Atomic interactions at the interface between iron or iron fluoride, and sodium by the first-principles calculation

Namie, Masanari; Saito, Junichi

Computational Materials Science, 239, p.112963_1 - 112963_7, 2024/04

https://doi.org/10.1016/j.commatsci.2024.112963

Wettability of pure metals with liquid sodium and liquid tin

Saito, Junichi; Kobayashi, Yohei*; Shibutani, Hideo*

Materials Transactions, 62(10), p.1524 - 1532, 2021/10

https://doi.org/10.2320/matertrans.MT-M2021107

no abstracts in English

A Study on sodium-concrete reaction in presence of internal heating

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

Journal of Nuclear Engineering and Radiation Science, 6(2), p.021305_1 - 021305_9, 2020/04

https://doi.org/10.1115/1.4045898

Sodium-concrete reaction (SCR) is one of the important phenomena during severe accidents in sodium-cooled fast reactors (SFRs) owing to the generation of large sources of hydrogen and aerosols in the containment vessel. In this study, SCR experiments with an internal heater were performed to investigate the chemical reaction beneath the internal heater (800C), which was used to simulate the obstacle and heating effect on SCR. Furthermore, the effects of the internal heater on the self-termination mechanism were discussed. The internal heater on the concrete hindered the transport of Na into the concrete. Therefore, Na could start to react with the concrete at the periphery of the internal heater, and the concrete ablation depth at the periphery was larger than under the internal heater. The high Na pool temperature of 800C increased largely the Na aerosol release rate, which was explained by Na evaporation and hydrogen bubbling, and formed the porous reaction product layer, whose porosity was 0.54-0.59 from the mass balance of Si and image analyzing EPMA mapping. They had good agreement with each other. The porous reaction products decreased the amount of Na transport into the reaction front. The Na concentration around the reaction front became about 30wt.% despite the position of the internal heater. 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.

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

https://doi.org/10.1080/00223131.2018.1449677

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 NaSiO, 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-generation rate. As the concrete ablation proceeds, they start settling down due to the decreased H-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.

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 and Na-HO-SiO reaction, which occurred around 100, 300 and 500C, respectively. Especially, the violent reaction around 500C caused the temperature peak to C, and the reaction heat of kW/g was estimated under the Na-concrete mixing ratio such as . The main components of the reaction products was identified as NaSiO 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 NaO-SiO ().

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

https://doi.org/10.1080/00223131.2016.1199979

A sodium concrete reaction (SCR) is one of the important phenomena to cause the structural concrete ablation and the release of H 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 generation. The reaction products, which became the small solids in liquid Na were transferred with slurry state by generated H bubbles. Though the Na transfers actively and ablated the concrete surface with the high H generation rate, the mass exchange coefficient defined as decreased and the reaction products settled gradually with decreasing the H generation rate. Therefore, the Na concentration decreased at the reaction front and resulted in the SCR terminating naturally.

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

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.