Preliminary test results and CFD analysis for Moderator Circulation Test (MCT)

The moderator flow circulation patterns in CANDU6 reactor are complicated slow flows that significantly vary from buoyancy dominated to inertia dominated patterns. Accurate predictions of flow patterns are essential for accurate calculation of moderator temperature distributions and the related moderator subcooling. The code and its analytical models have therefore to be validated against experiments representative of reactor conditions. Korea Atomic Energy Research Institute (KAERI) installed the Moderator Circulation Test (MCT) facility to simulate the 3 dimensional moderator circulation phenomena in the calandria of CANDU6 reactor and develop the optical measurement system using the Particle Image Velocimetry (PIV). From the present work it is shown that the PIV measurement results can capture the same flow pattern as that expected in the CANDU6 calandria tank under a momentum dominant flow condition, where the inlet jets penetrate the top of the tank and produce a downward flow through the center of the tube columns toward the outlet nozzle, and the flow fields are in symmetric distributions. The measurements of the downward velocities are performed at different locations. The velocity is shown to be axially uniform. The velocity is rapidly decreased as the measurement location is far from the center of the tank, since the downward flow is dominant along the center of the tube columns. The present PIV measurement data are collected and compared with CFX code predictions.