Abstract: The present invention concerns a fuel assembly for a nuclear power boiling water reactor. The fuel assembly comprises fuel rods. At least 95% of the fuel rods comprise nuclear fuel material in the form of U enriched in 235U. At least 20% of the fuel rods belong to a first set of fuel rods. The fuel rods in this first set comprise both U enriched in 235U and Th. The first set comprises a first and a second subset of fuel rods. The ratio, with regard to weight, between Th and U, in each fuel rod of said first subset, is higher than the ratio, with regard to weight, between Th and U, in each fuel rod of said second subset. The invention also concerns a nuclear power boiling water reactor and a manner of operating such a reactor.

Abstract: The present invention concerns a fuel assembly for a nuclear power boiling water reactor. The fuel assembly comprises fuel rods. At least 95% of the fuel rods comprise nuclear fuel material in the form of U enriched in 235U. At least 20% of the fuel rods belong to a first set of fuel rods. The fuel rods in this first set comprise both U enriched in 235U and Th. The first set comprises a first and a second subset of fuel rods. The ratio, with regard to weight, between Th and U, in each fuel rod of said first subset, is higher than the ratio, with regard to weight, between Th and U, in each fuel rod of said second subset. The invention also concerns a nuclear power boiling water reactor and a manner of operating such a reactor.

Abstract: A fuel assembly for a nuclear reactor includes a bundle of fuel rods with a first group of fuel rods and a second group of fuel rods. Each fuel rod includes a cladding tube and stack of fuel pellets enclosed within the cladding tube. At least a main portion of the fuel stack includes a fissile nuclear material comprising Plutonium and Thorium, and is arranged with an axial hole. Said main portion of the fuel stack of each fuel rod of the first group includes a first axial hole constituting a first volume and said main portion of the fuel stack of each fuel rod of the second group includes a second axial hole constituting a second volume. The first volume and the second volume are different.