The paper summarizes the experimental activities carried out at the University of Rome "La Sapienza" - DINCE on the performance evaluation of a passive system for heat removal in emergency conditions. This system simulates a part of the innovative emergency decay heat removal system of the “inherently safe” MARS NPP, initially proposed by the University of Rome “La Sapienza” in 1983. To experimentally analyze the transient performance of the innovative system, an experimental facility has been designed and built. The experimental plant is fully instrumented and controlled by a computerized system, by which also transient conditions in the power generations and pressure drops can be imposed. In the paper, the NICOLE facility is described, as well as well as the some preliminary experimental results obtained, compared with the results of theoretical simulations. A discussion on possible phenomena affecting negatively the reliability of the system, owing to wind or heat exchanger geometry, is also presented. To study the geometry of the internals, another simple experimental facility of a cooling tower is being realized and some preliminary CFD results are presented.