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Daido, Hiroyuki*; Yamada, Tomonori
ILT-APR-34; ILT 2023 Nempo (Internet), p.1 - 5, 2023/07
The decommissioning of Fukushima and the contribution to reconstruction have become national issues. The authors participated in the "Analysis of fine particles generated by laser processing and development of nuclide identification method" (represented by Professor Shuichi Hasegawa of the University of Tokyo), which was adopted as one of the JAEA's publicly solicited projects for this purpose, from FY 2018 to FY 2021 as a subcontractor, The authors conducted research on the observation, evaluation and analysis of the interaction between lasers and various laser-irradiated targets. This report outlines the results of the research in which the authors took part. In the experiments, laser irradiation was carried out on test specimens set up in an irradiation chamber, and shadowgraphs were taken using a high-speed camera and a He-Ne laser. As an example of the experimental results, shadowgraphs of metal (stainless steel) and metal oxide (zirconia), irradiation traces after laser irradiation, and the relationship between laser irradiation power and jet mass are shown, and the interaction between the laser and the metal or metal oxide is discussed. The results will not only contribute to the decommissioning technology of the Fukushima Daiichi NPP, but also to laser processing technology and laser interaction research.
Daido, Hiroyuki*; Yamada, Tomonori; Saruta, Koichi; Miyabe, Masabumi; Ito, Chikara; Shibata, Takuya; Inoue, Kaoru*; Terabayashi, Ryohei*; Hasegawa, Shuichi*
Physica Scripta, 98(3), p.035112_1 - 035112_22, 2023/02
Times Cited Count：0 Percentile：0.00(Physics, Multidisciplinary)Characterization of kW class quasi-continuous wave (a pulse duration of 10 ms) laser interaction with metal targets and those with metal oxide targets are presented in respect to the laser induced breakdown and the successive laser induced melting and evaporation coupled with a mechanical response followed by ejection of various kinds of particles and fragments. An experiment was performed using fiber lasers coupled with a high-speed camera to observe dynamics of the interaction. Ejected fine particles were collected using a cascade impactor and a home-made collector and were observed with electron microscopes. Shapes of irradiation marks were observed with a digital optical microscope. We also measured total ejected mass from a target. The experimental results reveal that firstly the laser threshold intensity of the interaction with the metal target was lower and more stable than those with the metal oxide targets. Secondly, in the stainless steel targets, the dynamics of molten layer created by thermal conduction from the laser heated thin layer and successive particle ejection with less mechanical response by the adjacent solid layer are dominant processes, while in the metal oxide targets, the fracturing in the relatively deeper interaction region coupled with brittle material response having relatively large laser shot to shot fluctuation appears to play a significant role in addition to the laser induced melting.
Yamada, Tomonori; Daido, Hiroyuki*; Shibata, Takuya
Journal of Nuclear Science and Technology, 59(5), p.614 - 628, 2022/05
Times Cited Count：2 Percentile：22.08(Nuclear Science & Technology)Shobu, Takahisa; Shiro, Ayumi*; Kono, Fumiaki*; Muramatsu, Toshiharu; Yamada, Tomonori; Naganuma, Masayuki; Ozawa, Takayuki
Quantum Beam Science (Internet), 5(2), p.17_1 - 17_9, 2021/06
The automotive industries employ laser beam welding because it realizes a high energy density without generating irradiation marks on the opposite side of the irradiated surface. Typical measurement techniques such as strain gauges and tube X-rays cannot assess the localized strain at a joint weld. Herein high-energy synchrotron radiation X-ray diffraction was used to study the internal strain distribution of laser lap joint PNC-FMS steels (2- and 5-mm thick) under loading at a high temperature. As the tensile load increased, the local tensile and compressive strains increased near the interface. These changes agreed well with the finite element analysis results. However, it is essential to complementarily utilize internal defect observations by X-ray transmission imaging because the results depend on the defects generated by laser processing.
Daido, Hiroyuki*; Yamada, Tomonori; Furukawa, Hiroyuki*; Ito, Chikara; Miyabe, Masabumi; Shibata, Takuya; Hasegawa, Shuichi*
Journal of Laser Applications, 33(1), p.012001_1 - 012001_16, 2021/02
Times Cited Count：2 Percentile：17.30(Materials Science, Multidisciplinary)Yamada, Tomonori; Takebe, Toshihiko*; Ishizuka, Ippei*; Daido, Hiroyuki*; Hanari, Toshihide; Shibata, Takuya; Omori, Shinya*; Kurosawa, Koichi*; Sasaki, Go*; Nakada, Masahiro*; et al.
Journal of Nuclear Science and Technology, 56(12), p.1171 - 1179, 2019/12
Times Cited Count：1 Percentile：9.12(Nuclear Science & Technology)We describe a new chipping technique combined with a water-jet technique as one of the candidate techniques for the retrieval of fuel debris and support structures as part of the decommissioning of the Fukushima Daiichi Nuclear Power Station. We performed proof-of-principle experiments to demonstrate the removal capability of metal parts, where we focused on the observation of removal processes from a metallic sample using a 5.5-kW continuous wave fiber laser combined with continuous and pulsed water jets.
Noda, Koichi; Nosaki, Nobuhisa; Ogawa, Toru; Yamada, Tomonori
Nihon Genshiryoku Gakkai-Shi ATOMO
, 61(12), p.843 - 846, 2019/12
The series of articles introduce the JAEA's R&D. In the first series, we introduce Fukushima Daiichi decommissioning and Fukushima remediation (1).
Naoe, Takashi; Teshigawara, Makoto; Futakawa, Masatoshi; Mizutani, Haruki; Muramatsu, Toshiharu; Yamada, Tomonori; Ushitsuka, Yuji*; Tanaka, Nobuatsu*; Yamasaki, Kazuhiko*
Proceedings of 8th International Congress on Laser Advanced Materials Processing (LAMP 2019) (Internet), 5 Pages, 2019/05
Laser cutting is one of the options in the disposal of radio-active waste, such as spallation neutron target vessel in J-PARC, etc. Due to unique characteristic of laser, such as non-contact system, it is more easily to provide remote-controlled system in comparison with conventional one, such as mechanical cutting machine, etc. However, a demerit of laser cutting is the sputter and fume caused by laser cutting, resulting in contamination with radio-active materials its surroundings. Recently it was developed that the spatter suppression technique by controlling laser beam profile in laser welding process. In order to apply this suppression technique to laser cutting, first of all, we attempted to observe the phenomenon at melting area during laser cutting using a high-speed video camera in order to make the physical model. The result showed that the appearance of fume and sputter were independently confirmed in the time evolution.
Nishimura, Akihiko; Yoshida, Minoru*; Yamada, Tomonori; Arakawa, Ryoki
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 3 Pages, 2019/05
JAEA support the development of remote sensing robotic system in the Naraha Remote Technology Development Center. A water tank is used as a mockup facility of nuclear reactor vessel. A compact seismic vibrometer based on an optical fiber interferometer is applied. A specially designed robotic system is also tested for installing the sensor unit. The experiment is prepared to clarify the transfer function of the water tank, using vibration noise of ground motion.
Daido, Hiroyuki*; Yamada, Tomonori
Oputoronikusu, 37(12), p.67 - 71, 2018/12
no abstracts in English
Nguyen, P. L.; Daido, Hiroyuki; Yamada, Tomonori; Nishimura, Akihiko; Hasegawa, Noboru*; Kawachi, Tetsuya*
Journal of Laser Applications, 29(4), p.041501_1 - 041501_11, 2017/11
Times Cited Count：19 Percentile：69.57(Materials Science, Multidisciplinary)no abstracts in English
Hanari, Toshihide; Takebe, Toshihiko*; Yamada, Tomonori; Daido, Hiroyuki; Ishizuka, Ippei*; Omori, Shinya*; Kurosawa, Koichi*; Sasaki, Go*; Nakada, Masahiro*; Sakai, Hideaki*
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 3 Pages, 2017/04
In decommissioning of Fukushima Daiichi Nuclear Power Station, a retrieval process of fuel debris in the Primary Containment Vessel by a remote operation is one of the key issues. In this process, prevention of spreading radioactive materials is one of the important considerations. Furthermore, an applicable technique to the process requires keeping of reasonable processing-efficiency. We propose to use the combined technique including a laser light and a water jet as a retrieval technique of the fuel debris. The laser processing technique combined with a repetitive pulsed water jet could perform an efficient retrieval processing. Our experimental result encourages us to promote further development of the technique towards a real application at Fukushima Daiichi Nuclear Power Station.
Segawa, Tomoomi; Fukasawa, Tomonori*; Huang, A.-N.*; Yamada, Yoshikazu; Suzuki, Masahiro; Fukui, Kunihiro*
Chemical Engineering Science, 153, p.108 - 116, 2016/10
Times Cited Count：7 Percentile：24.34(Engineering, Chemical)The influence of the heating method and rate on the morphology of CuO powders synthesized from Cu(NO
)
3HO aqueous solutions by denitration was investigated. The median diameter of the obtained powder was found to decrease as the heating rate increased, independent of the heating method. The microwave heating method remarkably reduced the particle size and enhanced the irregularity and disorder of the shape and surface of the particles, which were found to be more widely distributed. In contrast, the microwave hybrid heating method yielded the most spherical particles with the smoothest surface. It was also found that this heating method sharpened the particle size distribution and had higher energy efficiency than the MW method. Numerical simulations also indicated a difference in the energy efficiency between these two methods. The simulations also revealed that the hybrid method could heat the whole reactor more uniformly with a lower microwave output.
Kawamura, Hiroshi; Yamada, Tomonori
Kinzoku, 86(7), p.580 - 589, 2016/07
no abstracts in English
Segawa, Tomoomi; Fukasawa, Tomonori*; Yamada, Yoshikazu; Suzuki, Masahiro; Yoshida, Hideto*; Fukui, Kunihiro*
Proceedings of Asian Pacific Confederation of Chemical Engineering 2015 (APCChE 2015), 8 Pages, 2015/09
A mixed solution of uranyl nitrate and plutonium nitrate is converted to MOX raw powder by the microwave heating de-nitration method in nuclear reprocessing. Copper oxide synthesized by heating de-nitration was used as a model for the de-nitration process. The microwave heating method (MW) and infrared heating method (IR) were used, and how they and their heating rate influence the obtained particle morphology and size were investigated. The particles obtained by the MW and IR were sufficiently similar in the surface morphology and the mass median diameter was decreased by the increased heating rate. The mass median diameters by the MW were the heating rate and smaller than those obtained by IR. The particle size distribution of the particle obtained by the MW was broader than that by the IR. The relationship of the temperature distribution and particle size distribution by the MW was discussed by the numerical simulation.
Kono, Fumiaki; Sogame, Motomu; Yamada, Tomonori; Shobu, Takahisa; Naganuma, Masayuki; Ozawa, Takayuki; Muramatsu, Toshiharu
JAEA-Technology 2015-004, 57 Pages, 2015/03
JAEA-Technology-2015-004.pdf:20.87MB
Laser welding of ferritic/martensitic steel (PNC-FMS) sheets with different thicknesses (2 mm and 5 mm) was examined to investigate the weldability between the inner and outer duct in fast reactor fuel assemblies with inner duct structure (FAIDUS); the objective of the inner duct is to avoid the re-criticality in case of the core melting accident. Laser-spot and melt-run welding was performed at various laser powers, welding times and velocities to find out the appropriate welding conditions with few defects and enough penetration depth. As for the spot welding, furthermore, slow cooling rate or pulsed laser irradiation could reduce the crack and porosity in the welded zone. The strain of the welded zone almost disappeared and the hardness was comparable with that of the base metal by applying post welding heat treatment at 690 
C for 103 min. In addition, the shear strength of welded joints was confirmed to be sufficiently higher than the provisional allowance shear stress. These results indicate that laser welding would be probably applied to the PNC-FMS inner and outer ducts.
Yamada, Tomonori; Muramatsu, Toshiharu
JAEA-Research 2014-026, 28 Pages, 2015/02
JAEA-Research-2014-026.pdf:18.03MB
In this study the response of hardened cement pastes, which is a major component of concrete, to laser irradiation was investigated under various experimental conditions aiming at the future application to "laser-processing" of concrete. (1) Evaluation of water-cement ratio for laser irradiation. It was found that hardened cement paste subjected to laser irradiation explodes very easily to be hollowed in all the experimental conditions; this response is applicable to "laser-drilling" of a hardened cement paste. (2) Evaluation of the kind of mortar for laser irradiation. Totally 75 laser irradiation tests for fixed mortar blocks were performed with combinations of following experimental conditions: fine aggregate in the mortar blocks was either of quartz, limestone, or Nachiguro-ishi. Although it was found that all kinds of the mortar fuse under laser irradiation after all, difference in the response to laser irradiation among the mortars was also found.
Muramatsu, Toshiharu; Yamada, Tomonori; Hanari, Toshihide; Takebe, Toshihiko; Nguyen, P. L.; Matsunaga, Yukihiro
JAEA-Research 2014-018, 41 Pages, 2014/09
JAEA-Research-2014-018.pdf:42.21MB
In decommissioning works of the Fukushima Daiichi Nuclear Power Plants, it is required that fuel debris solidifying mixed materials of fuels and in-vessel structures should be removed. The fuel debris is considered to have characteristics, such as indefinite shapes, porous bodies, multi-compositions, higher hardness, etc. from the knowledge in the U.S. and the Three Mile Island nuclear power plant. Laser lights are characterized by higher power density, local processability, remote controllabilitiy, etc. and can be performed thermal cutting and crushing-up for various materials which does not depend on fracture toughness. This report describes a research program and research activities in FY2013 aiming at developing removal system of fuel debris by the use of laser lights.
Muramatsu, Toshiharu; Yamada, Tomonori; Hanari, Toshihide; Takebe, Toshihiko; Matsunaga, Yukihiro
JAEA-Research 2013-024, 49 Pages, 2013/08
JAEA-Research-2013-024.pdf:6.63MB
In decommissioning works of the Fukushima Daiichi Nuclear Power Plants, it is required that fuel debris solidifying mixed materials of fuels and in-vessel structures should be removed. The fuel debris is considered to have characteristics, such as indefinite shapes, porous bodies, multi-compositions, higher hardness, etc. from the knowledge in the U.S. and the Three Mile Island nuclear power plant. Laser lights are characterized by higher power density, local processability, remote controllabilitiy, etc. and can be performed thermal cutting and crushing-up for various materials which does not depend on fracture toughness. This report describes a research program and research activities in FY2012 aiming at developing removal system of fuel debris by the use of laser lights.
Yamada, Tomonori; Yamashita, Susumu; Sugihara, Kenta; Muramatsu, Toshiharu
Purazuma, Kaku Yugo Gakkai-Shi, 89(7), p.500 - 506, 2013/08
no abstracts in English
