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Journal Articles

Development on laser cutting technique to suppress spatter particles aiming at disposal of radio-active waste

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.

Journal Articles

Support for the development of remote sensing robotic system using a water tank installed in the Naraha Remote Technology Development Center

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.

Journal Articles

Concrete cutting technology with lasers

Daido, Hiroyuki*; Yamada, Tomonori

Oputoronikusu, 37(12), p.67 - 71, 2018/12

no abstracts in English

Journal Articles

Experimental characterization of concrete removal by high-power quasicontinuous wave fiber laser irradiation

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

no abstracts in English

Journal Articles

Demonstration of laser processing technique combined with water jet technique for retrieval of fuel debris at Fukushima Daiichi Nuclear Power Station

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.

Journal Articles

Influence of the heating method on the particle characteristics of copper oxide powders synthesized from copper nitrate aqueous solutions

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:1 Percentile:88.21(Engineering, Chemical)

The influence of the heating method and rate on the morphology of CuO powders synthesized from Cu(NO$$_{3}$$)$$_{2}$$$$cdot$$3H$$_{2}$$O 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.

Journal Articles

Creation of research center related to decommissioning Fukushima Daiichi Nuclear Power Station

Kawamura, Hiroshi; Yamada, Tomonori

Kinzoku, 86(7), p.580 - 589, 2016/07

no abstracts in English

Journal Articles

Influence of heating method on size and morphology of metallic oxide powder synthesized from metallic nitrate solution

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.

JAEA Reports

A Study on laser welding of ferritic/martensitic steel (PNC-FMS) for fast reactor fuel assemblies

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 $$^{circ}$$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.

JAEA Reports

Research on interaction of laser light and non-metals; Evaluation of laser irradiation behavior to concrete

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.

JAEA Reports

Research on removal technologies of fuel debris and in-vessel structures using laser light, 2; Research activities on FY2013

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.

JAEA Reports

Research on removal technologies of fuel debris and in-vessel structures using laser light, 1; Research plan and research activities on FY2012

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.

Journal Articles

Numerical simulation of laser processing

Yamada, Tomonori; Yamashita, Susumu; Sugihara, Kenta; Muramatsu, Toshiharu

Purazuma, Kaku Yugo Gakkai-Shi, 89(7), p.500 - 506, 2013/08

no abstracts in English

Journal Articles

Research and development of full-scale three-dimensional vibration simulator for nuclear plant

Nishida, Akemi; Suzuki, Yoshio; Yamada, Tomonori; Kino, Chiaki; Uzawa, Ken*; Miyamura, Hiroko; Kawamura, Takuma; Takemiya, Hiroshi; Nakajima, Norihiro

RIST News, (54), p.33 - 37, 2013/01

Nuclear plants are complicated and huge structures and consist of a large number of parts. To simulate the behavior of such a complicated huge structure, it becomes important the viewpoint as a general system including pre-post-processing. Therefore, the CCSE proposed an approach for assembly structure analysis and implemented a framework of a full-scale 3D vibration simulator for an entire nuclear plant. Until now, we performed numerical experiments using the data of a building and equipment of HTTR, Oarai R&D Center, JAEA, and demonstrated that earthquake response simulation of large-scale structure as an entire nuclear plant was possible so far. In this report, the framework of the full-scale 3D vibration simulator, the assembly structure analysis approach and visualization technology for an evaluation of the results are shown. And finally, an example of application of the simulator for probabilistic risk assessment, PRA, started from 2011, is shown.

Journal Articles

In-situ X-ray observation of molten pool depth during laser micro welding

Yamada, Tomonori; Shobu, Takahisa; Nishimura, Akihiko; Yonemoto, Yukihiro; Yamashita, Susumu; Muramatsu, Toshiharu

Journal of Laser Micro/Nanoengineering, 7(3), p.244 - 248, 2012/11

Small size and high-performance fiber lasers enable in-situ flaw sizing and repairs at nuclear power plants. In quantum beam science directorate, the new probing system was developed to treat micro cracks at the welded section of heat exchanger tubes, where a fiber laser beam passed through a composite-type optical fiber scope. Molten pool's diameter by laser welding gradually expanded more than the width of the micro crack's crevice caused by stress corrosion cracking. In this work, we have carried out in-situ X-ray observation of inside materials during laser welding. In-situ observation of inside materials during fiber laser welding provides a useful knowledge of repair welding because bubbles and cracks which cause the poor weld was clearly observed in non-destructive. This is very effective for control of weld defect and investigation of the mechanisms. As a result, we are able to confirm the molten pool depth of butt welding for heat exchanger units using the new probing system.

Journal Articles

Instrumentation device and surface control technology for coolant piping system of nuclear power plants

Nishimura, Akihiko; Terada, Takaya; Shimada, Yukihiro; Yonemoto, Yukihiro*; Yamada, Tomonori

Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 5 Pages, 2012/07

Instrumentation devices using laser technologies were developed for maintenance of coolant piping system. For instrumentation devices, seismic monitoring by optical fiber sensors was able to detect vibration of piping system. X-ray absorption contrast by synchrotron radiation clarified convection motion inside a molten pool produced by laser welding. For surface control technologies, a new probing system was under development for heat exchanger tubes by laser cladding. And laser ablation could be used for surface cleaning. These technologies are expected for maintenance of the piping system of nuclear power plants.

Journal Articles

Development of laser welding simulation code with advanced numerical models

Yamashita, Susumu; Yonemoto, Yukihiro; Yamada, Tomonori; Kunugi, Tomoaki*; Muramatsu, Toshiharu

Yosetsu Gakkai Rombunshu (Internet), 29(3), p.48s - 52s, 2011/08

Quantitative evaluation and controlling the residual stress which is induced by laser welding is of important problem for a life extension of FBRs (Fast Breeder Reactors) and the guarantee of the reliability of the repair processes. Numerical simulation is an effective tool for deep understanding of their problems and it needs to have high accuracy, robustness and reliability. We have recently constructed the fully parallelized laser welding simulation code which satisfies above aspects using some advanced numerical models. Concretely, VSIAM3 numerical model as the spatial discretization, an efficient free surface capturing scheme, THINC scheme, and FAVOR method as the solid phase expression has been applied to the code. We have conducted laser welding simulations and obtained some reasonable results. Therefore, the numerical model will be contributed to the repairing technology of a laser welding.

Journal Articles

In-situ observation of phase transformation during rapid cooling processes

Yamada, Tomonori; Yonemoto, Yukihiro; Yamashita, Susumu; Muramatsu, Toshiharu; Komizo, Yuichi*

Yosetsu Gakkai Rombunshu (Internet), 29(3), p.86s - 89s, 2011/08

It is known that residual stress is important to keep the structural integrity. Laser welding is effective for the residual stress decrease because heat input is smaller and heats have a very small effect. Therefore, the repairing technology by laser welding has draw wide attention for a life extension of FBRs (Fast Breeder Reactors). To establish the laser repair technology, special attentions should be paid to the morphological developments. In the present work, morphological developments were directly observed using laser scanning conforcal microscopy during laser weld cooling.

Journal Articles

Progress of large scale seismic simulation for nuclear power plant in its entirety

Yamada, Tomonori; Shioya, Ryuji*; Yoshimura, Shinobu*

Shimyureshon, 30(2), p.65 - 69, 2011/06

In this paper, recent progress of full-scale simulation of nuclear power plant in its entirety with the growth of supercomputing resource is described. Future directions and possibility and also difficulties are discussed.

Journal Articles

Preliminary study on the finite element analysis for solid mechanics on K computer

Yamada, Tomonori

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 16, 2 Pages, 2011/05

The Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) has been developing the next-generation supercomputer, which has capability of ten peta floating point operations per second, and will install it at Kobe city. As an application of macro-scale solid mechanics, Japan Atomic Energy Agency and his colleagues proposed a research activity on K entitled "next generation seismic analysis of large plants in its entirety" in Monodukuri field. In this paper, a preliminary study on the finite element analysis for solid mechanics on K is described.

166 (Records 1-20 displayed on this page)