Applicability Analysis of Onset Model for Debris Bed Relocation in Sodium-Cooled Fast Reactor

When the core disruptive accident (CDA) occurs in the sodium-cooled fast reactor (SFR), the melted core fuel is cooled and solidified into debris particles by the coolant, which accumulates in the lower plenum and forms the debris bed. In order to effectively remove the decay heat from the debris bed and implement the in-vessel corium retention (IVR), it is necessary to predict and simulate the relocation behavior of the debris bed. For this reason, Zhang et al. developed an onset model for judging the relocation of the debris bed based on the force balance analysis of the particle. In this paper, a large number of debris bed relocation experiments were carried out by bottom gas-injection method, and the relocation onset model was used to calculate and predict the relocation behavior of the debris bed under different experimental conditions, which further verified the applicability of the relocation onset model.