Part length rod fuel assembly with steam-water separator for boiling water reactor

The nuclear fuel bundle (B) includes a lower tie plate (L), an upper tie plate (U) and an array of side-by-side fuel rods (F). A channel (C) between the tie plates (L)(U) surrounds the fuel rod (F) array and confines a flow of water between the tie plates (L),(U). At least one of the fuel rods (F) in the fuel bundle (B) extends less than the full length from the lower tie plate to the upper tie plate, so that a volume (14) is defined overlying the end of the part length rods (P). The separation devices (D) is placed in the volume (14) overlying the end of the partial length fuel rods (P) entering the volume (14) overlying the part length fuel rod. The concentration of steam in the vent volume overlying the part length rods (P) and a high liquid fraction residing in the surrounding full length rods (F) results.