Abstract: The present invention provides a locking assembly for locking in place an upper support plate above a nuclear fuel bundle. The locking assembly includes several different components, including one rotatable member that is movable between a first position for locking the support plate in place and an unlocked position for releasing the support plate so that it can be removed from the guide tubes in the fuel bundle assembly. The rotatable member is resiliently maintained at its locked and released positions, and the entire locking assembly is an integral unit without any loose parts regardless of the position of the rotatable member.