Title: Importance of natural convection to in-vessel melt coolability
Abstract: In the event of a core meltdown accident, one of the accident progression paths is fuel relocation to the lower reactor plenum. In the heavy water new production reactor (NPR-HWR) design, the reactor cavity is flooded with water. In such a design, decay heat removal to the water in the reactor cavity and thence to the containment may be adequate to keep the reactor vessel temperature below failure limits. If this is the case, the accident progression can be arrested by retaining a coolable corium configuration in the lower reactor plenum. The strategy of reactor cavity flooding to prevent reactor vessel failure from molten corium relocation to the reactor vessel lower head has also been considered for commercial pressurized water reactors. From the molten corium, heat is transferred to the lower reactor vessel head by conduction and natural convection. Heat removal from the outer surface of the vessel wall, by convection and water boiling in the reactor cavity, cools down the molten corium in the vicinity of the wall. The density differences between the hot corium away from the wall and the colder corium layers close to the wall generate the driving force for natural convection. An additional mode ofmore » heat removal is thermal radiation from the top of the corium to its colder environment. The objective of this paper was to evaluate the significance of natural convection for heat removal from the molten corium to the water in the reactor cavity.« less
Publication Year: 1992
Publication Date: 1992-01-01
Language: en
Type: article
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