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Nishino, Shohei; Motohashi, Masahiro; Nishida, Tetsuro; Kawasaki, Ichio
Nihon Hozen Gakkai Dai-19-Kai Gakujutsu Koenkai Yoshishu, p.73 - 79, 2023/08
There are 4-boiler in Nuclear fuel Cycle engineering Laboratories (NCL). These boilers have been operated in the long term over 29 years. There are many water tube as one of many identical components which together make up a boilers. The leakage from water tube have occurred four times in recently. It was presumed that sulfur acid corrosion had caused the leakage. Therefore, to reduce generation of sulfuric acid corrosion, the operation term was changed to long, and regular inspection (non-destructive testing) have been carried out.
Ishibashi, Atsushi; Masui, Kenji; Goto, Yuichi; Yamamoto, Masahiko; Taguchi, Shigeo; Ishikawa, Satoshi*; Ishikawa, Tomoya*
Nihon Hozen Gakkai Dai-19-Kai Gakujutsu Koenkai Yoshishu, p.18 - 21, 2023/08
An inner-box typed hot cell for analysis of highly radioactive samples has been operated for about 40 years in Tokai Reprocessing Plant since its installation in 1980. During the operation of analytical hot cell, improvement and upgrades including auxiliary equipment have been performed, in addition to keep the equipment in proper condition through periodic inspections and maintenance. This paper describes about these efforts for analytical hot cell and its results.
Umino, Yoshinori; Kato, Keisuke; Tanigawa, Masafumi; Kobayashi, Daisuke; Obu, Tomoyuki; Kimura, Yuichi*; Nemoto, Ryo*; Tajiri, Kazuma*
Nihon Hozen Gakkai Dai-19-Kai Gakujutsu Koenkai Yoshishu, p.33 - 36, 2023/08
In the basic laboratory of the Plutonium Conversion Development Facility in Tokai Reprocessing Plant, tests had been conducted to obtain effective data for manufacturing mixed plutonium and uranium oxide powder by irradiating a mixture of plutonium and uranium solution with microwaves. The test has already been completed, and we are currently dismantling and removing equipment. In this paper, techniques related to equipment renewal, dismantling and removal works inside the glove-box are discussed.
Takeuchi, Kenji; Domura, Kazuyuki; Suzuki, Hisanori; Sasaki, Shunichi; Komori, Tsuyoshi; Uno, Shota
no journal, ,
no abstracts in English
Ono, Fumiyasu; Fukushima, Tsubasa; Naruse, Keiji; Matsui, Kazuaki; Obata, Ikuhito; Sawazaki, Hiromasa; Goto, Takehiro; Jo, Takahisa; Uchihashi, Masaya
no journal, ,
By storing fuel assemblies in the fuel pond in Phase 1, MONJU eliminates the residual risk of fuel assemblies remaining in the core, which holds chemically active liquid sodium, and from April 2023, Have moved to Phase 2 of decommissioning. As the decommissioning progresses, plant risks will continue to change. Therefore, we will organize the plant status at each Phase of decommissioning and formulate the concept of performance maintenance facilities for MONJU, which will be necessary in Phase 2, and Performance maintenance facilities were Reconsidered.
Fukushima, Tsubasa; Ono, Fumiyasu; Kuramoto, Shimpei; Nishino, Yuki; Nishino, Hajime; Uchihashi, Masaya
no journal, ,
"Monju" is a nuclear reactor facility that uses sodium to cool the reactor core. In order to reduce the risk of decommissioning, all liquid sodium in the cooling system piping was transferred to the tank and solidified in order to reduce the range of liquid sodium that may leak. Since this was the first attempt of this project, we dealt with issues such as the assessment of the impact on related equipment, the formulation of dedicated procedure manuals, and various operational changes, and streamlined equipment maintenance due to the reduction of the range of liquid sodium ownership, and summarized the results.
Mihalache, O.; Yamaguchi, Toshihiko; Maeda, Yukihiro*; Nakaishi, Sumitaka*
no journal, ,
no abstracts in English
Yoshikawa, Masanori; Seki, Akiyuki; Okita, Shoichiro; Takaya, Shigeru; Yan, X.
no journal, ,
Seki, Akiyuki; Yoshikawa, Masanori; Okita, Shoichiro; Takaya, Shigeru; Yan, X.
no journal, ,
Kondo, Yuki; Hashidate, Ryuta; Seki, Akiyuki; Yokoyama, Kenji; Takaya, Shigeru; Enuma, Yasuhiro
no journal, ,
JAEA is working on the development of Knowledge Management System (KMS) to collect technical information on fast reactor development so far and to utilize the information. This paper reports on examples of the use of technical and as-built data of the sodium test facility "PLANDTL-II" from the perspective of facility operation and technology transfer.
Hashidate, Ryuta; Kondo, Yuki; Yada, Hiroki; Takaya, Shigeru; Enuma, Yasuhiro
no journal, ,
In this study, we propose a new method for extracting maintenance preconditions. Graph structures are used to represent relationship among SSCs. Maintenance preconditions are extracted by analyzing the graph structures. Furthermore, we propose an automatic maintenance scheduling method using extracted maintenance preconditions. Design issues could be extracted based on the created maintenance schedule. A simple example is presented to illustrate the proposed method.
Shimada, Taro; Miwa, Kazuji; Sasagawa, Tsuyoshi; Takai, Shizuka; Takeda, Seiji
no journal, ,
For risk-informed implementation of nuclear regulatory inspections during the decommissioning phase of nuclear power plants, we are developing DecAssess-R, a code that evaluates changes in exposure risk over time according to the decommissioning process based on exposure dose and occurrence probability by accident sequence for each component to be dismantled. Event trees have been constructed from the initiating events that occurred during the decommissioning phase, and the occurrence frequency and accident progress probability of the events have been developed from past trouble cases. Using the developed risk assessment method, we evaluated the exposure risks due to fire as an example of dismantling of a 1.1 MW BWR in the United States. As a result, it was confirmed that the method can provide risk information according to the decommissioning process, not only the quantity of the residual radioactivity inventory, such as the result that the exposure risk is larger for a fire that occurs during air dismantling of peripheral equipment in the reactor building, which has a smaller radioactivity inventory, than for a fire that occurs during underwater dismantling of in-core structures, which has a larger radioactivity inventory. The results confirmed that the information on the risk according to the decommissioning process can be provided.
Shobu, Takahisa; Tominaga, Aki; Kisohara, Naoyuki; Maeda, Toshio*; Yamagishi, Ryuichiro*; Okihara, Shinichiro*; Tsuboi, Akihiko
no journal, ,
In this study, the internal defects and strain distribution in metal additive manufacturing and their changes by laser peening were evaluated. These studies using X-ray computed tomography and diffraction technique were carried out at BL22XU in synchrotron radiation facility SPring-8. As a result, it was confirmed that a large number of voids existed inside the additive manufacturing. However, almost no difference due to laser peening was confirmed. On the other hand, it was confirmed that the strain inside the additive manufacturing was almost
Suzuki, Masaaki*; Ito, Mari*; Hashidate, Ryuta; Takahashi, Keita; Yada, Hiroki; Takaya, Shigeru
no journal, ,
In order to achieve a smooth operation that balances safety and economic viability in next-generation reactors, it is essential to implement a design that considers maintenance. Currently, there is a lack of technology to repeatedly assess operability during the pre-construction phase and identify design aspects that pose challenges to maintenance, creating a bottleneck in the process. This study employs swarm intelligence techniques to learn and analyze inspection process schedules that satisfy various constraints in sodium-cooled fast reactors.
Takada, Tsuyoshi; Horiike, Hiroshi*; Miyano, Hiroshi*; Ebisawa, Katsumi*
no journal, ,
Trials related to seismic safety of nuclear power plants are being held in many places in Japan. Among many controversial issues, the study group on trials on nuclear power plants in JSM has studied the recent court decisions on nuclear safety against future earthquakes; that of the Osaka District Court, the Mito District Court, and the Sendai District Court. The concept of "substantial safety" and "procedural safety", along with the concept of "Defense in Depth (DiD)" proposed by International Atomic Energy Agency (IAEA), particularly the fifth protection level namely effective evacuation planning are discussed herein. Finally, the probabilistic risk assessment (PRA) study must be done to treat the substantial safety of nuclear power plants and to cover all levels of protection described in the DiD concept.
Nishimura, Akihiko; Ide, Tsugio*; Ishihara, Nobuyuki*; Takasaki, Koji
no journal, ,
Industrial deployment of FBG sensor fabricated by picosecond pulsed laser precision processing is reported. Application to the Fukushima Daiichi NPP decommissioning, a robot arm equipped with a feedback mechanism is assumed to keep the retention force of nuclear fuel debris appropriately. For this purpose, FBG processing into radiation-tolerant optical fibers are implemented. As a preparation for development, the stress measurement of high temperature piping under restraint was carried out. Furthermore, the gripping mechanism of the robot arm is manufactured as a simulator for FBG sensing telemetry.