The use of drift flux in predicting the fluid behavior in the primary system of a pressurized water reactor following a loss-of-coolant accident has received much attention in the past several years. However, applications have typically been directed toward predictions of the transient response wherein the depressurization is very rapid, resulting in vapor-liquid distributions that do not exhibit heterogeneous-type behavior. Drift flux can be successfully applied to transients exhibiting heterogeneity or phase separation and thus demonstrates an additional application of drift flux not previously emphasized in the literature.