COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF THE REACTOR CAVITY COOLING SYSTEM FOR VERY HIGH TEMPERATURE GAS-COOLED REACTORS

摘要

The design of passive heat removal systems is one of the main concerns for the modular Very High Temperature Gas-Cooled Reactors (VHTR) vessel cavity. The Reactor Cavity Cooling System (RCCS) is a key heat removal system during normal and off normal conditions. The design and validation of the RCCS is necessary to demonstrate that VHTRs can survive to the postulated accidents. The Computational Fluid Dynamics (CFD) STAR-CCM+/V5.02.009 code was used for three-dimensional system modeling and analysis of the RCCS. Different RCCS geometries were investigated to analyze heat exchange in the VHTR cavity. Heat removal from the RPV through the RCCS system during normal and off normal conditions is accomplished through radiation, convection and conduction heat transfer mode simultaneously. The objective of the present work was to use Computational Fluid Dynamics tools for addressing the behavior of the RCCS following accident conditions. Mesh convergence was achieved with an intensive parametric study for the different geometrical configurations and boundary conditions selected. Based on the results of previous studies, the Realizable k-ε turbulence model with two-layer all y+ wall treatment was used for the analyses discussed in the present work. The numerical results obtained from the CFD analyses were compared against the predictions from a scaling procedure developed to address the distortions introduced by the CFD model in simulating the physical phenomena inside the RCCS system with respect to the full plant configuration. The results comparison demonstrated that the CFD analyses can predict the behavior of the RCCS system from an integral-effect point of view.