CFD model of a moderator tank for a pressure vessel PHWR nuclear power plant

Abstract

The CFD thermal hydraulic simulation of a Pressurized Heavy Water Reactor (PHWR) moderator tank was performed. Heating was achieved by considering two heat sources, conduction/convection through the coolant channels and neutron thermalization. For the first method, a suitable 2D model for coupling the 3D with a 1D code to solve the in-channel coolant was implemented. For thermalization, a volumetric heat source was estimated. Due to the relevance of natural and forced convection in the heat transfer, the Boussinesq approach was assessed for high Rayleigh number flow before it was used to model the moderator tank. The results clarified the complex flow behavior and the temperature field. As expected from design, the thermal power transferred from coolant to moderator is not directly related to the fission power distribution but to the axial coolant temperature profile (nearly the same for all channels) and the non-homogeneous moderator temperature profile. The former was as expected for high-Rayleigh natural convection systems.