Validation of Fuel-Coolant Interaction Model for Severe Accident Simulations

Table 1

Description of FCI phenomena.

No	Phenomena	Description
(1)	Melt jet breakup	The core melt flows into the water in the form of jets and is progressively transformed into droplets (in a range from a few millimeters to centimeters) which are dispersed into the two-phase coolant. The interfacial melt-water area is determined by diameter and quantity of melt droplets.
(2)	Mixing of melt droplets with water	Dynamics of this process influences on amount of the water involved in FCI.
(3)	Steam production	Interaction of the high-temperature molten corium (~2500–3000 K) with water leads to the production of huge amount of steam. The steam is injected in the containment and increases pressure. The amount of the produced steam is determined by the heat transfer rate, which, in turn, is dependent on the interfacial melt-water area, melt-water temperature difference, and heat transfer mode (film boiling, convective heat transfer, etc.).
(4)	Hydrogen generation	Corium can contain metallic components (zirconium, steel), its oxidation leads to hydrogen generation. Also hydrogen generation was observed in the FARO test with interaction of the water and uranium-zirconium oxides mixture (without metallic).
(5)	Corium quenching	Due to interaction with cold water (~450–550 K), corium is quenched. The dynamics of this process is determined by heat transfer rate between corium and steam-water mixture.