Accurate simulation of subcooled boiling flow is essential for the operation and safety of nuclear power plants (NPP). In recent years, the use of computational fluid dynamics (CFD) codes has been extended to the analysis of multi-dimensional two-phase flow for the NPP. Among the applications of CFD code for the NPP analysis, the first target was selected as a mechanistic prediction of DNB (Departure from Nucleate Boiling) in PWR (Bestion et al, 2006). In DNB-type CHF (Critical Heat Flux), the expected flow regime is bubbly or churn turbulent flow in the high mass flux and high heat flux
condition and thus subcooled boiling is also one of the key phenomena for the precise prediction of DNB.In this paper, S,which is a mechanistic transport equation for the bubble parameters, was examined in a CFD code with the objective of enhancing the prediction capability of subcooled boiling flows. The models were applied in the STAR-CD 4.12 software.