Liquid metal thermal hydraulics - Outcomes of the SESAME project

Liquid metal cooled reactors are envisaged to play an important role in the future of nuclear energy production because of their possibility to use natural resources efficiently and to reduce the volume and lifetime of nuclear waste. Liquid lead(-alloys) and liquid sodium are good candidates for cooling such reactors. Thermal-hydraulics of these liquid metals plays a key role in the design and safety assessments of these reactors. Therefore, this was the subject of the Horizon 2020 collaborative project SESAME sponsored by the European Commission which ran from 2015 till 2019. This paper will present the main outcomes of this project. The main topics to be addressed are liquid metal heat transfer, core thermal-hydraulics, pool thermal-hydraulics, and system thermal-hydraulics. With respect to liquid metal heat transfer, the purpose was to start from the most promising RANS models which can simultaneously deal with different flow regimes (natural, mixed, and forced convection). To put these models to the test, a wide range of new reference data, both experimental and numerical has been generated. Regarding core thermal-hydraulics, further steps have been taken in liquid metal fast reactor fuel assembly modelling, mainly focusing on validation, both hydraulically and thermally, and on the effect of the inter-wrapper flow during accidental conditions. With respect to pool thermalhydraulics, new validation data was created to validate sufficiently accurate methods to model the coolant behavior in a liquid metal reactor pool. Special attention was given to the understanding and modelling of liquid metal solidification behavior. And finally, when considering the system scale, the new integral system scale validation data was generated to validate and improve system thermal-hydraulics models and codes, but also to further develop and validate multi-scale approaches under development. In all cases, experiments and numerical simulations were performed in a close cooperation. For all topics addressed above, development of best practice guidelines and methods for verification, validation and uncertainty quantification were also addressed.