Development of an underwater remote manipulator system for use in TMI-2 [Three Mile Island Unit 2] reactor defueling

Defueling operations in the original core region of the Three Mile Island Unit 2 (TMI-2) reactor vessel were conducted with long-handled tools that were manually positioned by operators on a rotating work platform over the reactor vessel. The difficulties encountered with these operations led GPU Nuclear Corporation (GPU) to consider other means of operation when defueling the core support assembly and reactor vessel lower head, which is ∼12 m (40 ft) below the work platform. GPU determined a heavy-duty remote manipulator system could be an effective alternative. The MANFRED (MANipulators For REactor Defueling) system was thus developed for this purpose by Ocean Systems Engineering and International Submarine Engineering under contract to GPU. The paper includes a description of MANFRED present status, and lessons learned