System / CFD Coupling For Reactor Transient Analysis.An Application To The Gas Fast Reactor With CATHARE And TRIO_U

摘要

In the frame of System/CFD coupling, two CATHARE / TRIO_U coupling methods were developed : a domain decomposition method and a domain overlapping method. The domain overlapping method was applied to a blackout transient in the Gas-cooled Fast Reactor, where the decay heat removal (DHR) relies on natural convection in a specific DHR loop. The CFD representation of the upper plenum shows a strong stratification. It modifies the temperature entering the DHR loop, but it has a small effect on the natural convection and the core temperatures. This effect can be understood via a simple analytical model, which shows that an additional power is extracted by increasing the temperature difference rather than the mass flow rate. The know-how learnt from this study will be applied to other transients in the frame of Generation 4 reactors design