Lower core support assembly defueling plans and tools

Prior to February 1985 it was the accepted technical opinion that little or no fuel melting had occurred in the TMI-2 core during the accident of March 28, 1979. However, at this time a camera was inserted between the core support cylinder and the reactor vessel wall. This camera was inserted into the vessel down to the vicinity of the lower head. Large rough pieces of corium were observed. The largest of which was approximately 8 inches across. Most of the lower head of the reactor vessel appeared full of rubble. This observation demonstrated that the material in the reactor vessel lower head did not pass through the steam generators with the reactor coolant water and deposit in the lower head due to passing through a region of low velocity. Instead, the rubble material in the lower head would have to have come directly from the core region above the lower head and the most likely transport method was that the core had melted and the core material flowed to its present resting place. Core melting and its impact on the reactor vessel lower internals and the reactor lower head must therefore be seriously considered. In order to defuel in lower head and remove large solidified pieces of corium a large hole would have to be made through the lower core support assembly (LCSA) to provide access to the lower head. This report describes the cutting planning, the cutting tools, the defueling tools and the methods of disposition of the cut pieces