Calculations of the reflooding phase during a loss-of-coolant accident (LOCA) have been performed for two homogeneous advanced pressurized water reactors (APWRs) with a wide [pitch-to-diameter (p/d) ratio = 1.2] and a tighter (p/d = 1.123) fuel rod lattice as well as for a reference 1300-MW(electric) pressurized water reactor (PWR). The FLUT computer code, developed by the Gesellschaft für Reaktorsicherheit in Garching for the reflooding phase of a PWR, has been improved: A new criterion for the determination of the onset of the upper quench front and a new water droplet model for the dispersed flow film boiling have been introduced in the code, as well as new friction factor correlations more suitable for the core geometry of an APWR. Finally, the interfacial drag coefficients between steam and water are not independent of the geometry as in FLUT, but rather the flow channel geometry is taken into account. The new version of the code (FLUT-FDWR) has been tested on the base of various reflooding experiments in PWR (FLECHT, FEBA, SEFLEX) as well as APWR (FLORESTAN) core geometries. In all the cases investigated, the FLUT-FDWR predictions are relatively good and generally better than with the original FLUT version. The reactor calculations with FLUT-FDWR indicate that the maximum cladding temperatures in the APWRs during the reflooding phase are lower than those for the PWR. This is due to the lower temperatures for the APWRs at the beginning of the reflooding phase and to the higher isostatic water pressure above the APWR cores, which are shorter and therefore placed in a lower position inside the reactor pressure vessel. The cladding temperatures calculated for the PWR and the two APWRs are quite acceptable and considerably lower than those calculated during the blowdown phase of the LOCA.