Abstract: A method and tool (40) for replacing jet pump holddown beams (17) in a nuclear reactor is disclosed. The tool (40) has an inner frame (41) and an outer frame (28). Each frame defines two spaced plates (33 and 30, respectively). Each inner and outer plate has a jaw (34, and 31, respectively), defined therein. The frames (41, 23) are movably nested such that the jaws (34, 31) of adjacent inner (33) and outer (30) plates form two pairs of opposed jaws (31, 34) each sized and positioned to receive and hold one of two protruding members (20) of the holddown beam (17) such that the beam (17) is suspended between the pairs of opposed jaws (31, 34). In removing a beam (17), the beam (17) is first unlocked, then its protruding members (20) are captured by the tool's (40) pairs of opposed jaws (31, 34), and finally the beam (17 ) is disengaged from its keeper (26). In installing a beam (17), this procedure is substantially reversed, care being taken to position the beam (17) properly for engagement of the keeper (26).