Experimental and CFD simulations of fluid flow and temperature distribution in a natural circulation driven Passive Moderator Cooling System of an advanced nuclear reactor

The feasibility of such a system should be assessed before it is implemented in the reactor. Thus, a scaled test facility was set up to simulate the thermal hydraulic characteristics of the PMCS. A set of time varying power experiments were performed, which capture the flow initiation from rest phenomena and the multidimensional natural convection flow in a coupled natural circulation system. Next, the experimental geometry was simulated using the three-dimensional computational fluid dynamics code (OpenFoam 2.2.0), which predicted temperature and flow distribution inside the system. The CFD results agree well with the experimental data within ±6%. The flow initiation phenomena shows that the initial flow generated recirculates within the Calandria, after ~900 s the flow is able to come out of the Calandria. The experiments show a time lag between the starting of the primary and secondary loop circulation. This work demonstrates the experimental and computational capability to understand and design an effective Passive Moderator Cooling System.