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Mori, Eito; Yamamoto, Masahiko; Taguchi, Shigeo; Sato, Soichi; Kitao, Takahiko; Surugaya, Naoki
Nihon Hozen Gakkai Dai-11-Kai Gakujutsu Koenkai Yoshishu, p.132 - 138, 2014/07
The contamination of the radioactive material was observed on the filter casing surface of the glove box installed at the analytical laboratory in Tokai Reprocessing Plant. The cause of the contamination was investigated with visual inspection, penetrant testing and ultrasonic thickness measurement. It was found that a micro through-hole due to the corrosion of stainless-steel was generated in the glove box filter casing. The repair work of the filter casing was performed keeping the glove box negative pressure. The corrosion part of filter casing was replaced and newly fabricated casing was connected to the glove box with Tungsten Inert Gas welding method.
Suzuki, Hisanori; Nagayama, Tetsuya; Horigome, Kazushi; Ishibashi, Atsushi; Kitao, Takahiko; Surugaya, Naoki
Nihon Hozen Gakkai Dai-11-Kai Gakujutsu Koenkai Yoshishu, p.214 - 219, 2014/07
The Tokai Reprocessing Plant (TRP) is developing the technology to recover uranium and plutonium from spent nuclear fuel. There is an analytical laboratory which was built in 1978, as one of the most important facilities for process and material control analyses at the TRP. Samples taken from each process are analyzed by various analytical methods using hot cells, glove boxes and hume-hoods. A large number of maintenance work have been so far done and different types of experience have been accumulated. This paper describes our achievements in the maintenance activities at the analytical laboratory at the TRP.
Nishida, Naoki; Suwa, Toshio; Tanaka, Naoki; Inada, Satoshi; Kuno, Takehiko
Nihon Hozen Gakkai Dai-11-Kai Gakujutsu Koenkai Yoshishu, p.121 - 126, 2014/07
Corroded pore was found at stainless pipe for liquid waste solution from the analytical laboratory. Part of the pipe was cut for preparing samples to investigate the cause of the corrosion. The same size of stainless pipe was welded to recover it, under the strict radiation control. The restoration work was done inside of the vinyl house, as it is called "greenhouse", which was the small room completely separated by vinyl sheet. All the works, cutting, decontamination, digging groove and welding with back seal gas, were done inside of the greenhouse. We report the work method for recovery of corroded pipe containing radioactive materials
Tanaka, Naoki; Suwa, Toshio; Nishida, Naoki; Kuno, Takehiko; Inami, Shinichi
Nihon Hozen Gakkai Dai-11-Kai Gakujutsu Koenkai Yoshishu, p.127 - 131, 2014/07
Corroded pore was found at stainless pipe for liquid waste solution from the analytical laboratory. In order to find out the cause of corrosion, analytical samples were prepared cutting from the pipe. Reagents contained chloride, which had been used analytical laboratory more than ten years before the date, were found to be the trigger of the localized corrosion. We checked up all the pipes, which have been wasted including chloride solutions, by phased array instrument. We report the investigation of cause of corrosion and results of non-destructive testing.
Ishiyama, Toru; Kawasaki, Ichio; Miura, Hirohito*
Nihon Hozen Gakkai Dai-11-Kai Gakujutsu Koenkai Yoshishu, p.33 - 36, 2014/07
There are 4-boiler systems in NCL. These boilers have been operated in the long term over 20 years. One of them, the leakage of boiler water was found at one of the generating tubes, and 2 adjoining generating tubes were corroded in Dec, 2011. These generating tubes were investigated by immersion ultrasonic testing (UT) for measure thickness of the tube. As a result, thinner tube was found in a part of a bend and near the water drum. These parts are covered with sulfide deposit, it seems that the generating tubes were corroded by sulfide.
Yuasa, Toyotaka; Abe, Teruyoshi; Nakamura, Takahisa; Myochin, Munetaka; Takagi, Hisatsugu
no journal, ,
Suffered SCC (stress corrosion cracking) at the primary cooling system in 1980, the Fugen power station introduced the three preventive technologies immediately. After the upgrade of the plant, no SCC occurred during the operation period. We have inspected the actual structural materials of the Fugen power station on its decommissioning stage to evaluate effectiveness of SCC management technologies, which are combining material replacement, induction heating stress improvement (IHSI) to reduce the welding residual tensile stress, and application of hydrogen addition to reduce oxygen in the water. No crack in the materials was found by metallurgical structure observation. Moreover, judging from the analysis of residual stress and the heat affected zone in the materials, the effectiveness of SCC management technologies was verified.
Watahiki, Kenji; Kawasumi, Hiroyuki; Yatogi, Hideo; Inami, Shinichi
no journal, ,
Off-gas of Tokai Reprocessing Plant, including gaseous radio-active element, has been emitted from main stack after through exhaust duct. There corrosion and crack at the part of the iron exhaust duct near the main stack. Repairing method was planned to be used iron plate covering the corroded and cracked area, which would be attached welded. To take into considering of reducing the weight of the attachment, much lighter materials namely carbon fiber reinforce polymer, CFRP, was applied except for the iron plate. Necessary numbers of layers of CFRP to be enough strength and inner pressure was calculated for designing. In order to achieve satisfying essential specification with workmanship, training for the workers was carried out using mock-up before the actual one. In this paper, we report the CFRP method is the efficient and effective method repairing corrosion and crack at the iron duct, in Tokai Reprocessing Plant.
Nakai, Satoru; Nishio, Ryuichi; Uchihashi, Masaya; Kaneko, Yoshihisa; Yamashita, Hironobu*; Yamaguchi, Atsunori*; Aoki, Takayuki*
no journal, ,
A sodium cooled fast breeder reactor (FBR) has unique systems and components and different degradation mechanism from light water reactor (LWR) so that need to establish maintenance technology in accordance with its features. The examination of the FBR maintenance technology is carried out in the special committee for considering the maintenance for Monju established in the Japan Society of Maintenology (JSM). As a result of the study such as extraction of Monju maintenance feature, maintenance technology benchmark between Monju and LWR components and survey of LWR maintenance experience, it is clear that principles of maintenance are same as LWR, necessity of LWR maintenance experience reflection and points to be considered in Monju maintenance. The road map to establish a FBR maintenance technology in the technical aspect became clear and it is vital to acquire operation and maintenance experience of the plant to implement this road map, and to establish a fast reactor maintenance.
Takaya, Shigeru; Asayama, Tai; Machida, Hideo*; Kamishima, Yoshio*
no journal, ,
This paper describes a procedure of structural reliability evaluation of passive components of fast breeder reactors for a failure due to fatigue-creep interaction damage, and also reports results of benchmark evaluation conducted by using two independently developed codes. The structural integrity of a reactor vessel was evaluated deterministically and probabilistically. The results estimated by two codes agree well for both of deterministic and probabilistic evaluations, which shows that these codes are programmed properly according to the evaluation procedure.