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Journal Articles

Overview of accident-tolerant fuel R&D program in Japan

Yamashita, Shinichiro; Ioka, Ikuo; Nemoto, Yoshiyuki; Kawanishi, Tomohiro; Kurata, Masaki; Kaji, Yoshiyuki; Fukahori, Tokio; Nozawa, Takashi*; Sato, Daiki*; Murakami, Nozomu*; et al.

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.206 - 216, 2019/09

After the nuclear accident at Fukushima Daiichi Power Plant, research and development (R&D) program for establishing technical basis of accident-tolerant fuel (ATF) started from 2015 in Japan. Since then, both experimental and analytical studies necessary for designing a new light water reactor (LWR) core with ATF candidate materials are being conducted within the Japanese ATF R&D Consortium for implementing ATF to the existing LWRs, accompanying with various technological developments required. Until now, we have accumulated experimental data of the candidate materials by out-of-pile tests, developed fuel evaluation codes to apply to the ATF candidate materials, and evaluated fuel behavior simulating operational and accidental conditions by the developed codes. In this paper, the R&D progresses of the ATF candidate materials considered in Japan are reviewed based on the information available such as proceedings of international conference and academic papers, providing an overview of ATF program in Japan.

Journal Articles

In middle Heisei period

Nozawa, Takashi

Senmon Toshokan, (295), p.18 - 19, 2019/05

no abstracts in English

JAEA Reports

Comprehensive evaluation system for environmental remediation of Fukushima; Toward integration of three components as a whole system

Saito, Hiroshi; Nozawa, Takashi; Takemiya, Hiroshi; Seki, Akiyuki; Matsubara, Takeshi; Saito, Kimiaki; Kitamura, Akihiro

JAEA-Review 2017-040, 34 Pages, 2018/03

JAEA-Review-2017-040.pdf:9.52MB

The accidents at Fukushima Daiichi Nuclear Power Station on March 11th 2011, released significant amount of radionuclide to the environment. It has migrated to the human habitation and raised concerns of possible effect on human health, and for that a lot of researches have been performed. JAEA created and opened "Database for Radioactive Substance Monitoring Data" for usage of obtained data. For accurate modelling and future forecast using numerical code and the data, "Supporting Environment for Processing Simulation Codes" has been operated. In addition, research results have been opened as Q&A style "Knowledge Base for Environmental Remediation" in JAEA's website. The "Comprehensive Evaluation System" composed of these components, should act more interrelated and integrated as one system. Besides, information dissemination is not enough to the outside. The report summarizes the current status, remaining issues and expected improvement of each component and the system.

Journal Articles

Technical basis of accident tolerant fuel updated under a Japanese R&D project

Yamashita, Shinichiro; Nagase, Fumihisa; Kurata, Masaki; Nozawa, Takashi; Watanabe, Seiichi*; Kirimura, Kazuki*; Kakiuchi, Kazuo*; Kondo, Takao*; Sakamoto, Kan*; Kusagaya, Kazuyuki*; et al.

Proceedings of 2017 Water Reactor Fuel Performance Meeting (WRFPM 2017) (USB Flash Drive), 10 Pages, 2017/09

In Japan, the research and development (R&D) project on accident tolerant fuel and other components (ATFs) of light water reactors (LWRs) has been initiated in 2015 for establishing technical basis of ATFs. The Japan Atomic Energy Agency (JAEA) has coordinated and carried out this ATF R&D project in cooperation with power plant providers, fuel venders and universities for making the best use of the experiences, knowledges in commercial uses of zirconium-base alloys (Zircaloy) in LWRs. ATF candidate materials under consideration in the project are FeCrAl steel strengthened by dispersion of fine oxide particles(FeCrAl-ODS) and silicon carbide (SiC) composite, and are expecting to endure severe accident conditions in the reactor core for a longer period of time than the Zircaloy while maintaining or improving fuel performance during normal operations. In this paper, the progresses of the R&D project are reported.

Journal Articles

The Recent improvements on circulation of research results at the Japan Atomic Energy Agency (JAEA)

Inagaki, Satomi; Hayakawa, Misa; Ebisawa, Naomi; Gonda, Mayuki; Nozawa, Takashi; Itabashi, Keizo

Proceedings of 18th International Conference on Grey Literature (GL-18), p.24 - 31, 2017/02

Sharing information of scientific research results on the Internet have developed in the global advancement of the open science today, such as archiving and disseminating scientific papers on institutional repositories, facilitating access to and use of research data etc. Accessibility to those contents in large volumes of information on the Internet is very important issue. Those contents might be grey literature without solving this accessibility issue. This presentation introduces the case study of the Japan Atomic Energy Agency (JAEA) Library as an example of efforts to improve circulation of research results in terms of grey literature. JAEA has disseminate information of our research results through the JAEA Originated Papers Searching System (JOPSS) on the Internet over decade, but we have three main issues to solve aiming at improving the accessibility of grey literature in the open science era; (1) to ensure accessibility of our Internet contents, (2) to consider how our target users find our contents, (3) to improve user interface of contents. We will continue to improve the system aiming to distribute various information of JAEA R&D results.

Journal Articles

The Recent improvements on circulation of research results at the Japan Atomic Energy Agency

Inagaki, Satomi; Hayakawa, Misa; Ebisawa, Naomi; Gonda, Mayuki; Nozawa, Takashi; Itabashi, Keizo

The Grey Journal; An International Journal on Grey Literature, 13(2), p.123 - 129, 2017/00

Sharing information of scientific research results on the Internet have developed in the global advancement of the open science today, such as archiving and disseminating scientific papers on institutional repositories, facilitating access to and use of research data etc. Accessibility to those contents in large volumes of information on the Internet is very important issue. Those contents might be grey literature without solving this accessibility issue. This presentation introduces the case study of the Japan Atomic Energy Agency (JAEA) Library as an example of efforts to improve circulation of research results in terms of grey literature. JAEA has disseminate information of our research results through the JAEA Originated Papers Searching System (JOPSS) on the Internet over decade, but we have three main issues to solve aiming at improving the accessibility of grey literature in the open science era; (1) to ensure accessibility of our Internet contents, (2) to consider how our target users find our contents, (3) to improve user interface of contents. We continue to disseminate research results by paying attention to the global trend of open science.

Journal Articles

Effect of helium on irradiation creep behavior of B-doped F82H irradiated in HFIR

Ando, Masami; Nozawa, Takashi; Hirose, Takanori; Tanigawa, Hiroyasu; Wakai, Eiichi; Stoller, R. E.*; Myers, J.*

Fusion Science and Technology, 68(3), p.648 - 651, 2015/10

 Times Cited Count:1 Percentile:12.03(Nuclear Science & Technology)

Pressurized tubes of F82H and B-doped F82H irradiated at 573 and 673 K up to $$sim$$6dpa have been measured by a laser profilometer. The irradiation creep strain in F82H irradiated at 573 and 673 K was almost linearly dependent on the effective stress level for stresses below 260 MPa and 170 MPa, respectively. The creep strain of $$^{10}$$BN-F82H was similar to that of F82H IEA at each effective stress level except 294 MPa at 573 K irradiation. For 673 K irradiation, the creep strain of some $$^{10}$$BN-F82H tubes was larger than that of F82H tubes. It is suggested that a swelling caused in each $$^{10}$$BN-F82H because small helium babbles might be produced by a reaction of $$^{10}$$B(n, $$alpha$$) $$^{7}$$Li.

Journal Articles

Improving the metadata of bibliographic information to enhance its access

Hayakawa, Misa; Nagaya, Shun; Ebisawa, Naomi; Inagaki, Satomi; Nozawa, Takashi; Itabashi, Keizo

Proceedings of 4th International Conference of Asian Special Libraries (ICoASL 2015) (USB Flash Drive), 8 Pages, 2015/04

Recently, a large quantity of digital contents is distributed on the Internet. Therefore, it is important for us to consider how we can add the value and increase the access to our library bibliographic information metadata. Availability from multiple channels and providing link to the full text may become a solution. This paper describes the case of Japan Atomic Energy Agency Library, as an example to improve our library database that is providing the R&D information (academic papers, oral presentation, and technical reports) of our institute. JAEA library provides this information through JAEA Originated Papers Searching System (JOPSS). This system was improved by providing access channels for the metadata and link to full text. In addition, user interface was constructed based on the information seeking behavior.

Journal Articles

Evaluation of damage accumulation behavior and strength anisotropy of NITE SiC/SiC composites by acoustic emission, digital image correlation and electrical resistivity monitoring

Nozawa, Takashi; Ozawa, Kazumi; Asakura, Yuki*; Koyama, Akira*; Tanigawa, Hiroyasu

Journal of Nuclear Materials, 455(1-3), p.549 - 553, 2014/12

 Times Cited Count:12 Percentile:75.09(Materials Science, Multidisciplinary)

SiC/SiC composite is a promising candidate material of fusion DEMO reactor. This paper aims to identify its damage tolerance and strength anisotropy by various characterization techniques such as acoustic emission (AE) monitoring, electrical resistivity (ER) measurement, and digital image correlation (DIC). The AE results identified that damage accumulation initiated prior to the proportional limit stress (PLS) by both tensile and compressive loadings for 2D composites. The preliminary AE waveform analysis implied that this AE detect strength corresponds to initiation of micro-cracking but the stress-strain curve shows further linearity due to the strong interfacial friction. Then fiber sliding occurred near the PLS, followed by the non-linearlity of the curve. The preliminary tensile test results using a notched specimen also suggest notch insensitivity of the composites in any loading directions. The detailed failure mechanism will eventually be discussed with ER and DIC results.

Journal Articles

Evaluation methods of the failure behavior of SiC/SiC composites with a scope of their application under severe environments

Nozawa, Takashi

Seramikkusu, 49(12), p.1034 - 1039, 2014/12

The small specimen test technique is a viable method for nuclear reactor materials irradiation because of reducing irradiation volume, radioactivity, and waste. It is important to develop the evaluation method to consider unique failure behavior of composites since composites generally show anisotropy due to discontinuity among various constituents with finite size. This paper reviewed recent progress of failure evaluation by various modes and summarized requirements and issues about the small specimen test techniques for composites. Finally, we discussed future perspectives of the small specimen test techniques toward standardization.

Journal Articles

Physical properties of F82H for fusion blanket design

Hirose, Takanori; Nozawa, Takashi; Stoller, R. E.*; Hamaguchi, Dai; Sakasegawa, Hideo; Tanigawa, Hisashi; Tanigawa, Hiroyasu; Enoeda, Mikio; Kato, Yutai*; Snead, L. L.*

Fusion Engineering and Design, 89(7-8), p.1595 - 1599, 2014/10

 Times Cited Count:31 Percentile:94.05(Nuclear Science & Technology)

The material properties, focusing on the properties used for design analysis were re-assessed and newly investigated for various heats including F82H-IEA. Moreover, irradiation effects on those properties were studied in this work. As for thermal properties, thermal conductivity that has significant impacts on the thermo-hydraulic properties of the blanket was investigated on several heats of F82H including F82H-IEA. According to the measurements, the thermal conductivity falls in the range 28.3$$pm$$1.1 W/m/K at 293 K. Although this is comparable with that of the other ferritic/martensitic steels, it is 20% lower than the published value for F82H-IEA. The re-assessment on the published value revealed that the thermal diffusivity was over-estimated. As for irradiation effects on the physical properties, electric resistivity was measured after irradiation up to 6 dpa at 573 K and 673 K. The reduction of resistivity in F82H and its welds were 3% and 6%, respectively.

Journal Articles

Stress envelope of silicon carbide composites at elevated temperatures

Nozawa, Takashi; Kim, S.*; Ozawa, Kazumi; Tanigawa, Hiroyasu

Fusion Engineering and Design, 89(7-8), p.1723 - 1727, 2014/10

 Times Cited Count:5 Percentile:43.74(Nuclear Science & Technology)

A SiC/SiC composite is a promising candidate material for the advanced fusion DEMO blanket. For the design of the DEMO, the stability of high-temperature strength of SiC/SiC composites needs to be identified. Additionally, strength anisotropy needs to be clarified because of its unique fabric architecture. This study therefore aims to evaluate mechanical properties by various modes at elevated temperatures, eventually providing a stress envelope for the design. A P/W Tyranno-SA3 fiber reinforced CVI SiC matrix composite with multilayered SiC/PyC interface was evaluated in this study. Tensile and compressive tests were conducted by the SSTT specifically arranged for the high-temperature use. In-plane shear properties were contrarily estimated by the off-axial tensile method assuming that the mixed mode failure criterion is valid for composites. All tests were performed in vacuum. The preliminary test results indicate no degradation of both proportional limit stress (PLS) and the ultimate tensile strength at temperatures below 1000$$^{circ}$$C. Similarly, no significant degradation of high-temperature compressive and in-plane shear properties were identified, finally providing the stress envelope at elevated temperatures for the design.

Journal Articles

Compatibility of Ni and F82H with liquid Pb-Li under rotating flow

Kanai, Akihiko*; Park, C.*; Noborio, Kazuyuki*; Kasada, Ryuta*; Konishi, Satoshi*; Hirose, Takanori; Nozawa, Takashi; Tanigawa, Hiroyasu

Fusion Engineering and Design, 89(7-8), p.1653 - 1657, 2014/10

 Times Cited Count:4 Percentile:36.81(Nuclear Science & Technology)

Journal Articles

4th Platform Meeting on DEMO Design

Sakamoto, Yoshiteru; Uto, Hiroyasu; Nozawa, Takashi

Purazuma, Kaku Yugo Gakkai-Shi, 90(5), P. 314, 2014/05

The 4th platform meeting was held with 35 participants from universities, industries and JAEA. The objective of the meeting is to discuss the technologies required for DEMO design by young scientists at the Rokkasho BA site. The participants have deeply discussed about design issues on fusion safety, standards, maintenance and requirements for electrical connection along the meeting theme of "Road to fusion electricity". The meeting was very meaningful and should be continued in the future.

Journal Articles

Determination of the carbon ion beam irradiation condition for barley

Iimure, Takashi*; Hoki, Takehiro*; Hase, Yoshihiro; Nozawa, Shigeki; Narumi, Issey*; Kihara, Makoto*; Ogushi, Kensuke*

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 109, 2014/03

Journal Articles

Radiation-induced effects in physical properties of materials, 2-6; Evaluation of irradiation creep for F82H steel by using pressurized tubes

Ando, Masami; Nozawa, Takashi; Hirose, Takanori; Tanigawa, Hiroyasu

Purazuma, Kaku Yugo Gakkai-Shi, 90(1), p.64 - 67, 2014/01

Reduced activation ferritic/martensitic steel (RAFM) is a candidate for the material of DEMO blanket structure. The irradiation creep behavior of F82H and JLF-1 steel has been measured at 300, 400 and 500$$^{circ}$$C up to 5 dpa using helium-pressurized creep tubes irradiated in HFIR. These tubes were pressurized with helium to hoop stress levels of 0$$sim$$400 MPa at the irradiation temperature. The results for F82H and JLF-1 with a 400 MPa hoop stress detected small creep strains ($$<$$ 0.25%) after irradiation at 300$$^{circ}$$C. Irradiation creep rate (creep strain/dose) was tendency to be a similar behavior for high-dose irradiated RAFM specimens in FFTF. In this paper, a procedure of irradiation creep test & evaluation was also summarized.

Journal Articles

Re-defining failure envelopes for silicon carbide composites based on damage process analysis by acoustic emission

Nozawa, Takashi; Ozawa, Kazumi; Tanigawa, Hiroyasu

Fusion Engineering and Design, 88(9-10), p.2543 - 2546, 2013/10

 Times Cited Count:14 Percentile:78.31(Nuclear Science & Technology)

A SiC/SiC composite is a promising candidate for a fusion DEMO blanket. Due to the inherent quasi-ductile failure of composites, determining failure scenario for this class of composites is undoubtedly important to develop design codes in practical use of them. This study aims to evaluate the failure behavior of the quasi-ductile SiC/SiC composites to provide a strength map. For this purpose, detailed tensile, compressive and in-plane shear failure behaviors were evaluated by the acoustic emission (AE) technique. The AE results distinguished damage accumulation processes by wavelet analysis. Of particular emphasis is that matrix cracking occurred prior to the PLS by both tensile and compressive loadings because the rough-surface of SiC fibers resulted in the strong frictional stress at the fiber/matrix (F/M) interface. In this paper, an updated failure envelope will be provided by referring the actual matrix cracking stresses as more realistic and reasonable failure criteria.

Journal Articles

Development of small specimen test techniques for the IFMIF test cell

Wakai, Eiichi; Kim, B. J.; Nozawa, Takashi; Kikuchi, Takayuki; Hirano, Michiko*; Kimura, Akihiko*; Kasada, Ryuta*; Yokomine, Takehiko*; Yoshida, Takahide*; Nogami, Shuhei*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 6 Pages, 2013/03

Journal Articles

Characterization of failure behavior of silicon carbide composites by acoustic emission

Nozawa, Takashi; Ozawa, Kazumi; Tanigawa, Hiroyasu

Ceramic Materials for Energy Applications II, p.95 - 110, 2012/11

This study aims to identify failure behavior of SiC/SiC composites by varied test modes. For this purpose, acoustic emission (AE) was applied to detect composites' failure. Tensile and compressive tests were conducted for a plain-weave (P/W) chemical vapor infiltration (CVI) composite. Various loading angles were applied to discuss an anisotropic issue. AE results distinguished damage accumulation processes in axial and off-axial loading cases. Specifically, test results indicated a clear difference of damage density between tensile and compressive tests. This study also classified the characteristic failure modes by separately discussing localized variations of power within a time series by wavelet analysis.

Journal Articles

Determination and prediction of axial/off-axial mechanical properties of SiC/SiC composites

Nozawa, Takashi; Ozawa, Kazumi; Choi, Y.-B.*; Koyama, Akira*; Tanigawa, Hiroyasu

Fusion Engineering and Design, 87(5-6), p.803 - 807, 2012/08

 Times Cited Count:21 Percentile:86.21(Nuclear Science & Technology)

A SiC/SiC composite is a candidate material for a demonstration fusion power reactor. Considering the inherent anisotropy of composites with variety of fabric architecture is required to precisely predict axial and off-axial mechanical properties by various failure modes. This study evaluated crack propagation behavior by the various modes to provide a strength anisotropy map and we discussed a methodology to analytically predict this trend. The strength anisotropy maps identified for various fabric orientations clearly indicate that the composites failed by the mixed modes. Specifically, due to the axial anisotropy, five individual modes such as tensile/compressive strengths in the axial/transverse directions, respectively, as well as the in-plane shear strength, are identified to be essential. In this study, with the analytical criterion based on the Tsai-Wu model, the strength anisotropy could satisfactorily be described.

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