Spacer associated pressure drop in a boiling water reactor bundle having part length rods

摘要

In a fuel bundle (40) for use in the core of a boiling water nuclear reactor, part length rods (p) having a tendency to reduce pressure drop are used in combination with spacers (S1-S8) and spacer attached devices tending to restore pressure drop to improve critical power. The addition of the part length rods has the advantage of lowering the pressure drop. Additional spacers or spacers attached devices substantially recapture the pressure drop. Exemplary spacer attached mechanisms for the recapture of pressure drop are set forth including vanes - preferably swirl vanes on the spacers, decreasing the spacer pitch to increase the total number of spacers in the upper two phase region of the fuel bundle, increasing the vertical height of the spacers, and increasing the thickness of the metal from which the spacers are constructed.