Abstract
The Direct Reactor Auxiliary Cooling System (DRACS), shown in Fig. 1 [1], is a passive heat removal
system proposed for the Advanced High-Temperature Reactor (AHTR). It features three coupled natural circulation/convection loops completely relying on the buoyancy as the driving force. A prototypic design of the DRACS employed in a 20-MWth AHTR has been discussed in our previous work [2]. The total height of the DRACS is usually more than 10 m, and the required heating power will be large (on the order of 200 kW), both of which make a full-scale experiment not feasible in
our laboratory. This therefore motivates us to perform a scaling analysis for the DRACS to obtain a scaled-down model. In this paper, theory and methodology for such a scaling analysis are presented.