Patent Number: 050193252
Section: abstract

A method for removing and installing a control rod drive from a drive housing mounted in the vessel of a boiling water reactor. The method comprises having a carriage supported by and movable along the service rails normally present in the undervessel cavity, and a cradle pivotally connected to the carriage and having a length substantially less than the length of a control rod drive. The pivot point between the cradle and the carriage is chosen such that the length of the carriage is subsumed within the length of the cradle when the cradle is pivoted into a horizontal position. The pivoting movement is accomplished by means of a hydraulic cylinder connected between the upwardly swinging end of the cradle. The carriage includes a lifting and lowering mechanism formed by the combination of a leadscrew drive and a hydraulic cylinder. The hydraulic cylinder is connected to the cradle so that it is movable between a recess within the cradle when not in use, to a position directly beneath and in tandem with the control rod drive when in use. The lifting and lowering mechanism can move a control rod drive an installed position within a drive housing without the need for installation of special end effectors or other components.