In the unlikely event of a terrorist nuclear blast, most casualties would be caused by radiation, especially the radioactive cloud carried by winds into surrounding areas. This map adapted from a White House Homeland Security Council report - which depicts an attack on Washington - shows a hypothetical radiation plume from a 10-kiloton weapon. The plume's direction is based on prevailing winds. Other wind conditions would provide different results. The statistics are based on a scenario in which little evacuation was possible.