Nuclear reactor control rod with uniformly changeable axial worth

A control rod is described for use in a nuclear reactor core to provide xenon compensation, comprising: (a) an elongated inner cylindrical member having a lower end; and (b) an elongated outer cylindrical member surrounding the inner member and having a lower end with concentrically-arranged inner and outer edge portions defined thereon; (c) each of the members being composed of alternating poison and nonpoison regions; (d) the inner member being axially movable relative to the outer member to adjust the degree to which the poison regions of the members overlap with the nonpoison regions thereof and thereby change the overall worth of the rod; and (e) the lower end of the inner member having defined thereon a radially outwardly projecting ledge for supporting in a rest relationship thereon the lower end of the outer member at only its inner edge portion for retaining the outer member about the inner member