Abstract
When nuclear reactor accidents such as steam generator pipe ruptures or core melting occur, radioactive aerosols will remain in the liquid pools. Bubbles may be generated by boiling or gas injection. Film droplets produced by bubble bursts may entrain radioactive aerosols from the liquid to the air. This long-lasting behavior can produce a considerable amount of aerosols. To evaluate radioactive source terms, many physical quantities related to bubble bursting need to be determined, such as bubble burst position, bubble lifetime, cap film roll-up velocity, and cap film thickness, which are very important parameters that influence the releasing of radioactive aerosols. In this research, the phenomenon of bubble bursting was investigated by visualization. The above parameters were measured. We obtained the lifetime distribution of bubbles under different conditions, and we found that the addition of an aerosol increased the lifetime of the bubbles. By comparing the bubble lifetime to the roll-up velocity and cap thickness, we showed that the increase of the liquid temperature thickened the cap at rupture and the increase of the air temperature thinned the cap. The addition of an aerosol increased the film roll-up velocity.
Highlights
Bubbles exist widely in industrial and environmental processes
For the aspect of nuclear power, the research of bubble bursting behavior mainly focuses on the entrainment phenomenon in a steam generator, i.e., gas-water separation [6] and radioactive aerosol release in a severe reactor accident [7]
When fuel cladding meltdown occurs in a reactor, a large number of fission products are released from the molten fuel, of which aerosol is more important
Summary
Bubbles exist widely in industrial and environmental processes. Bubbles burst after reaching a free surface for a period of time. e resulting droplets, as part of a key liquid-gas conversion process, have a wide range of impacts on our daily lives [1]. E bubbles will rise to the free surface, and droplets generated from the rupture of bubbles may entrain the aerosol in a liquid pool into the air [9]. E cap film thickness was measured with white light interference technology to study the effect of surfactants on the bubble drainage and rupturing [17]. E influence of the gas and liquid temperatures and the working fluid is not yet clear, especially in terms of the corresponding relationship between the bubble lifetime and the cap film thickness for different conditions. In liquid-phase working fluids where surface tension is difficult to measure, the application of the film roll-up velocity to characterize bubble behavior needs further research. E experiment conditions were changed (bubble radius, liquid temperature, and air temperature) to measure and calculate the bubble lifetime, cap film roll-up velocity, and cap thickness. Aerosol particles were added to the bulk to explore its influence on the experimental results
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