Abstract: A stud tensioner for tensioning the upright studs which secure the head to a reactor pressure vessel is suspended by a motor operated hoist from a motor operated trolley mounted on a circular rail supported above the studs. A single operator operates the motor operated hoist and motor operated trolley, and manually radially fine aligns the stud tensioner for engagement with a stud through a control handlebar. A pair of side-by-side switches adjacent a first hand grip at one end of the handlebar enable the operator to operate the trolley to move the stud tensioner left or right, while vertically aligned switches adjacent a second hand grip at the other end of the handlebar are used to operate the hoist to raise and lower the stud tensioner. Simultaneously, the operator can radially maneuver the stud tensioner by applying force through the handlebar. An adjustable mount allows the handlebar to be rotated about a horizontal pivot axis and locked into a selected angular position relative to the tensioner.

Abstract: An improved robotic arm system for servicing the tubesheet located within the channel head of a nuclear steam generator is provided. The system includes a robotic arm whose shoulder and elbow joints are rotatable only in the plane parallel to the tubesheet in order to eliminate the imposition of cantileverly-induced torques on the electric motors driving these joints, as well as to minimize the possibility of mechanical interference between the arm and the walls of the channel head. Each of the motorized joint assemblies of the arm includes resolvers connected not only to the output of the drive train that moves the joint, but also to the drive shaft of the electric motor that drives the drive train, wherein the feedback signal generated by the resolver connected to the drive shaft of the electric motor is the primary signal used to modulate the amount of electric power conducted to the motor of the joint. Such a configuration advantageously results in smoother robotic arm movement.