Analytical study of coolability of ex-vessel debris beds with downcomer(s)

Previous experiments have shown that the dryout heat flux of debris beds can be significantly enhanced by providing the debris bed with coolant through downcomer(s) embedded within:the bed. In this paper a simple model has been developed for the thermal hydraulics of a debris bed-with downcomer(s). It is shown that the enhancement of the dryout heat flux by using:downcomer(s) is affected by the particle size, bed height and porosity. The present model is compared with the available data, and good agreement is achieved. However more data are needed to validate the present model.