Overview of stratification studies in France

We present hereafter the efforts undertaken in France (mainly in CEA, Service des Transferts Thermiques and in EDF, Laboratoire National d'Hydraulique) to study stratifications in large sodium pools of LMFBR. The paper covers the following aspects: - Characteristics of thermal stratification which are important for the design; - Risks of occurrence of stratification in different parts of the reactor. Classification of these risks with the aid of non dimensional parameters; - Presentation of the different methods used for the investigation of thermal stratifications: small scale models using simulant fluid; numerical models; sodium tests; - Illustration of the methods in the determination of the characteristics of stratifications: basic studies; applied studies in plena and pipes. (author)