CFD transient simulation of natural convection characteristics based on detailed core rod bundles model in PLANDTL-DHX experimental device

If the plant blackout accident occurs in the pool-type sodium-cooled fast reactor, the decay heat of the core is discharged through natural circulation. The Plant Dynamics Test Loop (PLANDTL-DHX), an experimental device built in Japan, can simulate core coolant flow process and decay heat transfer phenomenon under decay heat discharged accident condition. In the present work, the numerical modeling of the experimental device is carried out based on the method of modular modeling and integrated coupling calculation, and the CFD commercial software FLUNET was used for calculation. The rod bundles of different forms in the core are modeled in fine detail. The initial conditions of transient are obtained under the steady boundary condition operation. Then, the change of key thermal parameters such as the temperature of the core and the temperature of IHX inlet and outlet are obtained by simulating the transient accident condition. In addition, there are obvious inner-flow and interflow in the core, meanwhile, the local backflow occurs at the core outlet. The influence of these phenomena on the heat transfer of the whole model is analyzed. The key results of simulation are compared with experimental data. The results can provide numerical references for the discharge of decay heat in the sodium-cooled fast reactor under power blackout accident.