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Ishibashi, Atsushi; Saegusa, Yu; Aoya, Juri; Yamamoto, Masahiko; Taguchi, Shigeo; Kuno, Takehiko
Nihon Hozen Gakkai Dai-18-Kai Gakujutsu Koenkai Yoshishu, p.241 - 244, 2022/07
no abstracts in English
Kobayashi, Daisuke; Yamamoto, Masahiko; Nishida, Naoki; Miyoshi, Ryuta; Nemoto, Ryo*; Hayashi, Hiroyuki*; Kato, Keisuke; Nishino, Saki; Kuno, Takehiko; Kitao, Takahiko; et al.
Nihon Hozen Gakkai Dai-18-Kai Gakujutsu Koenkai Yoshishu, p.237 - 240, 2022/07
All gloves attached to glove-box in Tokai Reprocessing Plant have a fixed expiration date and have to be replaced every 4-year. However, degrees of glove deterioration are different depending on its usage environment (frequency, chemicals, radiation, etc.), because of rubber products. Therefore, physical properties such as tensile strength, elongation, hardness of gloves are measured, and the life-time of gloves are estimated. As a result, gloves without any defects in its appearance have enough physical property for acceptance criteria of new glove. The extrapolated physical property of glove is sufficiently larger than the reported values of damaged glove. No deterioration in physical properties of gloves, that are periodically replaced without any defects in its appearance, is observed and the usable life-time of the glove is estimated to be 8 years.
Omori, Kazuki; Yamauchi, Sho; Yanagibashi, Futoshi; Sasaki, Shunichi; Wada, Takuya; Suzuki, Hisanori; Domura, Kazuyuki; Takeuchi, Kenji
Nihon Hozen Gakkai Dai-18-Kai Gakujutsu Koenkai Yoshishu, p.245 - 248, 2022/07
Tokai Reprocessing Plant (TRP), which is shifted to decommissioning stage, stores large amount of high-level radioactive liquid waste (HLLW). Although TRP is implementing vitrification of HLLW to reduce the risks related to HLLW storage, additional 20 years are required to complete vitrification of HLLW. Therefore, TRP is implementing safety countermeasure related to seismic resistance of HLLW storage facility as one of the top priorities. The results of the seismic evaluation indicate that although the facility itself is seismically resistant, there is a risk of insufficient binding force acting between the facility and the surrounding ground. Thus, replacement of the surrounding ground with concrete is performed. Since the countermeasures, to protect existing buries structure and coordinate with the other construction projects around the site, are required, the dedicated team was setup to handle the process and safety management of the concrete replacement construction.
Taguchi, Katsuya; Nakabayashi, Hiroki; Nakano, Takafumi
no journal, ,
The Tokai Reprocessing Plant (TRP) was taken out of service of spent fuel reprocessing operation and the first decommissioning plan was authorized by the Nuclear Regulatory Agency (NRA) at June 2018. Due to the complexity, numerousness of facilities and various condition of contamination, it would be expected the decommissioning plan requires over 70 years. In the view of maintenance following three major issues were arisen at this time, temporary increase of maintenance and testing works with additional equipment for safety enhancement to the storage of HAW, the ageing management for over 70 years decommissioning period and optimizing the replacement strategy for existing equipment considering of the risk level reduction with progress of the decommissioning plan. The presentation shows our perspective and conceptual procedures to take up these issues.
Demachi, Kazuyuki*; Dong, F.*; Abe, Toru*; Chen, S.*; Takaya, Shigeru; Seki, Akiyuki; Yoshikawa, Masanori; Miki, Daisuke*
no journal, ,
Ishii, Takayuki; Kawata, Tsuyoshi; Choki, Toshiyuki
no journal, ,
Approximately 70 valves (three-part ball valves) are installed in cells related to the low-radioactive liquid waste treatment process at the Tokai Reprocessing Plant. In order to prevent liquid leakage from the joints of these valves, we investigated the relationship between the sealing material of the joints and the tightening force of bolts, practiced maintenance management of the valves using a bolt/nut tightening management method (torque management) that takes into account the characteristics of gaskets (PTFE), and report the results obtained.
Takahashi, Keita; Yamaguchi, Toshihiko; Saito, Junichi; Ueda, Masashi; Nakaishi, Sumitaka*
no journal, ,
In order to visualize the phenomenon under opaque liquid sodium, which is coolant of fast reactors, we tried to made an ultrasonic visualization device. A buffer rod was implemented to cope with high temperatures, and as a result of improvements in frequency, shape, etc., a resolution of 0.5 mm was obtained under sodium. Using this device, the transmittance of ultrasonic waves at the interface between liquid sodium and stainless steel was investigated. As the result, it was confirmed that the temperature of sodium and the roughness of the surface of stainless steel affect the transmitting behavior of ultrasonic waves.
Yada, Hiroki; Takaya, Shigeru; Nakai, Satoru*; Wakai, Takashi; Kamishima, Yoshio*; Machida, Hideo*; Miyagawa, Takayuki*
no journal, ,
Fitness for service (FFS) code for nuclear power plants (NPP) is published by The Japan Society of Mechanical Engineers (JSME). However, this code covers only light water type NPP, and there was no code applicable to sodium-cooled fast reactors (SFRs). Therefore, the FFS code for SFRs has been developed. The first edition of it covers class 1 components and their support structures. Continuous leakage monitoring for the components that constitute the sodium boundary is employed in this code. Along with development of the FFS code for SFRs, a leak before break (LBB) evaluation guideline has been developed. LBB evaluation is used to establish requirement for the sensibility of leak detectors used continuous leakage monitoring. The FFS code for SFRs and LBB evaluation guideline were technically reviewed by the JSME standard committee and approved for publication in December 2021 after public reviews.
Yoshikawa, Masanori; Seki, Akiyuki; Okita, Shoichiro; Takaya, Shigeru; Yan, X.
no journal, ,
Hashidate, Ryuta; Yada, Hiroki; Takaya, Shigeru; Enuma, Yasuhiro
no journal, ,
This paper proposes an analysis method of design issues from the viewpoint of maintenance for the rational design of next-generation fast reactors. The proposed method determines whether the targeted maintenance can achieve an availability target from an economic point of view by organizing the design information and identifies the design issues that requires excessive maintenance. In order to confirm the effectiveness of the proposed analysis method, design information was organized for the RCWS, which is one of the critical paths of Monju, and design issues were extracted from the viewpoint of maintenance.
Kondo, Yuki; Takaya, Shigeru; Yada, Hiroki; Hashidate, Ryuta
no journal, ,
In sodium-cooled fast reactors, a large number of temperature sensors are used for temperature monitoring and heater control of sodium-containing equipment. In the conventional insulation resistance measurement method for temperature sensors, preparation work such as stopping the temperature measurement function and separating from the electric board is required, and the workload also increases with increasing the number of target equipment, which has become a problem from the viewpoint of inspection period. In this study, we have developed a new temperature sensor of which insulation resistance is measurable online, and evaluated the performance by experiments.
Seki, Akiyuki; Yoshikawa, Masanori; Okita, Shoichiro; Takaya, Shigeru; Yan, X.
no journal, ,
Kobayashi, Jun; Aizawa, Kosuke; Ezure, Toshiki; Kurihara, Akikazu; Tanaka, Masaaki
no journal, ,
no abstracts in English
Muramatsu, Ken; Kubo, Kotaro; Takada, Tsuyoshi
no journal, ,
no abstracts in English
Shobu, Takahisa; Mukai, Tomohisa*; Ariki, Katsuyoshi*; Choe, H.*; Yamamoto, Shin*; Han, B.*; Morooka, Satoshi; Kurita, Keisuke; Iikura, Hiroshi
no journal, ,
In this study, it was conducted to evaluate the long-term adhesion characteristics of post-installed anchors using neutrons, which have extremely high penetrating power for materials. In CT measurement, it was clarified that the observation inside the reinforced concrete of about 60 mm can be evaluated with the spatial resolution of about 0.2 mm. On the other hand, since the strain distribution under loading did not show a monotonous change in the strain distribution of the anchor, it was clarified that there are some problems.
Suzuki, Masaaki*; Ito, Mari*; Hashidate, Ryuta; Takahashi, Keita; Yada, Hiroki; Takaya, Shigeru
no journal, ,
Maintenance scheduling is typically performed manually, which is a time- and resource-consuming process due to the many components and constraints that must be considered. Besides, to develop next-generation power plants with excellent operability, it is necessary to make it possible to evaluate maintainability in advance at the design stage. Thus, this paper proposes a maintenance-scheduling model based on swarm intelligence to develop an automatic scheduling system for addressing the inspection process scheduling problem in a SFR plant.
Dong, F.*; Chen, S.*; Demachi, Kazuyuki*; Yoshikawa, Masanori; Seki, Akiyuki; Takaya, Shigeru
no journal, ,
Kawabata, Mamoru; Sawa, Mamoru; Ono, Fumiyasu; Shimosaka, Mitsuo; Muto, Keitaro; Uchihashi, Masaya
no journal, ,
As a replacement for the analog camera system which has become difficult to repair, a digital transmission system using VDSL technology was devised by reusing idle facilities such as the voice communication network. This paper presents an overview of the remote monitoring system that can flexibly respond to the installation of additional cameras for other remote monitoring needs such as decommissioning work and equipment operation status checks that will increase in the future MONJU, as well as the transmission of measurement data from temporary instruments at a low cost.