The Pressure Water Reactor (PWR) primary flow rate is determined using an enthalpy balance between the primary and the secondary circuits. Hot leg bulk temperature is necessary to estimate the enthalpy of the primary circuit. This bulk temperature is difficult to evaluate as the temperature is measured in the hot leg using a small number of local sensors in a region where its heterogeneousness is large. Measuring the bulk temperature in a real-life configuration is, to the authors’ knowledge, still a challenging task. Thus, Computational Fluid Dynamics (CFD) is an interesting approach to quantify the difference which may exist between the measured temperature and its bulk value. Deciding which turbulence model one has to use in order to have a satisfactory prediction of the fluid motion and the temperature field is not obvious. Indeed, the flow in the hot legs has strong secondary motions which may need a high order turbulence closure. The main objective of the present work is to compare a standard model such as the k-ε with a more sophisticated one (the Reynolds Stress Model from Speziale, Sarkar and Gatski (SSG)). EDF in-house CFD tool Code_Saturne is used for all the computations. The data coming from the so called “Banquise” experiment (1/5th scale, Re = 100.000, PIV, thermal tracing) representing the upper plenum of a 1300 MWe PWR and its hot legs are used for comparisons. It is, at the present stage, difficult to clearly distinguish the quality of the two models. Both give globally satisfactory results with the criteria used in the present article. One finds however that the SSG model is superior at the beginning of one of the two hot legs which has a direct impact on the prediction of the temperature field.

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