Containment safety analysis is a field in expansion given the complex phenomenology developed during an accident, and the recent code capabilities improvement. In this paper, a modeling strategy to create complex containments with porous CFDs in a single control volume is presented. This methodology involves using solely Computer Aided Design (CAD) tools, to manage the geometrical model, instead of using the GOTHIC code pre-processor interface. This methodology is applied to Trillo NPP (KWU 3 loops) where a LBLOCA is simulated to illustrate its capabilities. The results are compared against a Lumped Parameters model obtaining similar average values. Finally, a sensitivity analysis is made to quantify the influence of the modeling simplifications showing a small dependence. This implies that this modeling strategy is able to recreate models accurately, with an affordable computational cost, and with a time saving improvement, which nowadays is the main bottleneck for 3D containment models.