Patent ID: 6674831
Filing Date: 2004-01-06
Classification: G21C,Y02E

Abstract:
A fuel assembly comprising:a bottom nozzle set on a lower core plate of a nuclear reactor; a top nozzle with a hold down spring to urge said bottom nozzle against the lower core plate; a plurality of control rod guide tubes which guide control rods, having passed through said top nozzle, toward the lower core plate; a plurality of grids mounted on said control rod guide tubes; a plurality of fuel rods held by said grids to be substantially parallel to said control rod guide tubes; a thin tube-like dashpot formed on each of said control rod guide tubes to reduce a fall velocity of a corresponding one of the control rods; a thimble screw which connects each of said control rod guide tubes to said bottom nozzle; and a drain hole formed to extend through said thimble screw, wherein said dashpot has a large-diameter portion, at a lower portion thereof, with substantially the same diameter as that of each of said control rod guide tubes, and a diameter d of said drain hole falls within a range of 0.04 D