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Samples taken from the melted core of the Three Mile Island Unit 2 (TMI-2) reactor have been investigated as part of a co-ordinated accident evaluation programme. Samples included fuel rod segments, cladding, melted core rocks and debris from the reactor. Gamma spectroscopy of the core rocks indicated that volatile fission products such as 137Cs, 106Ru and 154Eu were still present (no 129I or noble gases were detected), despite the high temperatures experienced. Examination of the appropriate phase diagrams suggests temperatures for the molten core ranging from 1900 C minimum to 2600 C for substantial periods. Outer crust or agglomerate specimens were far more heterogeneous in structure and indicated lower temperatures of about 1400 C and shorter excursion times at the edge of the melted area. Fuel rod segments removed from the reactor pile's outer limits showed very little damage and showed how severe overheating was largely localised in the centre of the pile.

Additional information

Authors: BOTTOMLEY P D W, JRC Karlsruhe (DE);COQUERELLE M, JRC Karlsruhe (DE)
Bibliographic Reference: Paper presented: Conference of the Technical Committee on Reactor Materials Behaviour under severe Reactor Accident, Aix-en-Provence (FR), March 16-19, 1992
Availability: Available from (1) as Paper EN 36969 ORA
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