Set of fuel rods for nuclear reactors

A bar multiple segments of a fuel bundle of a nuclear reactor, comprising bar multiple segments: a plurality of rod segments (110), the bar segments removably coupled to one another being via coupling structures (300) in an axial direction; a target irradiation (620) disposed within at least one of the bar segments; and at least a portion of at least one coupling structure includes one or more neutron absorbing materials; characterized in that: the one or more neutron absorbing material includes a same material as the target of irradiation.