| 摘要 |
<p>A fuel assembly includes a bottom nozzle (4) set on a lower core plate of a nuclear reactor, a top nozzle (3) with a hold down spring (9) to urge the bottom nozzle (4) against the lower core plate, guide thimbles (2) which guide control rods, having passed through the top nozzle (3), toward the lower core plate, a dashpot (20) formed on each of the guide thimbles (2) to reduce the fall velocity of a corresponding one of the control rods, a thimble screw (14) which connects each of the guide thimbles (2) to the bottom nozzle (4), and a drain hole (15) formed to extend through each of the thimble screw (14). The dashpot (20) has a large-diameter portion, at a lower portion thereof, with substantially the same diameter as that of each of the guide thimbles (2). The diameter d of the drain hole (15) falls within a range of 0.04D < d < 0.08D where D is an inner diameter of the large-diameter portion.</p> |
