European outlook for LMFR thermal hydraulics

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. Typically, sodium and lead(-alloys) are envisaged as coolants for such reactors. Obviously, in the development of these reactors, thermal-hydraulics is recognized as a key (safety) challenge. This paper will present recent developments and initiatives with respect to liquid metal cooled reactor thermal-hydraulics. The initiatives to be discussed encompass liquid metal heat transfer, fuel assembly thermal-hydraulics, pool thermal-hydraulics, and system thermal-hydraulics. With respect to liquid metal heat transfer, the purpose is to start from the most promising routes and develop and validate a model which can simultaneously deal with different flow regimes (natural, mixed, and forced convection). Considering fuel assemblies, the aim will be to take the next steps in liquid metal fast reactor fuel assembly modelling, mainly focusing on validation and evaluation of accidental conditions. With respect to pool thermal-hydraulics, the purpose will be to develop and validate sufficiently accurate methods to model the coolant behavior in a liquid metal reactor pool. When considering the system scale, similarly, the purpose will be to validate and improve system thermal-hydraulics models, but also to further develop and validate multi-scale approaches.