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Molten Oxidic Particle Fracture during Quenching in Water
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.ORCID iD: 0000-0002-0683-9136
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
2010 (English)In: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings, 2010, P2.32- p.Conference paper (Refereed)
Abstract [en]

Present work is motivated by the observations of debris particles morphology obtained as a result of quenching of high temperature molten oxidic jet in a subcooled water pool. Insights gained from the Debris Bed Formation (DEFOR) experiments (Kudinov et al., 2010) paved way to suggestions that melt fragmentation and the resulting particle morphology are largely influenced by (i) melt droplet instability and breakup; (ii) melt cooling and solidification; (iii) cavity formation; and (iv) solid particle fracture. Analysis of the DEFOR results suggests that there is a strong influence of water subcooling on the debris morphology. Particles are round-shape if subcooling of water is less than 50°C, and, at subcooling higher than 80°C, most of the particles are fractured rock-like with sharp edges. In present work we are considering the following hypothesis which can explain an apparent strong influence of moderate changes in temperature of water on morphology of the debris particle: rapid increase of heat flux during transition from film to nucleate boiling can cause solid particle fracture due to thermal stress. To verify the hypothesis we perform transient heat transfer and thermo-elastic stress analysis for a melt droplet instantaneously immersed into water coolant. We are also examining competition between hydrodynamic fragmentation and freezing at transient boiling heat transfer to identify conditions at which characteristic time scales are competitive. In the paper we demonstrate that rapid change in transient boiling heat flux (which is highly sensitive to water subcooling) can cause fracture of the particle. As well there is an effect of competition between freezing and hydrodynamic fragmentation at high subcooling of water. By parametric study we develop a “map” of the debris morphology. The map defines whether or not the particle will be fractured taking into account intrinsic uncertainty in the transition boiling characteristics and particle material properties. The map appears to be in a good agreement with the experimental observations.

Place, publisher, year, edition, pages
2010. P2.32- p.
Keyword [en]
oxidic melt, fragmentation, quenching, transient boiling, thermal-stress, fracture, debris formation
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-53628OAI: diva2:470493
7th International Conference on Multiphase Flow ICMF 2010 Tampa FL May 30 June 4 2010
QC 20120120Available from: 2011-12-29 Created: 2011-12-29 Last updated: 2012-01-20Bibliographically approved

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