Abstract: An absorber cluster for a nuclear reactor includes at least a first absorber assembly and a second absorber assembly. Each absorber assembly respectively comprises neutron absorbing elements. Absorber elements of each of the first absorber assembly and the second absorber assembly are made from the same material or the same combination of materials selected from the group of neutron absorbing materials consisting of a first europium hafnate, a second europium hafnate, a first samarium hafnate, a second samarium hafnate, hafnium carbide, and samarium hexaboride. The first europium hafnate and the second europium hafnate have different compositions. The first samarium hafnate and the second samarium hafnate have different compositions. The absorber elements of the first absorber assembly have a cross-sectional structure different to that of the absorber elements of the second absorber assembly.

Abstract: An absorber cluster for a nuclear reactor includes at least a first absorber assembly (22) and a second absorber assembly (24). Each absorber assembly respectively comprises neutron absorbing elements (20). Absorber elements (20) of each of the first absorber assembly (22) and the second absorber assembly (24) are made from the same material or the same combination of materials selected from the group of neutron absorbing materials consisting of a first europium hafnate, a second europium hafnate, a first samarium hafnate, a second samarium hafnate, hafnium carbide and samarium hexaboride. The absorber elements (20) of the first absorber assembly (22) have a cross-sectional structure different to that of the absorber elements (20) of the second absorber assembly (24).

Abstract: This fuel assembly for a pressurized water nuclear reactor comprises fuel rods which are arranged at the nodes of a substantially regular network which has a polygonal outer contour, the fuel rods containing uranium which is enriched in isotope 235 and not containing any plutonium before the assembly is used in a reactor. The rods are distributed in at least a first central group which is constituted by fuel rods which have a first level of nuclear reactivity, and an outer peripheral layer of fuel rods which have a level/levels of nuclear reactivity which is/are strictly less than the first level of reactivity.

Abstract: This fuel assembly (3) for a pressurised water nuclear reactor comprises fuel rods which are arranged at the nodes of a substantially regular network which has a polygonal outer contour, the fuel rods containing uranium which is enriched in isotope 235 and not containing any plutonium before the assembly is used in a reactor. The rods are distributed in at least: a first central group which is constituted by fuel rods which have a first level of nuclear reactivity, and an outer peripheral layer (13) of fuel rods which have a level/levels of nuclear reactivity which is/are strictly less than the first level of reactivity.