Executive Summary Despite hundreds of above-ground nuclear tests and data gathered from Hiroshima and Nagasaki, the effects of a ground-level, low-yield nuclear detonation in a modern urban environment are still the subject of considerable scientific debate. Extensive review of nuclear weapon effects studies and discussions with nuclear weapon effects experts from various federal agencies, national laboratories, and technical organizations have identified key issues and bounded some of the

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... wns required to support response planning for a low-yield, ground-level nuclear detonation in a modern U.S. city. This study, which is focused primarily upon the hazards posed by radioactive fallout, used detailed fallout predictions from the advanced suite of threedimensional (3-D) meteorology and plume/fallout models developed at Lawrence Livermore National Laboratory (LLNL), including extensive global A Casualties are defined in this document as both injuries and fatalities. B This report focuses primarily on protection from fallout. Other issues, including planning for actions that would reduce injuries/fatalities arising from the prompt effects of a nuclear explosion (e.g., "duck and cover" to reduce injuries from broken glass), are only briefly discussed.