Patent Number: 
Section: claims

1. A fuel assembly for a pressurized water reactor, the fuel assembly comprising:upper and lower adjoining regions as a whole extending over the entire fuel assembly;a plurality of mutually axially separated spacers disposed in said upper region and a plurality of mutually axially separated spacers disposed in said lower region;a multiplicity of fuel rods extended in a longitudinal direction and guided in said spacers; andeach of said spacers of said upper region having a lower flow resistance in a transverse direction perpendicular to said longitudinal direction than each of said spacers of said lower region. 2. The fuel assembly according to claim 1, wherein said spacers have a lateral edge formed by edge webs, and said edge webs of said spacers of said upper region cover a smaller area than said edge webs of said spacers of said lower region, in said transverse direction. 3. The fuel assembly according to claim 2, wherein said spacers include a plurality of intersecting inner webs, and said inner webs of said spacers of said upper region cover a smaller area than said inner webs of said spacers of said lower region, in said transverse direction. 4. The fuel assembly according to claim 2, wherein only said spacers of said upper region have openings formed in said edge webs. 5. The fuel assembly according to claim 3, wherein only said spacers of said upper region have openings formed in said edge webs. 6. The fuel assembly according to claim 2, wherein said edge webs of all of said spacers have openings formed therein, and a total area of said openings in said edge webs of said spacers of said upper region is larger than a total area of said openings in said edge webs of said spacers of said lower region. 7. The fuel assembly according to claim 3, wherein said edge webs of all of said spacers have openings formed therein, and a total area of said openings in said edge webs of said spacers of said upper region is larger than a total area of said openings in said edge webs of said spacers of said lower region. 8. The fuel assembly according to claim 3, wherein only said spacers of said upper region have openings formed in said inner webs. 9. The fuel assembly according to claim 5, wherein only said spacers of said upper region have openings formed in said inner webs. 10. The fuel assembly according to claim 7, wherein only said spacers of said upper region have openings formed in said inner webs. 11. The fuel assembly according to claim 2, wherein said spacers have inner webs, and only said spacers of said upper region have openings formed in said inner webs. 12. The fuel assembly according to claim 4, wherein wherein said spacers have inner webs, and only said spacers of said upper region have openings formed in said inner webs. 13. The fuel assembly according to claim 6, wherein wherein said spacers have inner webs, and only said spacers of said upper region have openings formed in said inner webs. 14. The fuel assembly according to claim 3, wherein said inner webs of all of said spacers have openings formed therein, and a total area of said openings in said inner webs of said spacers of said upper region is larger than a total area of said openings in said inner webs of said spacers of said lower region. 15. The fuel assembly according to claim 5, wherein said inner webs of all of said spacers have openings formed therein, and a total area of said openings in said inner webs of said spacers of said upper region is larger than a total area of said openings in said inner webs of said spacers of said lower region. 16. The fuel assembly according to claim 7, wherein said inner webs of all of said spacers have openings formed therein, and a total area of said openings in said inner webs of said spacers of said upper region is larger than a total area of said openings in said inner webs of said spacers of said lower region. 17. The fuel assembly according to claim 8, wherein said inner webs of all of said spacers have openings formed therein, and a total area of said openings in said inner webs of said spacers of said upper region is larger than a total area of said openings in said inner webs of said spacers of said lower region.