Three-Dimensional Numerical Simulation of the Natural Circulation Characteristics Based on PLANDTL-DHX for Different Modeling Methods of the Core

The passive decay heat removal system based on natural circulation can passively remove the heat from the core, which greatly improves the safety of the nuclear reactor. The Plant Dynamics Test Loop (PLANDTL-DHX) experimental facility can simulate the flow and heat transfer characteristics of the pool-type sodium-cooled fast reactor with an independent decay heat removal system in a natural circulation state. However, the natural circulation experiments based on the PLANDTL-DHX facility are difficult to present the detailed flow characteristics in the core completely. So it is necessary to adopt numerical simulation analysis to obtain the flow characteristics in the core. While due to the complex structure of the core with wrapped wire bundles, the modeling and calculation of the pool-type fast reactor need very rich computing resources. To reduce the demand for computing resources, the model can be simplified to some extent. In this study, two modeling methods are adopted for the core: 1. The model of the rod bundles and wrapped wires are simplified by the porous media model; 2. The wrapped wires are simplified by the porous media model, while the rod bundles are retained. The PLANDTL-DHX experimental facility modeled by two different core modeling methods is numerically simulated. By analyzing and comparing the experimental data of PLANDTL-DHX, the feasibility of two different modeling methods for numerical simulation research is verified. By analyzing and comparing the calculation results of two different modeling methods, the flow characteristics in the core during natural circulation are also obtained, and the characteristics of different modeling methods are summarized. This work can provide a reference for the safety analysis and simulation calculation of pool-type sodium-cooled fast reactor.