Preliminary calculations of coolant flow in a SCWR Fuel assembly with the code ANSYS CFX 10.0

For the design of Supercritical-Water Cooled Reactors (SCWRs) it is important to get know the thermal phenomena and the flow field in the different fuel assembly concepts. The ANSYS-CFX-10.0 code, a commercial computational fluid dynamics code has been used for investigating this field. The specific feature of the supercritical heat transfer is that the material properties change dramatically in a specific temperature range around the so-called pseudo-critical temperature. Because of this specific feature, we had to validate the ANSYS-CFX-10.0 code to see if it is capable for handling the heat transfer phenomena for supercritical state fluids. The calculations of a 2950 mm long straight pipe model were compared with measurement data and the prediction of the Swenson correlation recommended by international literature. The validation has been successful and the study could keep on. Three different sub-channel models were developed based on the European SCWR fuel assembly concept. Several calculations were performed with these sub-channel models for different boundary conditions. The calculations performed have showed problems with imbalance values. This investigation has showed the difficulty of the calculation of heat transfer processes when the temperature is around the value of the pseudo-critical temperature