URSULA: Design of an Underwater Robot for Nuclear Reactor Vessel Inspection

Abstract

This paper describes the development of an underwater robotic system that will be used to perform ultrasonic inspections of nuclear reactor vessel weldments. The development effort consists of problem definition, various levels of conceptual design, evolving a final concept, and detailed design. The final concept, now under construction, is a six degree-of-freedom manipulator attached to a moveable base. Suction cups hold the manipulator base to the vessel wall while the arm generates precise scanning paths on the curved vessel surfaces. After completing a scanning area, a suction tool holds the manipulator end-effector to the vessel wall while the base is moved to a new scanning position. This concept minimizes the system complexity by using the same joints for global locomotion as are required for tool scanning. Other important issues such as global positioning, detailed design and the operation plan are also discussed.