Debris thermal interaction with lower plenum structures

The damaged core of the TMI-2 reactor contains a wealth of information that will aid in understanding severe accidents. That information is being obtained by pursuing a research effort of core examination in concert with analysis aimed at understanding observed phenomena. This paper presents a preliminary analysis of the potential damage state of the lower plenum resulting from thermal interaction between hot core debris and lower head structures. Analysis indicates that the instrument penetration nozzles in TMI-2 could have experienced melting at localized hot-spot regions, with attendant debris drainage and plugging of the instrument guide tubes. Only minor thermal attack on the vessel liner is predicted