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Journal Articles

Plutonium dioxide particle imaging using a high-resolution alpha imager for radiation protection

Morishita, Yuki; Kurosawa, Shunsuke*; Yamaji, Akihiro*; Hayashi, Masateru*; Sasano, Makoto*; Makita, Taisuke*; Azuma, Tetsushi*

Scientific Reports (Internet), 11(1), p.5948_1 - 5948_11, 2021/03

 Times Cited Count:0 Percentile:0.01(Multidisciplinary Sciences)

The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation. To determine the activity median aerodynamic diameter values at the working sites of nuclear facilities in real time, we developed a high-resolution alpha imager using a ZnS(Ag) scintillator sheet, an optical microscope, and an electron-multiplying charge-coupled device camera. Then, we designed and applied a setup to measure a plutonium dioxide particle and identify the locations of the individual alpha particles in real time. Employing a Gaussian fitting, we evaluated the average spatial resolution of the multiple alpha particles was evaluated to be 16.2 umFWHM with a zoom range of 5 x. Also, the spatial resolution for the plutonium dioxide particle was 302.7 umFWHM due to the distance between the plutonium dioxide particle and the ZnS(Ag) scintillator. The influence of beta particles was negligible, and alpha particles were discernible in the alpha-beta particle contamination. The equivalent volume diameter of the plutonium dioxide particle was calculated from the measured count rate. These results indicate that the developed alpha imager is effective in the plutonium dioxide particle measurements at the working sites of nuclear facilities for internal exposure dose evaluation.

Journal Articles

Residual stress distribution in water jet peened type 304 stainless steel

Hayashi, Makoto*; Okido, Shinobu*; Suzuki, Hiroshi

Quantum Beam Science (Internet), 4(2), p.18_1 - 18_12, 2020/06

Journal Articles

Energy of the $$^{229}$$Th nuclear clock isomer determined by absolute $$gamma$$-ray energy difference

Yamaguchi, Atsushi*; Muramatsu, Haruka*; Hayashi, Tasuku*; Yuasa, Naoki*; Nakamura, Keisuke; Takimoto, Misaki; Haba, Hiromitsu*; Konashi, Kenji*; Watanabe, Makoto*; Kikunaga, Hidetoshi*; et al.

Physical Review Letters, 123(22), p.222501_1 - 222501_6, 2019/11

 Times Cited Count:15 Percentile:86.53(Physics, Multidisciplinary)

Journal Articles

Evaluation of residual stress relaxation in a rolled joint by neutron diffraction

Hayashi, Makoto*; Root, J. H.*; Rogge, R. B.*; Xu, P. G.

Quantum Beam Science (Internet), 2(4), p.21_1 - 21_16, 2018/12

Journal Articles

Temperature of thermal spikes induced by swift heavy ions

Matsuzaki, Shota*; Hayashi, Hiroaki*; Nakajima, Kaoru*; Matsuda, Makoto; Sataka, Masao*; Tsujimoto, Masahiko*; Toulemonde, M.*; Kimura, Kenji*

Nuclear Instruments and Methods in Physics Research B, 406(Part B), p.456 - 459, 2017/09

 Times Cited Count:3 Percentile:40.62(Instruments & Instrumentation)

Journal Articles

Rapid measurement scheme for texture in cubic metallic materials using time-of-flight neutron diffraction at iMATERIA

Onuki, Yusuke*; Hoshikawa, Akinori*; Sato, Shigeo*; Xu, P. G.; Ishigaki, Toru*; Saito, Yoichi*; Todoroki, Hidekazu*; Hayashi, Makoto*

Journal of Applied Crystallography, 49(5), p.1579 - 1584, 2016/10


 Times Cited Count:19 Percentile:85.91(Chemistry, Multidisciplinary)

Journal Articles

Deuterium permeation behavior for damaged tungsten by ion implantation

Oya, Yasuhisa*; Li, X.*; Sato, Misaki*; Yuyama, Kenta*; Oyaizu, Makoto; Hayashi, Takumi; Yamanishi, Toshihiko; Okuno, Kenji*

Journal of Nuclear Science and Technology, 53(3), p.402 - 405, 2016/03

 Times Cited Count:10 Percentile:78.98(Nuclear Science & Technology)

The deuterium (D) permeation behaviors for ion damaged tungsten (W) by 3 keV D$$_{2}$$$$^{+}$$ and 10 keV C$$^{+}$$ were studied. The D permeability was obtained for un-damaged W at various temperatures. For both D$$_{2}$$$$^{+}$$ and C$$^{+}$$ implanted W, the permeability was clearly reduced. But, for the D$$_{2}$$$$^{+}$$ implanted W, the permeability was recovered by heating at 1173 K and it was almost consistent with that for un-damaged W. In the case of C$$^{+}$$ implanted W, the permeability was not recovered even if the sample was heated at 1173 K, indicating that the existence of carbon would prevent the recovery of permeation path in W. In addition, TEM observation showed the voids were grown by heating at 1173 K and not removed, showing the existence of damages would not largely influence on the hydrogen permeation behavior in W in the present study.

Journal Articles

R&D activities of tritium technologies on Broader Approach in Phase 2-2

Isobe, Kanetsugu; Kawamura, Yoshinori; Iwai, Yasunori; Oyaizu, Makoto; Nakamura, Hirofumi; Suzuki, Takumi; Yamada, Masayuki; Edao, Yuki; Kurata, Rie; Hayashi, Takumi; et al.

Fusion Engineering and Design, 98-99, p.1792 - 1795, 2015/10

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Activities on Broader Approach (BA) were started in 2007 on the basis of the Agreement between the Government of Japan and the EURATOM. The period of BA activities consist of Phase1 and Phase2 dividing into Phase 2-1 (2010-2011), Phase 2-2 (2012-2013) and Phase 2-3 (2014-2016). Tritium technology was chosen as one of important R&D issues to develop DEMO plant. R&D activities of tritium technology on BA consist of four tasks. Task-1 is to prepare and maintain the tritium handling facility in Rokkasho BA site in Japan. Task 2, 3 and 4 are main R&D activities for tritium and these are focused on: Task-2) Development of tritium accountancy technology, Task-3) Development of basic tritium safety research, Task-4) Tritium durability test. R&D activities of tritium technology in Phase 2-2 were underway successfully and closed in 2013.

Journal Articles

Effect of tritium on corrosion behavior of chromium in 0.01N sulfuric acid solution

Oyaizu, Makoto; Isobe, Kanetsugu; Hayashi, Takumi

Fusion Science and Technology, 67(3), p.519 - 522, 2015/04

 Times Cited Count:2 Percentile:22.25(Nuclear Science & Technology)

The effects of tritiated water on the corrosion behavior of chromium were electrochemically studied by anodic polarization measurements with changing tritium concentration and dissolved oxygen concentration as parameters in the electrolyte of 0.01N sulfuric acid solution, self-passivation due to dissolved oxygen could be observed in pure water without tritium. As a result, it was found that the self-passivation was inhibited in tritiated electrolyte as shown in the previous studies for SUS304 stainless steel. It is indicated from the result that the passivation inhibitory effect for SUS304 stainless steel could be induced by dissolution of chromium in passivation film on SUS304 stainless steel.

Journal Articles

Recent progress on tritium technology research and development for a fusion reactor in Japan Atomic Energy Agency

Hayashi, Takumi; Nakamura, Hirofumi; Kawamura, Yoshinori; Iwai, Yasunori; Isobe, Kanetsugu; Yamada, Masayuki; Suzuki, Takumi; Kurata, Rie; Oyaizu, Makoto; Edao, Yuki; et al.

Fusion Science and Technology, 67(2), p.365 - 370, 2015/03

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Journal Articles

Study of safety features and accident scenarios in a fusion DEMO reactor

Nakamura, Makoto; Tobita, Kenji; Gulden, W.*; Watanabe, Kazuhito*; Someya, Yoji; Tanigawa, Hisashi; Sakamoto, Yoshiteru; Araki, Takao*; Matsumiya, Hisato*; Ishii, Kyoko*; et al.

Fusion Engineering and Design, 89(9-10), p.2028 - 2032, 2014/10

 Times Cited Count:10 Percentile:68.92(Nuclear Science & Technology)

After the Fukushima Dai-ichi nuclear accident, a social need for assuring safety of fusion energy has grown gradually in the Japanese (JA) fusion research community. DEMO safety research has been launched as a part of BA DEMO Design Activities (BA-DDA). This paper reports progress in the fusion DEMO safety research conducted under BA-DDA. Safety requirements and evaluation guidelines have been, first of all, established based on those established in the Japanese ITER site invitation activities. The amounts of radioactive source terms and energies that can mobilize such source terms have been assessed for a reference DEMO, in which the blanket technology is based on the Japanese fusion technology R&D programme. Reference event sequences expected in DEMO have been analyzed based on the master logic diagram and functional FMEA techniques. Accident initiators of particular importance in DEMO have been selected based on the event sequence analysis.

Journal Articles

Hydrogen isotope behavior on a water-metal boundary with simultaneous transfer from and to the metal surface

Hayashi, Takumi; Isobe, Kanetsugu; Nakamura, Hirofumi; Kobayashi, Kazuhiro; Oya, Yasuhisa*; Okuno, Kenji*; Oyaizu, Makoto; Edao, Yuki; Yamanishi, Toshihiko

Fusion Engineering and Design, 89(7-8), p.1520 - 1523, 2014/10

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Tritium confinement is the most important safety issue in the fusion reactor. Tritium behavior on the water metal boundary is very important to design tritium plant with breading blanket system using cooling water. A series of tritium permeation experiment into pressurized water or water vapor jacket with He or Ar have been performed through pure iron piping with/without 7 micro-meter gold plating, which contained about 1 kPa of pure tritium gas at 423 K, with monitoring the chemical forms of tritium. Also, deuterium permeation experiments from heavy water vessel through various metal piping, such as pure iron (Fe), nickel (Ni), stainless steel (SS304), and pure iron with 10 micro-meter gold plating, were performed at 573 K and at 15 MPa. Recently, using the above heavy water system, we have succeeded to detect simultaneous hydrogen isotopes transfer from and to the metal surface by introducing H$$_{2}$$ gas to the metal piping after stabilized deuterium permeation was detected.

Journal Articles

Key aspects of the safety study of a water-cooled fusion DEMO reactor

Nakamura, Makoto; Tobita, Kenji; Someya, Yoji; Tanigawa, Hisashi; Gulden, W.*; Sakamoto, Yoshiteru; Araki, Takao*; Watanabe, Kazuhito*; Matsumiya, Hisato*; Ishii, Kyoko*; et al.

Plasma and Fusion Research (Internet), 9, p.1405139_1 - 1405139_11, 2014/10

Key aspects of the safety study of a water-cooled fusion DEMO reactor is reported. Safety requirements, dose target, DEMO plant model and confinement strategy of the safety study are briefly introduced. The internal hazard of a water-cooled DEMO, i.e. radioactive inventories, stored energies that can mobilize these inventories and accident initiators and scenarios, are evaluated. It is pointed out that the enthalpy in the first wall/blanket cooling loops, the decay heat and the energy potentially released by the Be-steam chemical reaction are of special concern for the water-cooled DEMO. An ex-vessel loss-of-coolant of the first wall/blanket cooling loop is also quantitatively analyzed. The integrity of the building against the ex-VV LOCA is discussed.

Journal Articles

Development of bulk texture measurement technique by time-of-flight neutron diffraction

Xu, P. G.; Hoshikawa, Akinori*; Hayashi, Makoto*; Akita, Koichi; Morii, Yukio*; Ishigaki, Toru*

Nihon Zairyo Gakkai Dai-48-Kai X Sen Zairyo Kyodo Ni Kansuru Shimpojiumu Koen Rombunshu, p.7 - 9, 2014/07

Journal Articles

Research and development of radiation measuring instruments for lake,pond and river sediments, 1

Yanagizawa, Koichi; Hayashi, Toshio*; Oinuma, Masaru*; Takemori, Makoto*; Ishikawa, Takanori*; Okaya, Tomoichi*; Nishigaki, Makoto*

Shadan Hojin Butsuri Tansa Gakkai Dai-129-Kai (Heisei-25-Nendo Shuki) Gakujutsu Koenkai Koen Rombunshu, p.287 - 288, 2013/10

The development of instrument aimed at the measurement of radiation dose in the sediment of lakes, rivers and sea bed been carried out. The radiation level contained in the sediment at the bottom of lake and so on is anticipated to indicate the existence of locally high radiation spots where the diffused radioactive substance is accumulated in ponds, rivers and lakes by rainwater. The radiation dose measurement system this time is to measure $$gamma$$-ray by dragging the detector, which is called probe, at the bottom of lakes to understand the radiation dose over wide areas. Furthermore, the measurement of resistivity value at the bottom of lakes is simultaneously dose to presume the condition of sediment.

Journal Articles

Overview of R&D activities on tritium processing and handling technology in JAEA

Yamanishi, Toshihiko; Nakamura, Hirofumi; Kawamura, Yoshinori; Iwai, Yasunori; Isobe, Kanetsugu; Oyaizu, Makoto; Yamada, Masayuki; Suzuki, Takumi; Hayashi, Takumi

Fusion Engineering and Design, 87(5-6), p.890 - 895, 2012/08

 Times Cited Count:1 Percentile:11.68(Nuclear Science & Technology)

In JAEA, the tritium processing and handling technologies have been studied at TPL. The main basic R&D activities in this field are: the tritium processing technology for the blanket recovery system; the tritium behavior in a confinement; and detritiation and decontamination. The R&D for tritium processing and handling technologies to a demonstration reactor (DEMO) are also planned to be carried out in the Broader Approach (BA) program in Japan by JAEA with Japanese universities. The ceramic electrolysis cell has been studied as a tritium processing method for the blanket system. The permeation behavior of tritium through pure iron into the gas containing water vapor has been studied. As for the behavior of high concentration tritium water, it was observed that the formation of the oxidized layer was prevented by the presence of tritium in water. Tritium durability tests were also carried out for the electrolysis cell of the chemical exchange column.

Journal Articles

Hydrogen isotope permeation from cooling water through various metal piping

Hayashi, Takumi; Nakamura, Hirofumi; Isobe, Kanetsugu; Kobayashi, Kazuhiro; Oyaizu, Makoto; Yamanishi, Toshihiko; Oya, Yasuhisa*; Okuno, Kenji*

Fusion Engineering and Design, 87(7-8), p.1333 - 1337, 2012/08

 Times Cited Count:7 Percentile:53.66(Nuclear Science & Technology)

In order to investigate the behavior of hydrogen isotope on the water-metal boundary, deuterium permeation experiments from heavy water vessel through various metal piping, such as pure iron (Fe), nickel (Ni), stainless steel (SS304), and pure iron with 10 $$mu$$m gold plating, were performed at 573 K and at 15 MPa. During the experiment, surfaces of metal piping except gold plating one were oxidized at the heavy water boundary and then deuterium would generate by the oxidation reactions. This deuterium could be detected by mass spectrometer, which monitored the inside gases of the piping under vacuum. The result showed clearly that the deuterium permeated through Fe, Ni, and SS304 piping was detected as deuterium gas (D$$_{2}$$) under vacuum, though that through gold plating one could not be detected effectively. The D$$_{2}$$ permeation rate through Fe, Ni, and SS304 piping reached some stabilized value. This paper summarizes the above experimental results and discusses the mechanism of deuterium behavior on the water metal boundary.

Journal Articles

Design study and comparative evaluation of JSFR failed fuel detection system

Aizawa, Kosuke; Chikazawa, Yoshitaka; Ishikawa, Nobuyuki; Kubo, Shigenobu; Okazaki, Hitoshi*; Mito, Makoto*; Tozawa, Katsuhiro*; Hayashi, Masateru*

Proceedings of 2012 International Congress on Advances in Nuclear Power Plants (ICAPP '12) (CD-ROM), p.465 - 474, 2012/06

A conceptual design study of an advanced sodium-cooled fast reactor JSFR has progressed in the "Fast Reactor Cycle Technology Development (FaCT)" project in Japan. JSFR has two failed fuel detection systems in the core. One is a failed fuel detection (FFD) system which continuously monitors a fission product from failed fuel subassembly. The other is a failed fuel detection and location (FFDL) system which locates when it receives signals from FFD. In this study, requirements to the FFD-DN and the FFD-DN design to meet the requirements were investigated for the commercial and demonstration JSFR. For the FFDL systems, experiences in the previous fast reactors and the research and development of FFDL system for JSFR were investigated. Operation experiences of the Selector-valve FFDL system were accumulated in PFR and Phenix. Tagging-gas system experiences were accumulated in EBR-II and FFTF.

Journal Articles

Effects of tritiated water on corrosion behavior of SUS304

Oyaizu, Makoto; Isobe, Kanetsugu; Hayashi, Takumi; Yamanishi, Toshihiko

Fusion Science and Technology, 60(4), p.1515 - 1518, 2011/11

 Times Cited Count:3 Percentile:28.8(Nuclear Science & Technology)

The effects of tritiated water on the corrosion behavior of SUS304 stainless steel was studied using Tafel extrapolation method, one of electrochemical techniques with changing tritium concentration, dissolved oxygen concentration and pH in electrolyte as parameters. It was indicated that there would be two or more effects of tritium that enhance the corrosion of SUS304 stainless steel under several experimental conditions. One is passivation inhibitory effect, which could be observed only in highly corrosive circumstance of 1N H$$_{2}$$SO$$_{4}$$ electrolyte. The other effects of tritium on corrosion behavior could be observed not only in 1N H$$_{2}$$SO$$_{4}$$ but also in corrosive circumstance of 1N Na$$_{2}$$SO$$_{4}$$ electrolyte, which would be affected by dissolved oxygen concentration as well as tritium concentration.

Journal Articles

Permeation behavior of tritium through F82H steel

Oyaizu, Makoto; Isobe, Kanetsugu; Nakamura, Hirofumi; Hayashi, Takumi; Yamanishi, Toshihiko

Journal of Nuclear Materials, 417(1-3), p.1143 - 1146, 2011/10

 Times Cited Count:5 Percentile:42.62(Materials Science, Multidisciplinary)

The tritium permeation behavior through F82H steel from carrier-free tritiated water vapor was investigated and the difference between as-received sample surface and that after the permeation experiments were analyzed by means of SEM, EDX and XRD. As the results, the permeability of tritium through F82H steel from tritiated water vapor is two to three orders of magnitude smaller than that from gaseous hydrogen. A thick and porous iron oxide layer composed of hematite and magnetite was formed in the permeation experiments. These results indicate that the oxide layer would hardly work as tritium permeation barrier, and that gaseous hydrogen could be generated by the redox reaction of water on the sample surface. Therefore, it could be considered that the tritium permeation through F82H steel from tritiated water vapor could result from the partial pressure of T$$_{2}$$.

122 (Records 1-20 displayed on this page)