Development of a method for BWR subchannel analysis

Abstract

This study deals with the development of a computer pro- gram for steady-state and transient BWR subchannel analysis. The conservation equations for the subchannels are obtained by area-averaging of the two-fluid model conservation equa- tions and reducing them to the drift-flux model formulation. The conservation equations are solved by a marching type technique which limits the code to analysis of operational transients only. The transfer of mass, momentum and energy between adjacent subchannels is split into diversion cross- flow and turbulent mixing components. The transfer of mass by turbulent mixing is assumed to occur in a volume-for- volume scheme reflecting experimental observations. The phenomenon of lateral vapor drift and mixing enhancement with flow regime are included in the mixing model of the program. The following experiments are used for the purpose of the assessment of the code under steady-state conditions: 1) GE Nine-Rod tests with radially uniform and nonuniform heating 2) Studsvik Nine-rod tests with strong radial power tilt 3) Ispra Sixteen-rod tests with radially uniform heating Comparison of calculated results with these data shows that the program is capable of predicting the correct trends in exit mass velocity and quality distributions.