A physical model of formation of thin-wall hollow solid particles in melt-coolant interaction is developed. Such bubble-like solid particles have been observed in the laboratory experiments with some oxide melts and water as a coolant. The considered range of the problem parameters corresponds to interaction of the core melt with water pool in hypothetical severe accident in some industrial nuclear reactors. The calculations showed that only very small corium droplets of diameter less than 1-2 mm can produce "solid bubbles" and it depends on initial overheating of the melt. The results obtained are in qualitative agreement with recently reported laboratory observations. (C) 2008 Elsevier Ltd. All rights reserved.