Coolability of a Corium Pool in a Debris Bed -Impact of Debris Size, Steam and Liquid Flowrate, Tilting Angle and Pressure on Critical Heat Flux (CHF)
Résumé
In case of severe accident in a light water reactor, a debris bed may form in the core and possibly melt, as it happened in TMI-2. Knowledge about the coolability of such molten pool surrounded by debris is crucial to investigate the possibility of stabilizing a part of the fuel inside the vessel. In particular, it is of primary interest to determine the maximum size of a molten pool surrounded by debris which may be stabilized under water. The maximum heat flux (CHF) that may be extracted from the pool boundary by water flowing within the debris bed is a key parameter. A facility was built at IRSN to determine the CHF under various conditions. A heated copper surface simulates the boundary of the pool and is placed in contact with a debris bed (monodisperse steel balls), under water. In this article, we first complete previous work on steam flowrate impact and we show the slight impact of liquid flowrate. We then illustrate the influence of the ball diameter and we compare to the situation of pool-boiling without any debris near the heated plate. All those tests are made for different tilting angles of the plate. In a last part, we study the impact of pressure with an extra pressure level of 1.5 bar abs. As a conclusion of this work and of results previously published, a general CHF correlation depending on the tilting angle and the steam flowrate is derived. An example of the use of this correlation to evaluate the maximum mass of corium pool that can be stabilized under water is given, for some typical reactor conditions.
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Licence : CC BY NC ND - Paternité - Pas d'utilisation commerciale - Pas de modification
Licence : CC BY NC ND - Paternité - Pas d'utilisation commerciale - Pas de modification