[en] The thermalhydraulics code ASTEC is used to predict flows for a 2 MW natural circulation test carried out in the prototype fast reactor (PFR). The simulation corresponds to a period 2 hours into the test when quasi-steady state conditions are well established. A finite element mesh, representing a 60⁰ sector of the PFR inner pool together with an associated intermediate heat exchanger, is used for a 3-dimensional calculation where buoyancy forces dictate both flow paths and flow rates. The predicted flow field is in close agreement with a 2-loop mode of flow. The predictions are also in good agreement with the experimental results, and confirm the 2-loop mode explanation for some anomalous temperature measurements. (author)