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Muto, Keitaro
Nihon Hozen Gakkai Dai-7-Kai Gakujutsu Koenkai Yoshishu, p.235 - 237, 2010/07
Monju is sodium cooled fast breeder reactor. Monju resumed operations on May 5th, 2010 after an intermission for about 14 years following a sodium leak accident. During the shut-down period, sodium system was operated and there were some troubles of sodium leak detectors. To improve leak detectors performance and reliability, detectors modification and improved maintenance activities were applied. For example, a contact type sodium leak detector (CLD) in the secondary sodium system was modified to increase to ion-migration resistance and periodical insulation measurement was added to the maintenance activities. Based on the maintenance and operation experience and the technology development will be reflected to the improvement of the performance and reliability of sodium leak detectors.
Kobayashi, Yuki; Takahashi, Tetsuro; Shinozaki, Tadahiro; Ogasawara, Koji; Koizumi, Kenji; Nakajima, Yasuo
Nihon Hozen Gakkai Dai-7-Kai Gakujutsu Koenkai Yoshishu, p.161 - 166, 2010/07
The negative pressure control valve is reliable apparatus which has been used in many nuclear facilities. In recent years, there are some troubles on those valves in CPF (Chemical Reprocessing Facility) by the aged deterioration because the valves were kept using for more than 25 years after facility had operated. Therefore, we have been carrying out renewal of driving units of the valves to assure performance of negative pressure control function and to keep stability of operation of the facility. In this presentation, we report knowledge provided through the renewal work, such as the renewal procedure, the deterioration situation of components and the cause of troubles.
Ihara, Ryohei*; Hashimoto, Tadafumi*; Mikami, Yoshiki*; Katsuyama, Jinya; Onizawa, Kunio; Mochizuki, Masahito*
Nihon Hozen Gakkai Dai-7-Kai Gakujutsu Koenkai Yoshishu, p.611 - 616, 2010/07
In light-water reactor nuclear power stations, stress corrosion cracking (SCC) has been observed near the welded joint in recirculation piping made of low-carbon austenitic stainless steel. Residual stress is one of the most important factors in the occurrence and propagation of SCC. The joining process of pipes which usually consists of surface machining and welding results in high tensile residual stress. In this study, finite element analysis method was developed to evaluate residual stress generated by surface machining considering the shape of machining tool and machining condition. Residual stress due to surface machining was measured by X-ray diffraction method and analysed the method developed. It was shown that high tensile residual stress due to machining occurred very limited surface region. It was also shown that surface machining affected SCC growth behavior significantly from the SCC analysis results based on residual stress distributions due to surface machining and welding.
Sumino, Kozo; Kobayashi, Tetsuhiko; Isozaki, Kazunori; Yoshida, Akihiro
Nihon Hozen Gakkai Dai-7-Kai Gakujutsu Koenkai Yoshishu, p.255 - 257, 2010/07
In the experimental fast reactor Joyo, maintenance work was conducted based on the classification of safety importance over thirty years. Through the experience, it was confirmed that particular effort was not necessary for the maintenance of sodium cooling systems by controlling the coolant purity properly. Additionally, as a result of the technical review on aging for whole plant, significant aging phenomenon that is particular with sodium cooled fast reactor was not observed.
Funaki, Isao; Tobita, Shigeharu; Nagai, Akinori; Nishino, Kazunari
Nihon Hozen Gakkai Dai-7-Kai Gakujutsu Koenkai Yoshishu, p.263 - 266, 2010/07
no abstracts in English
Suto, Masayoshi; Sugaya, Takashi; Sumino, Kozo
Nihon Hozen Gakkai Dai-7-Kai Gakujutsu Koenkai Yoshishu, p.258 - 262, 2010/07
no abstracts in English
Konno, Shotaro; Takaya, Shigeru; Nagae, Yuji; Yamagata, Ichiro; Ogawa, Ryuichiro; Akasaka, Naoaki; Nishinoiri, Kenji
no journal, ,
We are developing a method for evaluation of irradiation damage on structural materials in nuclear plants by using change in magnetic flux density due to irradiation damage. In this study, the magnetic flux density measurement technique has been improved by introducing a new magnetizer which enables local magnetizing by contacting the sample surface, and the calibration method of the flux gate sensor for the magnetic flux density. We can magnetize samples, especially ferromagnetic samples, more precisely compared to the existing method. Furthermore, the new method can remove many limitations for the application to real plants.
Aoki, Kenji; Hiyama, Hisao; Shibata, Satomi; Iwasaki, Shogo; Inami, Shinichi
no journal, ,
There are plural facilities having a radiation controlled area in the Tokai reprocessing plant, and an uninterruptible power supply system which considered a blackout is necessary for the power supply to each facility from the viewpoint of radiological management and nuclear material containment. In addition, at the time of the power supplying abnormality, intelligence gathering is necessary for prompt measures and restoration. In this report, the intensive monitoring system, which aimed for the unification of the power supply monitor place and the acceleration of the intelligence gathering to detect a power supply abnormality point, is described.
Ito, Chikara; Maeda, Shigetaka; Iwata, Yoshihiro; Aoyama, Takafumi; Iguchi, Tetsuo*
no journal, ,
no abstracts in English
Kawasumi, Hiroyuki; Sanyoshi, Hirotaka; Yatogi, Hideo; Fukuari, Yoshihiro; Inami, Shinichi
no journal, ,
In the ventilation facilities of the Tokai reprocessing plant, particle filters are generally installed both in air-intake and exhaust systems. In the air-intake system, atmospheric dust is filtered and the cleaned air is supplied into radiation controlled areas, whereas in the exhaust system, radioactive materials are filtered and discharge it to the environment. Because the filter of the exhaust system serves to prevent radiological release to the environment, a high-efficiency particle air (HEPA) filter that a decontamination factor is extremely high, is used for filtering radioactive particles. The HEPA filter is usually exchanged with new one when the filter is carried over with particles, or it is exchanged by the limit as an anti-aging deterioration measure in time. This report reviews the exchange period of a periodical filter by confirming the integrity of a filter installed in investigation and the enforcement of the past filter exchange results and reports the result that planned adequacy.
Takaya, Shigeru; Nagae, Yuji; Wakai, Eiichi; Aoto, Kazumi
no journal, ,
Proper management of neutron irradiation damage on structural materials is important to ensure the health of long-life fast breeder reactor (FBR) plants. Therefore, the effective index for irradiation damage or the combination of those should be developed. In this study, the effects of dose, helium, and the ratio of helium to dose on tensile and creep properties of FBR grade type 316 stainless steel were investigated in the assumed irradiation damage range of FBR structural materials, that is, up to about 1 displacement per atom for dose and up to about 30 appm for helium. As result, it was shown that dose is the most promising. In addition, a nondestructive evaluation method of dose using a vibrating sample magnetometer is also introduced.
Yamashita, Takuya
no journal, ,
Since the FBR plants in commercial stage is designed 60 years reactor life which is twice of the prototype FBR "Monju", maintenance technologies considering aging and damage for a long term using at high temperature are needed. Development of the in-service inspection and the repair technologies needed for maintenance of the commercial used FBR is discussed after reviewing the features of the FBR plants, and experience of ISI and repair of the experimental FBR "Joyo" and the "Monju".
Ito, Fuyumi; Nishimura, Akihiko; Norimatsu, Takayoshi*; Nagai, Keiji*
no journal, ,
The purpose of the research is to apply the micro capsule technology to the facility maintenance. The micro capsule technology for laser fusion target was developed at the institute of laser engineering Osaka University. We have a plan to apply the fabrication technology of polystyrene micro capsules to the facility maintenance where the magnetic particle testing for complex piping system is investigated.
Yamamoto, Tomohiko; Fujiwara, Takeshi*; Uesaka, Mitsuru*; Hirai, Shunsuke*
no journal, ,
We have been developed 9.4 GHz X-Band linac and 250kW magnetron for X-ray nondestructive testing system for Condition Based Maintenance (CBM). Our linac's energy is 950 keV, which fits to Japanese regulation to take them to outside of radiation controlled area. This small portable linac enables to diagnosis the moving facility, such as bearing in Nuclear Power Plants.