[en] The computer program BLOW-3A, describing sodium boiling phenomenon with a multi-bubble slug ejection model, has been used for theoretical interpretation of out-of-pile and in-pile 7-pin bundle experiments. Analysis demonstrates the applicability of the code to a wide range of experimental conditions and the possibility to model a bundle geometry by means of equivalent one-dimensional channels. It is shown that a single channel representation is sufficiently accurate for conservative evaluation of consequences of hypothetical accident situations. 5 refs