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Toyama, Shinichi; Minehara, Eisuke*
Dekomisshoningu Giho, (56), p.55 - 65, 2017/09
Development of the steel cutting technology which employs high power fiber laser for the industrial applicability of the laser technology has been carried out at The Wakasa Wan Energy Research Center (WERC). At present, the laser technologies for dismantling and decontamination are concurrently being developed to the application measure of nuclear dismantling for domestic nuclear power plants in the future. Dismantling of nuclear facilities is now under the development in the world. The necessity of the technology is increasing and the development is strongly expected. Beside the relative easiness to handle compared with other laser system, suppression of production of secondary radioactive waste and dose exposure can be realized by the dramatic improvement by excelled thermal density of fiber laser. This paper provides recent results from cutting technology for thick steels aiming disassembling nuclear pressure vessel, and decontamination machine technology which works under high radiation dose, explaining the results from cutting experiment of steels and the actual equipment and from the radiation resistance experiment for component devices.
Okada, Jumpei; Nishino, Saki; Terunuma, Ryuki; Takahashi, Naoki; Isomae, Hidemi
no journal, ,
no abstracts in English
Kisohara, Naoyuki; Minehara, Eisuke*; Kosuge, Atsushi
no journal, ,
no abstracts in English
Kosuge, Atsushi; Minehara, Eisuke*; Saruta, Koichi
no journal, ,
Decontamination is required when disposing of equipment contaminated by the accident at TEPCO's Fukushima Daiichi Nuclear Power Station. The decontamination method generally used at present has a problem that a large amount of secondary waste is generated. Decontamination using a laser is non-contact and can significantly suppress the generation of secondary waste. In this study, we used a method of instantly evaporating and peeling using a continuous wave fiber laser, and observed the time change of peeling of the metal surface using a high-speed camera.
Kosuge, Atsushi; Minehara, Eisuke*; Saruta, Koichi
no journal, ,
Decontamination is required when disposing of equipment contaminated by the accident at TEPCO's Fukushima Daiichi Nuclear Power Plant. The decontamination method generally used at present has a problem that a large amount of secondary waste is generated. Decontamination using a laser is non-contact and can significantly suppress the generation of secondary waste. In this study, we used a method of instantly evaporating and peeling using a continuous wave fiber laser, and observed the time change of peeling of the metal surface using a high-speed camera. Furthermore, a decontamination test was conducted using this laser decontamination method for the parts of the analyzer installed in Minamisoma City, Fukushima Prefecture, which was contaminated with radioactive substances.
Kosuge, Atsushi; Minehara, Eisuke*
no journal, ,
In the decommissioning of nuclear reactors, it is possible to reduce the amount of radioactive wastes and significantly reduce the storage cost by efficiently decontaminating the contaminated concrete used in the reactor building. Conventional decontamination methods have some disadvantages. Laser decontamination has been shown to be non-contact, remote-controlled, especially capable of a decontamination coefficient of 
100%, and significantly suppresses the generation of secondary wastes. Irradiation of the concrete surface with a laser causes the formation of a glass layer on the surface, thermal fracturing, and an explosive fracture by water and carbonate. In this study, we explain observations for elucidating the surface peeling mechanism of the concrete surface layer using high-speed scanning of a high-power density continuous-wave fiber laser.
Kosuge, Atsushi; Minehara, Eisuke*
no journal, ,
In the decommissioning of nuclear reactors, the amount of radioactive waste can be reduced by efficiently decontaminating contaminated concrete such as buildings. In this study, we used a method for metals, which uses a laser that is focused at high power density and scans at high speed to use instantaneous evaporation, to clarify the surface delamination mechanism of the concrete surface layer. We aim to establish a more efficient concrete surface decontamination method by visualizing high-speed phenomena using a high-speed camera.
Kisohara, Naoyuki; Aoyagi, Yuji*; Taguchi, Toshihiro
no journal, ,
Decontamination technologies, which remove radioactive substances from material surfaces, are significant to reduce radioactive wastes and recycle materials in decommissioning. Laser decontamination provides advantages such as remote processing and less produced secondary waste. The JAEA's experimental study has revealed that high-power density and high-speed Laser scanning irradiations achieve high decontamination efficiency by surface metal vaporization. The JAEA's computer code has been used to understand the phenomena induced by laser heating. This computer code has physical models including thermal conduction, metal melting, vaporization and radiation. The transient calculation is applied to simulate moving heat source by Laser scanning. The computer results have clarified surface melting, vaporization and solidification, explaining the relation between measured delamination depth and Laser irradiation conditions well.
Kosuge, Atsushi
no journal, ,
Decontamination using lasers is non-contact, can be operated remotely, and can significantly suppress secondary waste generation. We are developing a laser decontamination technique using instantaneous evaporation by focusing a high-power continuous-wave fiber laser to a small spot size and sweeping it at high speed with high power density, and are conducting experimental and analytical evaluations. In this presentation, samples were laser irradiated under various laser irradiation conditions, and the depth of melting was observed by cross-sectional measurement and surface observation of metal ablation. Simulated decontamination tests were also conducted by measuring fluorescence spectral intensity using fluorescent paint as a simulated contaminant, and changes in the amount of removal due to laser irradiation conditions were investigated.