reliability of integrity with a sufficient margin even for the earthquakes beyond the design basis earthquake. In application for nuclear plants, the vertical compression of the isolator is 2$$sim$$5 MPa and there is no experience for such a high compression as 10 MPa to be used for the ITER. Therefore, there is not enough design data of the rubber bearings with high compression, and thus a detailed estimation of performance is necessary. As a result of the endurance test after aging, it was validated that the bearing can be applied safely until 400th cycle even after 40 years of aging. On the other hand, the residual deformation was found at the 246th cycle. This means that the residual deformation can be observed enough earlier than the change of the macroscopic mechanical parameter such as stiffness. Therefore, it is possible to prevent break of the bearing during operation by sensing a sign of break with a periodical visual inspection.

Journal Articles

Research and development for gas turbine system in GTHTR300

Kunitomi, Kazuhiko; Katanishi, Shoji; Takada, Shoji; Takizuka, Takakazu; Yan, X.; Kosugiyama, Shinichi

JSME International Journal, Series B, 47(2), p.261 - 267, 2004/05

The GTHTR300 aiming at electric generation with its thermal efficiency of 46 % is a safe and economically competitive HTGR in 2010s. A helium gas turbine system connected with the reactor is designed based on existing technologies developed for fossil gas turbine systems. However, there are some uncertainties in performance of a helium gas compressor, electric magnetic bearings and control system. In order to confirm these technical uncertainties, a 1/3 scale model of the compressor and 1/3 scale magnetic bearings will be manufactured and tested in the simulated condition of the GTHTR300. This paper describes R&D plans focusing on the 1/3 scale compressor model test as well as unique design features of the GTHTR300.

Journal Articles

Development of EC H&CD launcher components for fusion device

Takahashi, Koji; Ishitsuka, Etsuo; Moeller, C. P.*; Hayashida, Kazunori*; Kasugai, Atsushi; Sakamoto, Keishi; Hayashi, Kenichi*; Imai, Tsuyoshi

Fusion Engineering and Design, 66-68, p.473 - 479, 2003/09

 Times Cited Count:11 Percentile:37.8(Nuclear Science & Technology)

For the purpose to confirm the reliability of the front steering concept, tests of the front steering launcher mock-up and neutron irradiation tests of bearings for a movable mirror were carried out under the ITER conditions. The max. stress of the flexible pipes for the movable mirror was measuerd to be 60MPa, much less than the allowable stress and agree with the calculation. No degradation on the performance of bearings was obtained for the assumed fluence of ITER. The mock-up of remote steering(RS) launcher was tested and RF radiation of 0.5MW-3sec and 0.2MW-10sec over 0-10$$^{circ}$$ were performed. No degradation was obseved, either. The new launcher which has the capability of wider range rf beam steering and the corrugated square waveguide with four miter bends that yield the dog-legged structure has been designed, based on the test results. It has been fabricating for high power experiments.

Journal Articles

Estimation of mechanical characteristics of actual size rubber bearings with scale models

Yabana, Shuichi*; Matsuda, Akihiro*; Nakahira, Masataka; Osaki, Toshio*

Nippon Kenchiku Gakkai 2002-Nendo Taikai Koen Kogaishu, P. 495, 2002/08

no abstracts in English

JAEA Reports

Characteristic evaluation of high compression seismic isolator for International Thermonuclear Experimental Reactor (ITER); Verification test of sub-scaled rubber bearings (Contract research)

Takahashi, Hiroyuki*; Nakahira, Masataka; Yabana, Shuichi*; Matsuda, Akihiro*; Otori, Yasuki*

JAERI-Tech 2001-064, 111 Pages, 2001/11

JAERI-Tech-2001-064.pdf:8.96MB

no abstracts in English

JAEA Reports

Development of radiation-hard electric connector with ball bearing for in-vessel remote maintenance equipment of ITER, 2

*; Obara, Kenjiro; Tada, Eisuke; Morita, Yosuke; Yagi, Toshiaki; *

JAERI-Tech 99-029, 36 Pages, 1999/03

JAERI-Tech-99-029.pdf:3.25MB

no abstracts in English

Journal Articles

Design and validation test of seismic isolation for ITER

Nakahira, Masataka; Takeda, Nobukazu; Takahashi, Hiroyuki*; Yagenchi, Akira*; Akutsu, Yoichi; Tada, Eisuke; Yabana, Shuichi*

Proceedings of 7th International Conference on Nuclear Engineering (ICONE-7) (CD-ROM), 10 Pages, 1999/00

no abstracts in English

JAEA Reports

Neutorn spectral tailoring calculation in the JMTR; Feasible study on irradiation test simulating the fusion reactor condition

Nagao, Yoshiharu; Shimakawa, Satoshi; ;

JAERI-Tech 95-006, 46 Pages, 1995/02

JAERI-Tech-95-006.pdf:1.45MB

no abstracts in English

Journal Articles

Development of turbo-viscous pump with ceramic rotor assembly and oil-free driving unit

Murakami, Yoshio; Abe, Tetsuya; *; *

J. Vac. Sci. Technol., A, 9(3), p.2053 - 2057, 1991/05

no abstracts in English

Journal Articles

Recent developments of rolling bearings for liquid sodium service

Junkatsu, 23(11), p.856 - 857, 1978/11

no abstracts in English

Journal Articles

液体ナトリウム環境におけるボールベアリングの実現可能性試験

S.IWAI*; M.ISHII*; Nozawa, Masao*; Tamura, T.*; Abe, Y.*; A.TERAMOTO*; M.AKIYAMA*

ANL-7520 PART-II, p.121 - 129, 1968/00

no abstracts in English

Oral presentation

Characterization of melt-solidified (U, Gd, Zr)O$$_{2-x}$$ as simulated corium debris

Morimoto, Kyoichi; Hirooka, Shun; Akashi, Masatoshi; Watanabe, Masashi

no journal, , 

The influence of Gd on characteristics of debris is important for removing the debris from the reactors of Fukushima Daiichi Nuclear Power Plant because subassemblies of nuclear fuels containing Gd$$_{2}$$O$$_{3}$$ were loaded in the some reactor cores. Additionally, it is important to assess the distribution state of Gd from the anxiety of re-criticality caused by the relocation of debris while removing them. In this study, sintered pellets of (U$$_{0.95-y}$$Gd$$_{0.05}$$Zr$$_{y}$$)O$$_{2-x}$$ (y=0,0.5, 2-x=1.989-2.000) were melted and solidified to prepare specimens of simulated corium debris. Phase states and fundamental properties of them were evaluated.

Oral presentation

Progress of 1F PCV contaminant analysis by TEM observation

Suzuki, Akihiro*; Kitsunai, Yuji*; Sato, Ikken

no journal, , 

Several contaminant samples from 1F1 primary containment vessel are carefully observed by transmission electron microscope to find micro-scale uranium-containing particles in their chemical forms of U-rich c-(U,Zr)O$$_{2}$$ and Zr-rich t-(Zr,U)O$$_{2}$$, which are also observed in fuel debris of TMI-2 and Chernobyl NPP-4.

Oral presentation

Computer simulation for short-term irradiation behavior of mixed oxide fuels containing Am in a fast reactor

Yokoyama, Keisuke; Ikusawa, Yoshihisa; Uwaba, Tomoyuki; Morimoto, Kyoichi; Tanaka, Kosuke; Hirooka, Shun

no journal, , 

We have developed analytical models for describing the effects of MAs on fuel physical properties such as vapor pressure, thermal conductance and density. These models were incorporated into a computer simulation code CEDAR, which predicts mechanical and thermal behaviors of a fuel pin irradiated in FRs. CEDAR was applied to the short-term irradiation experiments of the fuel pins in the experimental fast reactor Joyo. Mechanisms of these behaviors were investigated through the comparison between the PIEs and simulations and analyzing them.

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