CHARACTERIZATION OF THE INLET FLOW CONDITIONS FOR THE MODERATOR TEST FACILITY

Abstract

Flow in the Moderator of a CANDU reactor can be very complex due to the interplay of convective and buoyant effects. Experiments have been performed to measure temperature and velocity fields for these kind of flows, although concerns still exist. As a result a Moderator test facility has been built in order to validate CFD models for future predictions and safety analysis. To properly validate this experiment an accurate set of inlet flow conditions must be established in order to ensure a fair comparison.

A series of flow conditions indicative of the header assemblies which feed flow into the moderator test facility have been investigated through experimentation, empirical evaluation and numerical simulation. They include flow through curved tubes, turbulent free jets and flow through dividing manifolds. The goal of the present study is to establish the modelling approach to predict the flow distribution inside the manifold and velocity field out of the J-nozzles.

A variety of RANS based turbulence models and computational meshes were employed in the numerical study. The turbulence model that was found to perform best was the realizable k- model. It was also found that the velocity field of the J-nozzles is constant between Reynolds numbers of 6800-9300. These Reynolds numbers are indicative of those expected out of the header assemblies.