Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool

In a probable scenario for core disruptive accidents of Sodium-cooled Fast Reactors (SFRs), it is foreseen that molten core material would be discharged into lower sodium plenums through control rod guide tubes. Such material relocation might lead to a considerable thermal load on lower structures o...

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Autores principales:	Ken-ichi MATSUBA, Kenji KAMIYAMA, Jun-ichi TOYOOKA, Yoshiharu TOBITA, Vladimir A. ZUYEV, Alexander A. KOLODESHNIKOV, Yuri S. VASSILIEV
Formato:	article
Lenguaje:	EN
Publicado:	The Japan Society of Mechanical Engineers 2016
Materias:	sodium-cooled fast reactors core disruptive accidents in-vessel retention molten core material fragmentation Mechanical engineering and machinery TJ1-1570
Acceso en línea:	https://doaj.org/article/9877750203b441dda8153840459b7097
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spelling	oai:doaj.org-article:9877750203b441dda8153840459b70972021-11-26T06:51:30ZExperimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool2187-974510.1299/mej.15-00595https://doaj.org/article/9877750203b441dda8153840459b70972016-04-01T00:00:00Zhttps://www.jstage.jst.go.jp/article/mej/3/3/3_15-00595/_pdf/-char/enhttps://doaj.org/toc/2187-9745In a probable scenario for core disruptive accidents of Sodium-cooled Fast Reactors (SFRs), it is foreseen that molten core material would be discharged into lower sodium plenums through control rod guide tubes. Such material relocation might lead to a considerable thermal load on lower structures of the reactor vessels, while it has been suggested that in SFRs, as soon as the molten core material is discharged into coolant, it might be fragmented into smaller particles by fuel-coolant interactions and thus efficiently cooled in the reactor vessels. Hence, understanding of the fragmentation is crucial for achieving in-vessel retention of molten core material in SFRs. In this paper, based on the experimental results of a series of fragmentation tests, where around 10 kg of molten alumina (Al2O3) was discharged into a sodium pool (depth: 1.3 m, diameter: 0.4 m, temperature: 673 K) through a duct (inner diameter: 40mm to 63 mm) by using an experimental facility at National Nuclear Center of the Republic of Kazakhstan, dominant mechanisms for the fragmentation are discussed. In the present tests, mass median diameters of solidified Al2O3 particles were around 0.3 mm, which were comparable to the values predicted using conventional hydrodynamic-instability theories. However, even though the conventional theories predict that particle size becomes smaller with the increase of Weber number, such tendency was not observed in the present tests. Taking into account that in the present tests, the distances for fragmentation of molten Al2O3 were evaluated to be approximately 60 % to 70 % below the values predicted using an existing representative correlation which regards hydrodynamic instabilities as a dominant fragmentation mechanism, the observed independence on Weber number confirms a mechanism that before hydrodynamic instabilities sufficiently grow to induce fragmentation, thermal phenomena such as local coolant vaporization and resultant vapor expansion significantly accelerate fragmentation in SFRs.Ken-ichi MATSUBAKenji KAMIYAMAJun-ichi TOYOOKAYoshiharu TOBITAVladimir A. ZUYEVAlexander A. KOLODESHNIKOVYuri S. VASSILIEVThe Japan Society of Mechanical Engineersarticlesodium-cooled fast reactorscore disruptive accidentsin-vessel retentionmolten core materialfragmentationMechanical engineering and machineryTJ1-1570ENMechanical Engineering Journal, Vol 3, Iss 3, Pp 15-00595-15-00595 (2016)
institution	DOAJ
collection	DOAJ
language	EN
topic	sodium-cooled fast reactors core disruptive accidents in-vessel retention molten core material fragmentation Mechanical engineering and machinery TJ1-1570
spellingShingle	sodium-cooled fast reactors core disruptive accidents in-vessel retention molten core material fragmentation Mechanical engineering and machinery TJ1-1570 Ken-ichi MATSUBA Kenji KAMIYAMA Jun-ichi TOYOOKA Yoshiharu TOBITA Vladimir A. ZUYEV Alexander A. KOLODESHNIKOV Yuri S. VASSILIEV Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool
description	In a probable scenario for core disruptive accidents of Sodium-cooled Fast Reactors (SFRs), it is foreseen that molten core material would be discharged into lower sodium plenums through control rod guide tubes. Such material relocation might lead to a considerable thermal load on lower structures of the reactor vessels, while it has been suggested that in SFRs, as soon as the molten core material is discharged into coolant, it might be fragmented into smaller particles by fuel-coolant interactions and thus efficiently cooled in the reactor vessels. Hence, understanding of the fragmentation is crucial for achieving in-vessel retention of molten core material in SFRs. In this paper, based on the experimental results of a series of fragmentation tests, where around 10 kg of molten alumina (Al2O3) was discharged into a sodium pool (depth: 1.3 m, diameter: 0.4 m, temperature: 673 K) through a duct (inner diameter: 40mm to 63 mm) by using an experimental facility at National Nuclear Center of the Republic of Kazakhstan, dominant mechanisms for the fragmentation are discussed. In the present tests, mass median diameters of solidified Al2O3 particles were around 0.3 mm, which were comparable to the values predicted using conventional hydrodynamic-instability theories. However, even though the conventional theories predict that particle size becomes smaller with the increase of Weber number, such tendency was not observed in the present tests. Taking into account that in the present tests, the distances for fragmentation of molten Al2O3 were evaluated to be approximately 60 % to 70 % below the values predicted using an existing representative correlation which regards hydrodynamic instabilities as a dominant fragmentation mechanism, the observed independence on Weber number confirms a mechanism that before hydrodynamic instabilities sufficiently grow to induce fragmentation, thermal phenomena such as local coolant vaporization and resultant vapor expansion significantly accelerate fragmentation in SFRs.
format	article
author	Ken-ichi MATSUBA Kenji KAMIYAMA Jun-ichi TOYOOKA Yoshiharu TOBITA Vladimir A. ZUYEV Alexander A. KOLODESHNIKOV Yuri S. VASSILIEV
author_facet	Ken-ichi MATSUBA Kenji KAMIYAMA Jun-ichi TOYOOKA Yoshiharu TOBITA Vladimir A. ZUYEV Alexander A. KOLODESHNIKOV Yuri S. VASSILIEV
author_sort	Ken-ichi MATSUBA
title	Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool
title_short	Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool
title_full	Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool
title_fullStr	Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool
title_full_unstemmed	Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool
title_sort	experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool
publisher	The Japan Society of Mechanical Engineers
publishDate	2016
url	https://doaj.org/article/9877750203b441dda8153840459b7097
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Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool

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