| 摘要 |
The invention aims at improving the cooling in the upper part of a fuel assembly of a boiling water reactor during operation, thus reducing the risk of dryout. In a boiling water reactor, coolant flows upwardly through the fuel assembly and thereby changes from a single-phase state to a two-phase state. A fuel assembly comprises a top tie plate (3), bottom tie plate (4), a number of fuel rods (1) arranged in a bundle therebetween, and a number of spacers (2) to retain the bundle. The fuel assembly is divided in its axial direction into a plurality of fictitious first sub-lengths (L1) which correspond to the distance between two spacers arranged one after the other in the lower part of the fuel assembly. Two first sub-lengths adjoining each other constitute a second sub-length (L1+L1). In at least one second sub-length, which at least for the most part is located in the upper part of the fuel assembly, two spacers (S22,S23) are arranged in such a way that they divide said second sub-length into three essentially equally long third sub-lengths (L2). <IMAGE> |
