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Journal Articles

Microstructural evolution in tungsten binary alloys under proton and self-ion irradiations at 800$$^{circ}$$C

Miyazawa, Takeshi; Kikuchi, Yuta*; Ando, Masami*; Yu, J.-H.*; Yabuuchi, Kiyohiro*; Nozawa, Takashi*; Tanigawa, Hiroyasu*; Nogami, Shuhei*; Hasegawa, Akira*

Journal of Nuclear Materials, 575, p.154239_1 - 154239_11, 2023/03

 Times Cited Count:0 Percentile:0.02(Materials Science, Multidisciplinary)

JAEA Reports

Development of technologies for enhanced analysis accuracy of fuel debris; Summary results of the 2020 fiscal year (Subsidy program for the project of decommissioning and contaminated water management)

Ikeuchi, Hirotomo; Koyama, Shinichi; Osaka, Masahiko; Takano, Masahide; Nakamura, Satoshi; Onozawa, Atsushi; Sasaki, Shinji; Onishi, Takashi; Maeda, Koji; Kirishima, Akira*; et al.

JAEA-Technology 2022-021, 224 Pages, 2022/10


A set of technology, including acid dissolving, has to be established for the analysis of content of elements/nuclides in the fuel debris samples. In this project, a blind test was performed for the purpose of clarifying the current level of analytical accuracy and establishing the alternative methods in case that the insoluble residue remains. Overall composition of the simulated fuel debris (homogenized powder having a specific composition) were quantitatively determined in the four analytical institutions in Japan by using their own dissolving and analytical techniques. The merit and drawback for each technique were then evaluated, based on which a tentative flow of the analyses of fuel debris was constructed.

Journal Articles

Summary results of subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))"

Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.

Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08

JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.

Journal Articles

Development and operation of an electrostatic time-of-flight detector for the Rare RI storage Ring

Nagae, Daisuke*; Abe, Yasushi*; Okada, Shunsuke*; Omika, Shuichiro*; Wakayama, Kiyoshi*; Hosoi, Shun*; Suzuki, Shinji*; Moriguchi, Tetsuro*; Amano, Masamichi*; Kamioka, Daiki*; et al.

Nuclear Instruments and Methods in Physics Research A, 986, p.164713_1 - 164713_7, 2021/01

 Times Cited Count:5 Percentile:74.78(Instruments & Instrumentation)

Journal Articles

First direct mass measurements of nuclides around $$Z$$ = 100 with a multireflection time-of-flight mass spectrograph

Ito, Yuta*; Schury, P.*; Wada, Michiharu*; Arai, Fumiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Ishizawa, Satoshi*; Kaji, Daiya*; Kimura, Sota*; Koura, Hiroyuki; et al.

Physical Review Letters, 120(15), p.152501_1 - 152501_6, 2018/04

 Times Cited Count:56 Percentile:93.96(Physics, Multidisciplinary)

Masses of $$^{246}$$Es, $$^{251}$$Fm and the transfermium nuclei $$^{249-252}$$Md, and $$^{254}$$No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed $$N=152$$ neutron shell closure, have been directly measured using a multi-reflection time-of-flight mass spectrograph. The masses of $$^{246}$$Es and $$^{249,250,252}$$Md were measured for the first time. Using the masses of $$^{249,250}$$Md as anchor points for $$alpha$$ decay chains, the masses of heavier nuclei, up to $$^{261}$$Bh and $$^{266}$$Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter $$delta_{2n}$$ derived from three isotopic masses was updated with the new masses and corroborate the existence of the deformed $$N=152$$ neutron shell closure for Md and Lr.

JAEA Reports

Pretreatment works for disposal of radioactive wastes produced by research activities, 1

Ishihara, Keisuke; Yokota, Akira; Kanazawa, Shingo; Iketani, Shotaro; Sudo, Tomoyuki; Myodo, Masato; Irie, Hirobumi; Kato, Mitsugu; Iseda, Hirokatsu; Kishimoto, Katsumi; et al.

JAEA-Technology 2016-024, 108 Pages, 2016/12


Radioactive isotope, nuclear fuel material and radiation generators are utilized in research institutes, universities, hospitals, private enterprises, etc. As a result, various low-level radioactive wastes (hereinafter referred to as non-nuclear radioactive wastes) are produced. Disposal site for non-nuclear radioactive wastes have not been settled yet and those wastes are stored in storage facilities of each operator for a long period. The Advanced Volume Reduction Facilities (AVRF) are built to produce waste packages so that they satisfy requirements for shallow underground disposal. In the AVRF, low-level beta-gamma solid radioactive wastes produced in the Nuclear Science Research Institute are mainly treated. To produce waste packages meeting requirements for disposal safely and efficiently, it is necessary to cut large radioactive wastes into pieces of suitable size and segregate those depending on their types of material. This report summarizes activities of pretreatment to dispose of non-nuclear radioactive wastes in the AVRF.

Journal Articles

Cause investigation for thinning of anchor bolts and gaps between anchor bolt nuts and a flange plate at the JMTR Hot Laboratory exhaust stack

Shibata, Akira; Kitagishi, Shigeru; Watashi, Katsumi; Matsui, Yoshinori; Omi, Masao; Sozawa, Shizuo; Naka, Michihiro

Nihon Hozen Gakkai Dai-13-Kai Gakujutsu Koenkai Yoshishu, p.290 - 297, 2016/07

The exhaust stack of Japan Materials Testing Reactor Hot laboratory is a part of gaseous waste treatment system. It was built in 1970 and is 40 m in height. In 2015, thinning was found at some anchor bolts on base of the stack. When thinning of anchor bolts were investigated, gaps between anchor bolt nuts and flange plate was found. JAEA removed steel cylinder of stack which is 33 m in height for safety. In the end of investigation, thinning was found in all anchor bolts of the stack. Cause investigation for the thinning and the gaps were performed. It is concluded that the thinning was caused by water infiltration over a long period of time and the gaps were caused by elongation of thinning part of anchor bolts by the 2011 earthquake off the Pacific coast of Tohoku.

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:15 Percentile:76.05(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

Development of ion beam breeding technology in plants and creation of useful plant resources

Hase, Yoshihiro; Nozawa, Shigeki; Asami, Itsuo*; Tanogashira, Yuki*; Matsuo, Yoichi*; Kanazawa, Akira*; Honda, Kazushige*; Narumi, Issey*

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 102, 2014/03

Journal Articles

A Multi-reflection time-of-flight mass spectrograph for short-lived and super-heavy nuclei

Schury, P. H.*; Wada, Michiharu*; Ito, Yuta*; Naimi, S.*; Sonoda, Tetsu*; Mita, Koki*; Takamine, Aiko*; Okada, Kunihiro*; Wollnik, H.*; Chon, S.*; et al.

Nuclear Instruments and Methods in Physics Research B, 317(Part B), p.537 - 543, 2013/12

 Times Cited Count:27 Percentile:89.91(Instruments & Instrumentation)

A multi-reflection time-of-flight (MRTOF) mass spectrograph has been implemented at RIKEN to provide high-precision mass measurements of very short-lived nuclei. Of particular interest are mass measurements of r-process nuclei and trans-uranium nuclei. In such nuclei, the MRTOF can perform on par with or better than traditional Penning trap systems. We demonstrate that the MRTOF-MS is capable of accurately attaining relative mass precision of $$delta$$m/m $$<$$ 10$$^{-7}$$ and describe it's utility with heavy, short-lived nuclei.

Journal Articles

Development of ion beam breeding technology in plants and creation of useful plant resources

Hase, Yoshihiro; Nozawa, Shigeki; Okada, Tomoyuki*; Asami, Itsuo*; Nagatani, Takeshi*; Matsuo, Yoichi*; Kanazawa, Akira*; Honda, Kazushige*; Narumi, Issei

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 95, 2013/01

Journal Articles

New result in the production and decay of an isotope, $$^{278}$$113 of the 113th element

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sumita, Takayuki*; Wakabayashi, Yasuo*; Yoneda, Akira*; Tanaka, Kengo*; et al.

Journal of the Physical Society of Japan, 81(10), p.103201_1 - 103201_4, 2012/10

 Times Cited Count:161 Percentile:97.32(Physics, Multidisciplinary)

An isotope of the 113th element, $$^{278}$$113, was produced in a nuclear reaction with a $$^{70}$$Zn beam on a $$^{209}$$Bi target. We observed six consecutive $$alpha$$ decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector, in extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of $$^{262}$$Db and $$^{258}$$Lr both in decay energies and decay times. This indicates that the present decay chain consisted of $$^{278}$$113, $$^{274}$$Rg (Z = 111), $$^{270}$$Mt (Z = 109), $$^{266}$$Bh (Z = 107), $$^{262}$$Db (Z = 105), and $$^{258}$$Lr (Z = 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads the unambiguous production and identification of the isotope $$^{278}$$113, of the 113th element.

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:27 Percentile:88.17(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.

Journal Articles

Development of ion beam breeding technology in plants and creation of useful plant resources

Hase, Yoshihiro; Nozawa, Shigeki; Okada, Tomoyuki*; Asami, Itsuo*; Nagatani, Takeshi*; Matsuo, Yoichi*; Kanazawa, Akira*; Honda, Kazushige*; Narumi, Issei

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 100, 2012/01

Journal Articles

Japanese contribution to the DEMO-R&D program under the Broader Approach activities

Nishitani, Takeo; Yamanishi, Toshihiko; Tanigawa, Hiroyasu; Nozawa, Takashi; Nakamichi, Masaru; Hoshino, Tsuyoshi; Koyama, Akira*; Kimura, Akihiko*; Hinoki, Tatsuya*; Shikama, Tatsuo*

Fusion Engineering and Design, 86(12), p.2924 - 2927, 2011/12

 Times Cited Count:7 Percentile:49.87(Nuclear Science & Technology)

Several technical R&D activities related to the blanket materials are newly launched as a part of the Broader Approach (BA) activities, which was initiated by the EU and Japan. According to the common interests of these parties for DEMO, R&Ds on reduced activation ferritic/martensitic (RAFM) steels as structural material, SiCf/SiC composites as a flow channel insert material and/or alternative structural material, advanced tritium breeders and neutron multipliers, and tritium technology are carried out through the BA DEMO R&D program, in order to establish the technical bases on the blanket materials and the tritium technology required for DEMO design. This paper describes overall schedule of those R&D activities and recent progress in Japan carried out by JAEA as the domestic implementing agency on BA, collaborating with Japanese universities and other research institutes.

Journal Articles

Recent progress in blanket materials development in the Broader Approach Activities

Nishitani, Takeo; Tanigawa, Hiroyasu; Nozawa, Takashi; Jitsukawa, Shiro; Nakamichi, Masaru; Hoshino, Tsuyoshi; Yamanishi, Toshihiko; Baluc, N.*; M$"o$slang, A.*; Lindou, R.*; et al.

Journal of Nuclear Materials, 417(1-3), p.1331 - 1335, 2011/10

 Times Cited Count:14 Percentile:72.96(Materials Science, Multidisciplinary)

As a part of the Broader Approach (BA) activities, the research and development on blanket related materials and tritium technology have been initiated toward DEMO by Japan and EU. Recently, those five R&D items have progressed substantially in Japan and EU. As a preparatory work aiming at the RAFM steel muss-production development, a 5-ton heat of RAFM steel (F82H) was procured with the Electro Slag Re-melting as a secondary melting. The result of the double notch tensile test method for the NITE-SiC$$_{f}$$/SiC specimen indicated notch insensitivity and very minor size effect on proportional limit tensile stress and fracture strength. For the fabrication technology development of beryllide neutron multiplayer pebbles, Be- Ti inter-metallic pebbles have been sintered directly from the mixed powder of Be and Ti in Japan.

Journal Articles

Tensile, compressive and in-plane/inter-laminar shear failure behavior of CVI- and NITE-SiC/SiC composites

Nozawa, Takashi; Choi, Y.-B.*; Hinoki, Tatsuya*; Kishimoto, Hirotatsu*; Koyama, Akira*; Tanigawa, Hiroyasu

IOP Conference Series; Materials Science and Engineering, 18, p.162011_1 - 162011_4, 2011/09

 Times Cited Count:9 Percentile:96.64

A SiC/SiC composite is one of attractive candidates for fission and nuclear fusion due to the proven irradiation tolerance coupled with the excellent baseline properties as refractory ceramics. Considering the inherent anisotropy of composites due to the variety of fabric architecture, it is required to identify the crack propagation behavior of SiC/SiC composites by various failure modes. This study aims to evaluate crack propagation behavior by the axial and off-axial tensile/compressive tests, Iosipescu test for in-plane shear, double-notch-shear test for inter-laminar shear and diametral compression test for inter-laminar detachment. Preliminary test results identified strength anisotropy maps, implying that the composites failed by the mixed modes. Specifically, it was found that the in-plane/inter-laminar shear modes had significant impacts on the results.

Journal Articles

Production and decay properties of $$^{264}$$Hs and $$^{265}$$Hs

Sato, Nozomi; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Kaji, Daiya*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozeki, Kazutaka*; Sumita, Takayuki*; Yoneda, Akira*; et al.

Journal of the Physical Society of Japan, 80(9), p.094201_1 - 094201_7, 2011/09

 Times Cited Count:15 Percentile:65.9(Physics, Multidisciplinary)

Decay properties of $$^{264}$$Hs and $$^{265}$$Hs produced in the $$^{207,208}$$Pb($$^{58}$$Fe, $$xn$$) [$$x$$=1, 2] reactions were studied using a gas-filled recoil ion separator at the linear accelerator facility of RIKEN. A total of 6 decay chains were assigned to $$^{264}$$Hs. Cross sections for the $$^{264}$$Hs production in the $$^{208}$$Pb($$^{58}$$Fe,$$2n$$) and $$^{207}$$Pb($$^{58}$$Fe,$$n$$) reactions were measured to be $$2.8^{+6.5}_{-2.3}$$pb and $$6.9^{+4.4}_{-3.1}$$pb, respectively. The isotope $$^{264}$$Hs decayed with a half-life of $$0.751^{+0.518}_{-0.218}$$ms by $$alpha$$-particle emission and spontaneous fission. The $$alpha$$-particle energy of $$^{264}$$Hs was observed at 10.61$$pm$$0.04 and 10.80$$pm$$0.08 MeV. The spontaneous fission branch of $$^{264}$$Hs was found to be $$17^{+38}_{-14}%$$.

JAEA Reports

Investigation for methods of micro-structural observation of beryllium metals by TEM

Ito, Masayasu; Kawamata, Kazuo; Sozawa, Shizuo; Shibata, Akira; Tsuchiya, Kunihiko; Kitsunai, Yuji*; Kodama, Mitsuhiro*

JAEA-Testing 2011-003, 22 Pages, 2011/06


In JMTR, beryllium metal is used for neutron reflector. However, the periodical exchange of the neutron reflector is necessary due to degradation of strength and swelling under neutron irradiation. So it is required to select the material that bears long term from the viewpoint of the utilization rate improvement and the radioactive waste decrease in JMTR. It is important to evaluate the characteristics of beryllium metals precisely. This report describes the preparation method of the sample and observation results by the transmission electron microscope that is being examined as a evaluation method of the beryllium metal.

Journal Articles

Effect of ion beam irradiation for ${it Asclepias}$ species

Kobayashi, Nobuo*; Sasaki, Shinichiro*; Tasaki, Keisuke*; Nakatsuka, Akira*; Nozawa, Shigeki; Hase, Yoshihiro; Narumi, Issei

JAEA-Review 2010-065, JAEA Takasaki Annual Report 2009, P. 67, 2011/01

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