Multiple tubes (50, 52) are connected to steam supply and spent cooling steam return manifolds (42, 40) for supplying cooling steam to buckets and returning spent cooling steam from the buckets to the manifolds, respectively. The tubes are prevented from axial movement in one direction by flanges (62, 76) engaging end faces of the spacer (20) between the first and second-stage wheels (12, 14). Retention sleeves (86, 94) are disposed about cantilevered ends of the tubes. One end of the retention sleeve engages an enlarged flange on the tube, while an opposite end (90, 96) is spaced axially from an end face (89, 97) of the adjoining wheel, forming a gap ( a , b ), enabling thermal expansion of the tubes and limiting axial displacement of the tube in the opposite direction.