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Journal Articles

Melting behavior and thermal conductivity of solid sodium-concrete reaction product

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

Journal of Nuclear Science and Technology, 56(6), p.513 - 520, 2019/06

This study revealed melting points and thermal conductivities of four samples generated by sodium-concrete reaction (SCR). We prepared the samples using two methods such as firing mixtures of sodium and grinded concrete powder, and sampling depositions after the SCR experiments. In the former, the mixing ratios were determined from the past experiment. The latter simulated the more realistic conditions such as the temperature history and the distribution of Na and concrete. The thermogravimetry-differential thermal analyzer (TG-DTA) measurement showed the melting points were 865-942$$^{circ}$$C, but those of the samples containing metallic Na couldn't be clarified. In the two more realistic samples, the compression moldings in a furnace were observed. The observation revealed the softening temperature was 800-840$$^{circ}$$C and the melting point was 840-850$$^{circ}$$C, which was 10-20$$^{circ}$$C lower than the TG-DTA results. The thermodynamics calculation of FactSage 7.2 revealed the temperature of the onset of melting was caused by melting of the some components such as Na$$_{2}$$SiO$$_{3}$$ and/or Na$$_{4}$$SiO$$_{4}$$. Moreover, the thermal conductivity was $$lambda$$=1-3W/m-K, which was comparable to xNa$$_{2}$$O-1-xSiO$$_{2}$$ (x=0.5, 0.33, 0.25), and those at 700$$^{circ}$$C were explained by the equation of $$NBO/T$$.

Journal Articles

A Study on self-terminating behavior of sodium-concrete reaction, 2

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

Journal of Nuclear Science and Technology, 55(8), p.874 - 884, 2018/08

 Times Cited Count:2 Percentile:16.17(Nuclear Science & Technology)

As parts of severe accident studies in sodium-cooled fast reactor, experiments were performed to investigate the termination mechanism of sodium-concrete reaction (SCR). In the experiment, the reaction time was controlled to investigate the distribution change of sodium (Na) and the reaction products in the pool and around the reaction front. In the results, the Na around the reaction front decreased from the enough amount with the reaction time. The concentrations were 18-24 wt.% for Na, and 22-18 wt.% for Si after the termination. From the thermodynamics calculations, the stable materials around the reaction front comprised more than 90 wt.% solid products such as Na$$_{2}$$SiO$$_{3}$$, and no Na. Further, the distribution of Na and reaction products could be explained by a steady-state sedimentation-diffusion model. At the early stage of SCR, the reaction products were suspended as particles in the Na pool because of the high H$$_{2}$$-generation rate. As the concrete ablation proceeds, they start settling down due to the decreased H$$_{2}$$-generation rate, thereby allowing SCR termination. It was concluded that SCR termination was caused by the sediment of the reaction products and the lack of Na around the reaction front.

Journal Articles

Discussion about sodium-concrete reaction in presence of internal heater

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07

Sodium-concrete reaction (SCR) is one of the important phenomena during severe accidents in sodium-cooled fast reactors (SFRs) owing to the presence of large sources of hydrogen and aerosols in the containment vessel. In this study, SCR experiments with an internal heater (800$$^{circ}$$C) were performed to investigate the chemical reaction under the internal heater. Furthermore, the effects of the internal heater on the self-termination mechanism were discussed. Because the internal heater hindered the transport of Na, the moisture in the concrete, and reaction products, Na could permeate and react with the surface concrete at the periphery of the internal heater. As the SCR proceeded, the reaction products accumulated under the internal heater and disturbed the Na diffusion. Therefore, the Na concentration under the internal heater decreased relatively lower, and the concrete ablation depth under the internal heater decreased compared to that under the periphery of the internal heater. However, the Na concentration around the reaction front was about 30 wt.% despite the position of the internal heater. The Na concentration was similar to that of Na$$_2$$SiO$$_3$$, which was almost same as that in our past study. It was found that the Na concentration condition was one of the dominant parameters for the self-termination of SCR, even in the presence of the internal heater.

Journal Articles

Thermophysical properties of sodium-concrete reaction products

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

Netsu Sokutei, 45(1), p.2 - 8, 2018/01

Liquid sodium (Na) has been used as the coolant of fast reactors for the various merits, such as the high thermal conductivity. On the other hand, it is postulated that a steel liner may fail and lead to a sodium-concrete reaction (SCR) during the Na-leak accident. Because of concrete ablation and release of hydrogen gas due to the chemical reactions between Na and concrete components, the SCR is one of the important phenomena in the Na-leak accident. In the study, fundamental experiments related to the SCR were performed using Na and concrete powder. Here, the used concrete powder is milled siliceous concrete which is usually used as the structural concrete in Japanese nuclear power plants. The obvious temperature changes at 3 temperature regions were observed for the reaction process such as Na-melt, NaOH-SiO$$_{2}$$ and Na-H$$_{2}$$O-SiO$$_{2}$$ reaction, which occurred around 100, 300 and 500$$^{circ}$$C, respectively. Especially, the violent reaction around 500$$^{circ}$$C caused the temperature peak to $$836 sim 853^{circ}$$C, and the reaction heat of $$0.15 sim 0.23$$ kW/g was estimated under the Na-concrete mixing ratio such as $$gammaapprox 0.32$$. The main components of the reaction products was identified as Na$$_{2}$$SiO$$_{3}$$ with X-ray diffraction technique. Moreover, the measured thermophysical properties such as melting point, density, specific heat, thermal conductivity and viscosity were similar to those of $$x$$Na$$_{2}$$O-$$(1-x)$$SiO$$_{2}$$ ($$xleq 0.5$$).

Journal Articles

Thermal management of heat resistant FBG sensing for high temperature industrial plants

Nishimura, Akihiko; Takenaka, Yusuke*; Furusawa, Akinori; Torimoto, Kazuhiro; Ueda, Masashi; Fukuda, Naoaki*; Hirao, Kazuyuki*

E-Journal of Advanced Maintenance (Internet), 9(2), p.52 - 59, 2017/08

no abstracts in English

Journal Articles

A Study on self-terminating behavior of sodium-concrete reaction

Kawaguchi, Munemichi; Doi, Daisuke; Seino, Hiroshi; Miyahara, Shinya

Journal of Nuclear Science and Technology, 53(12), p.2098 - 2107, 2016/12

 Times Cited Count:3 Percentile:42.29(Nuclear Science & Technology)

A sodium concrete reaction (SCR) is one of the important phenomena to cause the structural concrete ablation and the release of H$$_2$$ gas in the case of sever accident of sodium cooled fast reactors. In this study, the long-time SCR test had been carried out to investigate the self-termination mechanism. The results showed the SCR terminated even if the enough amount of Na remained on the concrete. The quantitative data were collected on the SCR terminating such as temperature and H$$_2$$ generation. The reaction products, which became the small solids in liquid Na were transferred with slurry state by generated H$$_2$$ bubbles. Though the Na transfers actively and ablated the concrete surface with the high H$$_2$$ generation rate, the mass exchange coefficient defined as $$E_p$$ decreased and the reaction products settled gradually with decreasing the H$$_2$$ generation rate. Therefore, the Na concentration decreased at the reaction front and resulted in the SCR terminating naturally.

Journal Articles

Validations of multifrequency ECT algorithms for helical SG tubes of FBR

Mihalache, O.; Yamaguchi, Toshihiko; Ueda, Masashi

Electromagnetic Nondestructive Evaluation (XVII), p.109 - 119, 2014/00

 Times Cited Count:3 Percentile:5.53

Journal Articles

EMAT simulations based on a two-dimensional FEM coupled electro-mechanical formulation

Garcia Rodriguez, D.; Mihalache, O.; Ueda, Masashi

Proceedings of 16th International Symposium on Applied Electromagnetics and Mechanics (ISEM 2013), p.219 - 220, 2013/07

Journal Articles

Human development in Japan and abroad using prototype FBR Monju towards the next-generation age

Sawada, Makoto; Sasaki, Kazuichi; Nishida, Masaaki

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 12 Pages, 2012/00

Japan is aiming at starting commercial operation of a demonstration FBR around 2025 in the FaCT (Fast Reactor Cycle Technology Development) project. To prepare for such as the new FBR age, INITC has established a total of 27 JAEA staff training courses based on the teachings obtained from the Monju leak accident, regarding to FBR operation technology, sodium handling technology, maintenance technology and FBR plant system engineering technology, and also has been conducting energy environmental education for from under high school students to graduate students of the whole country including local universities. In addition, INITC aims become a central of excellent (COE) of the international technology training in Asia through the international educational training programs sponsored by MEXT. The variety of the activities of educational training mentioned above will contribute to the development of the human resource in Japan and abroad, towards the next generation age.

Journal Articles

High quality education & training towards Monju re-operation

Sawada, Makoto; Sakurai, Naoto

Proceedings of International Symposium on Symbiotic Nuclear Power Systems for 21st Century (ISSNP) (CD-ROM), p.275 - 283, 2007/07

The prototype FBR Monju which caused a sodium leak accident in Dec. 1995 is now under remodeling to attain its re-initial criticality in 2008. The success or failure of its safety operation is an important issue which influences development of nuclear fuel cycle. So, a high quality educational training is strongly required in order to assure its future safety operation. Based on the teachings learned from the accident, Monju has revised its educational training structure extensively such as, a new building a framework of educational training, a new open of Monju FBR Training School, a reinforcement of simulator training, etc.. A total of 29 established training courses, based on the mentioned above improvements, have been conducting towards Monju restarting.

Journal Articles

Fast reactor and nuclear fuel cycle

Shinoda, Yoshihiko

Enerugi No Gaibusei To Genshiryoku, p.219 - 230, 2006/09

The Multi-criteria evaluation on Fast Reactor are mentioned.

Oral presentation

Oral presentation

Sodium properties, impurities and safety in the 1st International Topical Seminar "Coolants and Innovative Reactor Technologies"

Sawada, Makoto

no journal, , 

With the aim of enhancement personnel development of nuclear engineers, the Cadarache Research Center, CEA and the INITC, JAEA agreed to dedicate mutually the educational topical seminar on the theme of "Coolants and Innovative Reactor Technologies" in cooperation. In response, INITC held the "Tsuruga Summer Institutes on Nuclear Energy 2006" by cosponsorship with the Wakasa-wan Energy Research Centre in Sep. 11 to 15 at Tsuruga. While, Cadarache Research Center will conduct the 1st International Topical Seminar "Coolants and Innovative Reactor Technologies" in this Nov. 27, 28 at Aix en Provance, France. And JAEA takes charge of two lectures, i.e. "Developments of Sodium Fast Reactors in Japan" and "Sodium Properties, Impurities and Safety". This presentation is related to the later and sodium properties, corrosion by impurities and safety handling, etc., are mentioned from the aspects of the advantage and disadvantage of sodium.

Oral presentation

Fundamental study of acoustic emission in rotating machines by non-contact measurement using laser interferometer

Ota, Yasufumi; Saruta, Koichi; Noguchi, Shotaro; Ueda, Masashi

no journal, , 

no abstracts in English

Oral presentation

Wetting of metallic plated stainless steels by liquid metal sodium

Kawaguchi, Munemichi; Hamada, Hirotsugu

no journal, , 

Since liquid sodium is used as a coolant of sodium-cooled fast breeder reactors, the optical visual inspection in the inner of the reactor is difficult. Then, Japan Atomic Energy Agency has developed the under sodium viewer (USV) for the purpose of visually inspecting, and it is important to understand the wetting mechanism between the liquid sodium and USV sensor surface. In order to improve the wettability, Au plating is used in the surface of USV sensor at the present. In this study, some various plating specimens including Au plating were manufactured, and their wettability by liquid sodium were measured experimentally. In the result, we confirmed that solubility of the plating is important parameter for the plating processing on the sodium wetting.

Oral presentation

Study on sodium-concrete reaction

Kawaguchi, Munemichi; Doi, Daisuke; Masuyama, Daisuke; Seino, Hiroshi; Konishi, Kensuke; Miyahara, Shinya

no journal, , 

As the purpose of investigation on terminating mechanism of Na-concrete reaction, the long-time test in which Na continued to be heated than threshold temperature was conducted. Under the condition that enough amount of Na existed and continued to be heated, we confirmed that the reaction stopped.

Oral presentation

Development of estimation technology for availability of measure for failure of containment vessel in sodium cooled fast reactor, 3; Corium/sodium-concrete interaction behavior

Kawaguchi, Munemichi; Uno, Masayoshi*; Konishi, Kensuke; Yamamoto, Ikuo*; Miyahara, Shinya*

no journal, , 

We started a project on "Development of Estimation Technology for Availability of Measure for Failure of Containment Vessel in Sodium Cooled Fast Reactor" as a program for R&D for nuclear system, development of basic technology for safety. We planed to develop an evaluation method based on experiments of hydrogen generation and concrete ablation in sodium-concrete reaction. This report shows the plan and a part of the sodium test.

Oral presentation

Peer review on the safety requirements of the prototype fast breeder reactor "Monju", 3; Summary of international review

Tobita, Yoshiharu

no journal, , 

An advisory panel on Monju safety requirements issued a report on the safety requirements for the Prototype Fast Breeder Reactor "Monju" in the last July. The issued report was reviewed both by domestic and international experts on FBR safety. The result of international review is reported in this presentation.

Oral presentation

Collapse load of beam subjected to both bending moment and shear force

Tsukimori, Kazuyuki; Moriizumi, Makoto; Abe, Masato; Sadahiro, Daisuke*; Ishigaki, Yoshinobu*

no journal, , 

The elastic limit and the collapse load of a rectangular or circular cross-section beam subjected to both bending moment and shear force are derived analytically with partially approximation. According to the result, there is no interaction between bending moment and shear force in the region of elastic, however, there is an interaction between them with some relation, which is complicated but seems to be close to oval shape. The validity of this relation is examined by FEM analysis.

Oral presentation

Development of estimation technology for availability of measure for failure of containment vessel in sodium cooled fast reactor, 13; Simulation of Na-concrete reaction process

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

no journal, , 

To evaluate the chemical reaction process of Na-concrete reaction, the model which adopted the thermodynamic database and the latest chemical reaction kinetics in COMSOL Multiphysics has been developed. The chemical reaction processes at each temperature were simulated well by the numerical calculation with this model.

25 (Records 1-20 displayed on this page)