Reduced number of PCI-protected fuel rods in a reactor core

摘要

The invention relates to a fuel assembly for a boiling water reactor in which the number of fuel rod positions is greater than 80, and to a fuel assembly for a boiling water reactor in which the number of fuel rod positions is smaller than 65, and to a fuel assembly for a pressurized-water reactor. A fuel assembly comprises a plurality of fuel rods each of which comprises a nuclear fuel surrounded by a cladding tube. The fuel assembly is located adjacent to one or more control rod positions (10). To protect a fuel rod against PCI damage, the inside of the cladding tube is provided with a protective layer of metal. Only fuel rods (7a) in especially exposed positions near a control rod position are provided with cladding protection. The other fuel rods (7b) have no cladding protection. The invention also relates to a core for a boiling water reactor and a pressurized-water reactor in which all the fuel assemblies, which either contain or are arranged adjacent to a control rod which during normal operation at some time is inserted into the core, comprise fuel rods with said protective layer. The total number of fuel assemblies in the entire core with said protective layer is smaller than 1.2 x C x M, where C is the average number of operating cycles during which a fuel assembly is allowed to sit in the core, and M is the number of fuel assemblies which either contain or are arranged adjacent to a control rod which during normal operation at some time is inserted into the core.