Three-Dimensional Numerical Simulation on DRACS and PRACS Heat Removal Ways of Natural Circulation Based on the PLANDTL-DHX Experimental Device

Abstract The sodium-cooled fast reactor (SFR) experimental device PLANDTL-DHX adopts a loop-type arrangement. In the event of station blackout, a natural circulation is required to remove the decay heat of core. There are two main ways to remove the decay heat from the reactor core, one is the direct reactor auxiliary cooling system (DRACS), the other is the primary reactor auxiliary cooling system (PRACS). In the present work, the modular modeling and integrated calculation approach was employed to build the device model and simulate the thermal hydraulic phenomena in the whole primary loop under the conditions of DRACS and PRACS respectively. The feasibility of the modular modeling and integrated calculation method is verified, and the differences between DRACS and PRACS decay heat removal methods were also analyzed. By means of PRACS or DRACS for decay heat removal, both inter-wrapper flow (IWF) and intra-subassembly flow are evident at the core locations. The temperature at the outlet of the core and the upper plenum is significantly higher with PRACS than with DRACS. Compared with the PRACS decay heat removal method, a return flow phenomenon at the core location emerges the DRACS decay heat removal, which is more conducive to the discharge of core decay heat. The results can provide important numerical reference for the design and operation of different forms of decay heat discharge ways.