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Pt-labeled platinum complex and evaluation of its biodistribution in healthy miceOmokawa, Marina*; Kimura, Hiroyuki*; Hatsukawa, Yuichi*; Kawashima, Hidekazu*; Tsukada, Kazuaki; Yagi, Yusuke*; Naito, Yuki*; Yasui, Hiroyuki*
Bioorganic & Medicinal Chemistry, 97, p.117557_1 - 117557_6, 2024/01
Times Cited Count：0 Percentile：0.01(Biochemistry & Molecular Biology)Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Ito, Chikara; Naito, Hiroyuki; Ishikawa, Takashi; Ito, Keisuke; Wakaida, Ikuo
JPS Conference Proceedings (Internet), 24, p.011038_1 - 011038_6, 2019/01
A high-radiation resistant optical fiber has been developed in order to investigate the interiors of the reactor pressure vessels and the primary containment vessels at the Fukushima Daiichi Nuclear Power Station. The tentative dose rate in the reactor pressure vessels is assumed to be up to 1 kGy/h. We developed a radiation resistant optical fiber consisting of a 1000 ppm hydroxyl doped pure silica core and 4 % fluorine doped pure silica cladding. We attempted to apply the optical fiber to remote imaging technique by means of fiberscope. The number of core image fibers was increased from 2000 to 22000 for practical use. The transmissive rate of infrared images was not affected after irradiation of 1 MGy. No change in the spatial resolution of the view scope by means of image fiber was noted between pre- and post-irradiation. We confirmed the applicability of the probing system, which consists of a view scope using radiation-resistant optical fibers.
Ito, Chikara; Naito, Hiroyuki; Nishimura, Akihiko; Oba, Hironori; Wakaida, Ikuo; Sugiyama, Akira; Chiyatani, Keiji
Journal of Nuclear Science and Technology, 51(7-8), p.944 - 950, 2014/07
Times Cited Count：30 Percentile：91.18(Nuclear Science & Technology)In the Fukushima Daiichi Nuclear Power Station, it is necessary to survey the locations and conditions of fuel debris inside reactor pressure vessels or primary containment vessels under water and radiation environment in preparation for removing fuel debris. An optical fiber is well known for features such as signal transmission, light weight, superior insulation performance, water resistance and electromagnetic noise resistance. These features allow the optical fiber to simplify the instrumentation systems for in-vessel inspection, as long as provide that the optical fiber can be used under high radiation dose environment. The radiation resistance of an optical fiber was improved by increasing the amount of hydroxyl up to 1000 ppm in pure silica fiber. The improved optical fibers were irradiated with 
-ray up to 1 
10
Gy using a 
Co source. They indicated a large peak around 600 nm and a peak tail from ultraviolet region, but no large absorption in infrared region except a hydroxyl absorption peak of 945 nm. We have confirmed that the optical fiber containing 1000 ppm hydroxyl has enough radiation resistance for radiation induced transmission losses and the infrared imaging is effective for observation under high radiation doses.
Ito, Chikara; Naito, Hiroyuki; Oba, Hironori; Saeki, Morihisa; Ito, Keisuke; Ishikawa, Takashi; Nishimura, Akihiko; Wakaida, Ikuo; Sekine, Takashi
Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 7 Pages, 2014/07
A high-radiation resistant optical fiber has been developed in order to investigate the interiors of the reactor pressure vessels and the primary containment vessels of the Fukushima Daiichi Nuclear Power Station. The radiation resistance of an optical fiber was improved by increasing the amount of hydroxyl up to 1000 ppm in pure silica fiber. The improved image fiber consists of common cladding and a large number of fiber cores made from pure silica that contains 1000 ppm hydroxyl. The transmissive rate of an infrared image was not affected after the irradiation of 1 MGy. We have developed the fiber-coupled LIBS system to detect plasma emission efficiently in near-infrared region. In addition, we have performed a ray dose rate measurement using an optical fiber of which scintillator is attached to the tip. As a result, the concept of applicability of a probing system using the high-radiation resistant optical fibers has been confirmed.
Naito, Hiroyuki; Itagaki, Wataru; Okazaki, Yoshihiro; Imaizumi, Kazuyuki; Ito, Chikara; Nagai, Akinori; Kitamura, Ryoichi; Shamoto, Naoki*; Takeshima, Yoshiyuki*
JAEA-Technology 2012-009, 100 Pages, 2012/05
JAEA-Technology-2012-009.pdf:9.89MB
The radiation characteristics of image fiber and light guide fiber were evaluated to develop a high radiation resistant fiberscope for the fast reactor in-vessel observation. It is known that a pure silica core fiber has a high radiation resistance and radiation resistance is influenced with impurities in silica. Moreover it is necessary to change the clad material of the light guide fiber because that of the current light guide fiber is acrylate, which is weak against radiation. Hence the improved fibers consist of a pure silica core with 1,000 ppm OH and fluorine-doped silica clad. As a result of a irradiation test, we confirm that OH inhibits the generation of the precursor by irradiation. About the clad material, we confirmed that the transmission loss of the fluorine-doped silica clad fiber is smaller than that of the acrylate clad fiber. About the mechanical strength of a fiber, we confirmed that there is no weakening the strength of the fiber and no exfoliation of the coating from the glass. In this study, we discovered the fiber which consists of a pure silica core with 1,000 ppm OH and fluorine-doped silica clad has a high radiation resistance and it is possible to observe using this fiber under the 200 
C after 510
Gy irradiation.
Ito, Chikara; Araki, Yoshio; Naito, Hiroyuki; Iwata, Yoshihiro; Aoyama, Takafumi
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 12 Pages, 2012/00
no abstracts in English
Ito, Hideaki; Maeda, Shigetaka; Naito, Hiroyuki; Akiyama, Yoichi; Miyamoto, Kazuyuki; Ashida, Takashi; Noguchi, Koichi; Ito, Chikara; Aoyama, Takafumi
JAEA-Technology 2010-049, 129 Pages, 2011/03
JAEA-Technology-2010-049.pdf:6.99MB
The in-vessel gamma dose rate was measured in the experimental fast reactor Joyo to evaluate the activation of reactor structural components and the radiation exposure of the fiber scope used for in-vessel visual inspection. The measurement system, which requires a wide sensitivity range and high durability in a high-temperature environment, was specifically developed for use in the sodium cooled fast reactor. Using this system, the in-vessel gamma dose rate with cooling times of 450 and 720 days after reactor shutdown was measured in Joyo, which has been operated for 71,000 hours over approximately 30 years. The gamma dose rate was calculated using QAD-CGGP2 code with the gamma source intensity obtained by the ORIGEN2 code. The neutron flux used as input to the ORIGEN2 was evaluated by the Joyo dosimetry method. The ratio between the calculated and experimental values ranged from 1.1 to 2.4, confirming the accuracy of gamma dose rate and component activation calculation.
dose rate distribution in JoyoMaeda, Shigetaka; Naito, Hiroyuki; Ito, Chikara; Aoyama, Takafumi
Progress in Nuclear Science and Technology (Internet), 1, p.182 - 185, 2011/02
In-vessel rate measurements have been conducted in the experimental fast reactor Joyo to obtain experimental data and to verify the analysis method. The in-vessel dose with cooling times of 500 and 700 days after reactor shutdown was measured in Joyo which had been operated for approximately 30 years. The dose was calculated using QAD code with the source obtained by ORIGEN2 code. The ratios between the calculated and experimental value was ranged 1.3 and 2.7. The accuracy of analys method for the amount and distribution of radioactive products and ray dose inside reactor vessel was confirmed for the in-vessel inspection or repair.
Yokoyama, Yutaka*; Mitsui, Hiroyuki*; Takahashi, Rieko; Taniguchi, Naoki; Asano, Hidekazu*; Naito, Morimasa; Yui, Mikazu
JAEA-Research 2008-072, 232 Pages, 2008/10
JAEA-Research-2008-072.pdf:45.2MB
It is possible that the corrosion resistance at the overpack welds is different from that at base metal due to the differences of material properties. In this study, corrosion behavior of welded joint for carbon steel was compared with base metal using the specimens taken from welded joint model fabricated by TIG (Tungsten Arc Welding, GTAW), MAG (Gas Metal Arc Welding, GMAW) and EBW (Electron Beam Welding) respectively. The results of these corrosion tests indicated that the corrosion resistance to general corrosion, pitting corrosion and crevice corrosion at welded metal of TIG and MAG was inferior to base metal. No deterioration of corrosion resistance was observed in any corrosion modes for EBW, which does not need filler material. Neither the base metals nor the welds is not susceptible to SCC under the carbonate concentration near that of the disposal environment.
Ito, Chikara; Naito, Hiroyuki; Ito, Hideaki; Imaizumi, Kazuyuki; Nagai, Akinori; Ito, Keisuke; Nishimura, Akihiko; Oba, Hironori; Wakaida, Ikuo; Sugiyama, Akira; et al.
no journal, ,
no abstracts in English
Ito, Chikara; Nishimura, Akihiko; Oba, Hironori; Wakaida, Ikuo; Naito, Hiroyuki; Sugiyama, Akira; Chiyatani, Keiji
no journal, ,
no abstracts in English
Ito, Chikara; Nishimura, Akihiko; Oba, Hironori; Wakaida, Ikuo; Naito, Hiroyuki; Sugiyama, Akira; Chiyatani, Keiji
no journal, ,
no abstracts in English
Naito, Hiroyuki; Ito, Chikara; Ito, Keisuke; Imaizumi, Kazuyuki; Ito, Hideaki; Nagai, Akinori
no journal, ,
no abstracts in English
Naito, Hiroyuki; Ashida, Takashi; Ito, Hideaki
no journal, ,
no abstracts in English
Ito, Chikara; Ito, Keisuke; Naito, Hiroyuki; Nishimura, Akihiko; Oba, Hironori; Sekine, Takashi; Wakaida, Ikuo
no journal, ,
A high-radiation resistant optical fiber has been developed in order to investigate the interiors of the reactor pressure vessels and the primary containment vessels of the Fukushima Daiichi Nuclear Power Station. We have been developed a radiation resistant optical fiber, which consists of 1,000 ppm hydroxyl doped pure silica core and fluorine doped pure silica clad. The number of the core of image fibers has been increased from 2,000 to 22,000 of the practical use level. The transmissive rate of an infrared image was not affected after the irradiation of 1 MGy. The spatial resolution of the view scope by means of the image fiber was not changed between before and after irradiation. We have proposed the concept of applicability of the probing system that consists of view scope, remote ultimate analysis by laser induced breakdown spectroscopy and radiation monitor using the radiation-resistant optical fibers.
Kaito, Yasuaki; Ashida, Takashi; Imaizumi, Kazuyuki; Izawa, Osamu; Naito, Hiroyuki
no journal, ,
In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test sub-assembly(S/A) of MARICO-2 (material testing rig with temperature control) had been bent onto the in-vessel storage rack as an obstacle, and the MARICO-2 S/A had been stuck in the transfer pot owing to its deformation. Since the MARICO-2 S/A cannot be retrieved with the existing handling equipment, special handling equipment was developed while considering the anomalous conditions. Emphasis had been placed on (1) how to precisely control the gripper position in the reactor vessel, and (2) how to retrieve the MARICO-2 S/A together with transfer pot with high reliability in the design and development of equipment. The MARICO-2 S/A was retrieved successfully together with transfer pot in 2014. This paper describes the in-vessel repair techniques for MARICO-2 S/A retrieval.
Nishimura, Akihiko; Furuyama, Takehiro*; Ito, Fuyumi*; Ito, Chikara; Naito, Hiroyuki; Oba, Hironori; Yamamoto, Shunya; Wakaida, Ikuo; Sugiyama, Akira
no journal, ,
no abstracts in English
Naito, Hiroyuki; Ito, Chikara; Araki, Yoshio; Aoyama, Takafumi
no journal, ,
no abstracts in English
Yamamoto, Masaya; Itagaki, Wataru; Naito, Hiroyuki
no journal, ,
To enhance understandings and utilization of Joyo, give a lecture on safety design and safety evaluation of sodium cooled fast reactor's fuel, and irradiation capability of Joyo.
