Given the rare nature of nuclear disasters, researchers must continually expand upon existing methods to increase the accuracy and validity of nuclear models that better support the emergency management, health care, and public health communities in their preparedness efforts. This dissertation takes measured steps towards such a goal, by using simulated 15 kiloton (kt) improvised nuclear device (IND) detonations in Atlanta, Georgia (GA). An analysis of the simulated fallout radiation plumes throughout 2019 identified four clusters that captured the variation in the geospatial and population impacts. The medoids of the clusters were used in expanding upon the existing nuclear modeling framework by integrating building-specific attributes to account for thermal and radiation effects in an urban environment. Under the thermal attenuation model, approximately half of the buildings that would have previously been assumed to have been exposed to enough thermal fluence to cause either burns or mass fires were shadowed by the surrounding environment and therefore were no longer exposed to such levels of thermal radiation. Under a warned scenario, in which people would have time to seek shelter in a basement or in the most interior room of a building, more than 90% of buildings that were externally exposed to more than 200 rads of fallout radiation received less than 200 rads internally due to the protection offered by building characteristics, such as construction material, height, and the presence of a basement. Across the four simulations, an estimated 185,896 to 196,537 individuals would not survive their injuries, and an additional 31,939 to 46,668 patients would require immediate health care. Another 454,015 to 1,060,235 individuals would require delayed or minimal care. While these estimates alone would overwhelm the health care infrastructure, the strain would be further exacerbated by losing health care facilities directly to the detonation. Even when surge capacity was considered, there would only be enough staffed beds in GA for approximately 25% of the patients requiring immediate health care. Multi-jurisdictional, innovative preparedness efforts to address these resource limitations, based on increasingly accurate models and simulations, will be imperative for a successful response to an IND detonation in the US/
