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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