| 摘要 |
A fuel assembly for a boiling water reactor comprises a plurality of rods (5) arranged in parallel with one another, a plurality of spacers (81, 8b) arranged at separate levels in the fuel assembly and a fuel channel (2). A coolant flows upwards through the fuel assembly and in so doing, changes from a single-phase state to a two-phase state. The fuel assembly may, in the axial direction, be divided into an upper two-phase part (13b) where, during normal operation, bulk boiling prevails, and a lower two-phase part (12b) where, during normal operation, subcooled boiling prevails. The invention is characterized in that at least two of the spacers (8a) in the lower two-phase part have a mutual distance which is smaller than the mean value of the distances between all the spacers in the entire fuel assembly. |
