Severe Accident Progression in CANDU Using a Detailed Model for the Core Disassembly Phase - Preliminary Results

The purpose of this paper is to investigate the accident progression timing of events, when a detailed core model is used for the core disassembly phase, in comparison with previous studies and results for a Station BlackOut (SBO) analysis. For the early phase of the severe accident analysis, up to the moment of the first fuel channel failure, the core model is described by 8 equivalent fuel channels per loop; and for the disassembly phase of the accident only half of the core was modeled with 32 equivalent fuel channels, assuming symmetry on the other face of the reactor core. The analysis preliminary results show major differences for the core disassembly phase of the accident in terms of beginning and end of core disassembly timings, but also regarding the axial and radial position of the disassembled segments of the fuel channels.