Experimental and numerical studies on mixing jets for sodium cooled fast reactors

Abstract Sodium cooled fast reactors (SFRs) have been developed in France for nearly 50 years with successively Rapsodie, Phenix and Superphenix plants. Nowadays, the so-called Astrid technology demonstrator is developed in the frame of Generation IV deployment. The core outlet region where subassembly jets are mixing below the above core structure is concerned with design and safety issues. Due to local temperature differences, high cycle thermal fatigue can occur in the mixing area and potentially produce thermal striping and cracks on the local structures. So, the prediction of temperature fluctuations characteristics is required. Moreover, the reliability of subassembly outlet temperature measurements is also an issue depending on the jets mixing behaviour in case of local temperature gradient. Experimental and numerical studies on mixing jets have been performed at CEA to meet the previous issues. The paper successively presents a brief survey on mixing jets studies for SFR, main experimental results obtained at CEA with a sodium facility and a similar air facility, numerical computations with TRIO_U code using a large eddy simulation (LES) approach, the status of validation based on previous experimental data and other available results.