Disassembly and Defueling of the Three Mile Island Unit 2 Upper Core Support Assembly

When the Three Mile Island Unit 2 core failed, molten core material melted through the peripheral region of the core support structure and flowed outside the normal confines of the core region into a normally inaccessible area behind the baffle plates. This molten core material flowed completely around the circumference of the core region and down into the lower head of the reactor vessel. As a result of this material relocation, a significant portion of the core support assembly must be disassembled to recover this material.