Control rod for nuclear reactor

A wing for a control rod comprises long lifetime neutron absorbers, for example, an alloy comprising hafnium diluted with a diluent, in which the dilution concentration can be varied for a plurality of regions and neutron absorbers such as boron carbide are filled in containing apertures. More specifically, the wing comprises a plurality of wing members each of different hafnium content and structured such that the alloy material of different hafnium content can be disposed properly depending on the distribution of the neutron radiation dose and the degree of reactivity worth required. (S.T.)