Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
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; 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.
Ito, Chikara; Ito, Keisuke; Ishikawa, Takashi; Yoshida, Akihiro; Sanada, Yukihisa; Torii, Tatsuo; Notomi, Akihiro*; Wakabayashi, Genichiro*; Miyazaki, Nobuyuki*
Hoshasen, 39(1), p.7 - 11, 2013/09
no abstracts in English
Ito, Keisuke; Kawahara, Hirotaka; Mori, Takero; Jo, Takahisa; Ariyoshi, Masahiko; Isozaki, Kazunori
JNC TN9410 2005-008, 267 Pages, 2005/03
JNC-TN9410-2005-008.pdf:108.4MB
Control characteristic tests of reactor coolant temperature control system were carried out to confirm its controlling constant to make MK-III hear transport system control stably, and stability against actual disturbance to the plant. The control characteristic test consists of three kinds of tests. As a result, the optimum PI parameters of the reactor coolant temperature control system was confirmed that the proportional gain is between from 0.36 to 1.12(approximately half of MK-II), the integral time is 80 respectively. The gain margin of the control system was between from 7 to 19dB of through the vane opening range.
Amemiya, Kuniaki*; Nakazawa, Masaharu*; Ariyoshi, Masahiko; Ito, Keisuke
JNC TY9400 2004-008, 52 Pages, 2004/04
JNC-TY9400-2004-008.pdf:2.65MB
A new monitoring system of nuclear reactor plants by means of optical fiber Bragg gratings (FBGs) was developed which have sensitivity in temperature, distortion and vibration. The reflective wavelength of FBGs was not influenced by gamma-ray irradiation up to 1.4MGy and by exposure to fast neutrons in excess of 10 sup14 n/cm sup2. A temperature-insensitive vibration sensing system was constructed and operated with no trouble in gamma-ray environments up to 100kGy. Furthermore, a multiple point vibration sensing system was designed and constructed. The system was successfully demonstrated on a cooling system at the "Yayoi" reactor. Thus, we tried to apply the monitoring system to a primary loop area of JOYO to confirm the applicability of FBG sensors for the commercial power reactors. Although a correlation of sodium flow in side pipes and vibration measured by FBG sensors was found before starting of the reactor, it became impossible after starting operation of the reactor because of a decline of signal amplitude. Investigating the reason, it was mainly caused by significant transmission losses at the splicing point and there were no problems with FBG sensors. Various methods, for example, using a more powerful light source and changing the splicing method, may be used to improve it in the future.
Ito, Chikara; Sanada, Yukihisa; Ito, Keisuke; Kondo, Atsuya; Ishikawa, Takashi; Nakano, Hironobu; Nozaki, Tatsuo; Torii, Tatsuo; Notomi, Akihiro*
no journal, ,
no abstracts in English
Shimada, Yukihiro; Nishimura, Akihiko; Suzuki, Hirokazu*; Ishibashi, Hisayoshi*; Ito, Keisuke; Ito, Chikara; Yoshida, Akihiro
no journal, ,
A Fiber Bragg Grating (FBG) sensor with heat resistance was produced via a point microfabrication technique using a femtosecond pulse laser. It can be used as temperature or a strain sensor by measuring change of the reflective wavelength of FBG. Heating test under operational temperature of Fast Reactors is now planed. This time, we did the withstand type test on the sensor by using the piping material in the environment of 400 degrees. As a result, it succeeded in a small oscillation and measuring a strain. The heat-resistant FBG sensor developed using ultra-short pulse laser processing will contribute to the surveillance of power plants for seismic safety.
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
Ito, Keisuke; Ishikawa, Takashi; Naito, Hiroyuki; Ito, Chikara
no journal, ,
no abstracts in English
Naito, Hiroyuki; Ito, Chikara; Ito, Keisuke; Imaizumi, Kazuyuki; Ito, Hideaki; Nagai, Akinori
no journal, ,
no abstracts in English
-ray measurement system using alumina scintillator and radiation-resistant optical fiberIshikawa, Takashi; Ito, Keisuke; Naito, Hiroyuki; Ito, Chikara; Sekine, Takashi
no journal, ,
no abstracts in English
ray irradiationIto, Chikara; Naito, Hiroyuki; Ito, Keisuke; Ishikawa, Takashi; Nishimura, Akihiko; Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo
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.
ray dose rate evaluation of upper core structureYamamoto, Takahiro; Ito, Keisuke; Ito, Chikara; Maeda, Shigetaka; Ito, Hideaki; Sekine, Takashi; Masui, Tomohiko*
no journal, ,
no abstracts in English
