Examination of Relocated Fuel Debris Adjacent to the Lower Head of the TMI-2 Reactor Vessel

摘要

As part of the Three Mile Island Unit 2 (TMI-2) Vessel Investigation Project, funded by the Organization for Economic Cooperation and Development, physical, metallurgical, and radiochemical examinations were performed on samples of previously molten material that had relocated to the lower plenum of the TMI-2 reactor during the accident of 28 March 1979. The report presents the results of those examinations and some limited analysis of these results as required for the interpretation of the data. Principal conclusions of the examinations are that the bulk lower head debris is homogeneous and composed primarily of (U,Zr)O2. The molten material reached temperatures greater than 2,600 C and probably reached the lower head as a liquid or slurry at temperatures below the peak temperature. A debris bed was formed, which was composed of particulate debris above a monolithic melt that solidified on the lower head.