Westinghouse Electric Company is developing its Next Generation of high-capacity nuclear power plant based on Lead Fast Reactor (LFR) technology: a Generation IV, compact, highly simplified, passively safe, and scalable nuclear power plant. In addition to superior economics for enabling competitiveness even in the most challenging electricity market, exceptional safety performance is actively pursued in the design of the plant, leveraging the inherent favorable properties of lead coolant as well as safety features intrinsic in the design. Being decay heat removal an integral part of any plant’s safety philosophy, a systematic process of concept selection has been employed across a wide variety of decay heat removal system designs. Among them, air cooling outside of the reactor vessel is one of the concepts that is being actively evaluated by Westinghouse. In this paper, the use of air cooling in nuclear reactors is discussed together with the identification of benefits and challenges associated with reactor vessel air cooling in LFR technology. The heat removal capability of this system is assessed with three computer codes, differing in complexity and suitability to “rapid prototyping” design activities carried out by Westinghouse during different phases of plant design. Though the computer codes were developed separately, the results of the three evaluation models tend to support each other, thus increasing the confidence in the information provided to progress the Westinghouse LFR design and establish its safety basis. Additional validation through existing and potentially new test data is foreseen as future work within the Westinghouse LFR program.