Rationalization and evaluation of a Phenomenon-driven improved bundle CHF model under PWRs condition with different axial power distributions

Abstract

In this paper, based on the bubble crowding bundle critical heat flux (CHF) mechanistic model proposed earlier by the author, which is applicable to the pressurized water reactors (PWRs) condition, more reasonable processes are considered, and a phenomenon-driven improved model was proposed. Firstly, the improved model describes the relationship between the latest visualization experimental results within PWRs ranges and bubble crowding concept, and clarifies the theoretical basis of the model. Secondly, based on the grid-effect CHF experiment, a more mechanistic turbulence mixing intensity factor was proposed in the process of model construction. Finally, the validation of the improved model for uniform axial power distribution (APD) CHF shows good prediction ability, and the previous tendentious problem about quality was eliminated. The model’s assessment of non-uniform APD CHF is performed for the first time, which shows that the improved model has good potential for predicting non-uniform APD CHF, and the CHF model needs to consider the upstream heating effect.