Transport and Residence Times of Airborne Radioactivity
Fallout of long-lived radioactivity from nuclear bomb detonations is illustrated by a paper exercise conducted in 1959 involving about 4,000 megatons of nuclear explosives. The local fallout, that is the deposition taking place within a few days of the explosions, results in much of the U.S. being covered by Strontium-90 deposition in excess of about 400 millicuries per square kilometer. Some of the land areas of the Northern Hemisphere with heavier rainfall, those favorable for agriculture, also receive Strontium-90 deposition in excess of about 400 millicuries per square kilometer from delayed fallout months to years after the explosion. This delayed fallout would be deposited on neutral countries as well as combatants.