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Miyazawa, Yu*; Ikegami, Masashi*; Miyasaka, Tsutomu*; Oshima, Takeshi; Imaizumi, Mitsuru*; Hirose, Kazuyuki*
Proceedings of 42nd IEEE Photovoltaic Specialists Conference (PVSC-42) (CD-ROM), p.1178 - 1181, 2015/06
Imaizumi, Kazuyuki; Saito, Takakazu; Tobita, Shigeharu; Nagai, Akinori; Kitamura, Ryoichi; Okazaki, Yoshihiro
JAEA-Technology 2012-027, 49 Pages, 2012/08
JAEA-Technology-2012-027.pdf:7.07MB
In-Vessel Observations (IVO) techniques for Sodium cooled Fast Reactors (SFRs) are important in confirming its safety and integrity. In order to secure the reliability of IVO techniques, it was necessary to demonstrate the performance under the actual reactor environment with high temperature, high radiation dose and remained sodium. During the investigation of an incident occurred in Joyo, the following observation systems were specifically developed for Joyo. And the following two observations were conducted. (1) Simple overhead observation using a standard video camera for the top of the sub-assemblies and the in-vessel storage rack (2) Narrow space observation using remote handling device equipped with radiation-resistant fiberscope for the bottom face of the upper core structure. As a result, the observations under the actual reactor environment were successfully made even in the narrow space in the reactor vessel and the results provided useful information on incident investigations and planning of restoration work.
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 5
10
Gy irradiation.
Takamatsu, Misao; Imaizumi, Kazuyuki; Nagai, Akinori; Sekine, Takashi; Maeda, Yukimoto
Journal of Power and Energy Systems (Internet), 4(1), p.113 - 125, 2010/00
During the investigation of an incident that occurred with the experimental fast reactor Joyo, in-vessel observations using a standard Video Camera (VC) and a Radiation-Resistant Fiberscope (RRF) took place at (1) the top of the Sub-Assemblies (S/As) and the In-Vessel Storage rack (IVS), (2) the bottom face of the Upper Core Structure (UCS) under the condition with the level of sodium at -50 mm below the top of the S/As. A simple 6 m overhead view of each S/A, through the fuel handling or inspection holes etc, was photographed using a VC fixed to the rotating-plug with the acrylic panel for making observations of the top of S/As and IVS. About 650 photographs were required to create a composite photograph of the top of the entire S/As and IVS, and a resolution was estimated to be approximately 1 mm. In order to observe the bottom face of the UCS, a remote handling device equipped with RRFs (approximately 13 m long) was specifically developed for Joyo with a tip that could be bent into an L-shape and inserted into the 70 mm gap between the top of the S/As and the bottom of the UCS. A total of about 35,000 photographs were needed for the full investigation. Regarding the resolution, the sodium flow regulating grid of 0.8 mm in thickness could be discriminated, and the base of thermocouple sleeves 6 mm in diameter located 450 mm above the top of S/As were also clearly observed. In both types of observations, it was confirmed that lighting adjustments play a critical role. Particularly in narrow space observations, scattered lighting with automatic dimming controlled light source was available for achieving close observations of the in-vessel structures. In addition to the successful result of the incident investigation, these experiments provided valuable insights for use in further improving and verifying in-vessel observation techniques in sodium cooled fast reactors.
Saito, Takakazu; Imaizumi, Kazuyuki; Oka, Kiyoshi; Aizawa, Hideyuki*; Katagiri, Genichi*
FAPIG, (179), p.3 - 9, 2009/07
The experimental fast reactor Joyo is the first sodium cooled fast reactor in Japan. In-vessel visual inspections have been conducted with an obstacle on the in-vessel storage rack in Joyo. Because of the high radiation dose in the reactor vessel, radiation-resistant fiberscope was applied to Joyo. The radiation-resistant fiberscope was inserted into the reactor vessel thorough the inspection hole and fuel handling hole on rotating plugs. In order to observe the top of the subassemblies and in-vessel storage rack, an I-shape device which had a downward and side view monitoring radiation-resistant fiberscopes was used. To observe the bottom face of the upper core structure, a remote handling visual device whose tip could bend into an L-shape was developed to insert the radiation-resistant fiberscope into the 70 mm gap between the bottom of the upper core structure and the top of the subassemblies. The observations of the top of the subassemblies and in-vessel storage rack were conducted from October 2007 to February 2008. The bottom face of the upper core structure was observed in July 2008. The number of photographs of the entire bottom face of the upper core structure reached approximately 35,000. Confirmation was made that the remote handling device equipped with the radiation-resistant fiberscope would achieve the expected performance. These observations results provided useful information on incident investigations. In addition, fundamental findings and the experience gained during this study, which included the design of equipment, operating procedures, resolution, lighting adjustments, photograph composition and the durability of the radiation-resistant fiberscope under radiation exposure, provided valuable insights into possible further improvements and verifications for in-vessel visual observation techniques in an sodium fast reactor.
Takamatsu, Misao; Imaizumi, Kazuyuki; Nagai, Akinori; Sekine, Takashi; Maeda, Yukimoto
Proceedings of 17th International Conference on Nuclear Engineering (ICONE-17) (CD-ROM), 10 Pages, 2009/07
During the investigation of an incident in Joyo, in-vessel observations using a Video Camera (VC) and a Radiation-Resistant Fiberscope (RRF) took place at (1) the top of the Sub-Assemblies (S/As) and the In-Vessel Storage rack (IVS), (2) the bottom face of the Upper Core Structure (UCS). A simple 6 m overhead view of each S/A was photographed using a VC fixed to the rotating-plug for making observations of the top of S/As and IVS. A resolution was estimated to be approximately 1mm. In order to observe the bottom face of the UCS, a remote handling device equipped with RRFs was specifically developed for Joyo with a tip that can be bent into an L-shape and inserted into the 70 mm gap between the top of the S/As and the bottom of the UCS. The sodium flow regulating grid of 0.8mm in thickness could be discriminated. These experiments provided valuable insights for use in further improving and verifying in-vessel observation techniques in sodium cooled fast reactors.
Itagaki, Wataru; Saito, Takakazu; Imaizumi, Kazuyuki; Nagai, Akinori; Aoyama, Takafumi; Maeda, Yukimoto
Dai-14-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.435 - 438, 2009/06
no abstracts in English
Itagaki, Wataru; Sekine, Takashi; Imaizumi, Kazuyuki; Maeda, Shigetaka; Ashida, Takashi; Takamatsu, Misao; Nagai, Akinori; Maeda, Yukimoto
Proceedings of 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications (ANIMMA 2009) (USB Flash Drive), 7 Pages, 2009/06
no abstracts in English
Imaizumi, Kazuyuki; Saito, Takakazu; Tobita, Shigeharu; Nagai, Akinori
no journal, ,
no abstracts in English
Sekine, Takashi; Ashida, Takashi; Imaizumi, Kazuyuki; Takamatsu, Misao; Nagai, Akinori; Maeda, Yukimoto
no journal, ,
Restoration works for restart of the experimental fast reactor Joyo need to retrieve the bent irradiation test subassembly (MARICO-2) left in the in-vessel storage rack and replace the damaged upper core structure (UCS). In-vessel visual observations using radiation resistant fiberscopes and cameras were conducted to investigate the MARICO-2 and the MARICO-2 was temporarily lifted to confirm the condition. The in-vessel ray dose rate was measured to evaluate the activation of the UCS which will be reflected to optimize the shielding design of a UCS replacement cask and a MARICO-2 handling tool.
Naito, Hiroyuki; Itagaki, Wataru; Ito, Chikara; Imaizumi, Kazuyuki; Nagai, Akinori; Tobita, Koichi
no journal, ,
no abstracts in English
Naito, Hiroyuki; Itagaki, Wataru; Okazaki, Yoshihiro; Imaizumi, Kazuyuki; Kitamura, Ryoichi; Shamoto, Naoki*; Takeshima, Yoshiyuki*
no journal, ,
no abstracts in English
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
Naito, Hiroyuki; Ito, Chikara; Ito, Hideaki; Imaizumi, Kazuyuki; Ito, Keisuke
no journal, ,
no abstracts in English
Naito, Hiroyuki; Ito, Chikara; Ito, Keisuke; Imaizumi, Kazuyuki; Ito, Hideaki; Nagai, Akinori
no journal, ,
no abstracts in English
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.
Imaizumi, Kazuyuki; Saito, Takakazu; Tobita, Shigeharu; Suzuki, Toshiaki
no journal, ,
no abstracts in English
Imaizumi, Kazuyuki; Tobita, Shigeharu; Saito, Takakazu; Katagiri, Genichi*; Aizawa, Hideyuki*; Yaginuma, Yoshihiro*
no journal, ,
no abstracts in English
