Two-phase dispersed-flow regimes have often been hypothesized for the disassembly analysis of hypothetical core disruptive accidents in fast reactors. The influence of particulate phase size on the power transient is examined. In general it is observed that the bigger the particle size the larger the energy release during the disassembly phase. The dependence of the power transient on the particle size itself depends on the drag force expression. The Stokes term and form factor of the drag force try to enforce a somewhat different particle size dependence. A flatter flux distribution decreases this dependence significantly. The choice of the equation of state also affects this dependence.