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Mikami, Satoshi; Tanaka, Hiroyuki*; Matsuda, Hideo*; Sato, Shoji*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Suzuki, Takeo*; Sakamoto, Ryuichi*; Ando, Masaki; Saito, Kimiaki
Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12
Times Cited Count：22 Percentile：66.33(Environmental Sciences)The deposition densities of radiocesium and the air dose rates were repeatedly measured in a large number of undisturbed fields within the 80km zone that surrounds the Fukushima Dai-ichi Nuclear Power Plant site between 2011 and 2016, and features of their temporal changes were clarified. The average air dose rate excluding background radiation in this zone decreased to about 20% of the initial value during the period from June 2011 to August 2016, which was essentially a result of the radioactive decay of 
Cs with a half-life of 2.06y. The air dose rate reduction was faster than that expected from the decay of radiocesium by a factor of about two, with most of this reduction being attributed to the penetration of radiocesium into the soil. The average deposition densities of Cs and 
Cs in fields that were not decontaminated were found to have decreased nearly according to their expected radioactive decay, which indicated that the movement of radiocesium in the horizontal direction was relatively small. The effect of decontamination was apparently observed in the measurements of air dose rates and deposition densities. Nominally, the average air dose rates in the measurement locations were reduced by about 20% by decontamination and other human activities, of which accurate quantitative analysis is and continue to be a challenge.
Ishikawa, Masao; Itoga, Toshio*; Okuji, Toshio*; Nakohostin, M.*; Shinohara, Koji; Baba, Mamoru*; Nishitani, Takeo
AIP Conference Proceedings 988, p.295 - 298, 2008/03
A line-integrated neutron emission profile is routinely measured using Stilbene neutron detector in JT-60U tokamak. Although the SND has many advantages as a neutron detector, the maximum count rate is limited up to 10
cps due to the analog pulse shape discrimination (PSD) circuit. To overcome this issue, a digital signal processing (DSP) system using a flash ADC has been developed In this system anode signals from photomultiplier of the SND are directory stored and digitized. Then, the PSD between neutrons and 
rays is performed using software. The DSP system has been installed in the vertical neutron collimator system inJT-60U and applied to deuterium experiments. It is confirmed that the PSD is sufficiently performed and collimated neutron flux is successfully measured with count rate up to 10
cps without the effect of pileup of detected pulses.
Ushigusa, Kenkichi; Seki, Masahiro; Ninomiya, Hiromasa; Norimatsu, Takayoshi*; Kamada, Yutaka; Mori, Masahiro; Okuno, Kiyoshi; Shibanuma, Kiyoshi; Inoue, Takashi; Sakamoto, Keishi; et al.
Genshiryoku Handobukku, p.906 - 1029, 2007/11
no abstracts in English
C heat resistant boron-loaded resin for neutron shieldingMorioka, Atsuhiko; Sakurai, Shinji; Okuno, Koichi*; Sato, Satoshi; Verzirov, Y. M.; Kaminaga, Atsushi; Nishitani, Takeo; Tamai, Hiroshi; Shibama, Yusuke; Yoshida, Shigeru*; et al.
Journal of Nuclear Materials, 367-370(2), p.1085 - 1089, 2007/08
Times Cited Count：25 Percentile：83.31(Materials Science, Multidisciplinary)A 300C heat-resistant neutron shielding material is newly developed, which consists of phenol-based resin with 6 weight-% boron. The neutron shielding performance of the developed resin, examined by the 
Cf neutron source, is almost the same as that of the polyethylene. The neutron shielding characteristic was also estimated by 3D Monte Carlo Code MCNP-4C2 using the continuous energy cross section data sets based on the JENDL-3.2. The calculation result agrees well with the experimental result. To understand the kinds of the outgas from the developed resin in the high temperature region, the mass spectrum of the outgas was measured until 
300C by Thermal Desorption Specroscopy (TDS). The observed mass number was 2, 17, 18, 28, 32, and 44. The number corresponds to hydrogen (H
), ammonia (NH
), water (HO), carbon monoxide (CO), oxygen (O), carbon dioxide (CO), respectively. The main outgas component from the resin at 100150C was NH and HO. The outgas of NH and HO from the resin have been measured, however, the neutron shielding performance of the resin after 200C baking was almost the same as that before baking. The quantitative analysis of the outgas from the resin in the high temperature region was done by the Temperature Programmed Desorption (TPD) / Gas Chromatography and Mass spectrometry (GC/MS). The 13 kinds of organic gases have been observed by the amount of 
g/g at 300C. The neutron shielding performance of the developed resin at 300C was simulated by the 3D analysis. The resonance cross section of the nucleus is broad at the high temperature region by the Doppler effect. The calculation results using 327C library and 20C library are almost same.
Ishikawa, Masao*; Itoga, Toshio*; Okuji, Toshio*; Nakhostin, M.*; Shinohara, Koji; Hayashi, Takao; Sukegawa, Atsuhiko; Baba, Mamoru*; Nishitani, Takeo
Review of Scientific Instruments, 77(10), p.10E706_1 - 10E706_3, 2006/10
Times Cited Count：22 Percentile：69.43(Instruments & Instrumentation)no abstracts in English
Kubota, Naoyoshi; Fujiwara, Yoshio*; Okumura, Kazutaka*; Ochiai, Kentaro; Kitamura, Akira*; Furuyama, Yuichi*; Taniike, Akira*; Nishitani, Takeo
JAEA-Research 2006-019, 15 Pages, 2006/06
JAEA-Research-2006-019.pdf:0.75MB
Surface analysis of lithium-6 (Li) was performed for both 95 % and 40 % Li-enriched lithium titanate (LiTiO) samples as the candidate tritium breeding material using 2.6 MeV-proton Rutherford Backscattering Spectroscopy (RBS). The depth resolution of this method was enough to measure the Li depth profile in terms of the evaluation of thermal neutron transportation. The atomic density of Li could be measured within the error of 27 % for both samples although the accuracy of 5 % was not achieved for the evaluation of tritium breeding. It was confirmed that the sample atomic compositions agreed with LiTiO within errors of 30 % for Li/Ti and 15 % for O/Ti. The whole errors were caused by the data accuracy of scattering cross sections predominately. Providing more accurate cross section data can lead to the utilization of the RBS method for tritium breeding materials analysis.
Nishimura, Arata*; Hishinuma, Yoshimitsu*; Seo, Kazutaka*; Tanaka, Teruya*; Muroga, Takeo*; Nishijima, Shigehiro*; Katagiri, Kazumune*; Takeuchi, Takao*; Shindo, Yasuhide*; Ochiai, Kentaro; et al.
AIP Conference Proceedings 824, p.241 - 248, 2005/09
Design activity of International Thermonuclear Experimental Reactor clarifies intense neutron streaming from ports for neutral beam injectors. Energy spectrum of the streaming is very wide and 14 MeV neutron and ray are the typical radiations. Large amount of glass fiber reinforced plastics will be used in a superconducting magnet system as an electric insulation material and a support structure, for such organic material is easy to manufacture, and light and cheap. In this report, effects of 14 MeV neutron and ray irradiation on interlaminar shear strength and fracture mode are investigated using G-10CR small specimen of which configuration was proposed as a standard for evaluation of the interlaminar shear strength.
Mori, Masahiro; Shoji, Teruaki; Araki, Masanori; Saito, Keiji*; Senda, Ikuo; Omori, Junji*; Sato, Shinichi*; Inoue, Takashi; Ono, Isamu*; Kataoka, Takahiro*; et al.
Nihon Genshiryoku Gakkai-Shi, 44(1), p.16 - 89, 2002/01
no abstracts in English
Ito, Takao; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Honda, Atsushi; Hu, L.*; Kawai, Mikito; Kazawa, Minoru; Kuriyama, Masaaki; Kusaka, Makoto*; et al.
Fusion Engineering and Design, 51-52, p.1039 - 1047, 2000/11
Times Cited Count：15 Percentile：68.6(Nuclear Science & Technology)no abstracts in English
CuOy by neutron diffraction and high-resolution electron microscopy*; *; *; *; *; *; *; Morii, Yukio; Funahashi, Satoru; *
Physica C, 221, p.261 - 268, 1994/00
Times Cited Count：19 Percentile：74.28(Physics, Applied)no abstracts in English
Nishimura, Arata*; Hishinuma, Yoshimitsu*; Seo, Kazutaka*; Tanaka, Teruya*; Muroga, Takeo*; Nishijima, Shigehiro*; Katagiri, Kazumune*; Takeuchi, Takao*; Shindo, Yasuhide*; Ochiai, Kentaro; et al.
no journal, ,
A fusion device which creates burning plasma will be equipped with a superconducting magnet system to provide strong magnetic field and maintain the burning plasma. The fusion device also will have plasma heating devices such as neutral beam injectors and electron cyclotron systems. Since these systems need several ports to carry in the energy into plasma, the fusion device has large ports connecting to the systems locates in outside of cryostat. Through these ports, D-T neutron will come out of the burning plasma and damage the surrounding materials. The superconducting magnets also will be irradiated by the streaming neutron. To investigate mechanisms of degradation of superconducting properties, and to construct database of irradiation effect on superconducting magnet materials, a cryogenic target system has been install in Fusion Neutronics Source (FNS) at Japan Atomic Energy Agency (JAEA). The irradiation tests with D-T neutron have been carried out three times and some irradiation effects on superconducting magnet materials are clarified. In this paper, the present status of the cryogenic target system and some irradiation test results will be summarized and presented.
Itoga, Toshio*; Nakhostin, M.*; Oishi, Takuji*; Okuji, Toshio*; Baba, Mamoru*; Ishikawa, Masao; Nishitani, Takeo
no journal, ,
no abstracts in English
Ishikawa, Masao*; Itoga, Toshio*; Okuji, Toshio*; Nakhostin, M.*; Shinohara, Koji; Hayashi, Takao; Morioka, Atsuhiko; Baba, Mamoru*; Nishitani, Takeo
no journal, ,
no abstracts in English
Ishikawa, Masao; Itoga, Toshio*; Okuji, Toshio*; Nakhostin, M.*; Baba, Mamoru*; Shinohara, Koji; Hayashi, Takao; Sukegawa, Atsuhiko; Nishitani, Takeo
no journal, ,
Line-integrated neutron emission profiles are routinely measured using Stilbene neuron detectors (SNDs) in JT-60U tokamak. Although the SND has excellent pulse shape discrimination (PSD) property between neutrons and rays, the maximum count rate is limited up to 10 cps due to its analog circuit. To overcome this issue, a digital signal processing (DSP) system using a flash ADC has been developed. In this system, anode signals from the photomultiplier of the SND are directory stored and digitized in the Flash ADC. Then, the PSD is performed using software. The DSP system has been installed in JT-60U and started to measure neutrons in deuterium experiments. As a result, it is confirmed that the DSP system is successfully measured neutron fluxes with count rate up to 10 cps.
Nakamura, Hiroo; Ida, Mizuho; Miyashita, Makoto; Yoshida, Eiichi; Ara, Kuniaki; Nishitani, Takeo; Okumura, Yoshikazu; Horiike, Hiroshi*; Kondo, Hiroo*; Terai, Takayuki*; et al.
no journal, ,
no abstracts in English
Ashikawa, Naoko*; Asakura, Nobuyuki; Hayashi, Takao; Fukumoto, Masakatsu; Kurata, Rie*; Kobayashi, Makoto*; Muroga, Takeo*; Oya, Yasuhisa*; Okuno, Kenji*
no journal, ,
Dust control is an important issue related to tritium retentions in thermonuclear fusion devices with magnetic confinements. In particular, remained hydrogen isotope in dust particles at shadow areas are serious problem related the limitation t capacity in ITER. In previous work of dust collection in LHD and JT-60U, typical diameters of dust particles were shown to be 0.001-10 micron in LHD, and 0.1-100 micron in JT-60U. Some tokamak device groups in TFTR, TEXTOR, JT-60 and JET tried to measure the hydrogen isotopes retentions in dust particles. However, they measured the retention only in the dust flakes with sizes exceeding about 10 microns. In this study, we tried to measure hydrogen isotope retentions in the dusts with small amount including those with small diameters. The estimation of the amount of remained hydrogen isotopes in the dust particles will be useful to estimate tritium inventory and optimize cleaning methods specific dusts in ITER and future fusion devices.
Ohira, Shigeru; Kikuchi, Takayuki; Oshima, Takayuki; Kasuya, Kenichi*; Yonemoto, Kazuhiro*; Sugimoto, Masayoshi; Nishitani, Takeo; Okumura, Yoshikazu
no journal, ,
For Broader Approach Activities, which are joint project between Japan and Europe, JAEA who is the Japanese implementing Agency, has established "International Fusion Energy Research Centre (IFERC)" in Rokkasho, Aomori Japan. At research facilities in IFERC, DEMO R&D Building and CSC&REC Building, in which research and development activities are carried out, experimental equipment and components had been installed and in operation until the end of 2011. The outline of those facilities are described in a poster.
