The benign termination of the transition phase of a hypothetical LMFBR accident rests on the avoidance of highly energetic recriticalities prior to escape of bottled molten core materials from the active core region. In scenarios where molten fuel is trapped due to axial blockages, the maintenance of subcritical configurations until radial flow paths develop requires stable boil-up of the molten fuel/steel mixture. This paper describes the analysis of an experiment investigating the behavior of closed boiling pools using the two-fluid hydrodynamics module of TRANSIT-HYDRO, a deterministic transition-phase analysis code.