Dismantling the Damaged Three Mile Island Reactor Vessel by Remote Plasma Arc Cutting

The use of remote robotic equipment has proven invaluable in the task of removing the fuel from Germany Public Utility’s damaged Three Mile Island Unit 2 reactor. The March 28, 1979 accident at Three Mile Island redistributed an estimated 300,000 pounds of core debris throughout all regions of the reactor vessel. Portions of the debris accumulated in areas that are inaccessible without major demolition efforts. The final stage of fuel removal requires gaining access to the regions below the lower core support assembly and behind the baffle plates where an estimated 67,000 pounds of fuel debris is trapped. The Automated Cutting Equipment System (ACES), a robotic manipulator controlled plasma arc cutting system, was developed to cut through the five plates comprising the lower core support assembly as well as the baffle plates, creating a passage to the fuel debris entrapped in these areas. This paper will provide a through description of the ACES system and its major components, as well as address the design challenges that had to be met to perform the designated task.