Sub-channel analysis of 8 × 8 and 9 × 9 BWR fuel assemblies with different two-phase flow models

Highlights: • Two sub-channel programs verified for boiling water reactor fuel assemblies. • A sub-channel program based on DFM is comparable to advanced two-phase codes. • DFM-based sub-channel program performs the computations with lowest computational cost. • 2FM sub-channel program provides more reliable result. - Abstract: The present study aims at verifying two sub-channel analysis programs, one based on drift-flux model and one based on two-fluid model, by applying them to traditional boiling water reactor fuel assemblies. The calculated parameters by the two sub-channel programs are compared with the predictions of the COBRA-EN code and VIPRE-01 code. The performance of the drift-flux model sub-channel analysis program is comparable to advanced two-phase codes. Agreement among the results of the programs appears to be due to the lack of details in modeling two-phase flow rod bundle transport phenomena, or numerical solution schemes