Status of Physical and Numerical Modelling of CANDU Moderator Circulation

Abstract

A moderator test facility has been designed as a two-dimensional physical model of a CANDU calandria, capable of reproducing the important thermalhydraulic phenomena in the moderator flow. The purpose of the facility is to provide an extensive experimental database for the verification of moderator computer codes used in reactor safety analyses, and to enhance the understanding of the complex moderator thermalhydraulics. A vital step in computer code validation was to compare computer predictions against data collected during isothermal tests; tests with heat input will be studied later, Predictions from the MODTURC (MQDerator Turbulent Circulation) computer code, which is currently used for licensing calculations, and the next generation of moderator circulation code, named MODTURC-CLAS (Co-Located ted Advanced Solution), are compared to data collected for several isothermal tests with the moderator test facility. The comparisons show that both the MODTURC and MODTURC-CLAS codes are fundamentally sound, and able to predict flow patterns which are both qualitatively and quantitatively close to observations and measurements, The analysis of the comparisons has already provided some indications of what aspects of the flow modelling could use improvement.