Performance of the Automated Cutting Equipment System During the Plasma Cutting of the Three Mile Island Unit 2 Lower Core Support Assembly

The lower core support assembly (LCSA) of the Three Mile Island Unit 2 reactor was not structurally damaged during the accident. In order to permit defueling of that region of the core, the LCSA was cut to permit access. A five-axis teleoperator was developed to deliver plasma cutting, rotary grinding, and abrasive water-jetting end effectors to the LCSA. In addition, the automated cutting equipment system (ACES) manipulator and plasma system were used for vertical sectioning of the baffle plates. The ACES and the end effectors were designed, fabricated, tested, and implemented in the field by PCI Energy Services. Complex geometry sectioning was completed in a mock-up facility at chemistry and pressure conditions simulating those of the vessel, prior to actual in-vessel operations. In-vessel activities began in early May of 1988 and were completed on April 11, 1989.