Subchannel analysis in BWR fuel bundles

Abstract

Steady-state two-phase-flow calculations have been performed with the multidimensional drift-flux code canal. Flow-regime-dependent drift-flux parameters have been used to evaluate the flow quantities in the subchannels. Consistent modeling of the mixing components, e.g. divergence cross-flow, turbulent mixing and void drift effect, has resulted in the good prediction capability of canal. Measurements of subchannel exit mass flux and quality from simulated BWR rod bundles have been used to assess the code capability. A wide range of operating conditions has been taken into consideration in addition to variations in uniform and nonuniform radial heat-flux profile. Comparison has been made with the familiar subchannel code cobra iiic. Prediction of corner subchannel quality and mass flux by canal are nearly always found to be better than cobra iiic. The overall performance of the drift-flux code canal is comparable to that obtained from advanced two-fluid codes. A review of the conservation equations and constitutive relations shows that the countercurrent transverse flow velocities are essential for accurate prediction of subchannel flow conditions.