Radioactive Fallout Distance from a 1 Megaton Surface Nuclear Burst: Implications for Emergency Planning

https://www.academia.edu/impact?from_navbar=true&product=podcastThis study presents a quantitative analysis of the downwind distance of lethal radioactive fallout from a 1‑megaton (Mt) surface nuclear burst, based on declassified U.S. government models and modern radiological protection data. The analysis shows that unprotected individuals would receive a lethal dose of 900 rad (9 Sv) within 24 hours at a downwind distance of approximately 145 km. The zone of severe radiation sickness (300 rad / 3 Sv) extends to 257 km, and detectable effects (90 rad / 0.9 Sv) reach 400 km. The fallout pattern forms an elongated “cigar” shape along the wind direction. The results highlight that fallout is the dominant lethal factor for surface bursts and underscore the importance of sheltering and the use of potassium iodide (KI) within the first 24 hours. These findings are critical for nuclear emergency planning and public protection.