Steady State 3-D Simulation of CANDU6 Moderator Circulation Under the Normal Operating Condition

Abstract

Moderator circulation inside the CANDU-6 reactor vessel of Wolsong 2/3/4 (KOREA) under normal operating condition is analyzed by using computational fluid dynamics for predicting the local subcooling of the moderator in the vicinity of the calandria tubes. The buoyancy effect induced by internal heating is accounted for by the Boussinesq approximation. The standard k-E turbulence model associated with logarithmic wall treatment is applied to predict the turbulent jet flows from eight inlet nozzles. The matrix of calandria tubes in the core region is simplified as porous media, in which anisotropic hydraulic impedance is modeled using an empirical correlation of frictional pressure loss. The governing equations are solved by CFX-4.4, a commercial CFD code developed by AEA technology. The CFD model has been successfully validated against experimental data obtained in the Stern Laboratories Inc. (SLI) in Hamilton, Ontario. Steady-state 3-D prediction of the CANDU-6 moderator circulation under normal operating conditions gives a maximum moderator temperature of 82.9 degrees C at the upper core region, which corresponds to the minimum subcooling temperature of 24.8 degrees C considering hydro- static pressure increase. The flow pattern on the normal plane to z-axis is determined as 'mixed-type'.