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Journal Articles

Improvement of the center boring device for the irradiated fuel pellets

Toyokawa, Takuya; Usami, Koji; Shiina, Hidenori; Onozawa, Atsushi

Proceedings of 49th Conference on Hot Laboratories and Remote Handling (HOTLAB 2012) (Internet), 6 Pages, 2012/09

JAEA Reports

Plan and reports of coupled irradiation (JRR-3 and JOYO of research reactors) and hot facilities work (WASTEF, JMTR-HL, MMF and FMF); R&D project on irradiation damage management technology for structural materials of long-life nuclear plant

Matsui, Yoshinori; Takahashi, Hiroyuki; Yamamoto, Masaya; Nakata, Masahito; Yoshitake, Tsunemitsu; Abe, Kazuyuki; Yoshikawa, Katsunori; Iwamatsu, Shigemi; Ishikawa, Kazuyoshi; Kikuchi, Taiji; et al.

JAEA-Technology 2009-072, 144 Pages, 2010/03

JAEA-Technology-2009-072.pdf:45.01MB

"R&D Project on Irradiation Damage Management Technology for Structural Materials of Long-life Nuclear Plant" was carried out from FY2006 in a fund of a trust enterprise of the Ministry of Education, Culture, Sports, Science and Technology. The coupled irradiations or single irradiation by JOYO fast reactor and JRR-3 thermal reactor were performed for about two years. The irradiation specimens are very important materials to establish of "Evaluation of Irradiation Damage Indicator" in this research. For the acquisition of the examination specimens irradiated by the JOYO and JRR-3, we summarized about the overall plan, the work process and the results for the study to utilize these reactors and some facilities of hot laboratory (WASTEF, JMTR-HL, MMF and FMF) of the Oarai Research-and-Development Center and the Nuclear Science Research Institute in the Japan Atomic Energy Agency.

Journal Articles

Improved technique for hydrogen concentration measurement in fuel claddings by backscattered electron image analysis, 2

Onozawa, Atsushi; Harada, Akio; Honda, Junichi; Nakata, Masahito; Kanazawa, Hiroyuki; Sagawa, Tamio

JAEA-Conf 2008-010, p.325 - 332, 2008/12

The measurement technique for hydrogen concentration using Backscattered Electron Image analysis (BEI method) had been developed by Studsvik Nuclear AB. The hydride in claddings is identified using BEIs with SEM and the hydrogen concentration is calculated from the area fractions of the hydride in those BEIs. In the RFEF, the sample polishing techniques and image processing procedure for BEI method were improved to measure the hydrogen concentration in the irradiated fuel claddings more precisely. In the previous tests using the un-irradiated fuel claddings, it is confirmed improved BEI method has high reliability. The radial and axial hydrogen concentration profiles of the irradiated fuel claddings were measured with improved BEI method. As the results of these measurements, the local hydrogen concentration could be indicated more precisely with the improved BEI method compared to the other methods for the hydrogen concentration measurement and observation.

Journal Articles

PIE technique of fuel cladding fracture toughness test

Endo, Shinya; Usami, Koji; Nakata, Masahito; Fukuda, Takuji*; Onozawa, Atsushi; Harada, Akio; Kizaki, Minoru; Kikuchi, Hiroyuki

HPR-366, Vol.1 (CD-ROM), 10 Pages, 2007/03

no abstracts in English

Journal Articles

Improved technique of hydrogen concentration measurement in fuel cladding by backscattered electron image analysis

Onozawa, Atsushi; Harada, Akio; Honda, Junichi; Yasuda, Ryo; Nakata, Masahito; Kanazawa, Hiroyuki; Nishino, Yasuharu

JAEA-Conf 2006-003, p.212 - 221, 2006/05

In the Reactor Fuel Examination Facility (RFEF), a measuring method of hydrogen concentration by backscattered electron image analysis was improved to obtain more local hydrogen concentration data in fuel claddings. The sample preparation and image analysis procedures of this were able to measure hydrogen concentration efficiently and precisely.

JAEA Reports

Hydrogen concentration measurement in fuel cladding by backscattered electron image analysis

Onozawa, Atsushi; Harada, Akio; Honda, Junichi; Yasuda, Ryo; Nakata, Masahito; Kanazawa, Hiroyuki; Nishino, Yasuharu

JAEA-Technology 2006-010, 19 Pages, 2006/03

JAEA-Technology-2006-010.pdf:2.3MB

A measurement technique for hydrogen concentration using Backscattered Electron Image analysis (BEI method) had been developed by Studsvik Nuclear AB, Sweden. The hydrides in claddings are identified using BEIs which are imaged with Scanning Electron Microscope, and the hydrogen concentrations are calculated from the area fractions of the hydrides in the matrix. The BEI method is very useful for the measurement in local hydrogen concentrations of fuel claddings. In the Reactor Fuel Examination Facility, a sample preparation, imaging conditions of SEM and image analysis procedures for the BEI method were improved. In addition, the hydrogen concentrations obtained by the improved BEI method and Hot Vacuum Extraction (HVE) method were compared to confirm the reliability of the improved BEI method. The results showed, the improved BEI method has the same reliability as that of HVE method and can be applied for the Post-Irradiation Examination.

JAEA Reports

Development of once-through type densitometer

Onozawa, Atsushi; Kushida, Teruo; Kanazawa, Hiroyuki

JAERI-Tech 2004-061, 39 Pages, 2004/11

JAERI-Tech-2004-061.pdf:8.64MB

The swelling observed on irradiated fuels is caused by the accumulation of fission products and irradiation defects. The swelling ratio is changed along with radius region in the pellet due to burn up difference caused by that of neutron flux. To investigate the swelling behavior at the small area of the pellet, it is needed to measure the density of fuel fragments picked from an irradiated pellet. In this circumstance, once-through type densitometer was developed to measure the density of the small irradiated specimen precisely and to handle the samples easily with remote control systems. Several kinds of metallic and ceramic standard specimens are prepared to investigate the dependence of the sample weight, density and porosity on the accuracy. The results of characteristic examination using these specimens indicate that this densitometer has enough accuracy. In addition, some parts of this apparatus are controlled by motor drive units, which made it possible to measure the density full-automatically.

JAEA Reports

A Study on density, porosity and grain size of unirradiated ROX fules and simulated ROX fuels

Yanagisawa, Kazuaki; Omichi, Toshihiko*; Shirasu, Noriko; Yamashita, Toshiyuki; ; Onozawa, Atsushi; ; Kanazawa, Hiroyuki; Kanaitsuka, Fumio; Amano, Hidetoshi

JAERI-Tech 99-044, 46 Pages, 1999/05

JAERI-Tech-99-044.pdf:4.66MB

no abstracts in English

Oral presentation

Improved technique to measure hydrogen concentration in the cross section of the fuel cladding

Onozawa, Atsushi; Harada, Akio; Honda, Junichi; Yasuda, Ryo; Nakata, Masahito; Kanazawa, Hiroyuki; Nishino, Yasuharu

no journal, , 

Oral presentation

Hydrogen concentration measurement in irradiated fuel cladding

Honda, Junichi; Onozawa, Atsushi; Fuketa, Toyoshi; Udagawa, Yutaka; Mita, Naoaki; Kikuchi, Hiroyuki

no journal, , 

no abstracts in English

Oral presentation

R&D project on irradiation damage management technology for structural materials of long-life nuclear plant, 3; Assembly and disassembly techniques of JRR-3 re-irradiation capsule in WASTEF

Usami, Koji; Ichise, Kenichi; Numata, Masami; Endo, Shinya; Onozawa, Atsushi; Takahashi, Hiroyuki; Kikuchi, Taiji; Ishikawa, Kazuyoshi; Yoshikawa, Katsunori; Nakata, Masahito; et al.

no journal, , 

In the R&D Project on Irradiation Damage Management Technology for Structural Materials of Long-life Nuclear Plant, the specimens to be obtained by coupling irradiation between JOYO and JRR-3 is necessary to establish the evaluation method by using the irradiation damage indicator of them. Therefore, the techniques for assembling of JRR-3 re-irradiation capsule in the Waste Safety Testing Facility (WASTEF) were developed to perform the coupling irradiation. The techniques contributed to the first coupling irradiation in the world.

Oral presentation

Improvement of the center boring device for the irradiated fuel pellets

Shiina, Hidenori; Usami, Koji; Sakuraba, Naotoshi; Harada, Akio; Onozawa, Atsushi; Nakata, Masahito

no journal, , 

Oral presentation

Restoration activities for Fukushima Daiichi Nuclear disaster; Towards decommissioning of nuclear power plants

Onozawa, Atsushi; Nagase, Fumihisa; Minato, Kazuo

no journal, , 

no abstracts in English

Oral presentation

Preparation and characterization of simulated MCCI products, 1; Phases and microhardness of solidified samples prepared by arc melting

Takano, Masahide; Onozawa, Atsushi; Sudo, Ayako

no journal, , 

no abstracts in English

Oral presentation

Preparation and characterization of simulated MCCI products, 2; Characterization of interface between concrete and core melt

Sudo, Ayako; Onozawa, Atsushi; Takano, Masahide

no journal, , 

no abstracts in English

Oral presentation

Study on dissolution technique for fuel debris in Fukushima Daiichi Nuclear Power Station, 2; Dissolution test of fuel debris sample of TMI-2

Matsumura, Tatsuro; Iijima, Takahiko; Ishii, Sho; Takano, Masahide; Onozawa, Atsushi

no journal, , 

no abstracts in English

Oral presentation

Preparation and characterization of simulated fuel debris specific to the Fukushima accident

Takano, Masahide; Nishi, Tsuyoshi; Onozawa, Atsushi

no journal, , 

Since the severe accident at the Fukushima Daiichi Nuclear Power Plant, we have been studying the characteristics of fuel debris in order to contribute to its removal operation and management. First, a series of reaction experiment on (U,Zr)O$$_{2}$$ with natural sea salt were performed to clarify the chemical influence of sea salt deposit on high-temperature corium. It was found that CaO decomposed from sulphate is most reactive to form (U,Zr,Ca)O$$_{2}$$ solid solution or Ca-U-O uranate on the surface, depending on the oxygen partial pressure. Then, some compacted mixtures of B$$_{4}$$C, stainless steel, Zr, and (U,Zr)O$$_{2}$$ were arc-melted to investigate the boron-containing compounds in the fuel debris. ZrB$$_{2}$$ and (Fe,Cr,Ni)$$_{2}$$B were found to precipitate in the alloy part of solidified sample. The phase relationships within these borides and alloy phases can be characterized by the initial B/Zr ratio in the mixture.

Oral presentation

Characterization of fuel debris (27'A), 9; Microhardness of simulated fuel debris and TMI-2 debris

Takano, Masahide; Onozawa, Atsushi; Suzuki, Miho; Obata, Hiroki

no journal, , 

no abstracts in English

Oral presentation

Reaction experiment on core melt concrete interface under temperature gradient

Sudo, Ayako; Onozawa, Atsushi; Takano, Masahide

no journal, , 

To characterize the layer structure and respective temperatures of MCCI products, MCCI experiments using a light-concentrating furnace were performed. As the core-melt constituents, a powder mixture of (U$$_{0.5}$$Zr$$_{0.5}$$)O$$_{2}$$ (No.1) and (U$$_{0.5}$$Zr$$_{0.5}$$)O$$_{2}$$/Zr/SUS316L/B$$_{4}$$C (No.2) were compacted into tablets (10 mm in diameter) respectively. The tablet was placed on a cylindrical piece of basaltic concrete (25 mm in diameter). The light was concentrated on the tablet under argon gas flow and samples were heated. After heating, the vertical cross-section of the solidified sample piece was subjected to phase identification and elemental analysis by XRD and SEM/EDX. No.1 sample seemed to maintain original shape, but EDX analysis showed the inner region melted. This melt was identified as-melted (U,Zr)O$$_{2}$$ particle and silicate glass containing U and Zr. Ca, Fe and Mg oxide were dissolved in the particle. UO$$_{2}$$ and ZrO$$_{2}$$ were dissolved in the silicate glass. No.2 sample had same phases, but Fe-Cr oxide deposits from SS was identified.

Oral presentation

Characterization of fuel debris (28'A), 3; Influence of minor additives on the phase relationships of (U,Zr)O $$_{2}$$ simulated fuel debris

Takano, Masahide; Onozawa, Atsushi; Sudo, Ayako

no journal, , 

no abstracts in English

27 (Records 1-20 displayed on this page)