A model for particle bed dryout based on the phenomenon of flooding is developed for particles greater than ∼1 mm in diameter. Dryout develops when vapor flow from boiling in the bed limits the influx of replenishing coolant. In the flooding model, the liquid-vapor counterflow is limited by the drag between the liquid and the vapor. In previous models, the counterflow is limited by the drag between the coolant and the bed particles. The flooding model predicts a dryout heat flux that depends on the square root of the diameter of the particles. Previous dryout models predict a dependence on the square of the diameter. The flooding model predicts significantly lower dryout heat fluxes for particle diameters in excess of ∼1 mm. These predictions agree well with experimental data.