Patent Number: 051695936
Section: abstract

A low-headroom tower is pivotably mounted to a trunnion cart that runs on rails in a slot in a work platform located in the sub-pile room of a reactor containment. An elevator in the tower raises an extension piece into contact with the bottom of a control rod drive. A detorquing guide is rotationally positioned to coincide with bolts holding the control rod drive in place. The elevator places an upward force on the control rod drive during detorquing of the bolts. This provides reaction torque to aid in bolt loosening and prevents leakage of contaminated effluent past the seal. A detorquing tool is fitted into the detorquing guide and is spring loaded to engage a selected bolt securing the control rod drive. An indexing device provides alignment for the detorquing tool with each succeeding bolt. The elevator is lowered until the bottom end of the control rod drive enters the tower. The load is transferred from the extension piece directly to the elevator. Lowering continues until the top end of the control rod drive emerges from the reactor vessel. Normally retracted rear wheels are attached to the tower. A winch rotates the tower to the horizontal position, and the rear wheels are extended to engage with the rails to permit rolling horizontal movement of the tower.