Benchmarking a sub-channel program based on a drift-flux model with 8 × 8 NUPEC BWR rod bundle

• Sub-channel program based on a drift-flux model is used to evaluate 8 × 8 NUPEC BWR.
• Turbulent mixing component, drift velocity and void fraction models provide appropriate results.
• The calculated parameters are in good agreement with the measured data.

This study deals with the verification of a sub-channel analysis computer program for steady-state and operational transients in boiling water reactors (BWR). Conservation equations based on a flow regime dependent drift-flux model, proper constitutive equations and correlations are assigned to evaluate sub-channel grade void distributions in the NUPEC (Nuclear Power Engineering Corporation) BFBT (BWR Full-size fine-mesh Bundle Tests) facility. Fifteen steady-state test series and two transient cases were selected to analyze the sub-channel void distributions. It was revealed that the steady-state void distributions calculated by the program agreed well with the measured data in the range of thermodynamic qualities from 5% to 25%. The results of the transient calculations were also to experimental data.